RAD H2O Manual (Old Aerator) 2012-05-11
Contents
1. E P E D EE D D HG erst RCE Ma AA RAA RA RS Da a Frit eee 8 2 k ry k gt gs a About 1 2 Aerator Fig 3 Schematic The components as shown automatically perform everything required to determine the radon concentration in the water 1 4 Running a Test purged for some time It is convenient to use the larger laboratory drying unit during the initial These are brief simple instructions just to gain an tu to save the small drying tubes for initial introduction to the technique more thorough measurement treatment foll later in th 1 ee mo Hook up the laboratory drying unit to the RAD7 inlet with the inlet filter in place see RAD7 manual Purge the unit with fresh dry air for ten minutes 1 4 1 Preparing the RAD7 After 10 minutes of purging with dry air push the Before making a measurement the RAD7 must be menu button push ENTER twice to go into the free of radon and dry To achieve this it should be 8 2012 DURRIDGE Company Inc GETTING STARTED status window and push the right arrow button twice to see the relative humidity If it is not yet down close to 6 start purging some more To conserve desiccant after the first ten minutes or so you may connect the RAD7 outlet to the2. 4 DURRIDGE RADON INSTRUMENTATION RAD H20 User Manual Radon in Water Accessory DURRIDGE Company Inc 524 Boston Rd Billerica MA 01821 Tel 978 667 9556 Fax 978 667 9557 service durridge com www durridge com 2012 DURRIDGE Company INTRODUCTION The RAD H20 is an accessory to the RAD7 that enables you to measure radon in water over a concentration range of from less than 10 pCi L to greater than 400 000 pCi L The lower limit of detection is less than 10 pCi L By diluting your sample or by waiting for sample decay you can extend the method s upper range to any concentration The equipment is portable and battery operated and the measurement is fast You can have an accurate reading of radon in water within an hour of taking the sample The RAD H20 gives results after 30 minutes analysis with a sensitivity that matches or exceeds that of liquid scintillation methods The method is simple and straightforward There are no harmful chemicals to use Once the procedure becomes familiar and well understood it will produce accurate results with minimal effort It is assumed that the user has a good working knowledge of the RAD7 If both the RAD7 and the RAD H20 are new to the user then time should be spent learning how to make good measurements of radon in air with the RAD7 before embarking on radon in water measurements Instructions for RAD7 operation with the RAD H20 are given in this manual but for more detail about the
3. correction factor DCF is given by the formula DCF exp T 132 4 where T is the decay time in hours You will notice that decay times of under 3 hours require very small corrections so you can ordinarily neglect the decay correction for samples counted quickly To correct your result back to the sampling time multiply it by the decay correction factor DCF from the chart figure 6 opposite 4 3 Dilution Correction If you intend to count samples that have very high radon concentrations you may wish to dilute the sample by a fixed ratio then correct the result back to its undiluted concentration Example You take a 4 mL sample and dilute it with 36 mL of distilled water in a 40 mL sample vial Overall this would be a 10 1 ratio of final volume to initial volume so you must multiply the result by 10 to correct for the dilution If the RAD H20 reports a result of 9 500 pCi L for the 10 1 diluted sample then the original concentration must have been 10 X 9 500 or 95 000 pCi L Great care must be taken in this process to avoid loss of radon from the sample The syringe should be filled and refilled several times from under water that is a true sample see method 2 in section 1 The 40 ml vial should contain 36 ml of radon free water 4 ml of the undiluted sample should be injected slowly at the bottom of the vial and the vial quickly capped Any air bubble should be very small 4 RESULTS Hours DCF Hours DCF Hours DCF Hour
4. 3 249 157 3 273 158 3 298 159 3 323 160 3 348 161 3 374 162 3 399 163 3 425 164 3451 165 3 477 166 3 504 167 3 530 168 3 557 169 3 584 170 3 611 171 3 638 172 3 666 173 3 694 174 3 722 175 3 750 176 3 778 177 3 807 178 3 836 179 3 865 180 3 894 181 3 924 182 3 954 183 3 984 184 4 014 185 4 044 186 4 075 187 4 106 188 4 137 189 4 168 190 4 200 191 4 232 192 4 264 193 4 296 194 4 329 195 4 361 196 4 395 197 4 428 198 4 461 199 4 495 200 4 529 201 4 564 202 4 598 203 4 633 204 4 668 205 4 704 206 4 739 207 4 775 208 4 811 209 4 848 210 4 885 211 4 922 212 4 959 213 4 997 214 5 035 215 5 073 216 5 111 217 5 150 218 5 189 219 5 228 220 5 268 221 5 308 222 5 348 223 5 389 224 5 429 225 5471 226 5 512 227 5 554 228 5 596 229 5 638 230 5 681 231 5 724 232 5 768 233 5 811 234 5 855 235 5 900 236 5 945 237 5 990 238 6 035 239 6 081 Fig 6 Decay Correction Factors 2012 DURRIDGE Company Inc 19 5 ACCURACY AND QUALITY CONTROL 5 ACCURACY AND QUALITY CONTROL 5 1 Calibration of System The RAD H20 method relies on a fixed volume closed loop extraction of radon from water to air Since the volumes are constant and the physical properties of radon are constant we do not anticipate a need to routinely adjust the conversion coefficient The only factors we anticipate will require calibration checks are sampling and laboratory technique and the RAD7 unit In sample handling you can lose a significant fraction of the radon if you do not follow c
5. aerator tube on the side opposite to the check valve The teflon coupler and special vial cap normally stay attached to the aerator If they have been removed please replace them Leave the glass frit in the case Stainless Steel Aerator Teflon Coupler re Special Cap Teflon Spacer Glass Frit Fig 4 Aerator assembly 2012 DURRIDGE Company Inc 9 1 GETTING STARTED until the last moment With the 10 25cm of large ID vinyl tubing connect the output of the aerator without a check valve to a small drying tube If one end of the drying tube is pink connect the aerator output to this end Connect the other end of the drying tube with 1 8 ID tubing to an inlet filter mounted on the RAD7 inlet The 5 16 to 1 8 adapter makes this connection easy and secure Connect the RAD7 outlet also with 1 8 ID tubing adapted up to 3 16 to the check valve on the aerator See figures 1 3 amp 4 With the system as connected so far set the RAD7 to purge for another few minutes While it is purging clamp the small drying tube on the retort stand thus supporting it vertically about 16 41cm above the table top Stop purging On go to Setup Protocol Wat 40 or Wat250 depending on which size of vial is being used and push ENTER It is essential that the correct protocol be entered here because this controls the pumping and counting cycle and the calculation according to the size o
6. and Potential Radiation Hazards Journal NEWWA 234 248 December 1989 Rydell S and B Keene CARBDOSE computer program for IBM PC U S EPA Region 1 Boston MA 1991 U S EPA Eastern Environmental Radiation Facility Radon in Water Sampling Program EPA EERF Manual 78 1 1978 U S EPA Office of Drinking Water Reducing Your Exposure to Radon 570 9 91 600 June 1991 U S EPA Office of Drinking Water Radionuclides in Drinking Water Factsheet 570 9 91 700 June 1991 Vitz Toward a Standard Method for Determining Waterborne Radon Health Physics 60 6 817 829 June 1991 Weigel F Radon Chemiker Zeitung 102 287 1978 Whittaker E L J D Akridge and J Giovino Two Test Procedures for Radon in Drinking Water Interlaboratory Collaborative Study U S EPA EMSL EPA 600 2 87 082 March 1989 2012 DURRIDGE Company Inc 29
7. of lung cancer due to inhaled radon decay products has been well documented through the study of underground mine workers The cancer risk due to ingestion primarily cancer of the stomach and digestive organs has been estimated from studies of the movement of radon through the gastrointestinal tract and bloodstream Radon has not been linked to any disease other than cancer The cancer risk from the inhalation pathway probably far exceeds that from the ingestion pathway Crawford Brown Federal Register In a typical house with typical water usage patterns a waterborne radon concentration of 10 000 pCi L will yield an average increase to indoor air concentrations of about 1 pCi L The 10 000 1 ratio while not to be considered a hard rule has been verified through theoretical models and empirical evidence Hess In a house with a high radon in water content air radon concentrations tend to rise dramatically with water usage especially in the vicinity of the water using appliance but decline steadily after the water usage tails off Henschel In most houses waterborne radon is a secondary source of indoor radon far exceeded by soil gas infiltration It is an exception though not a rare one that waterborne radon is the major contributor to elevated radon in air A homeowner who has 2 BACKGROUND discovered elevated air concentrations and whose house uses private well water should test the water for radon content to assess t
