RAD H 2 O User`s Manual
Contents
1. Mehra R K Badhan and R G Sonkawade Radon Activity Measurements in Drinking Water and in Indoors of Dwellings Using RAD7 Tenth Radiation Physics amp Protection Conference November 27 30 2010 Mehra R and P Bala Assessment of radiation hazards due to the concentration of natural radionuclides in the environment Environmental Earth Sciences 71 2 901 909 January 2014 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 N meth Cs et al Measurements of radon thoron and their progeny in Gifu prefecture Japan Journal of Radioanalytical and Nuclear Chemistry 267 1 9 12 December 1 2005 31 2015 DURRIDGE Company Inc BIBLIOGRAPHY 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 T F 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 Ricardo C P et al2. Continued on next page 5 2015 DURRIDGE Company Inc 1 GETTING STARTED Aerator Assembly Check valve Vinyl tubing Flow adaptor cap 40mL tygon coupler Glass frit 40mL glass vial Faucet Adaptor Plastic adaptor 20 inch vinyl tubing Drying Tubes Small drying tubes x 4 Tube of activated charcoal Enea Extra Accessories High vacuum grease container Spare flow adaptor cap RAD7 inlet filter x 2 Spare glass frit 250mL tygon coupler Labels for glass vials Continued on next page 6 2015 DURRIDGE Company Inc 1 GETTING STARTED Vinyl Tubing Set From RAD7 to check valve From aerator to drying tube From drying tube to RAD7 Retort Stand Small adjustable retort stand Clamp for retort stand 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 For more information on preventing water from entering the RAD7 see Section 6 2 Warning on Tipping the Aeration Unit 7 2015 DURRIDGE Company Inc 1 GETTING STARTED 1 3 Taking a Look Fig 1 Aerating a 250mL water sample Fig 2 Aeration in progress The setup consists of three components the RAD7 Du
3. 19 19 19 19 20 5 ACCURACY AND QUALITY CONTROL 5 1 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 Purging 5 2 5 Aeration 5 2 6 Counting Time 5 2 7 Temperature 5 2 8 Relative Humidity 5 2 9 Background Effects 5 3 Comparison of RAD H20 with Other Methods 5 4 Quality Assurance Fig 7 Method Comparison 6 CARE MAINTENANCE and TROUBLESHOOTING 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 Water Samples BIBLIOGRAPHY 4 2015 DURRIDGE Company Inc 21 21 21 21 21 21 21 22 22 22 22 22 23 23 24 25 25 25 25 25 26 26 27 27 27 27 28 28 28 29 1 GETTING STARTED 1 GETTING STARTED 1 1 Unpacking Examine the RAD H20 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 RAD H20 Carrying Case Rugged Pelican brand case Dust proof and crushproof Sculpted foam inserts to hold components 250mL Glass Vials 250mL glass vial x 6 Septum cap x 6 40mL Glass Vials 40mL glass vial x 12 Septum cap x 12
4. Pumping Time Required To Obtain Tube Well Water Samples With Aquifer Characteristic Radon Concentrations International Nuclear Atlantic Conference INAC 2011 Rydell S B Keene and J Lowry Granulated Activated Carbon Water Treatment 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 Schmidt A et al The contribution of groundwater discharge to the overall water budget of Boreal lakes in Alberta Canada estimated from a radon mass balance Hydrol Earth Syst Sci Discuss 6 4989 5018 2009 Sharma N R Sharma and H S Virk Environmental radioactivity A case study of Punjab India Advances in Applied Science Research 2 3 186 190 2011 Sharma N R K Sharma Survey of radon concentration in drinking water samples of Hoshiarpur and Ropar districts of Punjab India Advances in Applied Science Research 4 3 226 231 2013 Singh S et al Measurement of Radon concentration in ground water from some areas along the foot hills of North West Himalaya in Punjab ANNO LXIV N 4 2009 Singh S et al Radon Monitoring in Soil Gas and Ground Water for Earthquake Prediction Studies in North West Himalayas India Terr Atoms Ocean Sci 21 4 685 695 August 2010 Somashekar R K and P Ravikumar Radon concentration in groundwater of Varahi and Markandeya river basins Karnataka
5. a 25mL 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 and less expensive Prichard Whittaker Hahn Method 913 0 Lowry Vitz Kinner Hess In comparison with the above the RAD H20 offers a 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 influent radon concentration is high the GAC column is poorly shielded for high energy radiation and the residents are likely to spend signific
6. 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 should 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 250mL 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 L in 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 a
7. 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 workers 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 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 of
