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for the TWODANT SOLVER module.

1. es wird ein Makefile erzeugt das anschlie end zum Compilieren des schiedenen Rechnerfabrikaten Die Cray Version 80 14 vom 2 9 1994 95 erf llt die Anforderungen gerade w hrend auf HP mindestens HP UX Rel 10 0 M rz 1994 installiert sein mu Auf Sun SunOS 4 1 und IBM AIX 3 2 gibt es keine Probleme proginst wurde auf folgenden Rechnern getestet Rechner Typ Betriebssystem f77 Vers proginst funktioniert hdi3sun Sun 3 80 SunOS 4 1 ja hdirisc7 IBM RS 6000 AIX 3 2 ja hdicrayl Cray J916 I UNICOS 8 0 6 0 4 0 ja hdihp1 HP 9000 715 HP UX A 09 01 ja hikasun2 Sun SPARC 5 Solaris2 5 3 0 ja irscray1 Cray Y MP UNICOS 8 0 ja ee ee ee hdivist HP 9000 720 HP UX A 09 01 nein FORTRAN 77 Version fsplit HP UX Rel 10 0 M rz 1994 FORTRAN 77 Version fsplit HP UX Rel 9 0 Aug 1992 Autor Manfred Alef HDI Version 01 06 1995 Versionen fiir Sun HP und IBM 04 07 1995 Anpassung an Cray J90 11 07 1995 Parallele Compilation auf der Cray J90 27 07 1995 Fehler bei leerer Hauptprogrammliste behoben 14 09 1995 Letzte Zeile kann END oder end sein 21 12 1995 Abfrage uname m CRAY statt uname s sn9068 FH SR ORR OE HEE HEE d d HEE FE HF d d HR HEHE FH HE HE System feststellen betriebssystem uname s case betriebssystem in AIX SunOS sn HP UX if split v dev null J th
2. Forschungszentrum Karlsruhe Technik und Umwelt Wissenschaftliche Berichte FZKA 6290 A new SIMMER III Version with improved Neutronics Solution Algorithms G Buckel E Hesselschwerdt E Kiefhaber S Kleinheins W Maschek Institut fur Neutronenphysik und Reaktortechnik Projekt Nukleare Sicherheitsforschung Juni 1999 Forschungszentrum Karlsruhe Technik und Umwelt Wissenschaftliche Berichte FZKA 6290 A new SIMMER III Version with improved Neutronics Solution Algorithms G Buckel E Hesselschwerdt E Kiefhaber S Kleinheins W Maschek Institut f r Neutronenphysik und Reaktortechnik Projekt Nukleare Sicherheitsforschung Forschungszentrum Karlsruhe GmbH Karlsruhe 1999 Als Manuskript gedruckt Fur diesen Bericht behalten wir uns alle Rechte vor Forschungszentrum Karlsruhe GmbH Postfach 3640 76021 Karisruhe Mitglied der Hermann von Helmholtz Gemeinschaft Deutscher Forschungszentren HGF ISSN 0947 8620 Abstract When investigating several accident related reactor situations with the standard SIMMER II code package it turned out that sometimes the convergence behaviour of the neutronics part of the code was rather poor or even worse no convergence could be achieved with the implemented TWOTRAN like module for solving the neutron transport equation Extended test calculations outside of SIMMER II for the comparison of different transport codes available at FZK led to the recommendation t
3. nein tn j tf ti n tn echo minus_n M chten Sie Ihr Programm zun chst mittels Debugger testen nein strich_n read antwort if x antwort xj then fflags g debug_option gesetzt H fi if x fflags x then echo minus_n Soll Ihr Programm m glichst optimiert compiliert werden ja strich_n 101 read antwort if x antwort x o x antwort xj then case betriebssystem in AIX fflags O qhot sn echo minus_n Geben Sie bitte die Option en ein strich_n read fflags H fflags O esac fi fi if x betriebssystem xsn9068 then if uname m CRAY then echo Soll die Rechengenauigkeit verdoppelt werden z B echo minus_n REAL 8 statt REAL verwendet werden ja strich_n read antwort if x antwort x o x antwort xj then case betriebssystem in ATX fflags fflags qautodbl dblpad HP UX fflags fflags autodblpad SunOS fflags fflags r8 sn9068 echo minus_n Bitte die entsprechende Option eingeben strich_n read antwort fflags fflags antwort esac fi fi cat lt lt gt gt Makefile Aufruf dieses Makefiles mit dem Befehl make bzw wenn Sie andere als die im Makefile vorgegebenen Compileroptionen setzen wollen make FFLAGS if s dateiliste hp then cat lt lt gt
4. 7 Modifications in the TWODANT SOLVER routines For the solution of SIMMER relevant problems after the replacement of the TWOTRAN like routines by the independent TWODANT SOLVER module the following 27 TWODANT routines had to be modified as described and also listed in chapter 3 CHEBY CIFLSM DESTDA DIFFO DMPFLX DOUTER DRIVER HYLITE KEYWRD LCMADD MACMIX MASWEP MASWEPW PRNTIA PRTNFX RDSOL SCMADD SINNER TESTGO TFINAL TIGF20 TINITA TINP21 TINP22 TINP24 TOUTER TRANSO In addition the two completely new subroutines LINKM fully described in chapter 5 and CHIMOD had to be attached It is almost impossible to describe explicitly every alteration omission or introduction of a specific Fortran statement in these particular subroutines It was decided therefore the working version of the Fortran source program of the SIMDANT development of the ongoing development up to about end of 1997 to be stored for longterm purposes This dataset contains all alterations identified by comment cards usually comprising the date of its inclusion and the identification of the responsible person and moreover in many cases the explanation for the purpose that lead to the inclusion In this chapter the description of modifications is restricted to a more general explanation for their insertion 42 7 1 Subroutines TWODANT and TIGF20 as driver programs for the TWODANT SOLVER module In order to initialize properly variables data arrays and COMMON areas fo
5. Los Alamos National Laboratory report LA 6941 MS September 1977 6 S Kondo K Morita Y Tobita K Kamiyama D J Brear E A Fischer SIMMER III A Computer Program for LMFR Core Disruptive Accident Analysis Version 2 A User s Manual Internal Report 7 R E Alcouffe An Adaptive Weighted Diamond Differencing Method for Three Dimensional XYZ Geometry Trans Am Nuc Soc 68 Part A 206 1993 8 R D O Dell and R E Alcouffe Transport Calculations for Nuclear Analysis Theory and Guidelines for Effective Use of Transport Code Los Alamos National Laboratory report LA 10983 MS September 1987 9 Historian Plus User s Manual Release 4 3 137 August 1991 HPCSA Historian Plus Contract Servicing Administration c o 8850 Business Park Drive 200 Austin Texas 78759 10 W R Bohl L B Luck SIMMER II A Computer Program for LMFBR Disrupted Core Analysis Los Alamos National Laboratory report LA 11415 MS June 1990 11 W A Rhoades W W Engle Trans Am Nuc Soc 27 776 1977 12 K Lathrop J Comp Phys 4 475 1969 13 G I Bell G E Hansen H A Sandmeier Multiple Treatment of Anisotropic Scattering in SN Multigroup Transport Calculations Nucl Sci Eng 28 376 1967 14 F Parker M Ishikawa L B Luck MXS Cross Section Preprocessor User s Manual Nureg CR 4765 Los Alamos National Laboratory report LA 10856 M March 1987 83 15 O Marchand J L
6. NO CORE it is sufficient to restart the compilation of a corrected executable at step 6 of the example given above The required values for NFALSE and NSCM respectively may now be taken from the TWODANT protocol and used for the modification in subroutine twodant f The repetition of the instruction make in step 7 will cause only the compilation of those subroutines which have been changed since the last modification of the executable sunday x The corrected executable automatically replaces the previous one in subdirectory sunday 61 11 Test calculations The new neutronics version of the SIMMER III package has been applied to four representative test problems including static and transient cases in order to validate and verify the code In this section the brief descriptions of these test problems and the results are reported The test problems have first been calculated during the stay of one of us E H at the Japan Nuclear Cycle Development Institute JNC The results were published preliminarily in an internal report 16 At the time of performing these investigations the WDAMPA WDAMPE lt 0 option i e subroutine MASWEPD was not yet available 11 1 FCA Fast Critical Assembly A series of fuel slumping experiments has been performed in JAERI s FCA facility of which a cylindrical model of geometry and material arrangement is shown in Figure 3 Several disrupted core configurations were simulated in the FBR test
7. 44 IMACRX 42 ISOLIN 45 All file identifications for these five files are written in the same way consisting of the file names as contents of a CHARACTER 8 data string and for each file the same actual date and time is used as contents of two CHARACTER 8 data strings These parts of information are provided by a call of the system subroutine DATE_AND_TIME 17 5 1 Preparation of the interface file ASGMAT The file control block is written as MT NZONE MPZTOT FMMIX with MT NZONE ITJT as shown above As a result of specifying MPZTOT FMMIX 0 TWODANT is run with the IN SOLVER mixing table length 0 and prescribing NO fraction mixing by fine mesh As compatibility code words CODE and CODE2 the same CHARACTER 8 data strings are written as already used in the file identification containing the actual date and time As for SIMMER TWODANT the assignment of materials to zones is very simple each mesh in the neutronics grid represents one reactor zone possessing its own specific material two CHARACTER S8 data strings are prepared as MATNAM I 1 MT and ZONNAM I 1 NZONE They contain the labels ISO and ZONE respectively followed by the neutronics mesh number in CHARACTER representation MATNAM I 1 MT is written as material names block and ZONNAM D i 1 NZONE as zone names block on the ASGMAT file respectively The number of material names and the number of zone names are limited in
8. 9 3 Use of IGM lt 0 9 4 Separate output for important messages Applications of HISTORIAN for the preparation of new executables for SIMMER calculations Test calculations page 12 14 17 18 21 26 32 33 34 35 36 41 42 44 47 50 52 52 52 53 53 54 61 12 13 14 11 1 11 2 11 3 11 4 FCA Fast Critical Assembly SRA Static Reactor Analyses STN Standard Test problem for neutronics TRA Transient Reactor Analyses Experiences acquired from reactor analyses applying the new neutronics module SIMDANT and Summary Summary Acknowledgements References Appendix A B Adaptive Weighted Diamond Difference AWDD discretization scheme Survey of some C routines and shellscripts 61 65 67 71 76 80 81 82 84 84 91 1 Introduction The SIMMER III computer code is a two dimensional three velocity field multiphase multicomponent Eulerian fluid dynamics code coupled with a space time and energy dependent neutron dynamics model The neutronics is based on the discrete ordinate method Sy method coupled with a quasistatic dynamic model The SIMMER code development has been started originally at the Los Alamos National Laboratory LANL in 1974 Based on experiences gained with this SIMMER II code a next generation code was initiated in 1988 at LANL in collaboration with the Power Reactor and Nuclear Fuel Development Corporation PNC This collaboration was terminated in 1990
9. associated reactivity distributions Unfortunately using the TWOTRAN like solver module presently included in the SIMMER III 6 neutronics part no satisfying convergence behaviour with respect to accuracy and speed of the iteration process could be achieved in the past for some relevant applications In extensive reactor design calculations benchmark comparisons and calculations accompanying neutronics experiments the TWODANT code proved to be a more modern and a more suitable reliable and robust tool for solving problems occurring in SIMMER calculations In order to improve and speed up accident analysis calculations by SIMMER the replacement of the TWOTRAN like routines by the TWODANT SOLVER module comprises the following features Additionally to Chebycheff acceleration techniques usually included in transport codes the so called Diffusion Synthetic Acceleration DSA 2 3 4 scheme is available to accelerate the iteration process in the SOLVER module In this acceleration scheme mainly the diffusion equation has to be solved As described in more detail in the DANTSYS documentation 1 in each outer iteration at least one initial transport sweep is performed as an inner iteration for deriving the space dependent diffusion coefficients to be used subsequently for the solution of the diffusion equation In addition only the respective last iteration step is performed in the SIMMER environment as a so called single transport iter
10. corresponding to diamond difference DD discretization and equations 38 corresponding to adaptive weighted diamond differencing are repeated in the following 0 5 Wiens Pu 0 5 eee Yog gm i j 37 g m i j 0 5 VEN YP aaa m 1 MM i 1 IT j 1 JT YP mis1 2 Pe Gt RE Hon gt 0 Py gmi j Pens Pen Tai YF mi2 Hm lt 0 Ponipr Posi Tea Nm gt 0 1 Pics eee P emij tem Pin Nm lt 0 38 1 NE Yomi a g m i j YP ats T ER IE m 1 MM i 1 IT j 1 JT lt 1 Demi ed Es Pat Pisa The algorithm on which the subroutine MASWEPW of TWODANT is based was not documented in detail in the available literature However the fundamentals can be found in 7 although in 7 the treatment was restricted to X Y Z geometry For R Z geometry the 89 algorithms are very similar to those for X Y geometry the main deviation consisting in the prescription for determining the weights for the radial direction As obvious from 7 the AWDD scheme is particularly suited to deep penetration problems i e shielding calculations where the spatial meshes could be much larger than one neutron mean free path When using the AWDD scheme as implemented in MASWEPW for criticality related problems in R Z geometry we could not obtain the desired smooth transition from DD to AWDD as stated in 7 p 208 when varying the damping parameters But one should have in mind the impor
11. gt Makefile Beim Binden von Hauptprogrammen k nnen nur solche Unterprogramme gefunden werden die in diesem Directory pwd abgelegten Programmpaket enthalten sind Andernfalls bricht der make Lauf mit einer entsprechenden Fehlermeldung ab In diesem Fall m ssen Sie feh lende Module mittels des Parameters ZP angeben z B wird mit make ZP lib libxyz a SHOME programme grafik13 f das Programm HOME programme grafik13 f mitcompiliert und zusammen mit dem Bibliotheksarchiv lib libxyz a zu den Hauptprogrammen gebunden at lt lt gt gt Makefile date d m y O M HHH HHH HH HH if x betriebssystem xsn9068 then if uname m CRAY J then 102 cat lt lt gt gt Makefile Die Compilation soll auf maximal 16 der Make Lauf insgesamt dagegen auf nur einem Prozessor ausgefiihrt werden NPROC 16 NCPUS 1 Name des FORTRAN 77 Compilers FC CF fi cat lt lt gt gt Makefile Compiler Optionen f r den FORTRAN 77 Compiler FFLAGS fflags FFLAGS 02 NS1024 qmaxmem 1 Hinweis Bitte beachten Sie zur Wahl der richtigen Parameter auch die entsprechenden Handbiicher Optionen fiir den Archivierer ARFLAGS rcv Name des Bibliotheksarchivs das die compilierten Unterprogramme enth lt LIB s dateiliste up amp amp echo libname if s dateiliste hp then cat lt lt gt gt Makefile Liste der Hauptprogramm
12. responsible person and moreover in many cases an explanation for the purpose that lead to the inclusion alteration or omission In this chapter the description is restricted to a more general explanation for the alterations 35 6 1 Modifications in the main program SIIIPR SIMMER calculations normally require large computing times if they are performed for adequate models of actual safety related problems Therefore the restart option is applied in many cases Restart runs in SIMMER are frequently started by using the same input package as was used for the original run by replacing only the first line containing the START command by another first line containing the RESTART command being followed by the number of the restart file to be used This procedure is allowed in principle according to the SIMMER description 6 It should be noted that the restart file is overwritten by the sim05 input of the restart input file The user therefore has to check carefully which variables also p T data arrays etc he wants to overwrite Special attention should be given to the following six input data blocks If at least one of it is present in the actual input file SIMMER takes its parameters from these blocks which could disturb a smooth and proper continuation in a restarted run These six input blocks are amp NINI amp NISO amp XBND amp XCWD amp XRGN amp XSOS An adequate continuation could only be guaranteed if the parameters containe
13. subroutine LINKM by the variable MAT which could be set in a PARAMETER statement to a value of 10 100 1000 or 10 000 with IJMAT 1 000 as a default value at present If the currently implemented maximum value of MMAT 10 000 has to be increased subroutine LINKM has to be extended in the same way as is implemented for the values of 10 100 1000 and 10 000 respectively Possibly some FORMAT statements currently restricted to I4 will have to be modified too According to MPZTOT 0 the further blocks foreseen for the ASGMAT file are omitted 18 5 2 Preparation of the interface file GEODST The GEODST file is written according to its description given in 1 and as a subset of the description given in 5 It has to be noticed that according to the terminology of SIMMER in the TWODANT SOLVER module the number of fine meshes is always equal to the number of coarse meshes this means equal to the number of neutronics meshes as described above Each mesh in the neutronics grid represents a separate reactor zone as region possessing its own specific material which is assigned to a set of macroscopic group constants provided by SIMMER in subroutine SHLDXS and its associated subroutines The file specifications in the first record of GEODST are set logically according to its use in SIMMER TWODANT in the following way using the designations above IGOM 7 index for RZ geometry NZONE TJT number of zones in accordance with
14. 14 TWOTRAN POSDIF ON FIXUP OFF inner iteration failure o AMPLITUDE j 10 i H s i i i i t t CTE iter ee noen eterna i some arma vi one amen sea nem weine ager a 04aqanncen 100 z i i REACTIVITY 15107 praene ee sik peee Q 0 5 1 1 8 z TIME Figure 15 TWOTRAN POSDIF ON FIXUP OFF without inner iteration failure JaN Ldn Y 3aN Ldn Y 74 WUId d JANLIIINV REACTIVITY 0 5 I 1 3 2 TIME Figure 16 TWOTRAN POSDIF OFF FIXUP ON inner iteration failure Please note The left right position of the ordinate scales in Figs 12 13 and Figs 14 16 respectively has been changed When comparing Figures 14 and 15 it is evident that the transient behaviour of the SIMTRAN results was affected substantially by the non convergence of the inner iteration process Keeping in mind that Figure 16 shows results also obtained with a failure in the inner iteration process for the POSDIF OFF FIXUP ON case the correspondence with the results in Figure 15 without inner iteration failure for the POSDIF ON FIXUP OFF case is rather surprising But this fairly good agreement might be fortuitous and should not be considered as a validation of the reliability of these results Comparing SIMTRAN and SIMDANT results in Figures 13 and 15 it is important to observe that now the scales are nearly comparable Concerning the amplitude the first recriticality event is calculated by both code ve
15. 9000 und der SIEMENS VP400 EX der HDI entwickelten und bisher benutzten FORTRAN 77 Programmpaketen Aufruf proginst oder proginst Dateil Datei2 Im ersten Fall sucht proginst im aktuellen Directory nach FORTRAN Quellpro grammdateien diese m ssen mit dem Befehl END enden letzte Zeile Nach erfolgreicher Umstellung Ihrer Programme finden Sie im aktuellen Directory folgende neuen Dateien XXXXXX f enth lt das FORTRAN Programm xxxxxx Makefile Prozedur zum Compilieren 97 Um Ihre Programme zu compilieren rufen Sie einfach den Befehl make auf der die bersetzten Unterprogramme in dem Bibliotheksarchiv libname ablegt Sofern Sie sp ter Programme ndern wiederholen Sie zur Neucompilation einfach den make Befehl Wenn Sie ein Hauptprogramm compilieren und mit diesen Unterprogrammen binden m chten z B hp5 in der Datei hp5 f rufen Sie einfach folgenden Befehl auf make HP hp5 Falls dabei kein Fehler auftritt k nnen Sie dieses Hauptprogramm nun wie folgt starten und dabei die Eingabedaten Kanal 5 z B aus der Datei eingabe lesen hp5 lt eingabe Dateien die Sie aus anderen Kan len lesen wollen m ssen Sie vorher wie folgt vorbereiten hier gezeigt am Beispiel der Datei parameter31 die aus Kanal 8 gelesen werden soll rm fort 8 In s parameter31 fort 8 Sofern Sie auf einer HP arbeiten verwenden Sie Namen wie ftn08 statt fort 8 Nat rlich k nnen Sie die Zuordnung zwischen Kanalnumme
16. 99 tf Die Eingabedatei datei endet nicht mit einer Zeile der Form END und wird deshalb nicht als Programm sondern als Eingabedaten Datei angesehen in else cat lt lt Die Eingabedatei datei wird in UNIX Darstellung berf hrt eval split_befehl gt gt dateiliste fi else cat lt lt Die Eingabedatei datei wird in UNIX Darstellung berf hrt eval split_befehl gt gt dateiliste fi done if grep already exists dateiliste then cat lt lt 1 gt amp 2 tf Dabei sind die folgenden Fehlermeldungen aufgetreten tu grep already exists dateiliste sed s tn tf Die Dateien zzz f wurden inzwischen wieder gel scht make s f lt lt grep v up to date tmp proginst LOGNAME Z f rm cat lt lt 1 gt amp 2 ti tn ti tn Wegen dieser Fehler wird der Installationslauf abgebrochen ti tn Bitte berpr fen Sie Ihre Eingabedateien auf doppelt vorkom ti tn mende Programme und l schen diese bis auf eine Version ti tn ti tn tf ae ee SE Ee aa af 2 e fe fe ee af fe se fe Dee ae ae af ake a ee ae ae af ae af fe af a a af ae ake ae ae fe le Fe a a ae a aa ak of fe ae oe kkk oe eae Gern rm tmp proginst LOGNAME exit 3 fi cat lt lt Es wurden die folgenden FORTRAN Programmdateien gem den UNIX Konventionen angelegt tu cat dateiliste sed s fr tn Ps a ae re rn nr ne Mn Era Makefile erstellen 10
17. DD discretization Thus applying the AWDD scheme always means that the intra mesh neutron balance is modified compared to that one used customarily in standard DD discretization Naturally the global flux distribution is modified too as a consequence of the intra mesh deviation from the standard diamond difference spatial discretization rule In the end it is up to the user to take the most appropriate decision between two possibilities both affected by intrinsic deficiencies namely 1 using the conventional fixup solution algorithm with its well known disadvantage described already e g in in 11 namely Unfortunately all fixup methods can lead to spatial flux distortions or 2 switching to the alternative AWDD solution scheme with suitably chosen empirical tuning parameters thus avoiding negative flux fixups at the expense of fairly arbitrary modifying the relationship between the angular fluxes at the mesh edges and the associated mesh center At present there doesn t exist enough experience to give a general recommendation which choice is the most suitable one for certain classes of applications or which alternative is superior to the other one for particular kinds of problems In any case the flux and power distributions will be changed to some extent compared to the correct ones and it cannot be decided a priori which change will be the more severe one or which solution scheme will be the better one i e will come
18. ILINK 1 causing the calculation of the leakage values needed to build up the balance tables and the calculation of the reactivity values in SIMMER After the call of subroutine TWODANT the calculated adjoint or real scalar and angular flux values are read from the TWODANT interface files atflux rtflux and raflxm and stored in the corresponding data arrays ADFLUX CUFLUX CHEDGE and CVEDGE respectively for later use in the code The angular flux is separated into the horizontal part stored in CHEDGE and the vertical part store in CVEDGE respectively After their calculation the actual real flux values are saved on additional files so that the real scalar fluxes can be used as starting guess for the transient calculation The relation of file names and unit numbers is as follows Files prepared by TWODANT file name unit name unit number contents atflux IATFLI 21 adjoint flux rtflux IRTFLI 22 real flux raflxm IRAFL 11 real angular flux At the time being the option of printing the angular and space dependent adjoint fluxes has been disregarded in SIMDANT however its activation would be trivial if really needed b 37 Files prepared by GRIND ATFLUX IATFLO 23 adjoint flux RTFLUX IRTFLO 24 real flux guess In subroutine GRIND alterations for the input of reactivity ramps have been provided in order to get it in accordance with the input description 6 Now external reactiv