8. the RAD7 When the relative humidity is down once more the pump must be set back to GRAB 5 2 5 Temperature The temperature effect on accuracy is very small with the 40 mL sample vial but may begin to become noticeable with the 250 mL vial at very low or high temperatures The RAD H20 system has been calibrated for a sample analysis temperature of 5 ACCURACY AND QUALITY CONTROL 20 degrees C 68 degrees F At colder temperatures the water holds back a little more of the radon during the aeration process and at warmer temperatures the water gives up the radon more readily The maximum temperature effect at equilibrium for the 40 mL sample is about 1 over the range of 0 to 40 degrees C 32 to 104 degrees F The maximum temperature effect at equilibrium for the 250 mL sample is about 6 over the same range 5 2 6 Relative Humidity If the RAD7 is thoroughly dried out before use the relative humidity inside the instrument will stay below 10 for the entire 30 minutes of the measurement If not then the humidity will rise during the 25 minutes that the RAD7 is counting and the pump is stopped and may rise above 10 before the end of the measurement period High humidity reduces the efficiency of collection of the polonium 218 atoms formed when radon decays inside the chamber At around 60 humidity the collection efficiency may be only half that at 10 relative humidity or below However the 3 05 minute half life
9. to residual 218 Po on the alpha detector surface This will halve every 3 minutes until it approaches equilibrium with the radon concentration in the air in the measurement chamber The residual A window count rate must be much less than the value it reaches during a sample measurement After utilizing SNIFF mode to monitor the humidity and A window count rate before and between sample measurements please remember to put the RAD7 back into WAT 40 or WAT250 mode for the actual water measurement If a water measurement is started with the RAD7 still in SNIFF mode and the error noticed within the first few minutes the measurement can be stopped Test Clear the protocol changed to the correct one and the test restarted without fear of introducing error 6 5 Foaming While clean water causes no problem some natural waters contain foaming agents that will cause bubbles to rise up out of the aerator With the current RAD H20 setup a piece of 5 16 ID tubing extends up from the aerator to the small tube of desiccant held vertically in the retort stand This arrangement makes it difficult for bubbles to rise up as far as the desiccant and reduces the concern about foaming 2012 DURRIDGE Company Inc 23 6 CARE MAINTENANCE and TROUBLE SHOOTING If the water is so contaminated that the foam can climb the 5 16 tubing an empty small desiccant tube can be substituted for the tubing with short pieces used just to make the connecti
10. water measurement The pump will in any case stop after 5 minutes which is long enough to aerate the sample The final reading will be the same as for standard protocol except that it will be more precise So no multiplying factor is required Apart from it taking longer to finish the analysis the only issue is humidity which will have more time to build up to unacceptable levels A solution is to run the pump for short periods during the analysis so circulating dry air through the RAD7 and bringing down the humidity Setup pump on ENTER and Setup pump off ENTER A problem with this though is that it aerates the sample and delivers more water molecules to the desiccant so depleting it To be able to circulate sample air through the desiccant and through the RAD7 without aerating the water sample any further a bypass may be made for the air flow to bypass the aerator A valve in this bypass must be turned off during the first five minutes while the water sample is being aerated It may be opened for later circulation of the air round the loop to keep RAD7 dry It would be possible to use an entirely different protocol from WAT 40 or 250 In that case with say SNIFF protocol and 10 minute cycle times the pump will run for five minutes at the beginning of every cycle After the first cycle the by pass valve may be opened to prevent further aeration of the sample 26 2012 DURRIDGE Company Inc To determine t
11. 2012 DURRIDGE Company Inc is that of the water and is calculated automatically by the RAD7 All data except the spectrum is also stored in memory and may be printed or downloaded to a PC at any time 1 4 5 Finishing the Test Unscrew the cap raise the glass frit out of the water and set the RAD7 to purge This will blow water out of the frit and also introduce fresh air into the tubing If no more tests are to be analyzed the equipment may now be replaced in the case If there is another sample for analysis keep the RAD7 connected as above and purging for at least two minutes The laboratory drying unit may then be substituted for the small drying tube Continue the purge for another ten minutes Check the relative humidity as above and continue the purge until the relative humidity indication in the instrument drops to 6 or below After six or seven minutes the RAD7 air outlet may be connected to the input of the drying unit to form a closed loop to conserve desiccant When the relative humidity is down to 6 or less another test may be conducted Repeat from 1 4 1 above 1 4 6 Interpreting the results The printout will appear something like figure 5 below There are two grab sample advisory statements four five minute cycles and a test summary The summary shows the RAD7 run number the date and time of the measurement the serial number of the instrument the number of cycles in the test the average value
12. Calibration of System 5 2 Accuracy and Precision 5 2 1 Sampling Technique 5 2 2 Sample Concentration 5 2 3 Sample Size 5 2 4 Counting Time 5 2 5 Temperature 5 2 6 Relative Humidity 5 2 7 Background Effects 5 3 Comparison of RAD H20 with Other Methods 5 4 Quality Assurance Fig 7 Method Comparison 6 CARE MAINTENANCE and TROUBLE SHOOTING 6 1 Warning on Pump Direction 6 2 Warning on Tipping the Aeration Unit 6 3 Frit Maintenance 6 4 High Humidity 6 5 Foaming 6 6 Technical Support 7 DEVIANT SETUPS 7 1 Passive DRYSTIK 7 2 Large Drying Unit 7 3 Oversized Dome 7 4 Extended Cycle Time and Cycle Count 7 5 Active DRYSTIK 7 6 Large Aerator REFERENCES 4 2012 DURRIDGE Company Inc 22 20 20 20 20 20 20 20 20 21 21 21 21 23 23 23 23 23 23 24 25 25 25 26 26 26 26 28 1 GETTING STARTED 1 GETTING STARTED 1 1 Unpacking First make sure you have everything you are supposed to have Examine the case contents and verify that you have all the items shown below If anything is missing please call DURRIDGE immediately at 978 667 9556 or email sales durridge com Case 6 250 ml collection vials with septum caps 12 40 ml collection vials with septum caps Aerator assembly including Stainless Steel Aerator Teflon Coupler Modified Vial Cap 40 ml Vial Teflon Spacer Glass Frit Short Vinyl Tubing Check Valve Faucet Adapter Tube of Activated Charcoal 4 Tubes of Drierite 2
13. Inlet Filters Spare Modified Vial Cap Spare Glass Frit Long Teflon Spacer for 250 ml vials Vinyl tubing 3 pieces Retort Stand and Clamp 1 2 General Safety Instructions There is nothing particularly hazardous to the user in the RAD H20 but care should be taken to make sure that water never enters the RAD7 The check valve attached to the aerator should never be removed as it protects the RAD7 in the event that the tube connections to the instrument are reversed 2012 DURRIDGE Company Inc 5 1 GETTING STARTED 1 3 Taking a Look Fig 1 Aerating a 250 water sample The setup consists of three components the on the left the water vial with aerator in the case near the front and the tube of desiccant supported by the retort stand above The case provides a convenient stand for the vial in the foam cavity 6 2012 DURRIDGE Company Inc 1 GETTING STARTED Fig 2 Aeration in progress During the five minutes of aeration more than 95 of the available radon is removed from the water 2012 DURRIDGE Company Inc 7 1 GETTING STARTED RAD H20 Schematic Check Valve Tube Stainless re ras erator RES ot Ra al ge Teflon Union qe SANNA ASA SANNNAASNANANAABANARI AREAN ANANN SAANANE EE EVE ANS ER re Pe A RS l ANI RRA P po Roh RERA 40 ml Viat RNI RA _ LAN ESA i ae a Aaa A PA a A