8. 7 03V 1703 3374 234 p Wat 40 TUE 18 FEB 14 16 24 24 3 C RH 15 B 7 03V 1704 313 228 p Wat 40 TUE 18 FEB 14 16 29 24 3 C RH 154 B 7 03V Run 17 Begin 18 FEB 14 16 14 Seria Cycles Mean 306 pCi S D 23 4 pCi l High 337 pCi l Low 287 pCi 1 Ci Cumulative Run Spectrum AIBIC ID I Fig 5 RAD H20 printout 12 2015 DURRIDGE Company Inc 2 BACKGROUND 2 BACKGROUND 2 1 About Radon in Water Radon originates from the radioactive decay of naturally occurring 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 Radon is rarely found in large 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 US 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 are 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
9. D URRIDGE RADON INSTRUMENTATION RAD H20 User Manual Radon in Water Accessory e e e p WP DURRIDGE Company Inc 524 Boston Road Billerica MA 01821 Tel 978 667 9556 Fax 978 667 9557 Revision 2015 07 28 service durridge com Copyright 2015 Durridge Company Inc www durridge com 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 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 Ho0 gives results after a 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
10. 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 Kumar A et al Earthquake precursory studies at Amritsar Punjab India using radon measurement techniques International Journal of Physical Sciences 7 42 5669 5677 November 9 2012 Kumar A A Kumar and S Singh Analysis of Radium and Radon in the Environmental Samples and some physico chemical properties of drinking water samples belonging to some areas of Rajasthan and Delhi India Advances in Applied Science Research 3 5 2900 2905 2012 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 monitor 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
11. 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 40mL 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 overall 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 infor
12. sample vial but may begin to become noticeable with the 250mL vial at very low or high temperatures The RAD H20 system has been calibrated for a sample analysis temperature of 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 40mL 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 250mL sample is about 6 over the same range 5 2 8 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 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 a rise in humidity above 10 over the last ten minutes of the counti
13. the 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 2015 DURRIDGE Company Inc TABLE OF CONTENTS INTRODUCTION 1 GETTING STARTED 1 1 Unpacking 1 2 General Safety Instructions 1 3 Taking a Look Fig 1 Aerating a 250mL water sample Fig 2 Aeration in progress Fig 3 RAD H20 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 1 4 4 Starting the Test Fig 4 Aerator assembly 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 3 2015 DURRIDGE Company Inc onoo N O1 A Soe RSS CET N 13 13 13 14 14 14 15 16 16 16 16 18
14. 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 Figure 7 provides a basis for comping different methods of measuring radon in water samples The numbers are typical and 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 assurance plan The elements of a quality assurance plan include blank samples dup
15. 2012 El Taher A Measurement of radon concentration and their annual effective dose exposure in groundwater from Qassim area Saudi Arabia Journal of Environmental Science and Technology ISSN 1994 7887 2012 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 s80 s82 1991 Francesco S D et al Radon hazard in shallow groundwaters Amplification and long term variability induced by rainfall Science of The Total Environment 408 4 779 789 January 15 2010 Garcia Solsona E et al An assessment of karstic submarine groundwater and associated nutrient discharge to a Mediterranean coastal area Balearic Islands Spain using radium isotopes Biogeochemistry 97 2 3 211 229 March 2010 Gilfedder B G H Hofmann and I Cartwright Novel Instruments for in Situ Continuous Rn 222 Measurement in Groundwater and the Application to River Bank Infiltration Environ Sci Technol 47 2 993 1000 2013 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 o
16. 3 6 300 minute count 11 2 0 25 10 3 Fig 7 Method Comparison 24 2015 DURRIDGE Company Inc 6 CARE MAINTENANCE and TROUBLESHOOTING 6 CARE MAINTENANCE and TROUBLESHOOTING 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 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 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 If water ever enters the RAD7 or if the RAD7 ever goes swimming in the water it will probably cease to operate and immediate steps should be taken to minimize the impact on the instrum
17. 68 221 5 308 222 5 348 223 5 389 224 5 429 225 5 471 226 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 20 2015 DURRIDGE Company Inc 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 consistent 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 measur