19. Table 2 respectively an independently running TWODANT SOLVER module was prepared By running the TWODANT code in the framework of the DANTSYS code system the five binary interface files adjmac asgmat geodst macrxs and solinp were provided and stored for longterm use These five interface files contain all information necessary to run the independent TWODANT SOLVER module too Identical results of the TWODANT SOLVER module and the original separate TWODANT run for preparing the interface files can be taken as a proof that the TWODANT SOLVER module has been constructed correctly 12 4 Short description of the binary interface files connecting the TWODANT SOLVER module with the other TWODANT modules INPUT and EDIT The SOLVER module of TWODANT is capable to run independently of the DANTSYS system code package as described in chapter 3 provided that it has access to five binary interface files containing all necessary information for its regular program flow Some minor deviations compared to a standard TWODANT run regarding printing of results related to documentation of the input and the iteration protocol or some aspects of the complicated file handling capabilities have to be conceded but the correspondence of the final results with TWODANT in DANTSYS could be proved for all cases under consideration These five files are ADJMAC ASGMAT GEODST MACRXS SOLINP ASGMAT _ contains information for assigning materials to reactor zones to
20. activate the adaptive weighted diamond difference AWDD discretization scheme and replaces the former input variables for specifying POSDIF ON OFF and FIXUP ON OFF The variables NIOPT 30 and NIOPT 31 contained in the amp NCNTL NAMELIST block are no longer used in the new code In order to avoid possible confusion in the interpretation of the output listing it should be mentioned that when specifying NIOPT 30 0 and NIOPT 31 O the user will find in the SIMMER printout POSDIF OFF and FIXUP OFF However when using TWODANT without WDAMP input the standard negative flux fixup algorithm is applied in TWODANT The following table shows the corresponding options SIMMER TWOTRAN SIMMER TWODANT POSDIF ON AWDD ON FIXUP ON POSDIF OFF AWDD OFF The values for the AWDD parameters have to be specified within NAMELIST block amp NFIX in the following way WDAMPA NG NG 1 IGM WDAMPR NG NG 1 IGM 53 where the index NG denotes the corresponding neutron energy group The index starts with NG 1 for the group of highest neutron energy and ends with NG IGM for the group of lowest neutron energy as well for adjoint as for direct real calculations For energy groups NG with WDAMPA NG 0 or WDAMPR NG 0 no value has to be specified The meaning and consequences of inputting WDAMPA WDAMPR lt 0 0 is explained in Appendix A The parameters WDTHRSA and WDTHRSHR also necessary for the AWDD scheme are set 1 0 code inter
21. and the development effort was taken over solely by PNC Starting from 1992 the code is developed by PNC in cooperation with European partners Commissariat l Energie Atomique CEA France AEA Technology United Kingdom and Forschungszentrum Karlsruhe FZK Germany One of the contributions of FZK was to improve the neutronics module of the code When investigating specific accident related reactor situations with the standard SIMMER III code package it turned out that in exceptional cases no convergence could be achieved with the implemented TWOTRAN like module for solving the neutron transport equation In the past extended test calculations outside of SIMMER II for the comparison of different transport codes available at FZK led to the recommendation that TWODANT originally developed at Los Alamos National Laboratory proved to have the best characteristics with respect to accuracy and reliability of the results as well as robustness and calculation speed Therefore the decision was taken to replace the TWOTRAN like code package in SIMMER by the TWODANT code in order to solve the neutron transport equation TWODANT is part of DANTSYS 1 a general diffusion accelerated neutral particle transport code system for solving the neutron transport equation in different geometries for one two and three space dimensions DANTSYS a product of Los Alamos National Laboratory has been taken over from the OECD NEA Data Bank in its version
22. as well in the FIXUP ON case as in the POSDIF ON case These results verified the robustness and superiority of TWODANT over TWOTRAN The effect of the fixing up operation of negative fluxes is apparent from the difference in absolute value of the effective multiplication factor However the relative reactivity change between the compacted case and the uniform case is not affected by the choice of various differencing schemes i e the reactivity change due to compaction is 0 05784185 in the AWDD OFF case and 0 05764035 in the AWDD ON case which can be considered as negligibly small Again no efforts were devoted to investigations using refined calculational models 67 11 3 STN Standard Test Problem for Neutronics This sample problem is intended to test the space and energy dependent neutron kinetics model and its coupling with the fluid dynamics The considered problem set up is a fictitious disrupted LMFR core of an intermediate size for simulating a short time energetic recriticality event with 12 by 16 meshes In order to drive a very rapid reactivity insertion a slug of molten fissile fuel initially present at the bottom of the core axis is pushed toward the core midplane with its initial velocity 100 m s The geometric model and initial conditions used for this problem are shown in Figure 7 This reactor configuration and these initial conditions minimize the effect of non linear feedback processes between the material motion and reactor ki
23. closer to the true solution Most probably this decision will be case dependent and a final conclusion may only be achievable by a suitable mesh refinement 85 if that could be afforded without too severe penalties concerning the computational effort to be devoted to SIMMER neutronics Originally the DANTSYS package available at FZK more specifically subroutine MASWEPW only contained the AWDD option with adaptive weighting for the angular dependence as well as for the spatial dependence in R Z direction In the AWDD discretization scheme as implemented in MASWEPW the step start method was applied Unfortunately this fact did not allow a continuous transition to the standard DD scheme in subroutine MASWEP where the starting direction method was applied For that reason a new method was supplemented to the package subroutine MASWEPD where AWDD is restricted to the spatial discretization only and DD with the starting direction method and angular flux fixup is used for the angular discretization For the application of this method i e using MASWEPD the parameters WDAMPA IG and WDAMPR G have to be input with a negative sign internally the positive value is used see the section Remarks concerning AWDD in subroutine MASWEPD at the end of this Appendix The additional numerical burden for the AWDD compared to the standard DD with negative flux fixup remains fairly small for two reasons 1 At the beginning of the iterative treat
24. create the zone macroscopic cross sections GEODST contains the geometry description of the calculational model MACRXS contains the material macroscopic cross sections arranged in energy group order ADJMAC isthe adjoint reversed counterpart to the MACRXS interface file SOLINP contains characteristics for specifying the program flow in the SOLVER module normally given in the TWODANT input The structure and contents of these five code dependent files are described in detail in 1 In addition GEODST is a so called CCCC Standard Interface File and also described therefore in 5 The TWODANT SOLVER module usually provides as results the two CCCC Standard Interface Files RTFLUX and ATFLUX RTFLUX contains the real scalar neutron fluxes ATFLUX contains the scalar importance distribution Moreover a special improvement of the quasistatic method in the SIMMER code requires the use of the real angular neutron flux values provided by the TWODANT SOLVER module in the file RAFLXM 13 which is described in detail in 1 The ordering sequences and the mesh oriented positions for these fluxes are also mentioned there The details of the application of angular neutron fluxes are described in chapter 7 2 These three interface files are associated with the following Fortran reference numbers IRTFLI 51 IATFLI 50 IRAFL 11 It may be worthwhile to mention that the calculation of p tables is still done in the previous manner It
25. different SIMMER versions The authors would like to thank Walter G tzmann FZK INR for preparing most of the figures shown in this report They would also like to thank Dr C H M Broeders FZK INR and Dipl Math Manfred Alef for the abandonment of C programs and UNIX shellscripts as listed in Appendix B Last but not least the authors gratefully acknowledge the continuous interest and encouragement of Professor G nther Ke ler former director of the Institut f r Neutronenphysik und Reaktortechnik devoted to this activity and his patience until eventually finishing this documentation 82 13 References 1 RSIC COMPUTER CODE COLLECTION DANTSYS 3 0 One Two and Three Dimensional Multigroup Discrete Ordindates Transport Code System contributed by Los Alamos National Laboratory Los Alamos New Mexico 1995 http www xdiv lanl gov XTM 2 E M Gelbard L A Hageman The Synthetic Method as Applied to the Sn Equations Nucl Sci Eng 37 288 1969 3 R E Alcouffe Diffusion Synthetic Acceleration Method for the Diamond Difference Discrete Ordinates Equations Nucl Sci Eng 64 344 1977 4 E W Larsen Diffusion Synthetic Acceleration Method for the Discrete Ordinates Equations Proc Am Nucl Soc Top Meeting on Advances in Reactor Computations Salt Lake City Utah March 28 31 1983 p 705 5 R D O Dell Standard Interface Files and Procedures for Reactor Physics Codes Version IV
26. file SIMO6 36 6 2 Adaptation of SIMMER subroutines for the inclusion of the TWODANT SOLVER module a The most essential modification in subroutine GRIND is a call for subroutine TWODANT instead of subroutine OUTER In the past OUTER was used to solve the extended neutron transport equation using the TWOTRAN like algorithms in order to obtain the flux shape function for the stationary adjoint and real problems and for the instationary real cases as well Subroutine TWODANT comprises those parts of the DANTSYS main program DRIVER which are used for the organisation of storage locations and external file units as well as for the call of subroutine TIGF20 the driver program of the TWODANT SOLVER module Subroutine TWODANT is called by subroutine GRIND for the calculation of the stationary value of variable ITH 0 adjoint IAD 1 and real IAD 0 flux shape function respectively Subsequently TWODANT is called to calculate the instationary ITH 1 real IAD 0 flux shape function for each time cycle Each call of subroutine TWODANT is preceded by a call of the interface subroutine LINKM ILINK where the argument is set to ILINK 1 so causing the preparation of the interface files see chapter 5 which are needed to run the TWODANT SOLVER module After the calculations of the real flux distributions as well in the stationary case as in the instationary cases LINKM ILINK is called a second time where the argument now is set
27. for isotope M and energy group GRP FFISO p U M are the capture and fission resonance self shielding factors f FFISO J M factors respectively for isotope M in mesh I J for the energy group being considered Affected routines SHLDXS CALCXS 39 Some errors occurred during extensive SIMDANT calculations which were unexplicable at a first glance The introduction of unsuitable input files frequently led to those inconsistencies especially in restart runs Additional checks of the input parameters have been included into subroutine CHKPAR In case of errors the job is aborted at early runtime accompanied with a request to the user to check the input parameters Comment It would be desirable to include even more consistency checks to guarantee compatibility of redundant input data contained in the SIMMER input stream Affected routine CHKPAR d According to an implementation flaw in a preliminary SIMMER version a mistake occurred in restart runs As a consequence of using the time derivatives calculated from angular fluxes instead of the scalar fluxes the angular fluxes have to be included into the restart dump file too in order to assure a smooth and proper continuation of the restart calculation Inclusion and retrieval of a data area into a restart dump file in SIMMER is a relatively extended task First of all the data area has to be declared as a named COMMON area An integer variable has to be added at the end of the
28. for the angular dependence is assumed i e DD in angle 2 In the AWDD scheme the so called step start method is applied see e g 8 assuming PHIG j m 3 2 PHIG j m 1 m characterizing the angular index whereas in the DD scheme again the diamond in angle differencing i e the linear relation is assumed for the starting directions too As described before this smooth transition could be achieved by implementing the new subroutine MASWEPD Comment on an approximation when applying AWDD When using the AWDD discretization scheme there exists another minor deficiency in order not to store and pass the group and direction dependent weights of the past time step it is assumed for the inclusion of the time derivative of the shape function that these weights for the spatial discretizations are unity for the whole grid i e for all meshes both for the r as well as for the z direction and for all angular directions Since this time derivative term is considered to be small or almost negligible in most applications this approximation seems to be well justified Should further studies reveal that this approximation turns out to be too crude for exceptional cases a possible improvement could be envisaged consisting in not replacing the adaptive 90 weights of the past time step by unity weights but by those weights determined for the current time step Remarks concerning AWDD in subroutine MASWEPD From a purely formal point of
29. in 5 1 label for fission spectrum label for production nu fission cross section label for total cross section label for absorption cross section mean neutron velocities for all energy groups upper energy bounds of groups not necessary for SIMMER calculations and therefore transferred as 0 0D 00 for all values 23 EMIN 0 0 lower energy bound of set not necessary for SIMMER calculations and therefore transferred as 0 0D 00 For all energy groups NG from NG 1 IGM i e according to decreasing energy the cross section values are written on file MACRXS in the following way Principal cross sections for energy group NG to be given for all meshes of the neutronics grid CHILNG I 1 NMAT fission spectrum CHI CELFIS I NG I 1 NMAT production nu fission cross section NUSIGF CELREM NG I 1 NMAT total cross section TOTAL CELABS LNG I 1 NMAT absorption cross section ABS The scattering control block for energy group NG is written in the following way NGPB L J L 1 NORD J 1 NMAT With regard to NORD 1 according to the value given in the control block and in consideration of the transfer of the whole lower triangular down scattering matrix this means NGPE L J NG J 1 NMAT specifying NG as the number of groups scattering into the considered group NG IFSG L J L 1 NORD J 1 NMAT with IFSG L J NG J 1 NMAT defining NG as the group number of the first source group scattering into th
30. instead of the default option NIOPT 2 0 NIOPT 2 4 the recommended option for the modified incomplete lower and upper decomposition bi conjugate gradient scheme for the preconditioned conjugate gradient method for the rebalance equation matrix solver but the results were still not reliable Blanket Blanket Figure 6 R Z model of SRA Static Reactor Analysis Two series of test calculations were done for the SRA case too the first one by using the options POSDIF ON and AWDD ON respectively the second one using FIXUP ON and 66 AWDD OFF respectively The calculations were performed with SIMMER II version 2d using ISOTXS BRKOXS files prepared by the neutronics preprocessor MXS 14 for 9 energy groups and 5 materials The Sy order was specified to N 4 POSDIF ON AWDD ON SIMMER TWOTRAN SIMMER TWODANT adjoint real adjoint real compact 0 98338562 0 97725826 1 04216938 1 04190530 uniform 0 98453313 0 98452505 0 98448339 0 98426495 FIXUP ON AWDD OFF SIMMER TWOTRAN SIMMER TWODANT adjoint real adjoint real compact 0 98342664 0 97700906 1 04235340 1 04236921 uniform 0 98453422 0 98451724 0 98453418 0 98452736 see explanation given at the beginning of this chapter The new neutronics module based on TWODANT converged successfully for the compacted configuration in this test problem whereas the former TWOTRAN module failed
31. is performed on the basis of the direct and adjoint scalar fluxes and the suitably weighted leakage rates The complication needed for implementing a refined method based on transport perturbation theory which would in principle be feasible was not considered to be worthwhile because its effect was expected to be negligible but would require a major revision in SIMMER and the permanent storage of the adjoint angular flux and its inclusion in the restart file 14 5 LINKM a new LINKING Module for data exchange between SIMMER and the TWODANT SOLVER module Nearly all information to run the independent TWODANT SOLVER module as part of the SIMMER code is contained in specific SIMMER COMMON blocks and data areas Therefore it is not advisable to specify a special user input For that purpose it was decided to establish a so called linking module as an interface This linking module is called LINKM LINKM collects necessary information taken from SIMMER storage locations and prepares the five binary interface files ADJMAC ASGMAT GEODST MACRXS and SOLINP described in chapter 4 allowing the regular program flow of the SOLVER module For the small information part for the TWODANT SOLVER module that was not included in the SIMMER input up to now the SIMMER input was extended as for example the AWDD parameters explanation see chapter 8 A second task has to be fulfilled by LINKM SUBROUTINE INNET as part of the TWOTRAN like code package being
32. is then given as follows For the numbers NREGB 1 and NREGB 2 given in the SIMMER neutronics input and designating the first and the last neutronics mesh in the fluid dynamics grid in R direction ITMP1 NREGB 2 NREGB 1 1 is the number of fluid dynamics meshes related to the neutronics coarse grid in this direction Each fluid dynamics mesh length in this direction can be divided by a factor of 15 NCRAD D I 1 ITMP1 to obtain the mesh lengths of the neutronics coarse meshes The NCRAD I values are also given in the SIMMER neutronics input as the number of neutronic mesh cells per fluid dynamics cell in the radial direction The value of the variable IDIVR also to be given in the SIMMER neutronics input determines whether the neutronics mesh cells are constructed as an equal volume sub division IDIVR 0 used as default value or as an equal mesh width sub division IDIVR 1 of the fluid dynamics cells respectively The total number of the neutronics coarse meshes in R direction is then INCMX IT amp NCRAD D I 1 ITMP1 In the same way the mesh lengths and the total number of the neutronics coarse meshes in Z direction are calculated as ITMP2 NREGB 4 NREGB 3 1 INCMY JT U NCAXI J J LITMP2 where NREGB 4 NREGB 3 and NCAXI J are also values given in the SIMMER neutronics input The total number of meshes in the neutronics coarse mesh grid is then ITJT IT JT INCMX INCMY Each neutr
33. measured sufficiently accurate Z cm 81 28 Axial blanket Na voided 45 72 SS Normal core Na voided 30 48 4 M Fuel compacted 15 24 4 Void spacer 0 00 midplane 15 24 30 48 45 72 81 28 AO Al A2 A3 S Figure 4 Fuel relocation pattern in FCA VIII 2 experiments Two series of test calculations were done using different options with SIMMER TWOTRAN and SIMMER TWODANT The first table shows the result with POSDIF ON and the SIMMER TWODANT corresponding option AWDD ON the second FIXUP ON and AWDD OFF The calculations were performed with SIMMER II version 2d using ISOTXS BRKOXS files prepared for 9 energy groups and 11 isotopes The anisotropic scattering was approximated based on the Bell Hansen Sandmeier 13 prescription PIAPRX The Sx order was specified to N 4 63 POSDIF ON AWDD ON SIMMER TWOTRAN SIMMER TWODANT e p e u 1 005721157 4 8321E 4 1 00654697 1 00525523 adjoint AO 4 8477E 4 A2 1 1339E 3 A3 1 00841946 1 3360E 3 1 006592140 4 8567E 4 FIXUP ON AWDD OFF SIMMER TWOTRAN SIMMER TWODANT an ee fm e 1 006593275 1 006237366 4 8138E 4 1 00659306 1 00599712 A0 4 8183E 4 1 1260E 4 1 3241 E 4 4 8228E 4 kK yo RK ao Kg k g AO reai k a ky A k g Al eat Kog A2 reat kog A3 eat Kap Suar respectively p Effective multiplication fac
34. mentioned in chapter 10 some values given in the PARAMETER statements of the SIMMER code have to match exactly those values given in the input stream of the current run in input file sim05 Some of those values affected by this instruction are listed in chapter 10 When starting a SIMMER run this correspondence has to be assured in case of disagreement a new executable has to be established as also described in chapter 10 92 New NAMELIST blocks amp NFIX and amp NVIS By replacing the TWOTRAN like solver part by the TWODANT SOLVER module the general strategy was pursued not to change the SIMMER input This strategy could be applied with only two exceptions Using the POSDIF ON option in TWOTRAN the parameters necessary for applying the adapted weighted diamond difference discretization scheme AWDD are calculated code internally whereas these parameters have to be given as input values in TWODANT Thus a new NAMELIST block named amp NFIX had to be introduced in which two arrays for AWDD parameters can be specified Array WDAMPA is used for adjoint and WDAMPR for direct real calculations respectively In cases where the amp NFIX block is omitted in the input stream both arrays WOAMPA and WDAMPR are set equal to zero code internally by default The calculations performed in this way correspond to those applying the usual standard diamond difference DD discretization scheme with negative flux fixup The new NAMELIST block amp NFIX is used to
35. now replaced by the TWODANT SOLVER module contained a program part calculating the leakage values for the reactor system needed for reactivity determination As no comparable program part is provided in the TWODANT SOLVER module LINKM is extended to calculate these particular terms In order to make the preparation of the five interface files more transparent it seems to be necessary to describe the correspondence between the SIMMER fluid dynamics grid and the TWODANT neutronics coarse and fine mesh grid in more detail Please note Although the TWODANT SOLVER module performs calculations in various geometries only 2 dimensional XY and RZ geometries have been realized in SIMMER Neutronics calculations performed currently by TWODANT in SIMMER are restricted to 2 dimensional RZ geometry The geometry index IGEOM 0 is related to RZ geometry in SIMMER this index is transformed in LINKM into IGOM 7 for transmission to TWODANT The fluid dynamics mesh grid in SIMMER is arranged as follows In RZ geometry characterized by IGOM 7 in TWODANT there are IB columns in R direction and JB rows in Z direction The meshes within the grid are counted by starting with the first mesh at the lower left edge in the first row going to the right up to the IB th mesh and then running through the rows from the first at the lower boundary to the JB th row at the upper boundary The relation between the fluid dynamics and the neutronics coarse mesh grid
36. o lt 10 lt 0 5 107 1 0 0 005 0 01 0 015 0 02 he Figure 8 Plot of reactivity and power transient calculated by TWOTRAN using FIXUP ON e AMPLITUDE s REACTIVITY STN_SIMMER TWODANT_AWDDoff Lu 0 5 m O al an os lt lt 0 5 1 0 0 005 0 04 0 015 0 02 TIME Figure 9 Plot of reactivity and power transient calculated by TWODANT using AWDD OFF 70 s AMPLITUDE f e REACTIVITY STN_SIMMER TWOTRAN_POSDIFON AMPLITUDE ALAILOVAY 10 n ma 1 0 005 01 015 0 02 2 ONE 4 Figure 10 Plot of reactivity and power transient calculated by TWOTRAN using POSDIF ON e AMPLITUDE s REACTIVITY STN_SIMMER TWODANT_AWDDon 10 1 5 1 Lu 1 0 5 m Ee O m o Ss Z 10 P 0 5 6 1 0 0 005 ONE 0 015 0 02 Figure 11 Plot of reactivity and power transient calculated by TWODANT using AWDD ON 71 11 4 TRA Transient Reactor Analyses The final and integral test problem is the transient analysis of the early transition phase in a core disruptive accident The objective of this test problem is to verify the applicability of the new code package and to find out whether plausible results can be obtained The initial spatial distribution of the material temperature and pressure is taken from the final state of the initiating phase analysis by SAS4A using t
