Radon Progeny Rejection with CANBERRA Argos™
Contents
1. A single zone or single detector section would still be considered contaminated if it were determined to be above 5 000 dpm and 1000 dpm alpha activity or beta activity respectively Radon Rejection Enable Ratio Net Rate Ratio Sum Zones Enable p Hand Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Foot Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Body Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Head Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Shoe Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 If Radon is Detected Beta Alpha Ratio within limits Apply during Alarm Test Enable Apply to Gamma Detectors Disable Pee u a CA uai Detectors that show radon Sis Use CTP instead of ATP on No Detectors Use Multipliers on No Detectors More Aggressive 2 Don t allow any of the Sum Zones to alarm if any one 1 detector section or any one 1 Sum Zone has the correct beta alpha ratio For example if detector section 6a leg had a beta alpha ratio greater than or equal to 0 6 AND less than or equal to 6 0 no sum zone would alarm Again single detector sections would still alarm if they were above the alarm set points Radon Rejection Enable Ratio Net Rate Ratio Sum Zones Enable Foot Beta Aipha Ratio Lo Limit 0 60 Hi Limit 6 00 Body Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Head Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Shoe Beta Alpha Rat2. Sts 2 Acorns Tesi Menu F3 Setup Menu F4 Faults F5 Information Menu F6 Printout Menu F7 Demonstration Display Menu F8 Maintenance Log F9 Recent Event Log Alt F4 Exit Program Setup Menu F1 Common Values F2 Wait Timeouts F3 Detection Zones F4 Out of Service Causes F5 Configuration F6 Operation Voice amp Screen F7 Data Log F8 Printout F9 Data Network Transfer F10 Radon Rejection _ F11 Instructions Esc Return to Service Menu Note that currently as seen below while Enabled no action is actually taken by the monitor to change any settings If Radon progeny are is Detected Beta Alpha Ratio within Limits However in this Enabled state even though no action is being taken the Monitor starts to collect data in a file called RADON csv This file and the RESULTYYYYM MDDHHMMSS TXT files will contain the BETA ALPHA ratios for all Possible changes which might occur and how when the changes will be made is determined by several factors These are described in the following paragraphs By default the Radon Progeny Rejection will be set to the Disabled state Toggle the key to enable When enabled the monitor will come up in the Factory Default settings Radon Rejection Radon Rejection Radon Rejection Radon Rejection Enable ct cm Met Rate Ratio Sum Zones Enable Hand Beta Aipha Ratio Lo Limit 1 50 Foot Beta Aipha
3. 00 Foot Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Body Beta Alpha Ratio Lo Limit 0 60 Hi Limit 9 00 Head Beta Alpha Ratio Lo Limit 0 60 Hi Limit 7 00 Shoe Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 If Radon is Detected Beta Alpha Ratio within limits Apply during Alarm Test Enable Apply to Gamma Detectors Disable Don t allow Sum Zones to Alarm on Al Detectors if any show Hoes Use CTP instead of ATP on All Detectors if any show radon Use Multipliers on Detectors that show radon Hand Alarm Activity Multiplier 1 00 Foot Alarm Activity Multiplier 1 00 Body Alarm Activity Multiplier 2 25 Head Py pon Activity Multiplier 2 25 Shoe Alarm Activity Multiplier 1 00 10 As seen on the Monitor program Radon Rejection The Contaminated Screen bitmap generated from an individual with radon progeny on them is generated when a contaminated result is found The ratios are calculated for the individual detector zones detector 5 a leg detector for example has three sections 5a 5b and 5c The beta alpha ratio is calculated for each single zone In addition detector 5 also has SUM ZONES associated with it we will just consider single detector section zones for the purpose of illustration these are intra pairs 5a 5b and 5b 5c When we look at a RESULT TXT file for the front side denoted by a P1 C suffix on the file to denote that the result was contaminated C and the front side po