18. State India Journal of Radioanalytical and Nuclear Chemistry 285 2 343 351 May 1 2010 Stringer C E Assessment of Groundwater Discharge to Lake Barco Via Radon Tracing Electronic Theses Treatises and Dissertation Florida State University March 29 2004 Su N et al Natural Radon and Radium Isotopes for Assessing Groundwater Discharge into Little Lagoon AL Implications for Harmful Algal Blooms Estuaries and Coasts November 2013 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 E Toward a Standard Method for Determining Waterborne Radon Health Physics 60 6 817 829 June 1991 32 2015 DURRIDGE Company Inc BIBLIOGRAPHY 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 Winz R Tracing Groundwater Inputs into Anacostia Seep Habitats Using Radon Fall 2012 Spring 2013 Honors Capstones September 25 2013 Yakut H et al Measurement of 222Rn Concentration in Drinking Water in Sakarya Turkey Radiat Prot Dosimetry 2013 Zabadi H A1 et al Exposur
19. ant 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 Rydell 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 15 2015 DURRIDGE Company Inc 3 RAD H20 TECHNIQUE 3 RAD H20 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
20. ches 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 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 connections 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 c
21. cle 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 of 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 16 2015 DURRIDGE Company Inc 3 RAD H20 TECHNIQUE 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 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 40mL 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 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 250mL 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
22. 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 look similar to the one shown in Figure 5 on the next page 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 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 11 2015 DURRIDGE Company Inc 1 GETTING STARTED DURRIDGE RAD7 Vers 2 5f 991128 Model 711 Serial 03101 Calib 22 0CT 12 1701 Grab TUE 18 FEB 14 16 04 1701 Grab TUE 18 FEB 14 16 09 1701 _ 287 220 p Wat 40 TUE 18 FEB 14 16 14 24 3 C RH 12 B 7 03V 1702 289 222 p Wat 40 TUE 18 FEB 14 16 19 24 3 C RH 134 B
23. e One tube longer than the other In the instrument case as originally shipped the shorter tube is in the 40mL vial assembled on the aerator in the middle of the case With the glass vial removed the end of the frit should be 75mm or 3 from the bottom of the aerator cap Measure and adjust as necessary The longer tube is in the foam at the near left hand corner of the case immediately to the right of the 6th 250mL vial The end of the glass frit should be 150mm or 4 7 16 from the bottom of the aerator cap Measure and adjust as necessary Pick the tube appropriate to the size of vial containing the water sample short for the 40mL vial and long for the 250mL vial Push one end onto the aerator barb on the side opposite to the check valve With the 3 7 6cm of 1 4 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 1 4 to 1 8 adapter makes this connection easy and secure Connect the RAD7 outlet to the check valve on the aerator See Figures 1 3 and 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 Stop purging On the RAD7 go to Setup Pro
24. e 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 LS Gamma spectroscopy seeks to detect the gamma rays given off by radon s decay products from a closed 14 2015 DURRIDGE Company Inc 2 BACKGROUND 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
25. e assessment of radon in the drinking water supplies a descriptive study in Palestine BMC Research Notes 5 29 2012 33 2015 DURRIDGE Company Inc
26. ement instruments You can find more information about calibration in the RAD7 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 sample and the loss of a fraction of the radon By paying very careful attention to detail you may be able to get the variation down to under 5 When taking a sample it is important that the water being sampled has never been in contact with air When sampling from a body of water it is best to take the sample from beneath the surface as close to the source as possible Even opening an empty bottle beneath the surface does not completely satisfy that criterion because the air in the bottle itself can take radon away from the initial water entering the bottle It is very easy to lose radon from the sample in the process of collecting it It is also important to collect all of the samples to be analyzed at a
27. en 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 40mL vial should contain 36 mL of radon free water 4mL 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 19 2015 DURRIDGE Company Inc 4 RESULTS Hours DCF Hours DCF Hours DCF Hours 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 1 087 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 29 1 245 34 1 293 39 1 343 44 1 394 49 1 448 54 1 504 59 1 561 64 1 622 69 1 684 74 1 749 79 1 816 84 1 886 89 1 959 94 2 034 99 2 112 104 2 194 109 2 278 114 2 366 119 2 457 124 2 551 129 2 649 134 2 751 139 2 857 144 2 967 149 3 081 154 3 200 159 3 323 164 3 451 169 3 584 174 3 722 179 3 865 184 4 014 189 4 168 194 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 2