37. of the former superior option in contrast to the latter occasionally inferior option However it is worthwhile to mention that the negative flux fixup scheme as implemented in TWODANT is more refined than that one of the predecessor version based on TWOTRAN Therefore the reluctance to apply the negative flux fixup option which was most probably justified in the past should now be abandoned having available the extremely reliable and fairly robust TWODANT package 51 But in order to avoid any misinterpretation it should be emphasized that a too coarse mesh grid could cause negative flux fixups in regions where a correct flux distribution would be needed for a reliable neutronics behavior during the transient Thus a careful investigation of the fixup tables is highly recommended The contents of the fixup tables may be included in a special neutronics postprocessor data file named NISART from which the data may be taken over into the TECPLOT system 17 for visualisation The NISART file is written if the NAMELIST block amp NVIS is specified in the SIMMER II input and it is set IOUTNI 1 as the only input value If the accuracy of the neutron fluxes in an important part of the energy space phase space becomes questionable it would be good practice to adequately refine the grid and to check whether the essential results exhibit significant changes 52 9 Input 9 1 Check of some values used in the PARAMETER statements of SIMMER As
38. order to cause the preparation of this table together with the neutron flows variable IBALP 3 has to be specified in LINKM and transferred to the TWODANT SOLVER module via SOLINP file As already mentioned before in the same chapter in the TWODANT SOLVER module of SIMDANT the coarse mesh grid is identical to the fine mesh grid 33 5 6 General program flow using LINKM as interface between SIMMER and the TWODANT SOLVER module The general program flow for the interaction between SIMMER and the TWODANT SOLVER module is steered in the SIMMER main program STIIPR Whenever a neutron flux calculation has to be performed subroutine GRIND is called by SIIIPR The parameters for directing the flux calculations are set as follows With the assumption that no constant adjoint flux distribution is requested as quasistatic weight function IWTF 1 the calculation starts with the determination of the stationary adjoint flux for later use as quasistatic weight function IWTF 0 IWTF is given in the SIMMER input The parameters are set as ITH 0 and IAD 1 in SIJIPR before calling subroutine GRIND Subsequently IAD 0 is specified inducing the stationary direct flux calculation by a second call of GRIND The calculations of the stationary adjoint and direct fluxes respectively are omitted in case of a restart run RSTRUN TRUE Then with ITH 1 IAD 0 a series of instationary direct flux shape calculations is initiated In su
39. received from PNC in February 1998 The application of HISTORIAN for the preparation of new executables for SIMMER calculations is given in chapter 10 An example how to prepare a new executable by means of HISTORIAN is added too The new neutronics module has been applied to some test problems representative for accident related situations Results and conclusions are described briefly in chapter 11 A short summary is given in chapter 12 together with a description of experiences acquired from reactor analyses applying the new neutronics module SIMDANT In an Appendix in chapter 14 some details of the Adaptive Weighted Diamond Difference AWDD discretization scheme are described and some shellscripts and auxiliary subroutines are documented They are either used to produce new executables or are included into SIMMER for solving specific data processing tasks Sometimes the same details of some specific aspects concerning program flow data transfer and specifications are described at different places in the report in order to facilitate its reading and to avoid too many cross references within the report 2 Needs for an improved neutronics solution scheme in SIMMER II Appropriate accident analyses in SIMMER need a robust fast neutron transport module for the determination of criticality factors ker the neutron importance adjoint flux associated reactivity differences Ake the neutron flux the corresponding power distribution and
40. using TWODANT is initialized by a call of SUBROUTINE TIGF20 The very complex program flow of the outer subouter inner iteration scheme is directed by TIGF20 taking into consideration the diffusion synthetic acceleration method the Chebycheff acceleration technique the multigrid acceleration scheme and the controlling of the various convergence processes These tasks are performed in a lot of subroutines In addition a great number of variables COMMON values and data arrays such as unit numbers of external files time information machine specifications storage capacities etc are initialized in DRIVER and associated calls of subroutines belonging to the input package In order to assure the availability of all this information to the SOLVER part included in the SIMMER package it had to be constructed from an extract of PROGRAM DRIVER now called SUBROUTINE TWODANT and an extract of SUBROUTINE TIGF20 and all subroutines and functions being called directly or indirectly from these two extracts All subroutine and function calls in these subroutines not being used for initializing the SOLVER module itself or providing it with information have been suspended These subroutines and functions are divided into two groups The first group contains the system or architecture independent subroutines and functions The names of these ones belonging to the first group are ACOSH ADJBNK ADVUK AQFLUX ASUMFS BINS BSREAD CALC CHEBY CHIMOD CHKIFC CIFLS
41. view there exists a difference of possibilities of calculations between the SIMMER II versions SIMTRAN and SIMDANT In SIMTRAN calculations can be performed using the options POSDIF ON OFF and NEGATIVE FLUX FIXUP ON OFF This means calculations are possible using neither the POSDIF nor the NEGATIVE FLUX FIXUP option In SIMDANT initially only the AWDD option could be chosen or not A negative flux fixup was performed in any case Therefore for sake of completeness a particular feature of the implemented AWDD algorithm should be mentioned that could be of interest in certain cases or for investigating special aspects of the angular discretization When specifying WDAMPA IG and WDAMPR IG IG 1 IGM equal to 1 0 conventional diamond differencing will be applied Gn MASWEPD but excluding any fixup of negative angular fluxes Thus the difference equations are solved rigorously but the calculated solution will be affected by negative angular or even scalar fluxes In some cases the iterative solution process might even fail In any case the solution is not reliable in some parts of the energy space angle phase space But sometimes those unreliable parts of the phase space could be fairly unimportant for global reactor parameters like criticality or reactivity changes Therefore the application of this option could provide a deeper insight in the possible consequences of the flux fixups applied in the standard solution formalism and in the influe
42. 0 touch dateiliste hp touch dateiliste up for datei in grep main 0 9 0 9 0 9 f dateiliste do echo datei gt gt dateiliste hp done for datei in grep v main 0 9 0 9 0 9 f dateiliste do PROGRAM_zeile grep 1 PROGRAM datei head 1 program_zeile grep 1 program datei head 1 if PROGRAM_zeile o program_zeile then echo datei gt gt dateiliste hp else echo datei gt gt dateiliste up fi done libname lib basename pwd tr A Z a z a xname basename pwd tr A Z a z x if s dateiliste hp then cat lt lt gt Makefile PET we Fae SEE a Se ee Sa TO aS aoe lect Makefile zur Erzeugung des r lauff higen Programms e xname unter Verwendung des Bibliotheksarchivs libname fiir die Unterprogramme else cat lt lt gt Makefile Poser oslo E oe essa ee trees eee eR AEHEREE Makefile zur Erzeugung des Bibliotheksarchivs libname fiir Unterprogramme dieses kann beim Compilieren und Binden eines Hauptprogramms wie folgt verwendet werden am Beispiel des Programms hpname in der Datei hpname f make HP hpname hpname fi Compileroptionen erfragen cat lt lt Bit A a ae ae ake 2 2 ak ak ke 3K 2 2 sfe a 3k 3k 3k 3k 2 3K 3k 3k ake ak S ee k 2 2 2K A HEE ske a ok ae k he sfe SFe 2 2 3k fe ee oe ake A a 2S 2 2 of ee oe oe He ak 3K 2 2 tn ja tn tf ti j tn n
43. 0 4692 one value according to NBCS 1 see above internal black boundary constant one value according to NIBCS 1 see above not transmitted according to NZWBB 0 see above zone Classification zone number assigned to each region In the sixth record the region assignments to the neutronics meshes are specified This record has to be present for IGOM GT 0 AND NRASS EQ 0 see above I I 1 NREG region numbers assigned to the neutronics meshes The following records intended for the GEODST file are omitted according to the values given in the specification record 21 5 3 Preparation of the interface files MACRXS and ADJMAC The MACRXS and the ADJMAC files are written according to their descriptions given in 1 As described above sets of self shielded group constants are calculated in SIMMER in subroutine SHLDXS and its associated subroutines for all meshes of the neutronics grid Considering NEU and NEIGM as the maximum allowed number of meshes in the neutronics grid and the maximum allowed number of energy groups respectively the macroscopic principal group constant types previously prepared in SIMMER are stored in the COMMON CELXS data areas CELFIS NEI J NEIGM nu fission cross section NUSIGF CELREM NEI J NEIGM total cross section TOTAL The fission spectrum CHI and the neutron velocities VEL are stored for all energy groups in the COMMON RINCON data areas CHI NEIGM 1 prompt fission spectru
44. ANYGT RDCRI18 ADJLCM CLEAR4 CRYATX DRITS FIXFLT IKCCN ISCHD ISCHOU ISMIN LLDINP LODBMV LODINT LODQER LODSEQ MCRED MSGBOX OFFUGO RSTHLD RANYLE REED ANLVER CLEARX DOPC DST4C HOLCVT IKCR8N ISCHE ISCHP ISUMI LLHCVS LODBNI LODITP LODQRD LODSET MDOPC NAFIX ORDTUP R8THOL RANYLT RUT4C ASCOPW CLOSEQ DOPCA EFBYTE IANYGT IKR8CN ISCHL ISCHS LCMCHK LLHSET LODCKT LODICA LODRDC LODSHC MDRED N4FIX4 PAQA12 RSXHLD RANYNE SASUM AUN4C CLRLCM DOPCBD ENVSET IBM4HQ IKR8R8 ISCHLF ISDAMA LCMSET LOD7BD LODCTB LODORC LODRTA LODSPU MOVA4T4 NSGBOX PRTTRN RSXHOL RDCHR8 SATXOF 10 SAXPY SCMSEC SCOPY SDOT SECNDS SECONI SEEK4C SEEKBD SEKEST SEKPHL SGECO SGEFA SGESLA SHTOFF SIDRD SIGZFB SKOPRD SKOPWR SLDFNA SLDNAA SPBFA SPBSL SREED SSCAL SSUM STNAA STOPIT STOPLD STRIP SUBRD SUBWR SUNASG SUNOFF SWFILE TILOAD TIMDAT TIMER TRNSUM UGOLOC UGONOW USERDA WATRMD WDCHR8 WDCI6 WDCRI2 WDCRI8 Table 2 Routines of the TWODANT SOLVER module system or architecture dependent All routines mentioned above are originally TWODANT ones except for two A function named ISAMAX and a subroutine named ERROR as well are included in TWODANT and exist in SIMMER HI too with the same names So the names of the TWODANT routines were changed into ISAMAXT and ERRORT respectively 140 COMDECKs in the terminology of HISTORIAN which contain PARAMETER and COMMON blocks declaration DIMENSION and EQUIVALENCE statements are
45. COMMON area which is provided to store the length of the data array This COMMON area has to be introduced into the subroutine INILEN where its length is determined by a call of subroutine LENG and stored in the variable at the end of the data array Additionally the total length of all COMMON areas provided for the inclusion into the restart dump file is calculated in subroutine INILEN too The inclusion of the COMMON areas into the restart dump file is prepared in subroutine WRDMP Each COMMON area is transferred by a call of subroutine WRUNF In the same way the retrieval of COMMON areas is prepared in subroutine RDDMP Each COMMON area is transferred by a call of subroutine RDUNF Affected routines INILEN RDDMP RDUNF WRDMP WRUNF e In the same way the COMMON MISC LPRINT LSMISC has been prepared for inclusion into the restart dump file in order to make the logical variable LPRINT available in its original state in each program unit where it is used to decide whether additional output is required on a separate output file for important messages LPRINT is set according to the value of the input variable IGM for the number of neutron energy groups as follows LPRINT TRUE for IGM lt 0 LPRINT FALSE for IGM gt 0 Affected routines ADJLCM INPROD RDUNF TINP24 CHKPAR KEYWRD SCMADD TMONIT DMPFLX LCMADD TFINAL WPPN 40 GRIND PRNTFX TIGF20 WRDMP HILYTE PRNTIA TINP21 WRUNF INILEN RDDMP TINP22 41
46. INP 4 variables not used 100 variables not used Please note Three peculiarities have to be considered when starting a TWODANT stand alone run using the interface files of a preceding SIMMER TWODANT run l The algorithms are not identical in the different TWODANT versions 30 2 Usually the influence of the delayed neutrons and their precursors is taken into account in SIMDANT but not in TWODANT 3 The user should be aware that TWODANT destroys the SOLINP file before the end of its execution thus in a UNIX environment it is recommended to perform the TWODANT runs in a separate directory Floating data in double precision raw values 200 values EV 0 D 0 eigenvalue guess NORM 0 D 0 normalization constant EPSO EPSO outer iteration convergence criterion see explanation above EPSI EPSMIN inner iteration convergence criterion see explanation above BGHT 0 D 0 buckling height BWTH 0 D 0 buckling width EVM 0 D 0 eigenvalue modifier PV 0 D 0 parametric value XLAL 0 D 0 lambda lower limit for searches XLAH 0 D 0 lambda upper limit for searches XLAX 0 D 0 search convergence criterion POD 0 D 0 parameter oscillation damper EPSR 0 D 0 diffusion periodic boundary iteration convergence criterion EPSX 0 D 0 maximum fractional pointwise change criterion EPST 0 D 0 not used D I 1 10 0 D 0 vector of 10 variables not used E Q I 1 5 0 D 0 5 variables not used reserved for time depende
47. M COLL CONDIF CONSIST CONVCK DESTDA DIFFO DISKXS DMPFLX DOGLEG DOUTER DWNSRC DXEED DXITE EDTBAI ELAPSE ENORM EPXS2D ERADDP ERRORT EXCEED EXPANQ EXPCHRD EXPXS2D FCN FCNG FCSRCE FDJACI FHLPR FHLPRL FILECK FEXIT FIXSRC FS FUN FUN8 FUN8D FZERO GAUELM GAUS8 GENBIN GETMSK GRDFN GREYACC GRIDS GSUMFS HISTRY HKEEP HYLITE IIMACH IGPRNT IMTQ12 INTADD ISDAME ISITFC ISORT KEY KEYWRD LCMADD LGET LGNDRX LINKMC LINKO MACCOR MACIN MACMIX MACOUT MACSCG MACTRC MASWEP MASWEPW MASWMC MCBFADJ MCTOSN MCXS MCXSPT MESSAG MFSFC MGEODF MOMCOR MULTIG MVBTOZ NEWPAS NOWERR ONEGRP ONETBD OPENRD OPENWR PCMBAL PRINTMC PRNTIA PRTLAG PRTNFX PRTNGS PT23D PTFISS PTQ1D PUTC PYTHAG QBSGET QFORM QGET QRFAC QRSGET RIMACH RIMPYQ R1IUPDT RAN RDASGM RDFCOF RDFIXS RDFLUX RDGEO2 RDGEOD RDMACR RDQS RDSOL REGCMV RELAXR RELAXZ RESFIT RESPJ RESSRC REWASH RMGET RMHSTI RMHST2 RTFLUX RTGET RTHST1 RTHST2 RTSRC RTTRCK RW SCASTG SCASTH SCATTG SCATTH SCMADD SETUP SFTFIX SIGRAY SINNER SMOM SNFLUX SNMOM SNSQ SNSRCMC SNTOMC SORTIA SORTMC SORTRI SRCBAL SRCCAL SRCDEF SRCMC SRCVAR SSPDI SSPEV SSPFA SSWAP STACKV STOP SUMF2C SUMNEG SWDMPX SWFIX TESTGO TESTSC TFINAL TFINFM TFINP3 TFINP6 TFINQF TFINSN TFISCA TFRITE TGND25 TGSUMS TIGF20 TINITA TINITQ TINP21 TINP22 TINP23 TINP24 TLCMBL TLNLBC TLOCNW TMAPPE TMOINIT TNEWPA TOT28 TOT29 TOUTER TPNGEN TQLRAT TRANSO TRBAK3 TRCK TREADQ TRED3 TSMIXC TSNCON TSYNDI TWODANT UCFLUX VARACC VRSION XERMSG XREP XYRW XYSCORE ZEROF LINKM Table 1 Routines of the TWODAN
48. NKM was newly established It gathers all necessary information from SIMMER COMMON areas for the preparation of the five interface files which enable the TWODANT SOLVER module to perform the calculation of the stationary adjoint and real and the instationary real neutron flux respectively Using the flux values stored in COMMON areas LINKM produces the flux files atflux and rtflux Additional information as for example the dynamics parameter or time dependent terms for the calculation of the extended source used in the TWODANT SOLVER module is transferred directly via COMMON areas from SIMMER to TWODANT On the other hand information provided in TWODANT as for example the normalization integral is transferred directly from TWODANT to SIMMER also in COMMON areas The leakage values are calculated in LINKM and stored in COMMON areas making use of the coarse mesh currents calculated in TWODANT and also stored in COMMON areas The main information produced in TWODANT the adjoint real scalar and angular flux values are written on the interface files atflux rtflux and raflxm and directly transferred into SIMMER where they are read into COMMON areas Additionally rtflux is used as flux guess in instationary calculations in the TWODANT package within the SIMMER code Figure 2 General program flow and data transfer in SIMDANT In the main program of the program system DANTSYS called PROGRAM DRIVER the two dimensional transport calculation
49. P 15 MNIMS 2500 D NDIMEN 5 NEI 96 NEJ 104 D NDIMEN 6 NEIGM 9 NEIGD 6 NEISNN 4 NEINV 16 NERXS 6 Note The identifier for the Fortran statement to be replaced in the HISTORIAN program library has to be specified very carefully The correct identifier could be found from a HISTORIAN source listing Sometimes the statement under consideration is given there several times with different identifiers distinguished by HISTORIAN directives STEP 2 Call the shellscript histor in the new directory histor96x104 by using the instruction histor This causes the attachment of the HISTORIAN program library and renames it to OLDLIB The COMPILE file consisting of Fortran subroutines and functions is then produced Step 3 A new subdirectory named for example sunday is to be established in histor96x104 In this new subdirectory sunday the COMPILE file is to be attached for example by means of the instruction In sf COMPILE The instruction siminst causes the decomposition of the COMPILE file into the files name f containing the separated Fortran subroutines and functions and the preparation of the Makefile and adding it as file in the subdirectory 59 It is good practice to delete now the COMPILE file in subdirectory sunday as well as in the directory histor96x 104 in order to clear storage arrays Step 4 Now the new Makefile may be changed by using e g the vi editor in order e g to add change n
50. T SOLVER module system and architecture independent Most of these routines are original TWODANT routines some of them had to be changed or adapted respectively for SIMMER relevant problems These routines are CHEBY CHIMOD CIFLSM DESTDA DIFFO DMPFLX DOUTER DRIVER HYLITE KEYWRD LCMADD MACMIX MASWEP MASWEPW PRNTIA PRTNFX RDSOL SCMADD SINNER TESTGO TFINAL TIGF20 TINITA TINP21 TINP22 TINP24 TOUTER TRANSO Two subroutines are completely new The first one is LINKM Its task is a kind of link module between SIMMER and TWODANT A detailed description of LINKM is given in chapter 5 The second one is CHIMOD which modifies the fission spectrum for adjoint calculations It is described in more detail in chapter 7 3 The second group of subroutines and functions consists of the system or architecture dependent ones For running the independent TWODANT SOLVER module on different architectures the suitable package of routines will have to be chosen accordingly At the moment the DANTSYS code package contains the packages for CRAY SUN Hewlett Packard 9000 Silicon Graphics and IBM RS 6000 architectures For the IBM RS 6000 these routines are A4CRGT C4577D COMPAT DOPOFF FEBYTE IBM8HQ ISAMAXT ISCHOL ISHOLE LHKYIN LODBCL LODERP LODORI LODRTP LODSTH MOV8T8 NUMIGT PUNDTF RANYEQ RDCI6 AB4CRD CLEAR CRAYOF DRED8 FILLU IBM8R8 ISCHA ISCHOT ISMAX LHKYOT LODBLK LODERR LODPRV LODSCH LODSTO MPLY NXTSGE PUNFIDO R
51. TRAN package for specifying a suitable starting guess for the source distribution were suspended A series of variables is given in the SIMMER neutronics input for controlling the different iteration processes Four of them have to be transmitted to the TWODANT SOLVER module in order to control the iteration processes for calculating the neutron flux shapes EPSO the convergence precision for the total fission source EPSMIN the minimum convergence precision for inner iterations ITLMOU the maximum number of outer iterations permitted ITLMIN the maximun number of inner iterations per group permitted per outer iteration when fission source is near convergence 27 In order to assure convergence of the iteration process the values for ITLMOU and ITLMIN are not simply assigned to the corresponding variables OITM and IITM used in the TWODANT SOLVER module They are modified in dependence of EPSMIN in accordance with findings gained in numerous calculations As an example If EPSMIN given in the SIMMER input is less than or equal to 1 10 it is set for stationary calculations IITM MAX ITLMIN 50 OITM MAX ITLMOU 50 and for instationary calculations IITM MAX ITLMIN 50 OITM MAX ITLMOU 30 EPSO and EPSMIN are transmitted unchanged from SIMMER to the TWODANT SOLVER module as given in the input IITL as the maximum number of inner iterations per group at the beginning of the iteration process is set ITL 1 and thus is coincid
52. Utility program to be called by jobnam and macnam scopy c in its RS6000 version is given below assign strings a b include ksuxu h typedef short ftnlen ifdef KR_headers VOID SCOPY a b la lb register char a b ftnlen la 1b else void SCOPY register char a register char b ftnlen la ftnlen 1b endif register char aend bend aend a la if la lt lb while a lt aend a4 b else bend b 1b while b lt bend at b while a lt aend Fatt The programs jobnam macnam and scopy in their versions given above were programmed by C H M Broeders FZK INR for use in other code packages at FZK 5 histor Shellscript zur Erzeugung der Fortran Source COMPILE aus dem Historianne Directory histdr2e unter Verwendung der HISTORIAN Eingabe HINP Last Change 10 1 99 94 In sf fzk inr home kleinh1 simmer2e hsource histdr2e OLDLIB y date y m date m d date d H date H M date M S date S I whoami echo IDENT SKUERSNO gt versio tmp echo D SKVERSNO 20 cat gt gt versio tmp echo DATA VERSIO I y m d H M S7 cat gt gt versio tmp fzk inr home kleinh1 bin historianne 6 siminst siminst is used as a shellscript in order to decompose the COMPILE file which contains all Fortran subroutines and functions of the SIMMER code into separate files of a predefined subdirec
53. ained from previous SIMMER calculations The variable IAFLUX indicating whether the regular angular flux file RAFLUX has to be written or not is set according to the kind of calculation Yes IAFLUX 1 for direct and No IAFLUX 0 for adjoint calculations All information concerning controls and dimensions as well as floating input data has to be written twice on the SOLINP file as raw and defaulted values respectively Therefore two variables ISTART and ISTARTD are used to transmit the information from SIMMER to the TWODANT SOLVER module whether a flux file from a preceding run may be used as flux guess for the actual calculation In the case of stationary direct or adjoint calculations no flux guesses that could be used are available Therefore it is set 0 0 ISTART ISTARTD whereas for instationary calculations the form of two flux shapes calculated in successive runs is not too different so that the result of the preceding run can be used as flux guess for the succeeding one in order to save computing time and it is therefore set ISTART ISTARTD 1 4 In subroutine PRNTIA of TWODANT this information is used to switch the variable INFLUX 0 to INFLUX 1 assigning that a flux guess is to be read from the file RTFLUX in accordance with this variable normally given in the input for stand alone TWODANT calculations Note Due to the favorable performance of TWODANT the various options available when using the TWO
54. and in all VISART files jobnam c in its RS6000 version is given below include lt stdio h gt include lt string h gt include lt sys types h gt typedef short ftnlen 92 ifdef NEED_TRAILING_UNDERSCORES define JOBNAM jobnam_ else define JOBNAM jobnam endif NEED_TRAILING_UNDERSCORES ifdef KR_headers long int JOBNAM name name_len char name ftnlen name_len else long int JOBNAM char name ftnlen name_len endif char namf 9 int ij cuserid namf scopy name namf 8L 8L i strlen name l name_len i for G 0 j lt l j scopy name j i 1L 1L return 0 3 macnam Provides the name and classification of the computer of the current run and stores it for registration in the output protocol and in all VISART files macnam c in its RS6000 version is given below include lt stdio h gt include lt string h gt include lt sys types h gt typedef short ftnlen ifdef NEED_TRAILING_UNDERSCORES define MACNAM macnam_ else define MACNAM macnam endif NEED_TRAILING_UNDERSCORES ifdef KR_headers long int MACNAM name name_len char name ftnlen name_len else long int MACNAM char name ftnlen name_len endif char namf 255 int i j l 1 255 gethostname namf 93 printf MACNAM namf s 1 d n namf scopy name namf 8L 8L i strlen name l name_len i for G 0 j lt l j scopy name j i 1L 1L return 0 4 scopy