14. S Gamma spectroscopy seeks to detect the gamma rays given off by radon s decay products from a closed container of radon bearing water While simple in concept this method lacks the sensitivity to detect radon at the lower levels now considered important The Lucas Cell method has been in use for decades for laboratory analysis of radon 222 and radium 226 via radon emanation The LC method tends to be somewhat labor intensive using a complicated system of glassware and a vacuum pump to evacuate a Lucas scintillation cell then bubble gas through the water sample until the cell fills The cell is then counted by the usual technique In the hands of a skilled technician this method can produce accurate repeatable measurements at fairly low concentrations Whittaker Krieger Method 903 1 The Liquid Scintillation method dates to the 1970s A liquid scintillation cocktail is added to the sample in a 25 mL glass LS vial The cocktail draws the radon out of the water so that when it decays the alpha particles scintillate the cocktail The method uses standard LS counters which are highly automated and can count several hundred samples in sequence without intervention The EPA has determined that the LS method is as accurate and sensitive as the LC method but less labor intensive 2012 DURRIDGE Company Inc 13 2 BACKGROUND and less expensive Prichard Whittaker Hahn Method 913 0 Lowry Vitz Kinner Hess In compa
15. The radon present in the purge air will add unwanted background to the next measurement For example a purge air radon concentration of 4 pCi L will give about 4 x 25 or 100 pCi L additional radon concentration to the next water result 40 mL water sample This is too much background to neglect when measuring samples below 1 000 pCi L but if you are measuring only water samples above 1 000 pCi L you may consider this amount of error to be 2012 DURRIDGE Company Inc 15 3 RAD H20 TECHNIQUE acceptable To reduce the error due to purge air radon you may either subtract off the background from every measurement or adopt strategies to reduce the background to acceptable levels In any case for levels below 1 000 pCi L you should preferably use 250 ml vials when ambient air of 4 pCi L will give only 20 pCi L additional radon concentration to the next water result The best way to determine the background is to measure a blank a water sample containing no radon To get radon free water purchase distilled water from your local pharmacy or fill a container with tap water and allow the container to stand closed and undisturbed for 4 weeks or more The 4 week period allows any radon present in the water to decay away Store your radon free water in a closed air tight container Remember that the background due to purge air radon will change when the air radon concentration changes so if you intend to subtract background you shoul
16. assurance plan The elements of a quality assurance plan include blank samples duplicate samples and spiked samples Often the plan provides for blind samples to be measured in an inter comparison program If a quality control measurement deviates beyond the acceptable range the operator must cease to make measurements until the cause of the deviation has 2012 DURRIDGE Company Inc 21 5 ACCURACY AND QUALITY CONTROL been discovered and corrected Therefore the quality complete records of the quality control assurance plan should specify the range of acceptable measurements and their deviations measurement deviations often in the form of a control chart The operator should maintain Method Sample size ml Sensitivity cpm pCi L Background cpm 2 sigma error at 300 pCi L in pCi L 20 minute count 60 minute count 2 sigma error at 100 pCi L in pCi L 20 minute count 60 minute count RAD H O RAD H 0 Liquid Lucas Cell Scintillation 40 250 10 10 0 008 0 05 0 09 0 05 0 1 0 1 15 0 25 88 35 32 35 51 20 19 20 53 20 24 20 31 12 14 12 DL using 2 1 sqr 1 2 B in pCi L defined in NPDWR 40 CFR 41 25 20 minute count 60 minute count 300 minute count LLD using C 4 1 sqr B in pCi L following Altshuler 20 minute count 60 minute count 300 minute count 40 6 28 9 19 3 16 4 Ve 1 7 2 60 10 41 13 29 5 23 6 11 2 10 3 The RAD H 0 can do even better than th
17. aughter activity that can affect the next measurement After the high radon sample has been purged from the system its decay products stay behind until they decay away The polonium 218 isotope decays with a 3 minute half life In the 30 minutes following the purge the polonium 218 decays to about a thousandth of its original activity That still leaves a background of 100 pCi L after a 100 000 pCi L sample In addition to polonium 218 the RAD7 is sensitive to polonium 214 which can give counts for several hours after the radon has been removed The RAD7 uses alpha energy discrimination to reject polonium 214 counts from a measurement but a very small percentage of the polonium 214 decays slip past the discriminator This can add background to a measurement that follows a high radon sample The solution to the problem of daughter activity is time Simply wait for the activity to decay away Check the background with a blank sample If it is still too high keep waiting and keep checking The length of time you will wait depends on just how much radon your high radon sample had and just 3 RAD H20 TECHNIQUE how much background you are willing to tolerate before the next measurement If you expect the next sample to be high also you may want to go ahead with the next measurement right away considering a small amount of background acceptable In the case of extremely high radon samples you may develop a background that is more pe
18. creased difficulty in collecting the sample c the need for calibration of the setup and d significant temperature dependence of the sensitivity For a given air volume increasing the water volume gives reducing returns as the water volume gets bigger For a system with a laboratory drying unit and RAD7 the air volume is about 2 litre For such a setup there is little to be gained by having a water sample bigger than around 6 litre Aquarium aerator stones may be used to aerate the sample An array of them at the bottom of the flask containing the sample would be good 7 DEVIANT SETUPS Care must be taken to ensure that the water sample being analyzed has not lost any of its radon by exposure to air before it is placed in the loop It should be filled and sealed entirely under water If valves are placed in the inlet and outlet connections to the sample flask they should be kept closed at all times except when aeration is actually taking place It will take longer than 5 minutes to aerate the sample With the system connected put the RAD7 in SNIFF mode Start a measurement See how many 5 minute cycles it takes for the reading to reach close to the equilibrium value Subtract one cycle for the RAD7 response time multiply the resulting number by five and you have how many minutes it takes to aerate the sample in a flask of that size You can complete the measurement with the RAD7 in SNIFF protocol using five minute cycles if y
19. d measure a blank sample at every measurement session An alternative method to determine background is to make a measurement of the air in sniff mode and note the count rate in window A after 15 minutes From a previous printout of a water measurement with the format set to medium or long you can see the count rate in window A corresponding to the water radon concentration measured Typically for a 250 ml vial 1 000 pCi L in the water will generate about 50 cpm in window A A background count rate of 0 5 cpm in window A equivalent to about 2 pCi Lin air will then produce an error of 1 in the final reading The obvious way to reduce background is to purge with very low radon air Outdoor air rarely exceeds 0 5 pCi L at several feet above the ground so you can probably get the water background to below 13 pCi L by simply using outdoor air to purge To get even lower radon air fill a tank or balloon with outdoor air and let it age for several weeks If you are using compressed air or inert gas be very careful not to allow the RAD7 to pressurize as this may cause internal damage to the pump or seals Another method to reduce background is to use charcoal adsorption to clean the remaining radon from the system following the purge A small column containing 15 grams of activated carbon can remove up to 98 of the remaining radon from the RAD H20 system when connected in a closed loop This will reduce the system s radon to truly ne