4. Beta Alpha Ratio Lo Limit hoe Beta Alpha Ratic f Rador Radon Rejection S Aacqcor ne a Ratic iand Beta Alpha Rato Lo Limit Foot Beta Aloha Rato Lo Limit Beta Aloha Ratio Lo Limi Head Beta Alpha Ratio Lo Limit noe Seta Alpha Kato Li An individual steps into the monitor and is counted on the front side then turns around and is counted on the back side After each side s count is completed the monitor has calculated the beta alpha ratio for the individual zones and in the case for settings above the beta alpha ratio for the activity in any of the sum zones Ratio Sum Zones set to Enable are also considered The monitor then makes the following comparisons 1 It checks the ratios against the Lo Limit and the High Limit in each of the areas monitored 2 Ifthe beta alpha ratio is within the limits specified in the settings which are 0 6 to 6 0 as seen in figure X below it sets a Radon progeny Detected flag to YES for those zones 3 Ifthe beta alpha ratio is outside the limits in this case less than 0 6 or greater than 6 0 the Radon progeny Detected flag gets set to NO for those zones Now that the decision flags have been set some actions are then taken or not taken by the Monitor program SOME TYPICAL SETTINGS AND ACTIONS Many customers find settings for the Beta Alpha ratio in the 0 6 to 6 0 range to be effective However ratios as high as 15 have been u
5. Limit 0 60 Hi Limit 6 00 Body Beta Alpha Ratio Lo Limit 10 60 Hi Limit a Head Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Shoe Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 If Radon is Detected Beta Alpha Ratio within limits Apply during Alarm Test Enable Apply to Gamma Detectors Disable Don t allow Sum Zones to Alarm on All Detectors if any show radon So ALALE EAE All Detectors if any show radon Saas Use Multipliers on K Detectors More Aggressive 5 Now the Alarm settings use multipliers Alarm level setting times the multiplier of 5000 dom times 2 25 11 250 dpm for detectors on the monitor if that single detector has the beta alpha limit within the limits Detectors or SUM Zones which do not have the correct ratio do not have alarm multipliers applied The aggressiveness of this approach can be adjusted by the multiplier value Radon Rejection Radon Rejection Ratio tatio Sum Zones Hand Beta Aloha Ratio Lo Limit Foot Beta Alpha Ratio Lo Limit Body Beta Alpha Ratio Lo Limit Head Beta Alpha Ratio Lo Limit Shoe Beta Alpha Ratio Lo Limit if Radon s Detected Beta Alpha Ratio r Apply dur Alarm Test Apply to Gamma Detectors allow Sum Zones to Alarm on Use CTP instead of ATP on Jse Multipliers on Hand Alarm Activity Multiplier Foot Alarm Activity Multiplier Body Alarm Activity Multiplier Head Alarm Activity Multiplier Shoe Alarm Activity Multiplier Most Aggressive 6
6. Now the Alarm settings use multipliers Alarm level setting times the multiplier of 5000 dpm times 2 25 11 250 dpm for every detector on the monitor if any single detector or sum zone have the beta alpha limit within the limits The aggressiveness of this approach is now limited only by the value of the multiplier Note The value of a multiplier can target to the most problematic areas or left at 1 0 no effect for areas where one would not want to increase the alarm level setpoint Radon Rejection Radon Rejection Ratio Ratio Sum Zones Hand Beta Alpha Ratio Lo Limit Hi Limit Foot Beta Alpha Ratio L mit Hi Limit Body Beta Alpha