55. ansport equation It should be noted that in SIMMER highly transient dynamic processes with an interplay of neutronics and fluiddynamics are simulated Any change in the neutronics quantities influences the fluid motion which over a feedback loop has an impact on the neutronics quantities again This behavior reflects the reality of dynamical systems In addition some types of threshold effects such as sudden pin failure fission gas release and fuel relocation processes could exaggerate discrepancies of results Therefore differences as those observed e g between Figure 13 and Figure 15 are not too unusual for results of codes dealing with accident analyses and that is one of the reasons why with these code systems a band width of results with a possible enclosing envelope should usually be calculated 76 12 Experiences acquired from reactor analyses applying the new neutronics module SIMDANT and Summary In order to verify and validate the new treatment applied in SIMDANT comparisons with the SIMTRAN version were an inevitable task After the completion of extensive comparison calculations the general recommendation can be given Use the SIMDANT version containing the new neutronics treatment for future SIMMER II calculations Preliminary tests demonstrated that stationary and instationary problems could be run successfully using SIMDANT when the corresponding TWODANT SOLVER module was modified suitably to take into account the proper
56. arse mesh boundaries are then written on the GEODST file as follows XMESHB D I 1 NCBNDD coarse mesh boundaries for R direction YMESHB J J 1 NCBNDJ coarse mesh boundaries for Z direction IFINTS 1 i 1 NCINTD number of equally spaced fine mesh intervals per coarse mesh interval in R direction set 1 for all coarse meshes are equal to fine meshes JFINTS J 1 J 1 NCINTJ number of equally spaced fine mesh intervals per coarse mesh intervals in Z direction set 1 for all coarse meshes are equal to fine meshes The values for XMESHB and YMESHB for this data block are taken from SIMMER own data areas As SIMMER is based on the application of an Eulerian grid the values of XMESHB and YMESHB remain unchanged during a calculation of a reactor transient The fourth record of the GEODST file is not relevant for 2 dimensional calculations The fifth record contains geometry data and has to be present for all geometries IGOM GT 0 VOLR D region volumes for the neutronics mesh grid they are transformed to a I 1 NREG single precision representation from a SIMMER own data area in double precision representation BSQ not transformed according to NBS 0 see above BNDC 0 4692 BNCI 0 NZHBB NZC D 0 I 1 NZONE NZNR D I 1 NREG 20 boundary constant grad 0 C D gt D grad 3 K using K 0 7104 extrapolation length known from the Milne problem gt 1 3 K C
57. at in contrast to the previous SIMMER version in the current version the rigorous angular dependent shape function is really considered In the corresponding SIMMER subroutines the associated time derivatives d dt are treated in a completely analogous manner for interpolations and extrapolations in time as that previously applied to do dt Originally one reason for using d dt instead of d P dt was the increase of computer storage requirements when applying the latter rigorous option Although this argument is still valid with currently available computer capacities there is no longer any need to adhere to the decision of the past to insist on reduced storage requirements and corresponding decreased data transfer Admittedly the storage needed for the restart files increases significantly 45 The restriction to the final transport sweep is most probably well justified by the usually almost negligible influence of the d dt term on the reactivity and on the flux and power distributions of the system during a transient In one example the associated influence on the pseudo eigenvalue y gamma of the quasi static method was found to amount to about 3 10 In any case the mentioned final transport sweep is needed because in the TWODANT solution procedure the angular fluxes will only be provided and stored upon performing such an additional final transport sweep These angular fluxes are needed for preparing the mesh wise neutr
58. ation sweep The diffusion solver part in TWODANT is accelerated remarkably by making use of multigrid methods Improved algorithms are included especially with regard to neutron upscattering schemes and to the Legendre expansion method of anisotropic neutron scattering processes of arbitrary order But these upscattering schemes cannot be applied yet together with SIMMER because the corresponding group cross sections are presently restricted only to down scattering as that is considered to be sufficient for almost all LMFR Liquid Metal cooled Fast Reactor applications Suitable convergence criteria are implemented in order to guarantee reliable solutions Sophisticated and standardised data management and transfer capabilities are implemented as defined and developed by the Committee on Computer Code Coordination CCCC 5 both sequential and random access file handling techniques are used Also some other features are implemented in order to provide TWODANT with storage capacities suitable for the actual calculation The already available extensive user oriented error and warning diagnostics in the original TWODANT package were improved and extended for SIMMER applications 3 Provision of an independently operating TWODANT Solver Module The TWODANT code is a modular computer program designed to solve the two dimensional time independent multigroup discrete ordinates form of the Boltzmann transport equation It is based on the mod
59. bly developed originally in most criticality related problems it does not represent a very suitable choice i e when inputting wdamp 2 0 and omitting the wdthrsh entries which is equivalent to inputting wdthrsh 1 0 for all those energy groups suffering from negative flux fixups the resulting change in the criticality could be fairly pronounced and unacceptably large for SIMMER safety analyses Of course this undesirably big deviation in criticality could subsequently be mitigated by suitable decreasing wdamp to values closer to unity as indicated before for avoiding the excessive fixups percentage the minimum value of wdamp not leading to reappearance of a warning related to negative angular fluxes would be the most reasonable choice 88 Short description of the AWDD scheme Those readers or users who are not too familiar with various discretization methods in discrete ordinates transport methods may benefit from having a look to Chapter IV of 8 where in Section A the Angular Quadrature for Discrete Ordinates Codes and in Section B the Spatial Discretization Methods are described and the merits and disadvantages of various options are indicated A short overview can also be found in 1 where Chapter 12 provides information on TWODANT methods Especially the paragraph on pp 12 37 explains the principles of the Spatially Discretized Two Dimensional Transport Equation For those readers not having easy access to 1 equations 37
60. broutine GRIND the actual flux calculation is initiated by a call of subroutine TWODANT the main routine of the TWODANT SOLVER module dependent on the parameters ITH and IAD Before the call of subroutine TWODANT the parameter ILINK is set 1 and subroutine LINKM is called dependent on ILINK for preparing the interface files ASGMAT GEODST MACRXS ADJMAC and SOLINP Additionally for instationary calculations the adjoint flux file adflux as well as the direct flux file rtflux are written using the actual date and time in the file identification record and transmitting the values actually stored in the data areas for adjoint and direct fluxes ADFLUX and CUFLUX respectively In case of a restart run RSTRUN TRUE only the direct flux file rtflux is written When having terminated a stationary or instationary direct flux calculation in subroutine TWODANT subroutine LINKM is called a second time after having changed parameter ILINK 1 in this way only causing the calculation of the leakage values for the reactor system needed later on for the reactivity determination 34 6 Modifications in the original SIMMER routines As described in more detail in chapter 10 the SIMMER code consisting of a large number of subroutines functions and COMMON areas comprised in the so called HISTORIAN program library is managed by the code maintenance system HISTORIAN which has been used as a preprocessor from its very beginning HISTORIAN directives in
61. cheme was not available in TWODANT but a similar positive scheme the AWDD adaptive weighted diamond differencing which avoids 79 negative fluxes has been installed During the implementation and testing of this AWDD scheme the question of positivity and its impact on the solution accuracy was analyzed c It was realized that both in the POSDIF and the AWDD scheme the correlation between the mesh edged and mesh centered angular fluxes are modified considerably to avoid negative angular fluxes For the POSDIF the same correlation coefficient is used in r and z direction for AWDD a direction dependence is taken into account The neutron fluxes may be considerably distorted by the use of the correlation coefficients to enforce positivity These flux distortions have an impact on the criticality value too d Note that the reactivity in the quasistatic method is directly evaluated on the basis of the angular neutron fluxes For both schemes POSDIF and AWDD it is not clear if they conserve ramp rates when intra mesh correlations belonging to the same mesh are changed upon successive flux shape calculations for different configurations evolving e g due to material redistributions which is of utmost importance in transition phase analyses Verification of ramp rate conservation could not be found in literature and is not expected to be fulfilled e Not until additional investigations confirming ramp rate conservation etc the p
62. cluded in the HISTORIAN program library the so called master file of the SIMMER code allow the construction of different executables containing a large variety of diverse options In this way it is possible for example to build up specific executables of SIMMER which are able to run on different computers containing either the TWOTRAN like solver part as used in the past or the TWODANT SOLVER module recently included into the SIMMER code as well by starting from the same master file and activating different directives specified in the HISTORIAN input file HINP The following six subroutines OUTER OUTACC INNET FIXUP REBAL PCGNUC are no longer used to construct the TWODANT SOLVER module Instead more than 300 new subroutines and functions HISTORIAN DECKs and about 140 new COMDECKs have been added Nevertheless the six TWOTRAN routines are still included in the master file so allowing alternatively the construction of an executable containing the TWOTRAN like solver part for comparison calculations It is almost impossible to describe explicitly every alteration omission or introduction of a specific Fortran statement in these particular subroutines It was decided therefore to store for longterm purposes the working version of the ongoing SIMDANT development containing alterations until about end of 1997 This dataset contains all the alterations identified by comment cards comprising the date of its inclusion and the identification of the
63. d In those cases the SIMMER run is stopped at the very beginning and the actual values needed can be taken from error messages for example the constants I1 and I2 as shown in the following relation to be adjusted in the following way D DIMEN 4 MNMS I1 D DIMEN 7 MNS IBMP2 JBMP2 MREG 50 MAXTP 15 MNIMS I2 IBMP2 and JBMP2 have been calculated code internally in the PARAMETER statement The preparation of a new executable as it is performed at the moment at FZK is shortly demonstrated by means of an example The description given rather detailed in the following should enable experienced SIMMER users to generate their own executable without appreciable assistance by a local expert code administrator or even by an external guru An executable has to be compiled with adjusted dimensions for the following input values by 7 steps IB 17 JB 54 IGM 9 IT 96 JT 104 IGD 6 ISNT 4 It is known from former calculations that the dimensions MNMS 5600 and MNIMS 2500 are sufficient 58 Step 1 A new directory has to be established named e g histor96x 104 Preparation of the HISTORIAN input file HINP assumed only the adjustment to the input values is performed and no additional alterations have to be prepared in the new executable HISTOR P C READ versio tmp IDENT dummy IDENT MYDIM D DIMEN 3 IBM 17 JBM 54 DIMEN 4 MNMS 5600 DIMEN 7 MNS IBMP2 JBMP2 MREG 50 MAXT
64. d Adaptive Weighted Diamond Differencing AWDD discretization scheme was included in the TWODANT SOLVER module For more information see chapter 8 In contrast to SIMMER where in the POSDIF ON option the weighting parameters necessary for this discretization scheme are calculated code internally the TWODANT SOLVER module needs two associated sets of weighting parameters for the adjoint and direct calculations respectively These values are prepared in LINKM in three data areas for transmission from SIMMER to TWODANT in the next record of the SOLINP file WOAMPA and WDAMPR for adjoint or direct calculations respectively and in WDTHRSH WDTHRSH is prepared only for historical reasons and for consistency with the SOLINP file to maintain compatibility with the original MASWEPW subroutine of the TWODANT package Only the ratios WDTHRSH WDAMPA or WDTHRSH WDAMPR are the essential parameters for practical applications To obtain these specific weighting parameters for the TWODANT SOLVER module a new NAMELIST block named amp NFIX was introduced in the SIMMER input stream which could contain the values for WDAMPA and WDAMPR The corresponding values for WOTHRSH are set dependent on WDAMPA or WDAMPR WDTHRSH 0 for WDAMPA or WDAMPR EQ 0 and WDTHRSH 1 for WDAMPA or WDAMPR NE 0 If the NAMELIST block amp NFIX is omitted in the SIMMER input stream the arrays WDAMPA and WDAMPR are set to zero by default so corresponding to the standard Diamo
65. d by SUROUTINE LINKM on five interface files ASGMAT GEODST MACRXS ADJMAC and SOLINP described in detail in chapters 4 and 5 it is no longer necessary to retain the calls of those subroutines for input handling material mixing and cross section preparation and for preparing the edit output and the call of the edit routines which are not needed in SIMMER applications Furthermore it is important to drop the calls of those program parts in SUBROUTINE TWODANT which remove some special interface files by calling SUBROUTINE DSTROI especially the interface file SOLINP which was prepared by SUBROUTINE LINKM and will be used in the TWODANT SOLVER module afterwards By calls of the corresponding subroutines SCMDFT LCMDFT SUNASG SUNOFF SUNATX MDOPC and DOPOFF the storage extension is performed problem dependent according to the values NFALSE and NSCM to be set appropriately in SUBROUTINE TWODANT see chapter 10 SUBROUTINE TIGF20 is called by SUBROUTINE TWODANT and organizes and controls the course of the two dimensional neutron flux calculation Although the complicated scheme of inner subouter outer iterations is considered supplemented by pure diffusion calculations TIGF20 could remain nearly unchanged The COMDECKs COMECS and MISC included in Table 3 of chapter 3 and NEUFLG1 and IPARAM1 of the SIMMER III code had to be added in order to enable access to the unit numbers initialized for the TWODANT SOLVER module and to the variable LPRINT
66. d in the six data blocks are taken from the values included in the restart dump file This is assured if data blocks in question are omitted in the input file Therefore a program part has been included into SIHPR in order to check which input blocks are contained in the input stream If necessary the user is requested by a warning to check whether he really wants to introduce the values from the input file actually contained in the subdirectory in a UNIX environment Concerning unit numbers some changes had to be performed because some numbers formerly used in SIMMER are used in TWODANT as well Because of the complicated file handling in TWODANT the changes have been accomplished in SIMMER Unit BFU 10 for the SIMBF file has been changed to BFU 77 unit numbers VISFU 31 and VISNU 77 have been changed to VISFU 79 and VISNU 78 respectively A new file OUTDI has been introduced using unit number OUTDI 80 in order to provide a capability to write important messages concerning extraordinary program flow or the occurence of unusual values for certain variables on a separate file That important information from the SIMMER code to the user could otherwise get lost and remain undiscovered in the heap of ordinary SIMMER output on file SIMO6 on unit OUTFU 6 File OUTDI is used in accordance with input variable EDTOPT 80 of input block amp CNTL For EDTOPT 80 1 file OUTDI is used for EDTOPT 80 0 the important messages are written on
67. derungen am TWODANT L sungsmodul war erforderlich um alle Anforderungen zu erf llen die sich aus den SIMMER Anwendungen ergaben Sowohl Eigenwertrechnungen f r den station ren Zustand als auch inhomogene Rechnungen f r die instation ren Zust nde m ssen ordnungsgem mit demselben L sungsmodul durchgef hrt werden Zusatzterme zur Ber cksichtigung der Zeitabh ngigkeit und der verz gerten Neutronenanteile mit ihren Vorl ufern mu ten der zeitunabh ngigen Neutronen Transportgleichung hinzugef gt werden Au erdem mu te die quasistatische Methode insbesondere die sog y Iteration in das bisherige Verfahren einbezogen werden Zum ordnungsgem en Einbau des TWODANT L sungsmoduls mu te auch der SIMMER Code durch geeignete Anpassungen entsprechend vorbereitet werden Au erdem wurden einige Unzul nglichkeiten beseitigt die in der Vergangenheit durch Vereinfachungen und die n herungsweise Behandlung f r einige Problemstellungen im Hinblick auf eine Effektivit tssteigerung eingef hrt worden waren Diese R cksichten sind bei den heute zur Verf gung stehenden wesentlich leistungsf higeren Gro rechenanlagen z T nicht mehr notwendig Zur Verbindung von SIMMER IIT mit dem TWODANT L sungsmodul wurde ein Verbindungsmodul bereitgestellt der auch den Datentransfer ordnungsgem bew ltigt Die f r SIMMER III und den TWODANT L sungsmodul erforderlichen nderungen werden in diesem Bericht beschrieben Au erdem sind die Ergebnis
68. e PROGRAMMLISTE sed e s I e sA f V dateiliste hp S HP f fi cat lt lt gt gt Makefile Abh ngigkeiten Das Bibliotheksarchiv bei einem eventuellen Abbruch des Make Laufs nicht l schen PRECIOUS LIB if s dateiliste hp then cat lt lt gt gt Makefile all PROGRAMMLISTE Erzeugung ausf hrbarer Programme FY eRe RL nS Se Oe Wichtig Alle Zeilen im folgenden Abschnitt die einger ckt sind m ssen mit einem TABULATOR beginnen nicht mit LEERZEICHEN Der strip Befehl darf nicht verwendet werden falls die Debug Option gesetzt wird FFLAGS g if x betriebssystem xsn9068 J then if uname m CRAY then cat lt lt gt gt Makefile 103 PROGRAMMLISTE LIB f ZP FC FFLAGS o xname f LIB ZP else cat lt lt gt gt Makefile PROGRAMMLISTE f LIB ZP FC FFLAGS o xname f LIB ZP fi if x debug_option xgesetzt then echo strip xname gt gt Makefile else echo strip xname gt gt Makefile fi cat lt lt gt gt Makefile echo echo Das Programm xname wurde erfolgreich echo compiliert und gebunden echo else cat lt lt 1 gt amp 2 Warnung In dem Programmpaket wurden keine Haupt sondern nur Unterprogramme gefunden Deshalb wird in dem von proginst angelegten Makefile kein ausf hrbares Pr
69. e ak ake oo oo oo akee Die Umstellung Ihrer Programme ist nun abgeschlossen Sie finden im Directory pwd folgende neuen Dateien XXXXxx f fiir jedes FORTRAN Programm xxxxxx Makefile Prozedur zum Compilieren Um Ihre Programme zu compilieren rufen Sie einfach den Befehl make auf Sofern Sie sp ter Programme ndern wiederholen Sie zur Neucompilation einfach den make Befehl a ale k k ae aka ee ak ak ak ak aka seak 2 took 24 2 of 22 2 aie ake aie A ES 2 aie se ee 2 ake ak ake oo oe oe 2 3K ake ak a aK 3 eR AD py rm dateiliste dateiliste exit
70. e and well justified to improve the robustness and the overall accuracy and reliability of the SIMMER program package by a more rigorous treatment even if causing a minor increase in the computational effort In this sense the actual program version of SIMMER III will differ from the package SIMMER II version 2d which FZK received from PNC in May 1997 All improvements contained in SIMMER II versions 2e and 2f received from PNC in July 1998 and in January 1999 respectively are also considered in the current SIMMER version All essential differences will be described more detailed in the following chapters Replacing the TWOTRAN like solution algorithms by the TWODANT SOLVER module the following general strategy was pursued The TWODANT SOLVER module only requiring the data provided on five interface files compiled in the TWODANT INPUT and cross section providing modules by using the TWODANT input data for the regular program flow has been isolated from TWODANT and introduced into SIMMER as an entity The five interface files have to be compiled in a newly established interface module called LINKM which had to be added to the SIMMER program package The actual data for the interface files have to be gathered by LINKM from SIMMER own data areas In that way the original SIMMER input stream could remain nearly unchanged Of course the TWODANT SOLVER module had to be adapted to the requirements of SIMMER applications i e the delayed neutrons and t
71. e considered group NG I e the first value refers to the self scatter term within group scattering the next value to scattering from group NG 1 to group NG etc For the first group this means NG 1 in case of the MACRXS file only the within group scattering cross sections are transferred according to CELSCT LNG I 1 NMAT For all other groups the within group scattering cross sections and the down scattering cross sections are transferred with NGG NG 1 NG 2 2 CELSCT LNG I 1 NMAT CELDWN LNGG J J 1 NG 1 I 1 NMAT 24 where the energy of the source group increases with increasing J The ADJMAC file contains the same data but they are arranged in inverse group order i e according to increasing energy The file control block and the file data as written on the ADJMAC file are identical with the MACRXS file The principal cross sections are written for all energy groups NG in the inverse group order NG IGM 1 1 to be given for all meshes of the neutronics grid CHI NG I 1 NMAT fission spectrum CHI CELFIS I NG I 1 NMAT production nu fission cross section NUSIGF CELREM LNG I 1 NMAT total cross section TOTAL CELABS LNG I 1 NMAT absorption cross section ABS The scattering control block for energy group NG is written also observing the inverse group order as follows NGPB L J L 1 NORD J 1 NMAT With regard to NORD 1 according to the value given in the c
72. egative fluxes in the AWDD scheme monitored in these fixup tables 9 4 Separate output for important messages Another option has been added to SIMMER In cases where important messages should not perish in the enormous quantity of the SIMMER output variable EDTOPT 80 in NAMELIST block XCNTL has to be specified as gt 0 Messages describing deviations of the normal program flow or unusual situations during the run are then written additionally on the separate file named SIM80 with unit number OUTDI 80 54 10 Application of HISTORIAN for the preparation of new executables for SIMMER calculations The SIMMER code consisting of a large number of subroutines functions and COMMON areas is managed by the code maintenance system HISTORIAN 9 which has been used as a preprocessor from its very beginning At FZK HISTORIAN is now used in its clone HISTORIANNE as received from Japan Nuclear Cycle Development Institute JNC of May 1995 HISTORIAN directives included in the HISTORIAN program library the so called master file of the SIMMER code allow the construction of different executables containing a large variety of diverse options In this way it is possible for example to build up specific executables of SIMMER which are able to run on different computers containing either the TWOTRAN like solver part as used in the past or the TWODANT SOLVER module recently included into the SIMMER code as well by starting from the same master file and acti