20. e buildup of mineral deposits If the mineral buildup is light and low in radium content we see no reason for concern Heavy deposits may be removed from the frit by soaking it in a strong acid solution followed by a thorough rinse with clean water 6 4 High Humidity While the pump is stopped during the 25 minutes after aerating the sample water molecules will continue to desorb from internal surfaces If the relative humidity rises beyond 20 by the last counting cycle the result of the measurement will be low by more than 5 To prevent this from happening more time may need to be spent drying out the system with the laboratory drying unit in the sample path before the measurement After the initial purging of five minutes or more the humidity can be monitored by starting a SNIFF test Setup Protocol Sniff Enter Menu Enter Right arrow Enter and going to the third status window Menu Enter Enter Right arrow Right arrow The relative humidity is displayed in the upper right hand corner Watch the humidity as it comes down below 10 RH With experience you will learn just how long to keep the run going In any case the humidity must come down to 6 and you may find that 5 or lower is necessary At the same time as the humidity is coming down you can go to the fifth status window to observe the count rate in window A Provided that you have purged all the radon out of the system the window A count rate will be due
21. entration and lowers the water concentration At lower temperatures the distribution coefficient increases rising to 0 51 at 0 degrees C 32 F At higher temperatures the distribution coefficient decreases dropping to about 0 11 at 100 degrees C 212 F An empirical expression for the distribution coefficient of radon in water as a function of temperature can be found in Weigel 2 4 Radon as a Tracer for Groundwater movement Soil and rock typically contain significant concentrations of uranium and radium Radon is continually being created in the ground so that groundwater often has high radon content By contrast open water contains very little dissolved radium That together with the proximity of the water surface means that the background concentration of radon in sea and lake water far from land is very low Radon then with its 4 day half life is an almost perfect tracer for measuring and monitoring the movement of ground water into lake and sea water along the shore Lane Smith Burnett While open water monitoring often requires continuous fast response radon measurement at high sensitivity as provided by the RAD AQUA www durridge com for ground water in situ it is usually more convenient to use the RAD H20 2 5 Standard Methods for Radon in Water Analysis Several methods have been developed to measure radon in water Three of these are Gamma Spectroscopy GS Lucas Cell LC and Liquid Scintillation L
22. eviant setup to determine the average multiplying factor Corrections for sample decay over the period of the experiment should be applied At the end of each analysis a big proportion of the radon will be in the drying unit It is necessary to purge this out of the system before the start of the next reading To that end the drying unit and RAD7 must be purged for at least ten minutes after each measurement Please note that by increasing the air volume the sensitivity of the system is reduced With a large drying unit installed instead of the small drying tube the sensitivity is halved Thus the lower limit of detectability is doubled and the uncertainty of any reading is increased by SQR 2 or by a factor of 1 4 2012 DURRIDGE Company Inc 25 7 DEVIANT SETUPS 7 3 Oversized Dome Some RAD7s have high gain modifications installed one of which may be an oversized measurement chamber or dome This will increase the volume of the air loop For an otherwise standard setup the multiplying factor to compensate for the oversized dome is 1 2 If the large dome setup also uses the laboratory drying unit instead of the small drying tube the multiplying factor will be 1 68 7 4 Extended Cycle Time and Cycle Count After choosing the preset protocol WAT 40 or WAT250 depending on the size of vials used both the cycle time and cycle number Recycle may be increased to give more counts and hence higher sensitivity to the radon in
23. f sample vial Set the Format to short Place the printer on the RAD7 Make sure the printer has paper Switch on the printer Switch off the RAD7 then switch it on again It will print its identity and a review of the setup While the is printing the header insert the glass frit in the teflon spacer Remove the cap from the water sample and lower the glass frit into the water Some water will spill during this procedure Carefully watch the glass frit to make sure it does not hit the bottom of the vial adjust the position of the teflon coupler at the aerator if necessary Screw the special vial cap onto the sample vial The vial can be inserted in a space in the case to hold it secure It must be upright while aeration is in progress 1 4 4 Starting the test Everything is set up ready to go Once the RAD7 has finished printing out the header go to Test Start and push ENTER The pump will run for five minutes aerating the sample and delivering the radon to the RAD7 The system will wait a further five minutes It will then start counting After five minutes it will print out a short form report The same thing will happen again five minutes later and for two more five minute periods after that At the end of the run 30 minutes after the start the RAD7 prints out a summary showing the average radon reading from the four cycles counted a bar chart of the four readings and a cumulative spectrum The radon level 10
24. gligible levels for the most accurate low level radon in water measurement The charcoal filter works best if you 16 2012 DURRIDGE Company Inc use it only after a complete purge with low radon air which avoids overloading the filter with radon If the charcoal filter becomes badly contaminated with radon it can give off some of the radon and actually increase the background after a purge Store the charcoal filter with the end caps installed to allow the filter to self clean by waiting for adsorbed radon to decay over several weeks time Always keep the charcoal dry by using it in conjunction with a drying tube since water vapor can adversely affect charcoal s capacity to adsorb radon Even if you choose not to use fancy methods to reduce the background you should always purge the system between samples It is much better to purge with ordinary room air than not to purge at all In any case it is also necessary to purge to remove any accumulated water vapor from the system and bring the relative humidity back down to close to 5 3 4 Background and Residuals Purge air is one among several causes for background counts in the RAD H20 The most significant other causes are radon daughters and traces of radon left from previous measurements The RAD7 has the unusual ability to tell the difference between the new radon daughters and the old radon daughters left from previous tests Even so a very high radon sample can cause d
25. he original radon concentration in the water sample after a SNIFF protocol reading it will be necessary to multiply the radon in air measurement by a factor whose value may be found from a measurement with WAT 40 or WAT250 protocol In fact the two could be made with the same sample First make a normal RAD H2O measurement then without changing the physical setup change the preset WATXXX protocol to SNIFF bypass the aerator to conserve desiccant and start anew run The readings will now be radon in air and may be compared directly with the previous WATxxx readings of radon in the water 7 5 Active DRYSTIK If an active DRYSTIK is used instead of a passive device the RAD7 pump must be switched off and the DRYSTIK pump used instead This circulates air at only 0 2 L min It will therefore take 20 minutes instead of five to aerate the sample It is recommended therefore that after presetting WAT 40 or 250 the pump be turned off Setup pump off ENTER and the cycle time be extended to 10 minutes It will take an hour to make the analysis but virtually no desiccant will be used if the RAD7 was initially dried out properly 7 6 Large Aerator A number of users have fabricated their own aerator system using large water sample containers Lee and Kim Such an approach increases the sensitivity of the system so lowering the lowest limit of detection Disadvantages are a a significant increase in the complexity of the method b in