28. ent Keep the RAD7 upright This will prevent water from touching the detector which is close to the face plate at the top of the dome Put a piece of tubing on the RAD7 outlet with the other end in a sink Use the RAD7 pump if it still works or otherwise an external pump into the inlet to blow air through the instrument When water ceases to be blown out of the outlet put desiccant upstream of the RAD7 to dry out the air path When the air path is fully dry after dry air has been blown through it for approximately one hour remove the face plate from the case empty the water out of the case and blow dry the case and the RAD7 electronics Once there is no visible water in or on the instrument it can be put in an oven at 50 C for a few hours to dry out completely Additionally desiccated air can be passed through the air path until the air leaving the RAD7 drops below 10 RH After this treatment further corrosion will be prevented and the RAD7 will boot once more and you can use the internal RH sensor to measure how dry the air path is At this point the instrument should be returned to DURRIDGE for service 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 the 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 i
29. ept 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 the 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 To determine the 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 o
30. er 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 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 Check Valve A Adaptor Cap Rubber Gasket ne ID Tygon Tubing a 40 ml Vial Glass Frit Fig 4 Aerator assembly a 75 mm for 40mL 115 mm for 250mL 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
31. f 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 Hunkeler D et al Can 222Rn be sued as a partitioning tracer to detect mineral oil contaminations Tracer Hydrology 97 1997 Johns F B et al Radiochemical Analytical Procedures for analysis of Environmental Samples U S EPA EMSL LV 0539 17 March 1979 30 2015 DURRIDGE Company Inc BIBLIOGRAPHY Khan M A Radon based Geo Environmental Investigation of Karak Trough and its Adjoining Areas District Karak Khyber Pakhtunkhwa Pakistan National Centre of Excellence in Geology University of Peshawar Pakistan 2013 Khattakm N U et al Radon concentration in drinking water sources of the Main Campus of the University of Peshawar and surrounding areas Khyber Pakhtunkhwa Pakistan Journal of Radioanalytical and Nuclear Chemistry 290 2 493 505 November 2011 Kinner N E et al Effects of Sampling Technique Storage Cocktails Sources of Variation and Extraction on the Liquid Scintillation Technique for
32. ficially 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 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 13 2015 DURRIDGE Company Inc 2 BACKGROUND 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 especial
33. he 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 After 10 minutes of purging with dry air push the menu button push ENTER twice to go into the 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 the 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 9 2015 DURRIDGE Company Inc 1 GETTING STARTED 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 f
34. icks Use of automated radon measurements for rapid assessment of groundwater flow into Florida streams Journal of Hydrology 380 3 4 298 304 January 30 2010 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 Dimova N T Using Radon Isotopes for Studying Hydrological Processes in Marine and Aquatic Systems Electronic Theses Treatises and Dissertation Florida State University December 2 2009 Dimova N T et al Application of radon 222 to investigate groundwater discharge into small shallow lakes Journal of Hydrology 486 112 122 April 12 2013 Duggal V A Rani and R Mehra In situ measurements of radon levels in groundwater in Northern Rajasthan India Advances in Applied Science Research 3 6 3825 3830 2012 29 2015 DURRIDGE Company Inc BIBLIOGRAPHY Dulaiova H Multiple Isotopic Tracers for Study of Coastal Hydrological Processes Electronic Theses Treatises and Dissertation Florida State University June 28 2005 El Gamal A A R N Peterson and W C Burnett Detecting Freshwater Inputs via Groundwater Discharge to Marina Lagoon Mediterranean Coast Egypt Estuaries and Coasts 35 6 1486 1499 November
35. licate 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 been discovered and corrected Therefore the quality assurance plan should specify the range of acceptable measurement deviations often in the form of a control chart The operator should maintain complete records of the quality control measurements and their deviations 23 2015 DURRIDGE Company Inc 5 ACCURACY AND QUALITY CONTROL Method RAD H20 40 RAD H20 250 Big Bottle System Liquid Scintillation Lucas Cell Sample Size mL 40 250 2500 10 10 Sensitivity cpm pCi L 0 008 0 05 0 3 0 09 0 05 Background cpm 0 1 0 1 0 1 15 0 25 2 sigma uncertainty at 300 pCi L in pCi L 20 minute count 88 35 32 35 60 minute count 51 20 2 5 19 20 120 minute count 36 14 1 8 14 14 2 sigma uncertainty at 100 pCi L in pCi L 20 minute count 53 20 24 20 60 minute count 31 12 1 5 14 12 120 minute count 22 8 5 1 1 10 8 5 DL C 2 1 sqr 1 2 B in pCi L NPDWR 40 CFR 41 25 20 minute count 40 6 28 9 60 minute count 19 3 0 4 16 4 300 minute count 7 1 0 18 7 2 LLD C 4 1 sqrB in pCi L Altshuler 20 minute count 60 10 41 13 60 minute count 29 5 0 6 2