73. en cat lt lt 1 gt amp 2 proginst Kann auf diesem HP Rechner leider nicht laufen da er eine veraltete Version des fsplit Befehls enth lt exit 1 fi 53 cat lt lt 1 gt amp 2 Das Betriebssystem betriebssystem wird z Z von proginst nicht unterst tzt exit 1 5 esac 96 44 440 nnn nnn nnn nnn nn en Begr ung cat lt lt KRREK KEKE KEK KEKE KER KEK KEKE TH KK KT KT KH HT KT TH TH TH KK FH KT TH TH KT TH KK A KK KH TH KK KH TH KH TA KK KT TH TA TH AH KK AH KH KH KH kk proginst 3 pa T I A EE E E SAE EEA x Prozedur zur Installation von FORTRAN Programmpaketen auf UNIX Systemen k ETETE 2 AC 2A EEK SR ICC A EA RCS fA ER CIC 2 2 EEEE a E oa a Option des Echo Befehls fiir keine Zeilenschaltung am Ende case echo n x we T in 0 minus_n n 1 strich_n c esac Falls diese Prozedur in einem xterm Fenster aufgerufen wird sollen dessen Eigenschaften zur Darstellung von Zeichen fett invers unterstrichen ge nutzt werden if x TERM xxterm o x TERM xaixterm then tn Om tf Im tu 4m ti 7m fi Fa ee SR Ee a ee BEER a ne ee SHE Sollen Hilfsinformationen angezeigt werden if gt 0 then if 1 hilfe then more lt lt SOR oR Aa 2 Eee ok ER eof 2K He A 2 Ee oe ok a 2A RoE 22 oof EEEE of ER oR oR oe oe 2 EEE EEE E proginst dient zur Umstellung von auf einem MVS Rechner z B der IBM ES
74. ew compiler options Step 5 The four object modules mentioned before have to be attached by inclusion into the library libsunday a using the following instructions ar q libsunday a object_directory morec o ar q libsunday a object_directory jobnam o ar ar q libsunday a object_directory macnam o q libsunday a object_directory sscopy o Step 6 Some values for the provision of the storage space in TWODANT have to be adjusted by changing the default values by hand in subroutine twodantf in subdirectory sunday Increasing of actual values depending e g on number of energy groups Sn order number of meshes etc NFALSE 400000 to NFALSE 2000000 and NSCM 200000 to NSCM 2 010 000 and removing the statements IF NSCM GE NFALSE NSCM NFALSE 2 IF NFALSE LE 2 NSCM NSCM NFALSE 2 In subroutine linkm f one value has to be increased from IMAT 1 000 to IMAT 10 000 In which way IJMAT has to be specified correctly and particularly how to proceed if MAT increases the value of UMAT 10 000 is described in chapter 5 1 Step 7 The instruction make in subdirectory sunday causes the various calls of the compiler for all subroutines and functions the inclusion of the object modules into the library libsunday a and 60 the preparation of the new executable with the name sunday x in subdirectory sunday If the run stops immediately after having started this new executable showing the error message
75. f the fission spectrum CHI as can easily be deduced from Eq V 61 of 10 For this purpose in subroutine MACMIX the newly written subroutine CHIMOD is called which replaces the prompt fission spectrum by the total fission spectrum calculated in the following way CD 1 BPE AD LB fork 1 1GD with B LP fork 1 IGD where FS CHI total for neutron energy group g in mesh I J Betaeff LD CHI prompt for neutron energy group g in mesh I J Bk Beta of delayed neutron group k yore CHI delayed of delayed neutron group k and neutron energy group g IGD number of delayed neutron groups Affected routines for this modification MACMIX CHIMOD b A rather small correction had to be introduced in subroutine CHEBY in order to enable Chebychev accelerations to run properly in all cases that could occur c d e 48 Affected routine CHEBY As discussed in chapter 5 5 the leakage values in SIMDANT have to be calculated in subroutine LINKM for each mesh and simultaneously the sum over all meshes is determined To enable these leakage calculations in subroutine CIFLSM the accumulated horizontal and vertical neutron flows are multiplied by the corresponding geometric values see chapter 5 5 and stored in the data areas FMJX and FMJY respectively FMJX and FMJY are transferred to LINKM as parts of the COMMON array named LEAKAG Affected routines LINKM CIFLSM In subroutine RDSOL of the TWODANT SOLVER mod
76. for coarse meshes not used 0 1 2 3 4 bottom boundary condition vacuum used 0 1 2 3 4 top boundary condition vacuum used time limit in seconds 0 default value unlimited 1 0 1 2 37 47 5 top boundary source option 1 0 1 2 3 47 5 bottom boundary source option 0 1 no yes radial modifiers for x 0 1 no yes radial modifiers for y 0 1 no yes radial modifiers for z 0 1 no fine mesh density factors by ymesh IDENZ 0 ITMPX MFGACC JUPDCH JACC IBF IBK MC D 88 I 1 4 MCOPT 0 MC D 88 1 6 13 IQF 88 IQK 88 IBEDOL IBEDOR IBEDOB IBEDOT 0 IBEDOF IBEDOK NOSIGF IPLANT JSRITE JSBOTT JSTOP JSLEFT EIGONLY K 0 1 1 6 FCNRAY FCNTR NODAL 0 NPROC 1 L I 1 3 88 AVATAR 0 GREYACC 0 M IF1 2 0 M D I 3 6 88 IQ I 1 100 0 29 0 1 no fine mesh density factors by zmesh not used reserved not used reserved not used reserved not used reserved 0 1 2 3 4 front boundary condition not used 3 dimension 0 1 2 3 4 back boundary condition not used 3 dimension 4 values only used for Monte Carlo calculations never used for SIMMER applications Therefore set 88 0 1 no yes turn on Monte Carlo option 8 values only used for Monte Carlo calculations never used for SIMMER applications Therefore set 88 front boundary source option not used 3 dimension back boundary source option not used 3 dimension 0 1 2 n
77. gibt es keine Dateien Falls Sie die FORTRAN Programm Datei en nicht bereits beim Aufruf von proginst angeben wird im aktuellen Directory gesucht exit 2 else eingabe teste_eingabe ja fi else eingabe fi ff ca As lS OE hs ele Gea ate Dut es tS Zeitpunkt merken um im Fehlerfall evtl bereits angelegte Dateien mit make Technik wieder l schen zu k nnen touch tmp proginst LOGNAME Z if Is f 2 gt dev null then startsekunde date S aktuelle_sekunde 60 restsekunden expr 60 startsekunde 1 echo Analyse der Eingangsdateien ca restsekunden Sekunden echo minus_n strich_n while aktuelle_sekunde ge startsekunde do sleep 1 echo minus_n strich_n aktuelle_sekunde date S done else echo Analyse der Eingangsdateien fi echo fertig echo off oe ne ena plies oe ala Oh a al et oe a ae Programmdateien in UNIX Form bringen dateiliste tmp proginst LOGNAME touch dateiliste for datei in eingabe do case kommentare_lassen betriebssystem in ja HP UX _ split_befehl fsplit v datei 2 gt amp 1 grep v warning ja split_befehl fsplit datei HP UX split_befehl fsplit sv datei 2 gt amp 1 grep v warning split_befehl cut c 72 datei sed s fsplit esac if teste_eingabe then letzte_zeile tail 1 dateilegrep i ENDSIM END if x letzte_zeile x then cat lt lt 1 gt amp 2
78. hat the two dimensional neutron transport code TWODANT originally developed at Los Alamos National Laboratory proved to have the best characteristics with respect to accuracy and reliability of the results as well as robustness and calculational speed Therefore the TWOTRAN like code package in SIMMER has been replaced by the suitably adapted solver part of TWODANT for solving the neutron transport equation A number of modifications has been necessary for adapting the TWODANT SOLVER module to fulfill all demands given by SIMMER applications eigenvalue calculations for the initial state and inhomogeneous calculations for the transient states using the y iteration scheme developed for the quasistatic treatment have to be performed properly by execution of the same solver part Additional terms must be added to the original neutron transport equation especially for representing the time dependence and the delayed neutron parts and their precursors and the quasistatic method with its particular feature of the so called y iteration had to be introduced In order to prepare the SIMMER code for the inclusion of the TWODANT SOLVER module some modifications had to be performed in this code too In the past simplifications and approximate treatments were introduced with the intention of improving the computational efficiency Having now available far more powerful modern computers with associated large storage capacities some of these approximations we
79. he different scales as ranging from 250 to 50 in Figure 12 and from 20 to 5 in Figure 13 Therefore the calculated power and reactivity transient shown in Figure 13 is only qualitatively similar to the result obtained when using the former SIMMER II shown in Figure 12 in the sense that the first recriticality event takes place around 1 1s and this drives the second power burst by the sloshing pool However each recriticality event in the calculation by the TWODANT module is milder than for the TWOTRAN calculation The cause of this discrepancy is not yet fully understood at the moment and has to be investigated in future studies When repeating at FZK the JNC runs leading to Figures 12 and 13 it was observed that the results of the calculations for the TRA problem were affected by a deficiency namely the not fully converged inner iterations essentially due to the input value ITLMIN 10 The used SIMMER code version didn t monitor this fact in the output protocol as it had done in the former versions Therefore this failure i e not achieving convergence could not be identified by straightforward analysis of the output file After detection of this shortcoming at FZK the SIMTRAN calculations have been repeated at JNC and Figures 14 16 led to the following conclusions 73 W REACTIVITY l AMPLITUDE 4 10 01 g EE aa R a i a ETE 510 110 REACTIVITY 4 510 TIME Figure
80. he interfacing code SAME II According to the hypothetical assumption of a large diameter of the fuel particles the one dimensional fall down of the relocated fuel causes a recriticality event around 1s which drives the subsequent recriticality phase by a sloshing of molten core material The calculations were performed with SIMMER II version 2d using ISOTXS BRKOXS files prepared for 7 energy groups and 21 isotopes The Sn order was specified to N 4 AMPLITUDE f REACTIVITY TRA_SIMMER TWOTRAN_FIXUPon 10 _ 50 10 e a ee a ee eee 0 Lu 50 D A 2 2 10 m m 1009 t 10 lt x 150 lt 0 10 200 40 250 0 0 5 1 5 2 TIME Figure 12 Power and reactivity plot of TRA case calculated by TWOTRAN using FIXUP ON 72 e AMPLITUDE f amp REACTIVITY TRA_SIMMER TWODANT_AWDDoff 10 5 0 10 Lu Fe gt gt Fj 10 2 10 S lt 5 lt 10 15 1 10 20 0 0 5 1 5 2 TIME Figure 13 Power and reactivity plot of TRA case calculated by TWODANT using AWDD OFF Please note The scales used in Figures 12 and 13 are very different regarding amplitude as well as reactivity The normalized amplitude peak at the first recriticality event shows an increase by a factor of 40 Figure 12 and by a factor of 20 Figure 13 It is nearly impossible to compare the trend of the reactivity values because of t
81. heir precursors needed to be considered and the quasistatic method had to be introduced The needs for an improved neutronics solution scheme in SIMMER are put together in chapter 2 In chapter 3 the preparation of an independently operating TWODANT SOLVER module is described A short description of the binary interface files connecting the TWODANT SOLVER module with the TWODANT modules INPUT EDIT and cross section preparation is given in chapter 4 The newly established interface module LINKM connecting and enabling data exchange between the TWODANT SOLVER module and SIMMER is described in detail in chapter 5 In this interface module modifications have to be introduced if additional options contained in TWODANT should be made available to SIMMER in the future Programming modifications in the original SIMMER and in the TWODANT SOLVER subroutines as well are described in chapter 6 and chapter 7 respectively Motivation for an investigation of the special characteristics of the Adaptive Weighted Diamond Differencing AWDD discretization scheme in addition to the conventional Diamond Difference discretization scheme is described in chapter 8 Inevitable changes to the usual SIMMER input flow caused by the inclusion of the TWODANT SOLVER module are put together in chapter 9 In order to manage a computer code of the extension of SIMMER suitably the well known code maintenance system HISTORIAN 9 is used at FZK in its version HISTORIANNE as
82. ical reliability of the determined results it is recommended to decrease wdamp 87 gradually again by steps of 0 1 or 0 05 but not below values causing reappearance of non positive scalar fluxes or of fixups 4 When the AWDD parameters wdamp and wdthrsh were chosen suitably so that non positive scalar fluxes and excessive fixup percentages could be avoided in affected groups it may be still desirable to avoid also the non excessive fixups in other groups It is recommended to aim at a vanishing percentage but only if nodes are involved which are considered as having a significant influence or a relevant importance for the neutronic behaviour of the reactor and or for the investigated accident progression This means that the user has to look carefully to the spatial nodewise distribution of the percentages given in the fixup tables and to assess the influence of any negative angular fluxes in certain nodes on the reactor transient treated in the actual SIMMER safety analysis For this purpose a suitable procedure again consists in increasing wdamp gradually above unity 0 1 or 0 05 steps As indicated in 7 the consequences of choosing WDAMP GE 2 0 could show some adverse effects on the results As mentioned above some thoughts should be given to considering the feasibility of a more suitable spatial mesh grid e g mesh refinement instead of exaggerated adaptive weighting It is obvious that the use of the AWDD option corresponds t
83. iginal subroutine PRTNFX have been introduced and mainly the strategy of the output of important information concerning curious program flow or other irregularities for the user has been extended The value of the logical variable Iprint set according to the value of the input variable IGM number of energy groups see chapter 9 3 use of IGM lt 0 directs whether information is to be printed on different output files or not For more details see the file which was used as working version during the SIMDANT development containing the FORTRAN source program 49 Subroutine affected PRTNFX For routine applications the amount of standard output produced by TWODANT for SIMMER calculations should be limited On the other side there have been provided some feasibilities to extend the printing of output information for those cases where strange or unclear results have to be expected Controlled by the contents of the logic variable Iprint additional output is printed on the standard output unit or on the screen as well Iprint is set according to the value of the input variable IGM the number of neutron energy groups in the following way Iprint TRUE for IGM lt 0 Iprint FALSE for IGM gt 0 Another feasibility enables the output of essential information on a separate output file which could be lost otherwise if hidden in the heap of the standard output file In this case the input variable EDTOPT 80 of NAMELIST block XCNTL has t
84. ilt in constants are used flux guess flag as described above 0 1 no yes in solver mixing 0 1 2 none one chi zonewise chi 0 1 2 3 7 4 left boundary condition reflective used for z axis 0 1 2 3 4 right boundary condition vacuum used 0 1 2 none fine mesh density factors by XMESH fine mesh density factors for every mesh type of eigenvalue to search for in a concentration or dimension search 0 1 2 none Keg alpha 0 1 no yes do 2 angle slab calculation 0 1 2 3 4 5 6 inhomogeneous source option inhomogeneous Legendre order 1 0 1 2 3 4 7 5 left boundary source option 1 0 1 2 3 4 7 5 right boundary source option outer iteration limit see explanations above early inner iteration limit see explanations above near convergence inner iteration limit see explanations above time limit in seconds 0 default value unlimited not used 0 1 2 none isotropic all moments final flux print flag 0 1 2 none principal all cross section print flag 0 1 no yes fission rate print flag 0 1 2 3 no as input normalized both source print flag 0 1 no yes fine mesh geometry print flag 0 1 no yes angular flux print flag acceleration type 0 1 no yes write code dependent zone fluxes flag 0 1 no yes group dependent Sy orders GRPSN read in flag 0 1 no yes write angular flux file RAFLUX see explanation above albedo option print both balance tables and flux fixup monitor
85. indicating whether additional output should be prepared on the 43 standard output unit or not A message is written on the output file if the interface file raflxm containing the angular real flux is established dependent on the value of LPRINT The variable GAMMA is saved as a result of the y iteration for later use in SIMMER 44 7 2 Adaptation of TWODANT routines for specific SIMMER tasks In the quasistatic approach an inhomogeneous external source problem is treated as a pseudo eigenvalue problem where a pseudo eigenvalue parameter usually denoted y characterizes the quality of the obtained solution The standard TWODANT SOLVER module only allows to deal with a standard eigenvalue problem such as the real and adjoint stationary cases or an inhomogeneous source problem with specified external sources The conversion of a source problem in SIMMER e g due to the delayed neutrons and their precursors to a pseudo eigenvalue problem was a new feature which had to be implemented in the TWODANT routines in a very careful manner The associated modifications were much more complicated than in the existing SIMMER version based on the TWOTRAN solution scheme mainly caused by the diffusion synthetic acceleration DSA scheme This new and attractive feature improves considerably the convergence behavior but requires particular attention to be attributed to the correlation between the transport and diffusion part of the solution algorith
86. ing with the default value given in TWODANT During the execution of a run IITL is suitably changed depending on the convergence behavior as monitored internally by the code Please note The strategy for increasing IITL during the iterative solution process has been modified compared to the original DANTSYS version according to own experience for representative cases exhibiting unusually poor convergence performance with the standard strategy The SOLINP file is written as follows Title card count NHEAD 0 number of title cards to follow Title card not present according to NHEAD 0 Spatial dimension IDIMEN 2 number of spatial dimensions Controls and dimensions raw values 200 integer values 28 For SIMMER applications some data are not relevant but the associated explanation is given for completeness IEVT ITH ISCT ISN IQUAD ISTART ICSM INCHI IBL IBR IDENX IPVT IANG IQOPT IQAN IQL IQR OITM ITL ITM ITLIM 1 FLUXP XSECTP FISSPR SOURCP GEOMP IANGP IACC IRMFLX IGRPSN IAFLUX ISBEDO IBALP DUM3 IBB IBT ITLD IQT IQB IXM IYM IZM IDENY 1 IAD 0 ISNT 0 ISTART 0 0 1 0 0 0 0 0 0 0 0 OITM ITL ITM 0 0 0 0 0 1 0 0 0 0 0 IAFLUX type of TWODANT calculation 0 1 direct adjoint calculation Legendre order of scattering angular quadrature order as given in the SIMMER input source of quadrature set bu
87. ion source available in FISSA On the other side it has to be admitted that the particle balance obtained by using these flux values is no longer identical to the particle balance table that is printed in the TWODANT output listing Another feature contained in TWODANT improves the capability of calculations by using SIMDANT instead of SIMTRAN Whereas in SIMTRAN the fission neutron spectrum and the delayed neutron spectra are assumed to be only group dependent i e independent of position and or composition in SIMDANT the fission neutron spectrum is allowed to be composition or mixture dependent In SIMDANT subroutine DOUTER the transport fluxes are scaled by the diffusion results no equivalent scaling is performed for the delayed neutron precursor concentration in the stationary calculations The omission of this scaling during the iteration procedure is well justified because of the fairly small contribution of the delayed neutrons to the neutron source term For a sufficiently well converged solution this omission has practically no influence on the quality of the calculated results Some important findings have been made during the analyses of transient problems and led to the following recommendations given below 1 2 3 78 Use of an optimally refined neutronics mesh is recommended Calculations showed that a rather refined mesh is necessary for calculating the neutronics properly Initially the negative flux fixu
88. ition in R direction means extrapolated boundary condition diffusion grad C D where C is given as BNDC below and D is the group diffusion constant This means no entering of neutrons JMB1 2 first boundary condition in Z direction means extrapolated 19 boundary condition JMB2 2 last boundary condition in Z direction means extrapolated boundary condition KMB1 0 not relevant for 2 dimensional problems KMB2 0 not relevant for 2 dimensional problems NBS 0 number of buckling specifications no specifications are given NBCS 1 number of constants for external boundaries one single value is used everywhere NIBCS 1 number of constants for internal boundaries one single value is used everywhere NZWBB 0 no reactor zones are black absorbers NTRIAG 0 not relevant for RZ geometry NRASS 0 region assignments to coarse meshes NTHPT 0 not relevant for RZ geometry NGOP I 1 4 0 reserved for further use in GEODST file For 2 dimensional problems the second record of the GEODST file is not used In the third record using the TWODANT terminology the 2 dimensional coarse mesh interval boundaries and the numbers of fine meshes per coarse meshes are put together Keeping in mind that in the SIMMER neutronics grid the TWODANT fine mesh grid is identical with the coarse mesh grid the number of coarse mesh boundaries in both directions are precalculated as follows NCBNDI IT 1 NCBNDJ JT 1 The co
89. ity can be input as reactivity and or as ramp rate To provide the feasibility to check the correctness of the input ramps the values are printed in tables in the ordinary SIMMER output on file SIMO6 In predecessors of the actual SIMDANT version inconsistencies have sometimes occurred in reaching the time limit parameter TWFIN exactly using the actually calculated time steps These inconsistencies could be removed by adding a very small program part partially extracted from rudiments of former SIMMER packages In an extension of subroutine GRIND the summary for negative flux fixups for the adjoint case calculated and put together in subroutine PRNTFX is written on file VISNU 78 along with other neutronics postprocessor data for later use in evaluation and plot programs by calling subroutine WPPNK on request by the user In this case the number of neutron energy groups in the input package has to be set IGM lt 0 and input variable IOUTNI of input block amp NVIS has to be set 1 or 3 The corresponding task for the stationary and all instationary real calculations is initiated in subroutine PKDRIV by calling subroutine WPPN In this subroutine the tables for negative flux fixups are taken over from subroutine PRNTFX via COMMON area XNFX The values are put together and written on file VISNU 78 by calling subroutine WPPNK Files NISART unit number VISNU 78 and VISART unit number VISFU 79 are prepared by the postprocessor s
90. lar flux In the corresponding modified SIMDANT subroutines the associated time derivatives d dt are treated in a completely analogous manner for interpolations and extrapolations in time than that previously applied to d dt The time derivatives were treated in an approximate way as a part of the rebalancing acceleration capabilities in the former TWOTRAN version Since this technique was replaced by the much more efficient Diffusion Synthetic Acceleration DSA feature in the TWODANT package a new scheme had to be found for taking into account the time derivatives of the angular dependent shape functions In TWODANT the additional term d dt is neglected during the conventional iteration processes and is taken into account only in a last additional transport sweep This single final 71 transport sweep is performed after having finished all the usual iteration processes and when all accuracy requirements and convergence criteria are already fulfilled In this final transport sweep it is not necessary at all to deal with transport diffusion correlations because in those circumstances the diffusion part is completely avoided The approximative treatment consists in the fact that only a single last transport sweep is performed including d P dt without considering fulfillment of convergence criteria or the possible necessity of continuing the iteration procedure It has been confirmed by some test cases that the described approximati