26. he water s contribution to the airborne radon This test ought to be done before any attempt to mitigate soil gas infiltration particularly if other wells in the area have been found to have radon Henschel 2 3 Physical Properties of Waterborne Radon Radon gas is mildly soluble in water But being a gas it is volatile It tends to leave the water upon contact with air This is known as aeration The rate of radon transfer from water to air increases with temperature agitation mixing and surface area In household water usage showers baths dishwashers laundries and toilets all provide adequate aeration to release a high percentage of the water s radon content into household air Prichard In principle the radon will continue to be released from water as the aeration process continues until a state of equilibrium develops According to Henry s Law of dilute solutions equilibrium will occur when the water concentration and air concentration reach a fixed ratio for a certain temperature This ratio derivable from the Henry s Law constant for radon dissolved in water is known as the distribution coefficient or partition coefficient For radon in water at 20 degrees C 68 F the distribution coefficient is about 0 25 so radon will continue to release from the water until the water concentration drops to about 25 percent of the air concentration Remember that as the radon leaves the water into the air it raises the air conc
27. ill behave normally in every respect except that the desiccant will last about five times longer before it needs to be regenerated or replaced WAT 40 protocol will give readings of the radon in the water when 40 ml vials are used and similarly WAT250 when 250ml vials are used 7 2 Large Drying Unit A large laboratory drying unit as used for 2 day protocol monitoring may be used with the RAD H20 but it increases the volume of air in the system so reducing the concentration of radon in the loop after aeration of the sample To accommodate the change in air loop volume a multiplying factor of 2 0 must be applied to the RAD H20 reading Thus a reading of radon in the water of 300 pCi L taken with a laboratory drying unit in the setup instead of a small drying tube the radon concentration in the water was 600 pCi L The multiplying factors for 40ml vials and 250ml vials are sufficiently close to the same that only one figure needs to be remembered The multiplying factor of 2 0 was derived from a series of experiments performed at DURRIDGE Company The precise factor for any setup depends also on the choice and length of tubing For the most reliable assessment users should perform their own experiments with their own setup Collect a number of equal samples say six at least Be very careful in the sample taking to be sure they are all indeed the same Analyze half the samples with a standard setup and the other half with the d
28. ing uranium and radium deposits These elements can be found in trace amounts in almost all soils and rocks Being a gas radon can escape from mineral surfaces and dissolve in ground water which can carry it away from its point of origin We rarely find radon in significant concentrations in surface waters due to its rapid dispersal into the atmosphere High concentrations of groundwater radon prevail in parts of New England New Jersey Maryland Virginia and the mountainous western states of the U S Typical groundwater sources average between 200 and 600 pCi L of radon Roughly 10 percent of public drinking water supplies have concentrations of over 1 000 pCi L and around 1 percent exceed 10 000 pCi L Smaller water systems appear to be disproportionally affected by high radon Milvy EPA Radon was first noticed in water supplies by J J Thomson a pioneer in the science of radioactivity in the first decade of the 1900s Hess Frame At first scientists and doctors believed radioactivity to have benign even curative effects on the human body Early research linked high radon concentrations to natural hot springs long thought to have miraculous powers But eventually science came to understand the dangers of radiation exposure after a number of serious accidents and fatalities Caulfield In the 1950s airborne radon decay products emerged as the probable cause of high incidences of lung cancer among underground mine worke
29. inlet of the laboratory drying unit thus forming a closed loop This will continue to dry out the RAD7 but will not introduce more fresh air If the RAD7 has not been used for some time or if it has been left without the small tubing bridge in place between the air inlet and outlet then it will take longer to dry it out perhaps as much as 30 minutes of purging or even more Once it has thoroughly dried out however just 15 minutes of purging between measurements will generally be sufficient 1 4 2 Collecting a Sample Getting a good sample requires care and practice Sampling technique or lack of it is generally the major source of error in measuring the radon content of water The water sampled must be a representative of the water being tested and b such that it has never been in contact with air To satisfy a make sure that the sample has not been through a charcoal filter or been sitting for days in hot water tank To test a well choose a faucet at the well or outside the house before the water enters any treatment process Run the water for several minutes to make sure that the sample comes freshly from deep in the well To satisfy b several techniques are used One method attaches a tube to the faucet and fills the vial with this tube Another puts a bowl up to the faucet so that the water overflowing the bowl prevents the water when leaving the faucet from touching the air and the vial is filled with wate
30. instrument and its use the reader is referred to the RAD7 manual Grateful acknowledgment is made of the significant contribution to this manual by Stephen Shefsky who wrote most of the original NITON RAD H20 manual much of which is incorporated in this version However all responsibility for the content now rests with DURRIDGE Company 2 2012 DURRIDGE Company Inc CONTENTS 1 GETTING STARTED 1 1 Unpacking 1 2 General Safety Instructions 1 3 Taking a Look Fig 1 Aerating a 250 ml water sample Fig 2 Aeration in progress Fig 3 Schematic 1 4 Running a Test 1 4 1 Preparing the RAD7 1 4 2 Collecting a Sample 1 4 3 Setting up the equipment Fig 4 Aerator assembly 1 4 4 Starting the test 1 4 5 Finishing the Test 1 4 6 Interpreting the results Fig 5 RAD H20 printout 2 BACKGROUND 2 1 About Radon in Water 2 2 Health Risks Due to Waterborne Radon 2 3 Physical Properties of Waterborne Radon 2 4 Radon as a Tracer for Groundwater movement 2 5 Standard Methods for Radon in Water Analysis 2 6 Mitigation Strategies 3 RAD H20 TECHNIQUE 3 1 The Closed Loop Concept 3 2 Desiccant 3 3 Purging the System 3 4 Background and Residuals 4 RESULTS 4 1 How Calculation Is Made 4 2 Decay Correction 4 3 Dilution Correction Fig 6 Decay Correction Factors O1 11 12 12 12 13 13 13 14 15 15 15 15 16 18 18 18 18 19 2012 DURRIDGE Company Inc 3 5 ACCURACY AND QUALITY CONTROL 5 1
31. is if you reduce total background to its lowest possible value which is well below 0 02 cpm 22 2012 DURRIDGE Company Inc Fig 7 Method Comparison 6 CARE MAINTENANCE and TROUBLE SHOOTING 6 CARE MAINTENANCE and TROUBLE SHOOTING 6 1 Warning on Pump Direction The RAD H20 system cannot tolerate the reversal of the air connections at the aerator head or the RAD7 A check valve should be used at all times to prevent the disastrous possibility of sucking water into the RAD7 should a connector be accidentally reversed If a reversed connection occurs the check valve prevents the water from rising past the aerator head by blocking its path Do not allow the RAD7 to continue pumping against a blocked check valve as this may cause damage to the pump or to the RAD7 s internal seals 6 2 Warning on Tipping the Aeration Unit Never operate the RAD H20 aeration unit in any position other than upright If the aeration unit tips to any direction it may allow water to pass through the outlet tube toward the RAD7 unit If liquid water reaches the RAD7 it could permanently damage critical internal parts resulting in an expensive repair bill Use a solid stable base to hold the aerator unit when you operate the system The RAD H20 case makes a good base when placed on a level surface 6 3 Frit Maintenance After performing many radon in water measurements the glass frit may begin to show stains or even begin clogging due to th