36. ly 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 discovered elevated air concentrations and whose house uses private well water should test the water for radon content to assess the 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 concentratio
37. mation 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 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 cy
38. n 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 25 2015 DURRIDGE Company Inc 6 CARE MAINTENANCE and TROUBLESHOOTING 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 to residual 218 Po on the alpha detector surface This will halve every 3 minutes until it approa
39. n 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 concentration 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 lak
40. ng 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 4 1 5 2 9 Background Effects By paying 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 the RAD is less than 1 count per hour corresponding to a 40mL water sample concentration of less than 2 pCi L even lower for the 250mL sample In 22 2015 DURRIDGE Company Inc 5 ACCURACY AND QUALITY CONTROL principle you can achieve a background this low if you completely eliminate all radon and progeny from the system before a measurement but that will require a fair amount of effort and patience A more realistic background
41. niversity of the Western Cape February 2009 Abojassim A A Radon Concentrations Measurement for Drinking Water in Kufa City Iraq Using Active Detecting Method Advances in Physics Theories and Applications 26 2013 Al Attiyah K H H and I H Kadhim Measurement and Study of Radioactive Radon Gas Concentrations in the Selected Samples of River Hilla Iraq Journal of Natural Sciences Research Vol 3 No 14 2013 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 I 255 271 Rockville MD October 1991 Burnett W C et al Using high resolution in situ radon measurements to determine groundwater discharge at a remote location Tonle Sap Lake Cambodia Journal of Radioanalytical and Nuclear Chemistry 296 1 97 103 April 2005 Burnett W C et al Radon as a Tracer of Submarine Groundwater Discharge Continental Shelf Research 26 862 873 2006 Burnett W C and N Dimova A Radon Based Mass Balance Model for Assessing Groundwater Inflows to Lakes Global Environmental Studies 55 66 2012 Burnett W C R N Peterson I R Santos and R W H
42. oportion 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 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 27 2015 DURRIDGE Company Inc 7 DEVIANT SETUPS 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 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 exc
43. or days in a 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 an hour to make sure that the sample comes freshly from deep in the well To satisfy b one of three techniques may be used The first is to attach a tube to the faucet and fill the vial using the tube The second is to hold a bowl up to the faucet so that water overflowing from the bowl prevents the water leaving the faucet from touching air The vial is then placed at the bottom of the bowl and allowed to fill The third method combines the first two 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 250mL vial if the radon concentration is probably less than 3 000 pCi L or 100 000 Bq m3 or a 40mL 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 pieces of Tygon tub
44. orrection is necessary to the reading 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 26 2015 DURRIDGE Company Inc 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 will 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 reading
45. r WAT250 protocol In fact the two could be made with the same sample First make a normal RAD H20 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 Water Samples Properly aerating water samples larger than 250mL requires separate hardware specifically the Big Bottle System and involves a more complex procedure The Big Bottle System facilitates the measurement of water samples as large as 2 5 liters Please see the Durridge website www durridge com for details 28 2015 DURRIDGE Company Inc BIBLIOGRAPHY BIBLIOGRAPHY Abdalla S A T Measurement and Application of Radon in South African Aquifer and River Waters Department of Physics U
46. re 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 negligible levels for the most accurate low level radon in water measurement The charcoal filter works best if you 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 rela