91. m CHI VELCTY NEIGM neutron velocities VEL In addition to these principal neutronics data the TWOTRAN SOLVER module also expects the absorption cross section ABS because it is needed for determining the meshwise neutron balance Therefore the COMMON CELXS is extended by the data area CELABS NELU NEIGM absorption cross section ABS for storing the absorption cross section for all meshes of the neutronics grid and all energy groups The macroscopic self shielded absorption cross sections are calculated in an extension of subroutine SHLDXS and its associated subroutines analogously to the macroscopic self shielded fission and capture cross sections as CELABS I J GRP 2 DENISO I J M VF XSISOcapt M GRP FFISOcap I J M XSISO M GRP FFISO I J M where DENISO J M is the number density of isotope M in mesh I J VF is a factor for the approximate treatment of heterogeneity effects for thermal neutron reactors In case of fast neutron reactors VF 1 22 XISO ap M GRP are the microscopic capture and fission cross sections XISO s M GRP respectively for isotope M and energy group GRP FFISOcap I J M are the capture and fission resonance self shielding factors f FFISOg I J M factors respectively for isotope M in mesh I J for the energy group being considered Please note capture here means all absorptions excluding fissions i e including e g n p and n a reactions The self scatter a
92. ment usually only one single inner iteration transport sweep is performed per outer iteration 2 When approaching convergence the number of inner iterations per outer iteration is significantly increased but even then the extra effort for the necessary adaptive weighting algorithms is not significantly more time consuming than that needed for the standard negative flux fixup scheme The fraction of affected mesh cells angular directions and energy groups is most times fairly small so that in addition to solving the conventional DD equations the elimination of negative angular fluxes is not needed too frequently and the computational effort spent for the AWDD scheme does not exceed significantly that for execution of the negative flux fixup algorithms 86 How to use the AWDD scheme The original motivation for the implementation of the AWDD scheme was described in 1 and was indicated in the above section When applying the AWDD scheme particular attention has to be attributed to the choice of the associated parameters wdamp and wdthrsh see also 1 7 As is evident for X Y geometry from Eqs 11 in 7 only the ratio wdthrsh wdamp is the essential parameter for practical applications i e in most cases increasing wdamp or decreasing wdthrsh is almost equivalent Based on this rule various ways can be taken for achieving a solution without negative angular fluxes Presumably they will end up with fairly similar results so that they
93. ms In particular the inherent renormalizations of pseudo eigenvalues and associated fluxes had to be modified accordingly when converting the source problem to a pseudo eigenvalue problem A Time derivative The time derivative of the space and angular dependent shape function d dt with usually small influence is taken into account in an approximative manner in the previous SIMMER versions up to version 2d and is still handled in this way in the actual SIMTRAN version too a Only the space dependent scalar flux d dt is considered i e the angular dependence is neglected b The time derivative of the scalar flux do dt is dealt with approximately during the rebalancing procedure Since there doesn t exist such a rebalancing feature any longer in TWODANT an alternative method had to be found Due to the claimed minor effect of this term d dt an approximate treatment was still considered to be sufficient being aware that the contribution of this term is even neglected completely in some codes In the new version this additional term is neglected in all but the last transport sweep Therefore the computational effort remains almost unchanged and furthermore in this final transport sweep which is inevitably needed for other reasons explained below it is not necessary at all to deal with transport diffusion correlations because in those circumstances the diffusion part is completely omitted It should be mentioned th
94. n of histor is included in the Appendix B The following description of another shellscript and of four C routines explains in which way the generation of new executables is performed at FZK considering a UNIX environment as installed on RS6000 A second shellscript named siminst splits the Fortran source file COMPILE into different data files named name f containing all Fortran subroutines and functions where name designates their 55 different names and stores them into a special subdirectory provided for this purpose constructs a Makefile and adds it to the subdirectory mentioned before The actual version of siminst is also included in the Appendix B The Makefile can be called afterwards using the instruction make in order to cause the opening of a library for the inclusion of all object modules the various calls of the compiler for all subroutines and functions the linking of the object modules to the executable and to store it in the same subdirectory as an additional file Its name is created as the name of the subdirectory followed by x the comparison of the creation date and time of the executable with those of the creation or last modification of the different subroutines and functions Only those subroutines and functions are marked for compilation that have been changed after the creation of the executable This means if only small program modifications have to be performed after the creation of the executable it is
95. n subroutine CIFLSM of TWODANT the neutron flows are available for each coarse mesh in data array FMJ IT JT in order to accumulate the horizontal and vertical neutron flows The values of these flows are used to determine the partial leakage values at each horizontal and vertical coarse mesh boundary for each energy group by multiplying them with the geometric values r Ar Az n and Ar Az respectively and storing them in the data arrays FMJX IT 1 JT IGM and FMJY IT JT 1 IGM designating with IT and JT the number of coarse meshes in R and Z direction respectively and with IGM the number of energy groups These two data arrays are parts of the newly introduced COMMON area LEAKAG In this way FMJX and FMJY are transferred to subroutine LINKM Using the energy group dependent adjoint flux ADFLUX I J IG as weighting function which is calculated only once at the beginning of each SIMMER run in LINKM the leakage values are then calculated in the analogous way as previously performed in subroutine INNET for each coarse mesh of the neutronics grid as follows FMIX J IG FMIX I 1 J IG FMIY LJ IG FMJY LJ 1 1G ADFLUX LJ IG for IG CULEAK L J 1 IGM The sum over the leakage values of all meshes is calculated simultaneously and stored in variable CURINT as CURINT XCULEAK LJ forl 1 IT J 1 JT It has to be noted that horizontal and vertical neutron flows are only calculated if a particle balance table is also required In
96. nally for WDAMPA WDAMPR NE 0 0 Otherwise they are also set 0 0 The NAMELIST block amp NVIS has to be specified if the neutronics postprocessor file NISART containing among other things the data for the fixup tables should be written for later evaluation In this case IOUTNI 1 has to be specified as the only value in the NAMELIST block amp NVIS 93 UseofIGM lt 0 The amount of output produced by TWODANT in the SIMMER environment should be limited for routine applications However for non standard cases e g when dealing with a new core design for the first time or when observing strange or unexpected results of the neutronics calculations or when trying to determine suitable values of the damping parameters WDAMPA WDAMPR for the adjoint and real stationary case it is most desirable to be able to have a closer look into the details usually provided in the conventional TWODANT output Inclusion of this output in the normal SIMMER output file SIM06 can be achieved by setting the number of neutron energy groups IGM negative in the SIMMER input stream This is a rather new option Additional information about the TWODANT run e g storage allocation print of fixup tables also a sketch showing the core layout the dimensions and the material distribution of the neutronics mesh etc can also be obtained by setting IGM lt 0 As mentioned before particular attention should be paid to excessive flux fixups in the DD scheme and to n
97. nce TRCOR 0 D 0 transport correction indicator PLANET 0 D 0 planet indicator FCSRC 0 D 0 use first collision source option XMCSB 0 D 0 biasing parameter in Monte Carlo option not used XMCBLT 0 D 0 boundary layer in Monte Carlo option not used FCWCO 0 D 0 weight cutoff for first collision rays D I 1 54 0 D 0 54 variables not used EXTRAS 0 D 0 this data area of 110 variables is foreseen to transmit some special A 1 110 parameters for example to avoid diffusion acceleration etc no use is made hereof in the TWODANT application in SIMMER Then the record controls and dimensions follows with another 200 integer values in the same format as in the record above but it contains the defaulted values for each variable For SIMMER applications this means that only the variable ISTART is replaced by variable ISTARTD the values for all other variables remain unchanged Now the record floating data follows with another 200 floating point data in double precision representation but it contains the defaulted values for each variable For SIMMER applications not only the format of these data but also the contents of all variables remain unchanged The following 9 records included in the TWODANT description are of no meaning for SIMMER applications and are therefore not present according to the flags put in the preceding records 31 In order to avoid negative angular flux values at mesh edges the so calle
98. nce of using the AWDD formalism with values of WDAMPA and WDAMPR whose absolute magnitude is larger than 1 0 91 B Survey of some C routines and shellscripts In this Appendix some shellscripts and auxiliary subroutines written in the programming language C are documented They are prepared for application at FZK and are either used to produce new executables or are included into the SIMMER code for solving specific data processing tasks 1 morec The allocation of arrays in TWODANT is not done via variables that are defined in PARAMETER statements but dynamically and therefore problem dependent There exists a C source program morec c which is system dependent and arranges the dynamical storage allocation of all arrays used in the TWODANT code morec c in its RS6000 version is given below double morec need int need char calloc return double calloc need sizeof double lessc ifrevs int ifrevs int ihave ihave ifrevs free ifrevs return ihave iaccess name mode iaccess name mode char name int mode return access name mode This routine was distributed together with the DANTSYS package Further information about the use and handling of this routine may be found in comments of subroutine TWODANT 2 jobnam Provides the user s identification for the current run and stores it for registration in the output protocol
99. nd Difference DD discretization scheme with negative flux fixups Thus the last two records of the SOLINP file are written as follows for adjoint calculations WDAMPA D I IGM 1 1 WDTHRSH D I IGM 1 1 Comment Please note that in amp NFIX the values WDAMPA are specified according to usual physical group ordering but are written on SOLINP for the adjoint calculation in reversed ordering and for direct calculations WDAMPR D I 1LIGM WDTHRSH I 1 IGM Remark Those users being already familiar with the input specifications of the DANTSYS package could easily change some default values e g XSECTP for the cross section print by changing the default value used in LINKM when preparing the SOLINP file to the desired value Moreover specialists having sufficient experience and knowledge of particular details and features may even influence the choice of the solution algorithms by attributing suitable input values to the so called EXTRAS being part of the SOLINP file 32 5 5 Leakage calculation In SIMMER calculations using the TWOTRAN solver part for determining reactivity values p and neutron fluxes a special program part is contained in subroutine INNET to calculate the leakage values for each mesh of the reactor system needed later on for the reactivity determination As INNET is no longer used in the TWODANT SOLVER module and no equivalent program part is included these leakage values are calculated in LINKM I
100. nd TOUTER the delayed neutrons and their precursors have to be taken into consideration According to the original SIMMER formalism the neutron source is built by summing the two separate components stemming from prompt and delayed neutrons respectively Even in the stationary case the precursor concentrations DELAYC are always determined immediately after having obtained new neutron fluxes during the outer iterations Therefore a few statements had to be added in DOUTER and TOUTER for calculating the steady state precursors during the sub outer diffusion and outer transport iterations An alternative possibility would have been to determine a converged flux solution first using a modified fission neutron spectrum as described in the following and then to determine the precursor concentrations by using these fully converged fluxes This simplification results from combining the equation for the precursor concentrations with the equation for the neutron flux distribution for stationary conditions see e g Eqs V 29 and V 31 in 10 To maintain consistency with the solution scheme originally implemented in OUTER of the existing SIMMER version we did not incorporate the simplification but kept the inclusion of the DELAYC component for the calculation of the real flux distribution for the stationary case within the outer iteration process For the adjoint case however this procedure could simply be replaced by a modification o
101. nd the downscatter cross sections are stored in SIMMER in the COMMON CELXS in the data areas CELSCT NEI NEIGM and in CELDWN NED NEIGM NEIGM 1 2 respectively For reasons of simplicity the whole lower triangular scattering matrix is transferred from SIMMER to the TWODANT SOLVER module via MACRXS and ADJMAC files If no other values are present i e in case of an empty matrix entry a 0 0 is transferred The corresponding control numbers for the TWODANT SOLVER module are transferred according to the specifications of the file control blocks The file MACRXS is written as follows File control block NGROUP IGM number of energy groups NMAT ITJT number of materials in accordance with the number of meshes in the neutronics grid NORD 1 number of Legendre scattering order NED 0 number of EDIT cross sections IDPF cross section data are of double precision LNG IGM number of last neutron group no coupled neutron gamma cross section set MAXUP 0 no upscatter groups MAXDWN IGM 1 maximum number of downscatter groups NPRIN 4 the four basic principal cross sections which have to be always present for TWODANT SOLVER calculations I2LP1 0 the 2L 1 term for the higher order moments of the scattering matrix is not included in the library File data HMAT MATNAM I HED 1 CHI HED 2 NUSIGF HED 3 TOTAL HED 4 ABS VEL N VELCTY N N 1 IGM EMAX N 0 0 N 1 IGM material labels as described
102. netics The resulting rapid positive reactivity insertion brings the core to prompt criticality The power excursion terminates in a short period of several milliseconds due to a negative reactivity feedback mechanism of continued axial fuel motion in the core center beyond the core midplane The reactivity and power transient are plotted in Figures 8 11 for both the TWOTRAN and the TWODANT module respectively The discrepancy between the two codes is fairly small and one can conclude that the implementation of the transient terms into the TWODANT module and the coupling of SIMMER III fluid dynamics and TWODANT have been performed successfully In addition the effect of the fixing up procedure of negative flux is larger than the effect of the difference between the neutronic modules Both TWOTRAN and TWODANT produce a little bit larger amplitude peak around 6ms with the fixing up procedure than with the positive differencing scheme or AWDD scheme The calculations were performed with SIMMER II Version 2d using ISOTXS BRKOXS files prepared by the neutronics preprocessor MXS 14 for 7 energy groups and 5 materials The Sy order was specified to N 4 68 60 7mm a Ta ee lea una etree 1722 YET Figure 7 Configuration of the STN Standard Test Problem for Neutronics 69 e AMPLITUDE amp REACTIVITY STN_SIMMER TWOTRAN_FIXUPON 10 15 1 w 10 I 05 M E O S 3
103. not necessary to use the whole extensive and cumbersome procedure of writing correction sets and HISTORIAN input files HINP introducing it by HISTORIAN into the master file and thus creating a new COMPILE file Those small modifications can be performed in the Fortran source programs name f and a corrected executable can be produced easily and rather quickly by a new call of the Makefile by using the instruction make again The Makefile may be extended by introducing other compiler calls or by adding or changing the compiler options It has to be noticed that all alterations in the Makefile have to be done by using an editor which preserves preset tabulators e g vi Before calling the Makefile four program parts have to be added as object modules by including them into the corresponding library to those object modules created by compiling the Fortran source routines These four object modules are morec o Jobnam o macnam o SCOPY O The purpose of these program parts is morec The allocation of arrays in TWODANT is not done via variables that are defined in PARAMETER statements but dynamically and therefore problem dependent There exists a C source program morec c which is system dependent and arranges the 56 dynamical storage allocation of all arrays used in the TWODANT code morec c in its RS6000 version is given in the Appendix Further information about the use and handling of this routine may be found in comments of subrou
104. nterested in more details of the reactivity contributions may obtain relevant information from the post processing file see EDTOPT 1 First try to avoid non positive scalar transport fluxes at mesh centers or excessive GE 50 flux fixups for angular fluxes at mesh edges by using wdamp 2 0 in the affected groups Omitting any input for wdthrsh internally corresponding to wdthshr 0 will cause the application of the default values wdthrsh 1 0 2 As a result of the first step the non positive scalar transport fluxes may not yet have completely disappeared or the percentage of negative flux fixups may still remain above zero in some of the involved energy groups In those cases wdamp should be gradually increased e g in steps of 0 1 or 0 05 until the desired goal could be achieved But an increase above 2 0 should in general be considered as an indication that a refinement of the spatial mesh grid could be a more appropriate alternative for the considered configuration if feasible from other points of view or compatible with other aspects of the whole SIMMER calculation 3 As a result of the first step the desired goal will already have been immediately achieved in some of the affected energy groups but the used default value of wdamp 2 0 might have been too extreme In those cases the adaptive weighting might have been overtuned In order to avoid unnecessary deterioration of the calculational accuracy and of the phys
105. o be set gt 0 so causing special output to be printed on output file SIM80 with unit number OUTDI 80 Subroutines affected DMPFLX HYLITE KEYWRD LCMADD PRNTIA SCMADD TINP21 TINP22 TINP24 50 8 Adaptive Weighted Diamond Differencing AWDD The Adaptive Weighted Diamond Differencing AWDD method can be used in TWODANT to avoid negative angular fluxes at mesh edges This method replaces the former SIMMER NI input parameter NIOPT 30 POSDIF The standard discretization method used in TWODANT corresponds to conventional diamond differencing DD with negative flux fixup It is therefore equivalent to the former SIMMER II input parameter NIOPT 31 FIXUP i e AWDD OFF in TWODANT corresponds to FIXUP ON in TWOTRAN The user should be aware that the former input options NIOPT 30 and NIOPT 31 have no longer any influence when running TWODANT however the corresponding output list produced by SIMMER still reflects the choice of the options specified in the input In addition to the standard fixup procedure i e setting to zero negative angular fluxes and resolving the balance equation again under this condition to maintain the particle balance there two different AWDD methods are available described in Appendix A which when applied in a suitable manner can avoid negative fluxes as well They are based upon a weighted diamond approximation for the spatial discretization or even including the angular discretization which will give po
106. o the application of additional usually not physically motivated or based assumptions concerning the intra mesh correlation between the mesh centered and the mesh edged angular fluxes In the currently implemented AWDD algorithm also the angular dependence of mesh centered flux is subjected to AWDD i e all three equations of 37 are replaced by the equivalent ones in 38 of Chapter 12 in 1 for the convenience of the readers these equations are given in the next section As a consequence the associated reactor physics properties of the configuration e g leakage rates might undergo slight or more pronounced deviations from the physically true values which however could only be obtained from a calculational model using a more refined spatial mesh grid The user has to decide which disadvantage might have more severe consequences for his calculation 1 accepting the negative flux fixups or 2 tolerating variations of the calculated neutron distribution due to modifications of the intra mesh correlations between angular fluxes In both cases some caution regarding the accuracy and reliability of the results seems to be appropriate As a final comment it may be worthwhile to mention that a brute force application of the default option provided in TWODANT for using the AWDD option is usually not adequate for SIMMER related problems Although this default option may be adequate for shielding problems for which this option was presuma
107. of 5 23 1995 release 3 0 A number of modifications has been necessary for adapting the TWODANT code to fulfill all demands given by SIMMER II applications eigenvalue calculations for the initial state and inhomogeneous calculations for the transient states using the y iteration scheme developed for the quasistatic treatment have to be performed properly by execution of the same solver module Additional terms have to be added to the original neutron transport equation especially for representing the time dependence and the delayed neutron parts Therefore the modified version of TWODANT now included into SIMMER is no longer identical to the version contained originally in the DANTSYS code system This name was changed into Japan Nuclear Cycle Development Institute INC in October 1998 In the course of improving the SIMMER neutronics not only the TWOTRAN like code package was replaced by TWODANT but also some deficiencies were eliminated Originally SIMMER has been designed by deliberately incorporated simplifications and approximate treatments with the intention to improve the computational efficiency without a significant loss of accuracy for standard applications Taking into consideration the far more powerful modern computer configurations with regard to calculational speed and storage capacities it is no longer necessary to insist on all of the previous approximate efficiency oriented procedures By way of contrast it is advisabl
108. ogramm erzeugt und die HP und ZP Option sind nicht aktiviert Sofern doch Hauptprogramme enthalten sein sollten f gen Sie am Anfang bitte PROGRAM Anweisungen ein und wiederholen proginst fi if s dateiliste up J then cat lt lt gt gt Makefile Unterprogramme compilieren und archivieren LIB if cat dateiliste up we l gt 1 then ed s lt lt gt gt Makefile 2 gt dev null e dateiliste up s N LIB 1 1sA f 0 WV Ss f 0 P q else ed s lt lt gt gt Makefile 2 gt dev null e dateiliste up s N LIB Ss A f 0 P q fi if uname s r cut c 8 SunOS 4 then cat lt lt gt gt Makefile FC FFLAGS c 0 f 104 AR ARFLAGS RM ranlib echo echo Das Bibliotheksarchiv ist nun vollst ndig echo Achtung Die obigen Befehlszeilen beginnen mit einem TABULATOR nicht mit LEERZEICHEN La elif uname m CRAY then cat lt lt gt gt Makefile FC FFLAGS c 0 f AR ARFLAGS rm echo echo Das Bibliotheksarchiv ist nun vollst ndig echo Achtung Die obigen Befehlszeilen beginnen mit einem TABULATOR nicht mit LEERZEICHEN L a fi fi cat lt lt gt gt Makefile cat lt lt G EPE ara He ae a ske ake ske ee 3k 3k 3k ee a 2K K 3K 3k 3k 3K E ae ale af ea ae fh he aka 2 se 2 kostet