32. l Aeration brings water into contact with a stream of low radon air which strips the radon from the water then exhausts the radon bearing air to the atmosphere Aeration systems offer effective removal of radon without the buildup of gamma radiation or waste material but tend to be substantially more expensive than GAC to install and maintain in a residential setting Aeration can be used over the entire range of influent concentrations though very high influent concentration may require a multiple stage system to reduce the effluent concentration to acceptable levels Henschel Lowry NEEP 3 RAD H20 TECHNIQUE 3 RAD H2O TECHNIQUE 3 1 The Closed Loop Concept The RAD H20 method employs a closed loop aeration scheme whereby the air volume and water volume are constant and independent of the flow rate The air recirculates through the water and continuously extracts the radon until a state of equilibrium develops The RAD H20 system reaches this state of equilibrium within about 5 minutes after which no more radon can be extracted from the water The extraction efficiency or percentage of radon removed from the water to the air loop is very high typically 99 for a 40 mL sample and 94 for a 250 mL sample The exact value of the extraction efficiency depends somewhat on ambient temperature but it is almost always well above 90 Since the extraction efficiency is always high we see little or no temperature effect on the ove
33. n and progeny from the system before a measurement but that will require a fair amount of effort and patience A more realistic background to shoot for in routine analysis might be between 10 and 20 pCi L Remember if you know the background well enough you can subtract it off and have reasonable confidence in the result 5 3 Comparison of RAD H20 with Other Methods Fig 7 is a table of typical numbers to give a basis for comparison Some laboratories may be able to get better results than this table indicates while others may not The precision figures include counting statistics only with no adjustment for sampling variation or decay of the sample Note that standard laboratory analysis often entails a long delay between sampling and analysis which can significantly increase the error and raise the detection limit DL and the lower limit of detection LLD Also note that the background figure used to calculate the RAD H20 precision DL and LLD is conservatively estimated to reflect typical field usage The most demanding and patient RAD H20 operator should be able to reduce background to less than 0 02 cpm rather than the 0 10 cpm given in the table which will allow for DL s and LLD s lower than those listed 5 4 Quality Assurance A proper quality assurance plan should follow the guidelines set by the USEPA as described in Goldin Compliance with future certification programs will certainly require an approved quality
34. nd the dimensions of the equipment 2012 DURRIDGE Company Inc 27 REFERENCES REFERENCES Altshuler B and B Pasternack Statistical Measures of the Lower Limit of Detection in a Radioactivity Counter Health Physics 9 293 298 1963 BEIR IV Committee Health Effects of Radon and Other Alpha Emitters National Academy Press Washington DC 1988 Burkhart J F et al A Comparison of Current Collection Sampling Techniques for Waterborne Radon Analysis 1991 Annual AARST National Fall Conference 255 271 Rockville MD October 1991 Burnett W C et al Radon as a Tracer of Submarine Groundwater Discharge Continental Shelf Research 26 862 873 2006 Caulfield C Multiple Exposures Chronicles of the Radiation Age University of Chicago Press 1989 Cothern C R and P A Rebers editors Radon Radium and Uranium in Drinking Water Lewis Publishers Chelsea MI 1990 Crawford Brown D J Analysis of the Health Risk from Ingested Radon Chapter 2 in Cothern and Rebers 1990 Federal Register National Primary Drinking Water Regulations Radionuclides Proposed Rule 40 CFR Parts 141 and 142 56 138 33050 33127 July 18 1991 Federal Register Interim Primary Drinking Water Regulations Promulgation of Regulations on Radionuclides 40 CFR Part 141 41 133 28402 28405 July 9 1976 Frame P W Natural Radioactivity in Curative Devices and Spas Health Physics 61 6 supplement
35. of polonium 218 means that almost all the decays that are actually counted come from atoms deposited in the first 20 minutes of the measurement So arise in humidity above 10 over the last ten minutes of the counting period will not have a significant effect on the accuracy of the result If the first two counting periods are below 10 relative humidity you may ignore humidity effects On the other hand if the humidity rises above 10 before the end of the first counting cycle there will be an error whose size is indeterminate However you can be sure that any error due to high humidity will be in a direction to reduce the reading so that the true value must be higher than the observed value For accurate readings the RAD7 should be dried out thoroughly before making the measurement see section 1 5 2 7 Background Effects By careful attention to details you can reduce the background in the RAD H20 system to insignificant levels We previously discussed how to control the background due to purge air radon content and residual radon and its progeny The uncontrollable or intrinsic background of the RAD7 is low enough to ignore in all but the most demanding cases The intrinsic background of RAD7 is less than 1 count per hour corresponding to a 40 mL water sample concentration of less than 2 pCi L even lower for the 250 mL sample In principle you can achieve a background this low if you completely eliminate all rado
36. on By paying very careful attention to detail you may be able to get the variation down to under 5 5 2 2 Sample Concentration You can usually determine high concentrations with a better precision than low concentrations when precision is expressed in terms of percent error This is because a higher concentration gives a greater number of counts per minute above the background and its fluctuation yielding more favorable counting statistics If the concentration is too high however you can exceed the upper limit of the RAD7 s range 5 2 3 Sample Size A larger sample size gives a greater number of counts per minute above back ground so improves sensitivity and precision at low radon concentrations But the larger sample size limits the method s range somewhat and increases temperature effects 5 2 4 Counting Time Longer counting times improve sensitivity and precision by accumulating a greater total number counts above background which gives more favorable counting statistics Increasing the usual 20 minute count time to 80 minutes 4 times 20 will improve counting statistics by a factor of 2 square root of 4 For this to work however it is necessary that the RAD7 be thoroughly dried out so that the relative humidity does not climb too high during the 80 minutes of count time It is possible during a measurement to set the pump from GRAB to ON which will turn it on thus moving air through the desiccant and into
37. onitor Journal of Environmental Radioactivity 89 219 228 2006 Lowry J D et al Point of Entry Removal of Radon from Drinking Water Journal AWWA 79 4 162 169 April 1987 Lowry J D Measuring Low Radon Levels in Drinking Water Supplies Journal AWWA 83 4 149 153 April 1991 McHone N W M A Thomas and A J Siniscalchi Temporal Variations in Bedrock Well Water Radon and Radium and Water Radon s Effect on Indoor Air Radon International Symposium on Radon and Radon Reduction Technology Volume 5 Minneapolis MN September 1992 Milvy P and C R Cothern Scientific Background for the Development of Regulations for Radionuclides in Drinking Water Chapter 1 in Cothern and Rebers 1990 National Council on Radiation Protection Ionizing Radiation Exposure of the Population of the United States NCRP Report No 93 Bethesda MD September 1987 North East Environmental Products Inc Shallow Tray Low Profile Air Strippers and VOC and Radon Removal from Water pamphlets NEEP 17 Technology Drive West Lebanon NH 03734 1992 Prichard H M and Gesell Rapid Measurements of 222 Rn Concentrations in Water with a Commercial Liquid Scintillation Counter Health Physics 33 6 577 581 December 1977 Prichard H M The Transfer of Radon from Domestic Water to Indoor Air Journal AWWA 79 4 159 161 April 1987 Rydell S B Keene and J Lowry Granulated Activated Carbon Water Treatment
38. ons The empty tube provides an even greater inside diameter to prevent bubbles from reaching the desiccant The increase in total air loop volume is insignificant so that no correction is necessary to the reading 24 2012 DURRIDGE Company Inc 6 6 Technical Support DURRIDGE does not expect the RAD H20 apparatus to require routine maintenance or service beyond the replacement of damaged parts The RAD7 unit may require periodic service beyond routine calibration particularly the air pump and rechargeable batteries For help contact service durridge com or phone 978 667 9556 7 DEVIANT SETUPS 7 DEVIANT SETUPS 7 1 Passive DRYSTIK Use of a 12 passive DRYSTIK is not really a deviant setup but rather a supplement to the standard setup The DRYSTIK may be installed with the membrane tubing upstream of the desiccant and the purge line between the RAD7 outlet and the aerator Great care should be taken to ensure that no liquid or foam enters the membrane tubing Water inside the DRYSTIK can at best temporarily disable it and at worst destroy it With normal clean water the DRYSTIK placed vertically above the aerator and with 12 of 5 16 tubing between the two there should be no problem But if the water sample is particularly foamy the DRYSTIK should not be used in the system until it is determined the setup is such that no foam will climb up into it With the 12 DRYSTIK installed the RAD7 RAD H20 system w