47. ring the five minutes of aeration the radon on the left the water vial with aerator and the tube concentration in the air loop approaches equilibrium of desiccant supported by the retort stand above with the remaining radon in the water 8 2015 DURRIDGE Company Inc 1 GETTING STARTED 1 4 to 1 8 Reducer P L 1 4 D Air ron se Manna en mmm kam Small Retort P L 14 ID Stand Aerator Cap 2 fi Small Drying Tube T Valve 24 L 1 8 ID 24 L 1 8 ID 3 L 1 8 ID RAD7 Outlet c Inlet Filter RAD7 40 or 250 ml Collection Vial Glass Frit EE Fig 3 RAD H20 Schematic When the RAD7 is set to Wat250 or Wat 40 mode it automatically calculates the radon concentration in a 250mL or 40mL water sample based on the radon concentration of the air entering the instrument For this calculation to be performed accurately the components must be assembled exactly as shown 1 4 Running a Test These are brief simple instructions just to gain an initial introduction to the technique A more thorough treatment follows later in the manual 1 4 1 Preparing the RAD7 Before making a measurement the RAD7 must be free of radon and dry To achieve this it should be purged for some time It is convenient to use the larger laboratory drying unit during the initial purging process to save the small drying tubes for the actual measurement Hook up t
48. round the same time so that the results can be compared without having to make separate corrections for radon decay or any other time based factors See Section 1 4 2 for more information on sampling technique 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 the background improving sensitivity and precision at low radon concentrations But the larger sample size also limits the method s range somewhat and increases temperature effects 5 2 4 Purging A common cause of error is incomplete purging of the system before a measurement If residual radon exists in the RAD7 and tubing when the RAD H20 vial is hooked up to it that residual radon will be added to the radon provided by the aeration of the sample In the case of a 40mL vial 1 Bq L of 21 2015 DURRIDGE Company Inc 5 ACCURACY AND QUALITY CONTROL residual radon in the loop will be reflected as 25 Bq L additional radon in the original 40mL water sample 5 2 5 Aeration If a 250mL analysi
49. s of the radon in the water when 40mL 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 deviant 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 pr
50. s reads low a common reason is because the glass frit was not at the bottom of the bottle but set for a 40mL vial thus incompletely aerating the 250mL sample Care should be taken to check that the frit is close to the bottom of the vial If a mistake is discovered after the system is properly set up it is permissible to allow some aeration to take place before the WAT250 measurement is started That way the water can be partly aerated with some of the radon already in the closed loop at the start of the test allowing a more complete overall aeration after the five minutes of aeration in the first 5 minutes of the WAT250 measurement 5 2 6 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 the RAD7 When the relative humidity is down once more the pump must be set back to GRAB 5 2 7 Temperature The temperature effect on accuracy is very small with the 40mL
51. 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 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 persistent 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 tha
52. t 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 18 2015 DURRIDGE Company Inc 4 RESULTS 4 RESULTS 4 1 How Calculation Is Made The RAD7 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 volume of the air loop the volume of the sample and the equilibrium radon distribution coefficient at room temperature For the 40mL sample volume the conversion coefficient is around 25 For the 250mL 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 coun
53. ted 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 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 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 4mL sample and dilute it with 36mL of distilled water in a 40mL 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 tak
54. tive humidity back down to close to 5 17 2015 DURRIDGE Company Inc 3 RAD H20 TECHNIQUE 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 daughter 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
55. tocol 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 of 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 RAD7 is printing the header insert the glass frit into the tygon tubing extending from the cap 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 tygon tubing if necessary Screw the flow adaptor cap onto the sample vial The vial can be inserted in a space in the RAD H20 case to keep it secure It must be upright while aeration is in progress 10 2015 DURRIDGE Company Inc 1 GETTING STARTED 1 4 4 Starting the Test 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 lat
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