109. on balance tables which in turn are a prerequisite for establishing the associated mesh leakages These leakages together with the adjoint fluxes are evaluated for determining the corresponding contribution to the overall reactivity of the system and its reactivity variation during a transient B Negative flux fixups Being well known the standard diamond difference discretization scheme is affected by negative fluxes frequently arising due to extrapolations in rather coarse meshes with dimensions sometimes appreciably exceeding one average transport mean free path This might not always be a severe disaster Lathrop s comment in the second paragraph of the introduction in 12 should be recalled In many cases the negative fluxes while annoying can be tolerated because they occur in regions in which fluxes are small and unimportant but in an increasing number of situations negative fluxes interfere with the solution process As a potential remedy negative flux fixup is applied for obtaining non negative solutions for the distributions of scalar and angular fluxes although mesh refinement would be the more suitable alternative but this could sometimes lead to a prohibitive increase of the computational effort Therefore in all SIMMER versions existing up to now an option could be used that yields nonnegative scalar fluxes However as mentioned in the SIMMER Manual even this modification cannot completely exclude negative angular fl
110. on is well justified and has a completely negligible influence on the calculated pseudo eigenvalue Therefore the additional approximation mentioned in the Appendix A in Section Comment on an approximation when applying AWDD is of no practical relevance Performing calculations in this way it has to be stated that no additional effort is needed The mentioned final transport sweep is needed in any case because in the TWODANT solution procedure the angular fluxes will only be provided and stored upon performing such an additional final transport sweep These angular fluxes are needed for preparing the mesh wise neutron balance tables which are a prerequisite for establishing the associated mesh leakages These leakages together with the adjoint fluxes are evaluated for determining the corresponding contribution to the overall reactivity of the system and its variation during a transient Due to this additional transport sweep the resulting scalar and angular transport fluxes are in perfect agreement with the corresponding fission source available in the array FISSA Usually i e without the need to prepare angular fluxes this correlation is less rigorous because after having determined FISSA in subroutine DOUTER by a Chebyshev acceleration and calculating an updated eigenvalue the iteration process will be terminated supposed all relevant criteria are fulfilled without redetermining the fluxes on the basis of this most recent fiss
111. one left albedo albedo spatial distribution 0 1 2 none right albedo albedo spatial distribution 0 1 2 none bottom albedo albedo spatial distribution 0 1 2 none top albedo albedo spatial distribution 0 1 2 none front albedo albedo spatial distribution 0 1 2 none back albedo albedo spatial distribution 0 1 none set NUSIGF zero for source problems 0 1 none planet variable present 0 i no yes write right boundary flux ati 0 i no yes write bottom boundary flux at i 0 i no yes write top boundary flux ati 0 i no yes write left boundary flux at i 0 1 no yes only converge eigenvalue and fissions 6 variables reserved for future use number of ray tracings batch ray trace option number of batches in the ray trace option 0 1 2 diamond difference DD or adaptive weighted diamond difference AWDD CL LL nodal spatial discretization scheme number of processors to be used in PVM version 3 variables reserved for time dependence 0 1 no yes write the AVATAR file 0 1 no yes grey upscattering accelerator to be used defining these variables in this way it is possible for test purposes to interrupt a SIMMER run suitably simply by setting the largest cycle number CYCFIN 0 in the SIMMER III input during execution and to start TWODANT in its stand alone version only using the Title Line and Block I of the input and copied from SIMMER the interface files ADJMAC ASGMAT GEODST MACRXS and SOL
112. onics coarse mesh is treated in SIMMER as a separate reactor zone possessing its own material Consequently the number of zones is given by NZONE ITJT And the number of materials is also given as MT ITJT Using the terminology of TWODANT each coarse mesh of the neutronics mesh grid corresponds to a fine mesh this means the neutronics coarse mesh grid prepared by SIMMER HII is identical with the fine mesh grid for which the transport equation is solved in the TWODANT SOLVER part So from now on we only speak of the fluid dynamics mesh grid and the neutronics mesh grid respectively The correspondence between the different meshes in SIMMER II and TWODANT is shown in Table 4 16 Mesh correspondences TWODANT SIMMER III stand alone fluiddynamics mesh coarse mesh neutronics mesh fine mesh Table 4 Mesh correspondence between SIMMER II and TWODANT The SIMMER II fluid dynamics mesh grid is adjusted code internally to the neutronics mesh grid in subroutine PSARR by extending the data areas XMESHB and YMESHB initially containing the fluid dynamics mesh boundaries to the neutronics mesh boundaries in both directions For each material and consequently for each neutronics mesh a set of self shielded group constants is provided by SIMMER in subroutine SHLDXS and its associated subroutines The five interface files are associated with the five Fortran unit reference numbers IADJIMA 41 IASGMA 43 IGEODS
113. ontrol block and in consideration of the transmission of the whole lower triangular down scattering matrix this means NGPB L J IGM NG 1 J 1 NMAT specifying NG as the number of groups scattering into the considered group NG IFSG L J L 1 NORD J 1 NMAT with IFSG L J IGM NG 1 J 1 NMAT defining NG as group number of the first source group scattering into the considered group NG For the first group this means NG IGM in the case of the ADJMAC file only the within group scattering cross sections are transferred according to CELSCT LNG I 1 NMAT For all other groups NG NG running from IGM 1 to 1 the within group scattering cross sections and the down scattering cross sections are transferred to the ADJMAC file as CELSCT I NG I 1 NMAT CELDWN LNGG J NG J J 1 2 J 1 IGM NG I 1 NMAT 25 where NGG NG 1 NG 2 2 and the energy of the source group decreases with increasing J 26 5 4 Preparation of the interface file SOLINP Before writing all necessary information for controlling the program flow in the SOLVER module of TWODANT on the SOLINP file some integer and real variables are to be set properly in subroutine LINKM according to the TWODANT application in SIMMER for the actual problem being calculated It has to be noticed that the values for some variables are sometimes set differently from the default values given in TWODANT as a consequence of findings g
114. ositive schemes might probably be applied f According to the experience gained up to now no evidence exists that with respect to accuracy and reliability of the results the POSDIF ON option in SIMTRAN or the AWDD option in SIMDANT might be superior to the conventional FIXUP ON option that can be applied in both packages unless for the observation that the iteration performance of the POSDIF ON option is sometimes more favorable than that of the FIXUP ON option in SIMTRAN g At the time being it is recommended to choose an optimally adapted refined mesh on the basis of information given by both the FIXUP monitoring tables and the RHO reactivity tables in SIMMER M 4 Realization of the SIMTRAN capability POSDIF OFF FIXUP OFF For the sake of completeness it should be mentioned that the particular feature of SIMTRAN namely of disregarding any correction of negative angular fluxes which can be activated by specifying NIOPT 30 0 i e POSDIF OFF and NIOPT 31 0 ie FIXUP OFF can be applied in SIMDANT too in that case WDAMP parameters 1 0 have to be used see remark in Appendix A 80 Summary After termination of the SIMDANT development two operational versions of SIMMER IH are available e SIMTRAN using the TWOTRAN like solution algorithms and e SIMDANT using the extended TWODANT SOLVER module for the calculation of the neutron flux shapes The SIMDANT version is the new reference version and in future code relea
115. ouvet Commissariat l Energie Atomique CEA Cadarache France Comparison TWODANT TWOTRAN ERANOS Private communication January 1999 16 E Hesselschwerdt Implementation of TWODANT in SIMMER II Private communication February 1998 17 Tecplot User s Manual Amtec Engineering Inc Bellevue Washington August 1996 84 14 Appendix A Adaptive Weighted Diamond Difference AWDD discretization scheme General remarks and motivation Hints for busy readers After implementation of the AWDD scheme detailed investigations led to the conclusion that in general the merits of using the AWDD scheme may be quite limited and the obtained benefit rather questionable compared to the standard DD scheme with fixups Therefore those readers not too much interested in that particular topic could skip reading this part of the Appendix Historically the Adaptive Weighted Diamond Difference AWDD discretization scheme was mainly intended to deal with deep penetration shielding problems see 7 However it may be useful too for SIMMER applications related to criticality problems with a rather coarse mesh spatial discretization Nevertheless it should be emphasized that its application implies that the intra mesh correlation between the angular fluxes is modified and no longer corresponds to the familiar linear relationship between the fluxes at the mesh center and the mesh edges assumed to be valid in the diamond difference
116. ps should be below 50 and they should be restricted to neutronically less important regions In regions with material boundaries strong changes of absorbing scattering media a detailed mesh refinement of the neutronics grid is necessary Calculations have shown that even in blanket regions the arrangement of the neutronics meshes can be a sensitive problem One has to bear in mind that new material boundaries will be created during transient calculations possibly leading to negative fixup percentages above 50 The current recommendation is to use as refined meshes as feasible At the moment applying of adaptive meshes is not possible in SIMMER Preparation of a suitable neutronics mesh grid can be facilitated by a careful inspection of the information provided in the fixup tables which can be visualized if desired In addition the RHO tables written on the postprocessor file provides useful information so that the user could more easily assess the importance of the individual meshes for the global reactivity balance One could even envisage that it might be desirable to prepare group dependent RHO tables currently only group summed are given so that the significance of the fixup percentages appearing in the group dependent fixup tables for a precise determination of reactivity changes could be judged more easily Sharper convergence criteria for the y iteration are recommended The default value of EPSG 1 0 10 as usually given in
117. r later use in the TWODANT SOLVER module it turned out to be the best solution to include the DANTSYS main program called PROGRAM DRIVER The name was changed into SUBROUTINE TWODANT in order to make its call more obvious in the SIMMER IIT SUBROUTINE GRIND The information used for initialization is either stored in BLOCK DATA units or has to be provided by some auxiliary routines called by SUBROUTINE TWODANT as for example the actual date and time or the actual computer configuration As a consequence some subroutines called in SUBROUTINE TWODANT had also to be attached to the TWODANT SOLVER module in order to perform the data initialization making use of the contents of 6 BLOCK DATA units which had to be added too These subroutines are contained in Table 1 and Table 2 of chapter 3 Three COMDECKs COMECS LNSINP and TIA all of them contained in Table 3 of chapter 3 were also introduced into SUBROUTINE TWODANT Within the independently running program system DANTSYS PROGRAM DRIVER organizes the general flow according to the input data given As SUBROUTINE TWODANT in the framework of SIMMER III is used only to initialize variables data arrays and COMMON areas and to call specifically SUBROUTINE TIGF20 in order to perform the calculations for the solution of the two dimensional neutron transport equation large program parts in SUBROUTINE TWODANT could be omitted As the TWODANT SOLVER module gets all the relevant information suitably prepare
118. re eliminated when implementing the TWODANT SOLVER module A new linking module had to be provided and added to the SIMMER code package in order to couple both program parts SIMMER II and the TWODANT SOLVER module and to enable the data exchange properly Program modifications of the TWODANT SOLVER module and the SIMMER II code are described in this report The results of some test calculations for accident related problems are also included together with experiences acquired by these calculations Eine neue SIMMER II Version mit verbesserten L sungs verfahren im Neutronikteil Zusammenfassung Bei der Untersuchung von St rfallsituationen mit der SIMMER II Standardversion konnte bei der L sung der Neutronentransportgleichung mit dem eingebauten TWOTRAN hnlichen Verfahren nur sehr m hsam oder manchmal gar keine Konvergenz erzielt werden Ausgedehnte Testrechnungen die au erhalb von SIMMER II zum Vergleich verschiedener im FZK verf gbarer Transportcodes durchgef hrt wurden ergaben da der zwei dimensionale Neutronentransportcode TWODANT der urspr nglich im Los Alamos National Laboratory entwickelt wurde ber die besten Eigenschaften sowohl hinsichtlich Genauigkeit und Zuverl ssigkeit der Ergebnisse als auch Robustheit und Rechengeschwindigkeit verf gt Der TWOTRAN hnliche Programmteil wurde deshalb durch den TWODANT L sungsmodul zur L sung der Neutronentransportgleichung in SIMMER II ersetzt Eine ganze Reihe von n
119. region with 14 Pu enriched fuel The test section was surrounded by the driver region with 29 U235 enriched fuel and further blanket regions with natural or depleted U fuel Upper blanket FBR test region Radial blanket 1 63 m Fuel slumping region Lower blanket 075m Figure 3 R Z model of FCA VIII 2 experiments 62 In a central part of the test region 3 by 3 drawers of 5 5cm x 5 5cm each the fuel distribution was varied from a reference uniform distribution AO to three levels of compacted configurations Al A2 and A3 and to a fuel dispersed configuration S The patterns of fuel re configurations are depicted in Figure 4 where a dark hatched region represents compacted fuel having twice as dense fuel as the reference fuel density simulating an intact core Fuel slumping into a compact configuration from AO to A3 makes the axial flux distribution peaky and this increases the fission rate in the dense fuel region causing a positive reactivity change Because of a large void region developed above the fuel region the reactivity change must be evaluated by suitably treating negative reactivity effects due to increased neutron leakage This means the use of neutron transport theory is inevitable in simulating the experiments Although the scales of fuel re distribution were only limited in the FCA experiments reactivity changes from the reference configuration were
120. rn und Dateinamen auch in OPEN Anweisungen in Ihrem FORTRAN Programm vornehmen Falls die Quellprogrammdateien ein oder mehrere Hauptprogramme enthalten erzeugt make nach M glichkeit bereits lauff hige Module daraus Aufruf analog dem obigen Beispiel des Hauptprogramms hp5 Dies setzt voraus da z B alle Unterprogramme gefunden werden Sofern Sie Programme aufrufen die in Ihrem Programmpaket nicht vorhanden sind m ssen Sie die Bibliothek en angeben die durchsucht werden soll en dazu dient der Parameter ZP z B make ZP libxyz a usr lib libm a Bitte stellen Sie sicher da jedes Hauptprogramm mit der FORTRAN Anweisung PROGRAM Programmname beginnt Weitere Hinweise finden Sie im Leitfaden zur Umstellung von MVS nach UNIX und speziell auch zum make Befehl im UNIX Fortgeschrittenenkurs der HDI ck Die vom MVS Gro rechner kommenden Original Quellprogrammdateien k nnen Sie nach erfolgreicher Umstellung wieder l schen KERLE EHE RAK 2 A ER 2 E22 oR 2 2 oe ok oR 2 9 2 oO ok 2 ok ok ak ok oko ok E exit 0 elif 1 k then kommentare_lassen ja shift Falls keine Datei en als Option angegeben wurden Gibt es mindestens eine Datei im aktuellen Directory Falls Eingabe Dateien bekannt sind Liste erstellen if eq 0 then if Is wc w eq 0 then cat lt lt 1 gt amp 2 ti tf 98 Fehler tn Im Directory pwd in dem die Prozedur proginst aufgerufen wurde
121. rsions at 1 1 s showing an amplitude peak of approximately a factor of 30 initially normalized to unity The second recriticality event is calculated by SIMTRAN exactly at 1 5 s and by SIMDANT at 1 45 s The maximum amplitude factor is calculated by SIMTRAN to 7 10 and could be estimated in the SIMDANT calculation as to be not too different The scale ends in this case at 1 10 The reactivity curves show a similar trend up to the first recriticality event Afterwards the course of the reactivity and amplitude curves is different Whereas the SIMDANT results reach a local minimum of approximately 0 5 SIMTRAN calculates a local minimum of 2 After the second criticality event SIMDANT ends at a reactivity value of 18 at 2 s whereas 75 SIMTRAN determines the reactivity curve with a rather steep gradient leading to values far below 20 The intercomparison verifies that SIMDANT can be applied for complicated transient analyses and increases the confidence in the suitability of this upgraded tool There are still some nonnegligible discrepancies remaining between the results shown in Figures 13 and 15 in particular in the peak amplitude at about 1 5 s and the time behavior of the reactivity and the amplitude afterwards The origin of these differences is not clear presently In particular it would be premature to conclude that they will essentially be caused by the different algorithms applied for the solution of the neutron tr
122. s an attractive capability the monitored percentages of negative flux fixups can be printed in tabulated form which can also be used for visualization Inspecting the corresponding plots permits a deeper insight regarding the importance of these fixups in the various energy groups and different regions of the reactor On the basis of this information it is now much easier for the user to prepare a more suitable calculational model if necessary with a well adapted refinement of the neutronics mesh grid In total the implementation of the TWODANT package in the most recent version 2f of SIMMER II led to the desired and expected success of providing a more robust and reliable tool for safety analyses with the additional considerable advantage of a very stable performance and a significant reduction in overall computing time 81 Acknowledgements The authors gratefully acknowledge the support of their Japanese colleagues at JNC who supported the testing of the new code package and provided the input for the sample problems One of us E H would particularly like to thank them for their help and kind hospitality during her stay in Japan contributing to the success of the joint effort and also to making the stay an extraordinary and exciting personal experience The authors also want to express their gratitude to the French colleagues at CEA Cadarache for making available rather early the results of their time intercomparisons of calculations using
123. se f r einige Testrechnungen f r unfallrelevante Reaktorsituationen sowie die bei diesen Rechnungen gewonnenen Erkenntnisse und Erfahrungen in den Bericht aufgenommen Contents 10 11 Introduction Needs for an improved neutronics solution scheme in SIMMER Provision of an independently operating TWODANT Solver Module Short description of the binary interface files connecting the TWODANT SOLVER module with the other TWODANT modules INPUT and EDIT LINKM a new linking module for data exchange between SIMMER and the TWODANT SOLVER module 5 1 Preparation of the interface file ASGMAT 5 2 Preparation of the interface file GEODST 5 3 Preparation of the interface files MACRXS and ADJMAC 5 4 Preparation of the interface file SOLINP 5 5 Leakage calculation 5 6 _ General program flow using LINKM as interface between SIMMER and the TWODANT SOLVER module Modifications in the original SIMMER routines 6 1 Modifications in the main program SHIPR 6 2 Adaptation of SIMMER routines for the inclusion of the TWODANT SOLVER module Modifications in the TWODANT SOLVER routines 7 1 Subroutines TWODANT and TIGF20 as driver programs for the TWODANT SOLVER module 7 2 Adaptation of TWODANT routines for specific SIMMER tasks 7 3 Some minor modifications in several subroutines Adaptive Weighted Diamond Differencing AWDD Input 9 1 Check of some values used in the PARAMETER statements of SIMMER 9 2 New NAMELIST block amp NFIX and amp NVIS
124. ses the SIMTRAN version will be eliminated Both versions are included in the HISTORIAN program library being managed by means of the code maintenance system HISTORIAN Executables of both versions can be prepared they have to be distinguished in the HISTORIAN input file HINP by adding the directive DEFINE TWOTRAN in the case a SIMTRAN executable or by omitting this directive if a SIMDANT executable is requested respectively As described in chapter 11 the expected advantage of using SIMDANT instead of SIMTRAN could be clearly demonstrated for some stationary cases As a further favorable result the instationary test case the Space Time Neutronics Problem from the SIMMER II User s Manual 6 could be run successfully using the extended TWODANT SOLVER module incorporating the conventional diamond differencing scheme and applying the negative flux fixup method Comparing SIMDANT and SIMTRAN with regard to computing times roughly a factor of about two has been observed during verification and validation tests of the new version at JNC and FZK in favor of SIMDANT as compared to SIMTRAN These experiences could be confirmed recently by our French colleagues 15 For configurations leading to a poor convergence performance in the iteration process the factor of two is improved remarkably in favor of SIMDANT More detailed comparisons of computing times will be necessary and should be performed in the future The new SIMDANT version provide
125. sitive angular fluxes at mesh edges using a predictor corrector method to determine the appropriate weights The application of the AWDD method can be chosen by specifying according parameters WDAMPA and WDAMPR described in Appendix A which have to be input in the new NAMELIST block amp NFIX of the SIMMER input file However one important difference to the previously applied POSDIF ON scheme should be mentioned in the AWDD scheme up to now the user has to find out by trial and error the most suitable values leading to acceptable weight parameters and this can practically be done only for the stationary cases adjoint and real but the parameters cannot be considered as the most suitable choice for all core configurations that have to be analyzed during a reactor transient In the former POSDIF ON scheme the appropriate weights were determined on the basis of an approximate criterion which usually yielded positive fluxes except in a few extraordinary circumstances Those users adhering to the combination of the options NIOPT 30 0 and NIOPT 31 0 in previous SIMMER versions i e POSDIF OFF and FIXUP OFF will find in Appendix A a possibility how to run TWODANT in the equivalent manner using AWDD For the sake of completeness a concluding comment may be adequate according to past experience the POSDIF ON option was in general more robust than the FIXUP ON option Most probably this was the essential reason for the preference
126. solution scheme The analysis of these tables which were slightly extended provides very useful information regarding space and energy dependence from which experienced users could obtain a deeper insight into the potential 46 significance and relevance of the monitored fixups with respect to the accuracy and reliability of the associated solution The same tables could as well be used for monitoring negative angular fluxes when trying to apply the AWDD scheme Such negative values may still be encountered when the tuning parameters specified in the input were not chosen suitably The choice of appropriate values still has to be done on a trial and error basis However it can be expected that experienced users with sufficient knowledge in reactor neutronics will be able to determine near optimum input values when applying the AWDD option The subroutines of the TWODANT SOLVER module which are affected from the adaptation to SIMMER applications are TOUTER DOUTER SINNER TFINAL TESTGO MASWEP MASWEPW MASWEPD The detailed description of the extensive alterations omissions or introductions of Fortran statements may be found together with some explanations in a file which was used as working version during the SIMDANT development and contains the FORTRAN source program This file is stored at FZK INR for longterm access 47 7 3 Some minor modifications in several subroutines a For the calculation of the neutron source in DOUTER a