39. onsistent procedures For this reason we recommend that you regularly review your method and compare your results to those of other methods in side by side comparisons One way to check the accuracy of your analysis technique is to take side by side identical samples analyze one yourself and send the other to an independent laboratory As part of your quality assurance plan you should regularly check the RAD7 unit for its ability to determine radon in air and periodically send the RAD7 in for a check up and recalibration Government agencies usually recommend or require annual or bi annual recalibration of radiation measurement instruments You can find more information about calibration in the RAD7 Operation Manual Durridge recommends against the use of radium 226 solutions in the RAD H20 system due to the risk of permanent contamination 5 2 Accuracy and Precision A number of factors affect the accuracy and precision of a radon in water measurement Most critical among these factors is the sampling technique which was discussed in greater detail in a previous section Other factors include the sample concentration sample size counting time temperature and background effects 5 2 1 Sampling Technique You can expect a sample to sample variation of from 10 to 20 due to sample taking alone probably caused by the uneven aeration of the 20 2012 DURRIDGE Company Inc sample and the loss of a fraction of the rad
40. ou wish To conserve desiccant however you may wish to assemble an aerator bypass and switch to a longer cycle time or a different protocol e g 1 day that has half hour cycles and continue the analysis until you have enough counts to give you the statistical precision you desire With such a setup the sensitivity of the RAD H20 system can be improved by an order of magnitude over standard protocol and standard setup With a large water sample the RAD7 preset protocols WAT 40 and WAT250 are no longer of service The user has to decide on the protocol to use and then has to calibrate the system using that protocol One way to calibrate the system is to take multiple samples of the same water and analyze them in different ways including with the large aerator sample flask Direct comparison with a standard analysis using the standard setup of a RAD7 and RAD H20 would work Comparison with a RAD AQUA measurement would also be good The temperature dependence will vary from setup to setup depending principally on the volume of the water sample and the volume of the air loop One way to deal with this is always to allow the sample to reach the same laboratory temperature as that when the system was calibrated before making the analysis Another would be to calibrate the system at different temperatures and determine the temperature coefficient A third would be to calculate the temperature coefficient from the theoretical equations a
41. r at the bottom of the bowl A third combines both methods by having a tube attached to the faucet feeding water to the interior of the vial at the bottom of the bowl Using the third method above allow water to overflow freely from the bowl Take a 250 ml vial if the radon concentration is probably less than 3 000 pCi L or 100 000 Bq m3 or a 40 ml vial if it is probably more Take samples in both sizes if you have no idea of the concentration Place the vial in the bottom of the bowl and put the tube end into the vial Let the water flow for a while keeping the vial full and flushing with fresh water Cap the vial while still under the water Make sure there are no bubbles in the vial Tighten the cap Remove the vial from the bowl dry it and immediately apply a label stating the date time and source of the water 1 4 3 Setting up the equipment Find the two Teflon unions or spacers small pieces of teflon rod with holes through the center one longer than the other In the instrument case as originally shipped the shorter spacer is in the 40 ml vial assembled on the aerator in the middle of the case The longer spacer is in the foam at the near right hand corner of the case Pick the spacer appropriate to the size of vial containing the water sample short for the 40 ml vial and long for the 250 ml vial Note that the hole at one end of the teflon spacer is bigger than at the other Push the end with the larger hole onto the
42. rall measurement 3 2 Desiccant The RAD H20 requires that the desiccant be used at all times to dry the air stream before it enters the RAD7 If the desiccant is not used properly the RAD7 may give incorrect radon concentrations or may become damaged due to condensation on sensitive internal components For water sample analysis always use the small drying tubes supplied as the system has been calibrated with these tubes Do not use the large drying column as its much larger volume would cause improper dilution of the radon Make it a habit to inspect the RAD7 humidity reading to be sure the desiccant is and has been effective through the entire measurement session All relative humidity readings during the measurement should remain below 10 In the worst case at least the first two counting cycles should be below 10 If the relative humidity is higher than that then the RAD7 should be purged see below See the RAD7 Operator s Manual for more information on maintaining the desiccant 3 3 Purging the System After performing a water or air measurement the RAD 7 s internal sample cell will continue to contain the radon that was measured If this radon is still present when you start a new measurement it will erroneously influence the next measurement This is of special concern when the radon concentration of the last measurement was high relative to the next measurement To prepare for the next water measurement you must
43. remove as thoroughly as possible the radon from the RAD7 and its air conducting accessories including the aerator head tubes and desiccant This procedure is known as purging the system To purge the system you must have a source of radon free or relatively radon free air or inert gas For most occasions ambient air is good enough but see below Put the RAD7 into a purge cycle with the Test Purge command and allow the RAD7 pump to flush the clean air through the entire system for at least 10 minutes After measuring very high radon concentrations you should purge the system for at least 20 minutes A purge time of 30 minutes should be long enough to remove almost all the radon after measuring a sample at 100 000 pCi L Be sure to allow all the hoses and fittings to flush thoroughly by keeping them attached during the purge cycle for at least the first five minutes Also be sure that the drying tube does not deplete its desiccant during the purge cycle If the depleted pink desiccant gets to within 1 inch of the drying tube outlet replace the tube with a fresh blue drying tube After the first two or three minutes or purging you may replace the small drying tube with the large laboratory drying unit to conserve the small drying tube desiccant and continue purging the system Be careful about the air you use to purge Ambient air may not be adequately free of radon to properly prepare the system for a low level sample
44. rison with the above the RAD H20 offers method as accurate as LS but faster to the first reading portable even less labour intensive and less expensive It also eliminates the need for noxious chemicals 2 6 Mitigation Strategies Two main strategies have emerged for the removal of radon from water Both of these are applicable to point of entry POE water treatment in residences and small public water supplies Granular Activated Carbon GAC attempts to filter the water by adsorbing radon on a charcoal bed that holds onto the radon until the radon decays GAC systems can be effective and relatively inexpensive for residential use but can create new problems As the radon and its progeny decay in the GAC column they give off gamma radiation The gamma radiation may be a health concern to residents when the 14 2012 DURRIDGE Company Inc influent radon concentration is high the GAC column is poorly shielded for high energy radiation and the residents are likely to spend significant periods of time in the radiation field Over time a long lived decay product lead 210 builds up in the column which may pose disposal problems in systems with moderate to high radon concentrations in the influent For that reason GAC is most often recommended for influent concentrations of up to around 5 000 pCi L GAC maintenance is simple and inexpensive and the GAC bed has an expected service life of 5 to 10 years Henschel Lowry Rydel