Ratio Lo Limit Hi Limit Head Beta Alpha Ratio Lo Limit Hi Limit Shoe Beta Alpha Ratio Lo Limit Hi Limit If Radon is Detected Beta Alpha Rat Apply during Alarm Test Apply to Gamma Detectors Don t allow Sum Zones to Alarm on Use CTP instead of ATP on Use Multipliers on Hand Alarm Activity Multiplier Foot Alarm Activity Multiplier Body Alarm Activity Multiplier Head Alarm Activity Multiplier Shoe Alarm Activity Multiplier Final Safety Fallback So you ask Where is your ultimate safety fall back position on this The answer is in enabling the High Contamination Alarm in the Common Values Section F1 from the Setup menu and its associated High Activity Limit set globally for the monitor in the Global Setting F3 Shift F5 from the Setup Menu and then Alt 1 for beta Alt 2 for alpha Al
7. elevated alpha contamination or not at all Applicable Guidance and Acceptance Criteria e The Institute for Nuclear Power Operations INPO and the American Nuclear Insurers ANI have acknowledged the ability of monitors to identify naturally occurring materials such as radon progeny For example INPO states the following If the monitor does not have the ability to account for radon have procedures in place to evaluate alarms for short lived or natural radioactivity e Similarly the American Nuclear Insurers ANI notes in ANI Section 8 5 Radiation Protection Bioassay The bioassay program should be governed by a set of procedures which describe the following 8 5 2 7 Methods to determine whether PCM PM alarms are caused by radon noble gas internal contamination distributed external contamination or discrete hot particles and If Radon is determined to be the cause of the alarm a PCM with Radon alpha discrimination capabilities may be used to clear the individual e EPRI states the following Radiation Protection Response to Indicated Contamination If contamination is indicated on a person the following steps should be taken 4 Determine if contamination is due to short lived radioactivity i e half life lt 2 hours Such may not be considered a PCE Refere to the EPRI PCE guideline EPRI 2005 And If the suspected contamination is cause by noble gas radon or medical radi
8. progeny when correctly implemented Reduction of these alarms also results in major productivity improvements enabling the radiological protection staff to focus on true contamination events without the distraction of false alarms and management of personnel with radon progeny related alarms Please contact your sales representative to learn how the radon progeny rejection algorithm can be implemented in your facility and obtain customer references References 1 Institute of Nuclear Power Operations INPO INPO 05 008 Guidelines for Radiological Protection at Nuclear Power Stations 2005 2 American Nuclear Insurers ANI ANI Section 8 5 Radiation Protection Bioassay 2008 3 Argos 3 5 Whole Body Surface Contamination Monitors User s Manual Canberra Industries 2010 CE Agos is a trademark of CANBERRA Co iCAM is a trademark of Canberra UK Ltd iSolo is a registered trademark of Canberra Industries Inc CANBERRA Measurement Solutions for Nuclear Safety and Security CANBERRA is the Nuclear Measurements Business Unit of AREVA For more information please visit www canberra com C39338 9 12