127. tained with the coarser grid Even the fairly good agreement between the SIMTRAN and SIMDANT results cannot be taken as a proof that the results can be considered as sufficiently accurate primarily it only means that both results are affected by roughly the same uncertainty The dominant feature is that the discretization error although usually being sufficiently small is about the same in both solution algorithms Experimer ent Di ffusion A THOTRAN m TWODANT THOTRAN 8 THODANT r gt POSDIF on AWDD on POSDIF off AWDD off i AQ Al AZ AS S Figure 5 Predicted reactivity change by TWOTRAN and TWODANT module 65 11 2 SRA Static Reactor Analyses Parametric cases are set up to investigate the reactivity change due to the hypothetical one dimensional compaction in the core of a large scale LMFBR see Figure 6 In the compacted configuration an upper blanket region lies above the empty space produced by the compaction in the core This problem is a good example for demonstrating the superiority of the new neutronics version based on the TWODANT code because the former neutronics package in SIMMER II based on TWOTRAN initially failed to converge for the compacted configuration In order to describe the situation in more detail initially calculations performed with TWOTRAN didn t converge at all subsequent calculations performed at FZK INR did converge indeed mainly as a result of using
128. tant aspect that in 7 only X Y Z geometry was considered In addition the prescription for attributing the direction dependent weights to the individual mesh cells of the grid might have been established mainly for the purpose of shielding applications Therefore for the sake of a more smooth transition between DD and AWDD for criticality calculations in R Z geometry we decided to slightly revise the prescription for the radial weight This revision becomes most important close to the cylinder axis At these positions the adaptive weights for the horizontal direction termed px in MASWEPW are now fairly similar to those for X Y geometry This modification would have been negligible for the main original purpose of AWDD namely shielding applications But for whole core criticality calculations it leads to an increased similarity between the AWDD and the standard DD solution scheme However when a rather coarse grid was chosen and fairly pronounced flux gradients exist close to the axis of the cylinder e g due to the presence of a strong absorber the angular fluxes at the core center may become fairly unreliable in corresponding regions A smooth transition between the DD and the AWDD scheme as it was initially implemented using MASWEPW could at that time not be perfectly achieved in cylindrical geometry for two reasons 1 In the AWDD scheme a weighted in angle discretization is used whereas in the DD scheme the conventional linear relation
129. the SIMMER code is not sufficient although it is internally multiplied by the value of CP1 Transient analyses led to the recommendation to sharpen this criterion for reliable results as y represents a kind of eigenvalue especially if the default values for the other quasistatic criteria are taken from the manual Normally a value of EPSG 1 0 10 is recommended Another possibility is the general sharpening of the quasistatic criteria which may reduce error accumulation One may even consider to implement some correlation between the size of the time steps and the convergence criterion EPSG for the y iteration so that always the reliability of the ramp rate Ap At will be sufficient during the whole transient Application of POSDIF or AWDD scheme is not recommended a Traditionally according to LANL experience the POSDIF scheme has been recommended for transition phase analyses Though not stated explicitly the essential reason for this suggestion was probably the problem of instabilities with the FIXUP option during calculations Note that during the eighties computing power was much more limited and calculations using optimal mesh grids were nearly impossible to realize However it was always known that POSDIF was only of accuracy of first order whereas that one of the FIXUP option was of second order in flux accuracy b When implementing the extended TWODANT SOLVER module it was realized that the POSDIF s
130. the number NREG ITJT number of regions of meshes in the neutronics grid NZCL 0 not relevant for SIMMER TWODANT NCINTI IT number of neutronics meshes in R direction number of coarse meshes in the meaning of TWODANT NCINTJ JT number of neutronics meshes in Z direction number of coarse meshes in the meaning of TWODANT NCINTK I number of neutronics meshes in the third dimension set 1 for 2 dimensional problems NINTI IT number of neutronics meshes in R direction number of fine meshes in the meaning of TWODANT NINTJ JT number of neutronics meshes in Z direction number of fine meshes in the meaning of TWODANT NINTK 1 number of neutronics meshes in the third dimension set 1 for 2 dimensional problems Please note In accordance with the SIMMER treatment of preceding versions no flexibility regarding geometry and boundary conditions is allowed i e the application is currently restricted to RZ geometry and vacuum boundary conditions on all outside surfaces assuming reflective boundary conditions at the cylinder axis In subroutine LINKM the GEODST and the SOLINP files for the TWODANT SOLVER module are prepared based on these assumptions As a consequence simplified mathematical models having symmetry with respect to the core midplane have to be treated without taking advantage of that symmetry property IMB1 first boundary condition in R direction means reflective boundary condition IMB2 2 last boundary cond
131. tine TWODANT jobnam is used to provide the user s identification of the current calculation and to store it for registration in the output protocol and in all VISART files jobnam c in its RS6000 version is also given in the Appendix macnam is used to provide the name and classification of the computer of the current run and to store it for registration in the output protocol and in all VISART files macnam c in its RS6000 version is also given in the Appendix scopy is a utility program to be called by jobnam and macnam scopy c in its RS6000 version is also given in the Appendix Because of different array handling or allocation in SIMMER and TWODANT respectively the dimensions of several data arrays dependent on the number of meshes in each direction the number of neutron energy groups or the Sy order etc specified in the PARAMETER statements have to match exactly those of the values given in the input stream of the current run If the values in the PARAMETER statements do not agree precisely with those given in the actual run arrays may overlap In cases like that the calculated results are completely meaningless or show the nonsense value NaNQ As a consequence for each calculational model that differs at least in one value from those figures specified in the PARAMETER statements of actually used executables a new executable has to be compiled whose dimensions match exactly the respective values given in the input s
132. tors calculated for individual configurations were converted into reactivity changes from the reference configuration AO and compared with experimental measurements in Figure 5 The predicted reactivity change agreed fairly well with the experiments with deviations in C E of less than 20 The TWODANT module is judged to be implemented into SIMMER IN correctly since the results of SIMMER using TWOTRAN and TWODANT modules agree almost completely as shown in this Figure The effect of negative flux fixing up on the relative reactivity change seems to be negligible in this case although the maximum percentage of the fixing up operation in the AWDD OFF case was around 20 64 For TWODANT the same calculational model was used as was originally specified for TWOTRAN For these restricted investigations no refinement of the calculational model such as increasing the Sn order or reducing the mesh sizes was considered Cautious remark 15 10 10 The fairly good agreement between the POSDIF ON and POSDIF OFF FIXUP ON results although being rather satisfactory does not necessarily mean that for that reason both results can be considered as reasonably reliable This conclusion would only be justified if a either the inspection of the fixup tables gives no indication of significant fixup percentages for important regions of the energy space phase space or b a refinement of the spatial and angular mesh grid confirmes the results ob
133. tory The names of the separate files are of the type name f where name are the names of the subroutines or functions siminst was established at the FZK Computer Center by Manfred Alef mainly to transfer large programs or program packages between different computer installations Comments and hints are given in German in this program unit Name Aufruf usr local fzk basis bin proginst Dateil Datei2 Zweck Installation eines FORTRAN Programmpakets auf einem UNIX System Es werden folgende Schritte ausgefiihrt etwaige Zeilennummern in den Spalten 73 80 werden entfernt sofern am Zeilenende Leerzeichen stehen werden auch diese entfernt jede Programmeinheit wird in eine eigene Datei geschrieben welche in der Form xxxxxx f benannt wird wobei xxxxxx im allgemeinen der Name der Programmeinheit ist Programmpakets verwendet werden kann Argumente Beim Aufruf k nnen die z B vom MVS System iibertragenen FORTRAN Quell programme aufgez hlt werden Alternativ kann proginst ohne Argumente aufgerufen werden In diesem Fall wird im aktuellen Directory nach Quellprogrammdateien gesucht dabei wird jede Datei akzeptiert deren letzte Zeile die Form END oder end hat Hauptprogramme miissen eine PROGRAM Anweisung enthalten Portabilitat Ein wesentlicher Bestandteil dieser Prozedur ist der fsplit Befehl Leider unterscheidet sich dieser Befehl sehr stark zwischen den ver
134. tream The correspondence of the values is shown in the following table input value dimension in the code explanation IB IBM number of radial fluid dynamics mesh cells JB JBM number of axial fluid dynamics mesh cells IGM NEIGM number of neutron energy groups IT NEI total number of neutronics radial mesh cells JT NEN total number of neutronics axial mesh cells IGD NEIGD number of delayed neutron precursor groups ISNT NEISN Sn order 57 The adjustment has to be performed as part of the HISTORIAN input file in the following way IDENT MYDIM D DIMEN 3 IBM IB JBM JB D NDIMEN 5 NEI IT NEJ JT D NDIMEN 6 NEIGM IGM NEIGD IGD NEISN ISNT NEINV 16 NERXS 6 The indented lines are parts of PARAMETER statements in COMMON DECKs which overwrite the original statements in the code thus adjusting the DIMENSIONS in the SIMMER code Therefore 5 blanks have to be written in order to place the sign into column 6 IB JB IT JT IGM and IGD have to be the same integer constants as given in the SIMMER input stream For NEISN the absolute value of ISNT is to be set Some values are used in the SIMMER code as maximum values for dimensioning several data arrays for example MNMS 5000 or MNIMS 2000 as default values The exact values are calculated code internally summarizing the lengths of a lot of data arrays For the calculations of big runs these dimensions may be too small and will have to be enlarge
135. treatment of the delayed neutrons and their precursors and the quasistatic solution method as well In the quasistatic approach an external source problem is treated as a pseudo eigenvalue problem using the so called y iteration approach as successfully demonstrated in the SIMTRAN version of SIMMER M The standard TWODANT SOLVER module only allows to deal with standard eigenvalue and standard source problems The conversion of a source problem to a pseudo eigenvalue problem via y iteration was a new feature that had to be implemented in the TWODANT subroutines in a very careful manner The associated modifications were fairly complicated due to the new favourable features of TWODANT namely the Diffusion Synthetic Acceleration scheme which considerably improves the convergence performance of the iterative solution process In SIMTRAN the usually small influence of the time derivative of the flux shape function d P dt is taken into account in an approximative manner e only the space dependent scalar flux is considered i e the angular dependence is neglected e the time derivative of the scalar flux d dt is dealt with approximately during the rebalancing procedure In the new version on the basis of SIMDANT an approximate treatment is still considered to be sufficient Some improvements of the quasistatic method can be expected by approximately applying the time derivative of the angular dependent flux shape function Y instead of the sca
136. ular construction of the DANTSYS code system package 1 which was developed by the Los Alamos National Laboratory Los Alamos New Mexico USA This modular construction separates the input processing including group constant preparation the solution of the transport equation and the postprocessing or edit function into distinct independently executable code modules the INPUT SOLVER and EDIT modules respectively These modules are connected to each other solely by means of binary interface files see Figure 1 In addition interface files in ASCH format are used as problem input and cross section files and provided for the EDIT module as output files GEODST N SOLINP ADIMAC ASGMAT MACRNS Figure 1 General program and data flow in TWODANT Considering this modular construction of the TWODANT code it turns out to be sufficient to replace in SIMMER the TWOTRAN like program package essentially by the SOLVER part of TWODANT This is also advisable because a special process for the preparation of macroscopic group constants is included in SIMMER making use of results coming from the SIMMER hydrodynamics part for example number densities and temperatures for the different reactor zones All necessary information can then be provided on the binary interface files and in specific COMMON areas The general program flow and data transfer of the newly developed code SIMDANT is represented in Figure 2 The linking module called LI
137. ule relevant information which is necessary for controlling the program flow is read from interface file SOLINP Additionally introduced error checks assure the validity of some specific input data which were collected in subroutine LINKM from SIMMER own data areas Other additional error checks have been introduced in subroutine TOUTER in order to assure the correct use of the TWODANT SOLVER module for SIMMER applications In cases of errors or inconsistencies the run is stopped and some relevant information is given in the output protocol The user is requested to check the consistency of the input data and to start SIMMER again after having corrected the errors Affected routines RDSOL TOUTER The negative flux fixup monitor is printed in subroutine PRTNFX The flux monitor gives the percentage of possible negative flux fixups in each neutronics mesh The fixups are counted on each fine mesh cell face and accumulated and printed as neutronics mesh quantities Thus if there should be more than 50 fixups according to general experience the quality of the pointwise flux in the neutronics mesh is suspect If based upon the importance of an accurate solution for that group and coarse mesh the user wishes to increase the accuracy it is recommended that the neutronics mesh cell size be reduced Whether refinement should be in the R or Z directions can be assessed by which faces have shown the excessive fixups A lot of complementations to the or
138. used in the subroutines of Table 1 and Table 2 These COMDECKs are ALITLE AVGNUM BCDUNT BDNAME BDTYPE BSNAME BSTYPE BULLSH CHEBYDS CM CMBDCK CMMESH CMTRANS COMECS COMEK COMINP DIMENT DOTRANC EDLCM EDSTR ERRORS FACESC FIVEDS FIVEMSD FMIXC FOURDS GCHECKS GCOUNTS GDSTIO GEONAM GEONAMD GMSIZE GOMODS HALFDS HED HIDDEN HILITE IA IBMPCX IBMSTF INARRY INSTAL IPSPEC ISPC ISPCEQ JDSPEC L500 LENLPEN LNCONS LNSINP LNSTAL LOCAL LODFLG LONERR LONGHL LSCRAT MISC MVLCK NCSIZE NCSZ80 NCSZCX NCSZFN NDIM1 NWPASS OBJECTS OIAE OIAEEQ OIAI OIAIEQ OIAIN ONEDS ONEM10D ONEM18D ONEM2DS ONEM3DS ONEM4DS ONEMSDS ONEM6DS ONEM8DS ONEM9DS ONEP20D ONEP2DS ONEP4DS ONEP9DS PARAMT PIDS PNTRII PNTRI12 PNTR13 PNTR14 PNTRI18 PNTR19 POST31 POWER PRESIZN PRNTIDO REAIA RESOL RMDM RUSS SAD2SV SAVMON SCOMPS SCRATMO SEEKGEN SHORTU SHSTRY SOLIND SOLINR SPECEQ SPECXS SQRT3DS STACK STGDAT STKFCK STKNER STKSTO SYSBET SYSTM THREEDS THSTRY TIA TIAN TINY TRANSI TRANST TWOMIDS UNDWR UNTAP VECT VRDATE VSCONS XBIG XLITLE XSDECK XTRAS ZERODS MISC1 ANG CNFIX Table 3 COMDECKs of the TWODANT SOLVER module 11 Concerning the unit reference numbers a change was necessary In SIMMER II the SIMBF file is written by using the unit reference number 10 This unit reference number is used in TWODANT as well Because of the complicated file handling in TWODANT the unit reference number of the SIMBF file in SIMMER was changed to BFU 77 By assembling the subroutines and functions of Table 1 and
139. uxes at the mesh edges or surfaces In fact in a test case such negative values were really detected when using the TWOTRAN based SIMMER III version 2d and adding the corresponding diagnostic features Considering that the angular fluxes are used for determining the mesh leakages and subsequently the reactivity even the application of such an improved discretization scheme casts some slight doubts concerning the reliability of such a method for some exceptional cases Unfortunately the user was not notified in the past about the occurrence of such a situation presumably because there was no easy way to avoid it when using the former SIMMER versions C Adaptive Weighted Diamond Differencing AWDD Fortunately there was an option available in the TWODANT SOLVER too that allowed the application of the AWDD method in R Z geometry 7 indicates the basic features for XYZ geometry This option can be applied too in the current version of SIMMER by specifying the associated TWODANT input data WDAMP see chapter 14 Appendix A Short description of the AWDD scheme The application of this option as an alternative to the standard solution scheme with fixups i e setting negative fluxes to zero and recalculating the other values is appreciably facilitated by the existence of the fixup tables obtained for IGM lt 0 which indicate the percentages of negative flux fixups in each energy group and for each coarse mesh when using the standard
140. vating different directives Alterations extensions and additional directives are introduced into the code dependent on the HISTORIAN input file HINP and on those directives already being included in the SIMMER program library The basis for all management operations with HISTORIAN is the master file for the actual version of SIMMER called OLDLIB containing all subroutines functions and COMMON areas that belong to the code as HISTORIAN DECK For the generation of new SIMMER executables including the TWODANT SOLVER module the actual starting point as master file is SIMMER II in its version 2e as distributed by JNC on June 1998 Since January 1999 this master file is replaced by version 2f distributed by JNC This master file may be completed by a number of correction sets in order to correct detected errors or to extend the SIMMER code by new program options HISTORIAN is called as a preprocessor in order to introduce all modifications to the master file given in the input data set HINP and to define options either in the master file itself or also contained in the input file HINP As a result HISTORIAN can produce a Fortran source file named COMPILE These different tasks attaching the master file to the actual directory causing HISTORIAN to introduce properly all alterations into the master file determining the actual date and time to mark the new version of the executable are carried out in a shellscript named histor The actual versio
141. vity increment for the initial flux shape time step is less than the absolute value of reactivity residual or if the absolute value of the reactivity increment is less than the convergence accuracy or comparable to the computer accuracy Affected routines PKDRIV POWCAL The TWODANT SOLVER module needs the macroscopic absorption cross sections ABS to be included into the principal neutronics data for the determination of the meshwise neutron balance Therefore the COMMON CELXS used to store the macroscopic cross sections has been extended by the data area CELABS NEI J NEIGM for storing the absorption cross sections for all meshes of the neutronics grid and for all energy groups The macroscopic self shielded absorption cross sections are calculated in an extension of subroutine SHLDXS and its associated subroutine CALCXS dependent on the fact whether the macroscopic cross sections have to be calculated for isotopes or materials analogously to the macroscopic self shielded fission and capture cross sections according to CELABS I J GRP 2 DENISO I J M VF XSISOcap M GRP FFISO apt I J M XSISOg M GRP FFISOs 1 J M where DENISO J M is the number density of isotope M in mesh I J VF is a factor for the approximate treatment of heterogeneity effects for thermal neutron reactors In case of fast neutron reactors VF 1 XISO a M GRP are the microscopic capture and fission cross sections XISOf M GRP respectively
142. will be almost equivalent Therefore only one possible way for a suitable choice will be mentioned in the following Users have to gain their own experience and should have in mind that the appropriate choice may be case dependent and up to now needs empirism and intuition However the following suggestions might be helpful for beginners and less experienced users It is recommended that the user verifies on the basis of the fixup tables whether the indicated negative flux fixups affect important nodes of the reactor layout or only nodes not belonging to the core region The percentage of negative flux fixups is counted coarse mesh wise as follows having in mind that the number of coarse meshes is equal to the number of fine meshes in the neutronics grid in the extended TWODANT SOLVER module for SIMMER applications The negative flux fixups for all affected angular directions on the four boundaries are added for each fine mesh and summed up over all fine meshes belonging to a coarse mesh The result is divided by the total number of all possible angular directions in the coarse mesh under consideration According to their fairly peripheral position those off core nodes may have no significant influence on the neutronic behaviour of the reactor In order to facilitate the user s judgement of the importance of the affected nodes the map of reactivity contributions shows the relative contribution of each node to the total reactivity Those users i
143. ystem VISART in use at FZK for several years Affected routines GRIND LINKM PKDRIV PRINFX TIMSTP WPPN WPPNK As described in more detail in chapter 7 2 the time derivative of the scalar flux d dt is replaced by the corresponding time derivative of the angular flux d P dt Therefore in subroutine PKDRIV the associated time derivatives d dt are treated in a completely analogous manner for extrapolations and interpolations in time as that had been previously applied to d dt Subroutine EXTRAP has to be called in subroutine PKDRIV not only to extrapolate and interpolate the scalar fluxes to the current time of the accident analysis but also the horizontal and vertical angular fluxes respectively At the end of the procedure the previous values of the angular fluxes have to be replaced by the actual ones As a consequence of using the time derivatives calculated from angular fluxes in subroutine POWCAL additionally to the scalar fluxes the angular fluxes have to be power normalized too After power normalization the actual angular fluxes are transferred into the storage location for the previous angular fluxes c 38 In subroutine PKDRIV warnings are printed on the ordinary output file SIMO6 and if requested by the user additionally on the special output file OUTDI for important messages if no reliable ramp rate could be expected in the actual calculations This may be possible in cases where the absolute value of the initial reacti

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