45. rs Study of environmental radioactivity revealed unusually high groundwater radon concentrations in the vicinity of Raymond Maine Bell In the 1960s scientists began to investigate the effect of ingested and inhaled radon gas observing the uptake of radon by digestive organs and its dispersal through the bloodstream Crawford Brown By the 1970s radon was widely recognized as a major component of our natural radiation exposure By the late 1970s Maine had initiated a program to attempt to reduce public exposure to waterborne radon having discovered cases in which groundwater concentration exceeded 1 million pCi L Hess 12 2012 DURRIDGE Company Inc Federal action on the problem of radon in drinking water picked up in the 1980s with a nationwide program to survey drinking water supplies for radioactivity and to assess the risk to public health Congress directed the Environmental Protection Agency EPA to take action on radioactivity in drinking water and in 1991 the EPA officially proposed a Maximum Contaminant Level MCL for radon in public drinking water of 300 pCi L This MCL may one day become binding on public water supplies Federal Register EPA 2 2 Health Risks Due to Waterborne Radon Waterborne radon leads to health risk by two pathways inhalation of radon and its decay products following the release of radon gas from water into household air and the direct ingestion of radon in drinking water The risk
46. rsistent than daughter activity That is possibly due to off gassing of residual radon that has absorbed into internal surfaces In particular rubber and plastic parts can absorb a small fraction of the radon that passes through the system A small fraction of a very large amount can still be a significant amount The radon may desorb from these materials over many hours In the worst case you may have to allow the system to sit idle for a day or more for the absorbed radon to finish leaking out of these materials then purge the system again to remove the radon A radon concentration high enough to cause a concern of this kind is very rare in natural ground water but is possible in artificial radon sources such as radium crocks or Revigators Sustained counting of very high radon concentrations can lead to the buildup of long lived lead 210 contamination of the RAD7 s alpha detector This possibility is described in the RAD7 Operator s Manual It suffices to say that the RAD7 s ability to distinguish alpha particles by energy makes it far less susceptible to the build up of lead 210 related background than other radon monitors 17 2012 DURRIDGE Company Inc 4 RESULTS 4 RESULTS 4 1 How Calculation Is Made The calculates the sample water concentration by multiplying the air loop concentration by a fixed conversion coefficient that depends on the sample size This conversion coefficient has been derived from the vol
47. s DCF Hours DCF 0 1 000 1 1 008 2 1 015 3 1 023 4 1 031 5 1 038 6 1 046 7 1 054 8 1 062 9 1 070 10 1 078 11 1087 12 1 095 13 1 103 14 1 112 15 1 120 16 1 128 17 1 137 18 1 146 19 1 154 20 1 163 21 1 172 22 1 181 23 1 190 24 1 199 25 1 208 26 1 217 27 1 226 28 1 236 29 1 245 30 1 254 31 1 264 32 1 273 33 1 283 34 1 293 35 1 303 36 1 312 37 1 322 38 1 332 39 1 343 40 1 353 41 1 363 42 1 373 43 1 384 44 1 394 45 1 405 46 1 415 47 1 426 48 1 437 49 1 448 50 1 459 51 1 470 52 1 481 53 1 492 54 1 504 55 1 515 56 1 526 57 1 538 58 1 550 59 1 561 60 1 573 61 1 585 62 1 597 63 1 609 64 1 622 65 1 634 66 1 646 67 1 659 68 1 671 69 1 684 70 1 697 71 1 710 72 1 723 73 1 736 74 1 749 75 1 762 76 1 775 77 1 789 78 1 802 79 1 816 80 1 830 81 1 844 82 1 858 83 1 872 84 1 886 85 1 900 86 1 915 87 1 929 88 1 944 89 1 959 90 1 973 91 1 988 92 2 003 93 2 019 94 2 034 95 2 049 96 2 065 97 2 081 98 2 096 99 2 112 100 2 128 101 2 144 102 2 161 103 2 177 104 2 194 105 2 210 106 2 227 107 2 244 108 2 261 109 2 278 110 2 295 111 2 313 112 2 330 113 2 348 114 2 366 115 2 384 116 2 402 117 2 420 118 2 438 119 2 457 120 2 475 121 2 494 122 2 513 123 2 532 124 2 551 125 2 571 126 2 590 127 2 610 128 2 629 129 2 649 130 2 669 131 2 690 132 2 710 133 2 731 134 2 751 135 2 772 136 2 793 137 2 814 138 2 836 139 2 857 140 2 879 141 2 901 142 2 923 143 2 945 144 2 967 145 2 990 146 3 012 147 3 035 148 3 058 149 3 081 150 3 105 151 3 128 152 3 152 153 3 176 154 3 200 155 3 224 156
48. s80 s82 1991 Goldin A S Evaluation of Internal Control Measurements in Radio assay Health Physics 47 3 361 374 1984 Hahn P B and S H Pia Determination of Radon in Drinking Water by Liquid Scintillation Counting Method 913 0 U S EPA EMSL Radioanalysis Branch May 1991 Henschel D B Radon Reduction Techniques for Detached Houses Technical Guidance 2nd Edition U S EPA EPA 625 5 87 019 revised January 1988 Hess C T et al Radon Transferred from Drinking Water into House Air Chapter 5 in Cothern and Rebers 1990 Hess C T and S M Beasley Setting up a Laboratory for Radon in Water Measurements Chapter 13 in Cothern and Rebers 1990 Johns F B et al Radiochemical Analytical Procedures for analysis of Environmental Samples U S EPA EMSL LV 0539 17 March 1979 Kinner N E et al Effects of Sampling Technique Storage Cocktails Sources of Variation and Extraction on the Liquid Scintillation Technique for Radon in Water Environ Sci Tech 25 1165 1171 1991 Krieger H L and E L Whittaker Prescribed Procedures for Measurement of Radioactivity in Drinking Water U S EPA EMSL August 1980 28 2012 DURRIDGE Company Inc REFERENCES Lane Smith D R et al Continuous Radon 222 Measurements in the Coastal Zone Sea Technology Magazine October 2002 Lee J M and Guebuem Kimm A simple and rapid method for analyzing radon in costal and ground waters using a radon in air m
49. standard deviation highest and lowest readings a bar chart of the complete set of readings and a cumulative spectrum The radon content of the water at the time of the analysis is the mean value shown in the printout This value takes into account the calibration of the RAD7 the size of the sample vial and the total volume of the closed air loop as set up It is important that the setup be as specified above using the tubing and a small drying tube as provided Deviations from the standard setup may cause errors in the result The final step is to correct the measured value for decay of the radon in the water during the time between taking the sample and analyzing it 1 GETTING STARTED 15 1 Grab sample WED 3 N0v 39 10 14 581 Grab sample WED 3 MOV 99 10 19 1581 197260 7 Watz5 HED BS NOV 99 19124 26 4 C RH 4 B 7 12V 1592 216163 3 Wat250 WED 3 NOV 99 10 29 26 4 C RH 54 B 7 124 1593 172 57 2 Watz5 WED G3 N0V 33 10 34 26 4 C RH 54 B 7 094 1584 179 58 2 Mat258 WED 3 NOV 39 16 39 26 4 C 5 B 7 12V Run 15 Begin 93 NOV 99 19 24 Serial 06580 Cycles 684 Mean 191 1 1 D 2 19 7 1 1 High 216 pci l Low 172 pCi l i 18 2 10 2 1933 19 3 Cumulative Run Spectrum ialBlc Fig 5 RAD H20 printout 2012 DURRIDGE Company Inc 11 2 BACKGROUND 2 BACKGROUND 2 1 About Radon in Water Radon originates from the radioactive decay of naturally occurr
50. ume of the air loop the volume of the sample and the equilibrium radon distribution coefficient at room temperature For the 40 mL sample volume the conversion coefficient is around 25 For the 250 mL sample volume the conversion coefficient is around 4 The RAD7 does not presently make any correction for the temperature of the water sample In theory such correction would slightly improve the analytical accuracy for the larger 250 mL sample volume but would make little or no difference for the smaller sample volume 4 2 Decay Correction If you collect a sample and analyze it at a later time rather than immediately the sample s radon concentration will decline due to the radioactive decay You must correct the result for the sample s decay from the time the sample was drawn to the time the sample was counted If the sample is properly sealed and stored and counted within 24 hours then the decay corrected result should be almost as accurate as that of a sample counted immediately Decay correction can be used for samples counted up to 10 days after sampling though analytical precision will decline as the sample gets weaker and weaker The decay correction is a simple exponential function with a time constant of 132 4 hours The mean life 18 2012 DURRIDGE Company Inc of a radon 222 atom is 132 4 hours which is the half life of 3 825 days multiplied by 24 hours per day divided by the natural logarithm of 2 The decay
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