9. 2 10 2 4 3 2 5 53 4 4 9969 2 8 46 16a Body 3 0 304 9 fad 10 1 4 4 ad 50 35 4 9909 2 6 47 16b Body 2 9 304 9 6 9 Da T 4 1 2 3 52 4 44 9969 2 6 48 16 Body 3 2 304 9 6 8 9 6 4 0 2 4 55 2 4 9969 3 0 No radon ratio Radon Progeny Not Present According to the monitor Thus per the setup multipliers were only to be used on Detectors that show radon since the beta alpha ratios were zero No multiplier was applied However since the CTP was to be used across the entire monitor Use CTP instead of ATP on All detectors if any show radon But the CTP of 10 1 was just 0 7 cps below the actual net count rate of 10 8 and thus the result was considered to be contaminated No radon ratio no beta alpha ratio was found When no ratio is present radon progeny flag is set to NO and the proper ratio does not exist according to the monitor Thus per the setup multipliers were only to be used on Detectors that show radon since the beta alpha ratios were zero No multiplier was applied However since the CTP was to be used across the entire monitor Use CTP instead of ATP on All detectors if any show radon But the CTP of 10 1 was just 0 7 cps below the actual net count rate of 10 8 and thus the result was considered to be contaminated 12 Practical Determination of the Beta to Alpha Ratio Determination of the Beta to Alpha ratio can be achieved by analyzing the results of the RESULT TXT files however this is time consuming when m
10. 41 4 9967 8 204 3 156 0 98 5 112 8 0 75 0 0 0723 Clean 9 3c Leg 62 4 9965 12 41 3 198 0 98 9 275 180 5 1658 8 0 0754 R Skipped 27 10 4a Leg 15 4 9968 3 002 3 129 0 98 0 9 7 75 0 0 0913 Clean 11 4b Leg 24 464 9968 4 803 3 047 0 98 1 817 9 5 75 0 0 0900 Clean l2 4c Leg 346 4 996 6 803 2 936 1 00 3 867 9 3 73 0 0 0898 Clean i3 5a Leg 20 4 9968 4 003 3 402 1 00 0 601 9 7 75 0 0 0907 Clean 14 5b Leg 26 4 9967 5 203 3 342 0 98 1 927 10 0 75 0 0 0945 R Clean 15 5e Leg 66 4 9965 13 61 3 372 1 00 10 24 180 5 168 8 0 0888 R Skipped 23 2 Radon Rejection 3 Already Skipped 4 Already Contaminated Sum Zone Ratio Below Limit Beta Alarm Test Point zone Description Rib Tb ALS CTP ATP LLO Equiv used Cale Sum Radon cps 5 cps cps cps cps Eq 5 s Ratio Ratio 4 2a FOOT 4 3 304 9 9 6 12 9 6 2 2 8 44 1 4 9969 2 0 2 23 5 b Foot 4 3 304 9 10 4 13 7 0 2 8 40 6 4 9069 1 6 2 03 6 2c Foot 4 0 304 5 10 5 13 9 fob ad 38 9 d 9909 1 f 7 3a Leg 3 1 304 9 6 0 8 7 3 3 d 2 3 4 09069 3 7 amp 3b Leg 3 1 304 9 5 4 8 0 2 8 2 4 68 1 4 9969 4 2 9 3 Leg a 304 5 3 7 180 5 157 0 2 4 63 6 4 9969 4 0 4 27 10 4a Leg 3 1 304 9 6 8 of 4 0 2 4 53 7 4 9969 2 9 11 4b Leg 4 0 304 9 6 7 9 5 3 59 2 3 53 95 4 9969 2 9 12 4 Leg 2 9 304 9 6 7 9 5 3 9 2 3 53 7 4 9969 2 9 13 5a Leg 3 4 304 9 6 8 9 7 3 59 2 5 56 4 4 9969 3 1 14 5b Lag 3 3 304 9 fal 10 0 4 2 2 4 J3 35 4 9969 2 8 2 05 15 5c Leg 3 4 304 9 6 7 180 5 157 0 2 5 57 4 4 9969 3 2 13 gt 11 While the radon prog
11. A CANBERRA Application Note Radon Progeny Rejection with CANBERRA Argos 5AB Personnel Contamination Monitors ATOMIC MASS A ATOMIC NUMBER Z CANBERRA personnel contamination monitors and in particular the ARGOS 5AB gas flow proportional model are used throughout the world s nuclear industry Typically these monitors are designed to detect surface contamination from alpha beta and gamma emitters if the gamma option is installed however the units also have the capability to reject the presence of radon progeny which often plates out on synthetic clothing materials and plastic objects such as polyester clothing fleece and hard hats Activity levels of these progeny have the potential of exceeding the alarm set points for external surface contamination typically set to detect 5000 dpm 8 1000 dpm a 83 33 Bq amp 16 67 Ba respectively thus presenting results which appear to be Contaminated when the alarm indication is due to naturally occurring radioactive materials and not plant or facility related licensed material To complicate matters many plants have set more conservative alarm level settings sometimes considering the presence of difficult to detect isotopes in the station radionuclide mix as recommended by INPO INPO 05 008 In this application note the following topics will be covered Background of the problem Method of rejection Guidance and Acceptance Crit
12. Ratio Lo Limit 1 50 Body Seta Alpha Ratio Lo Limit 1 50 Head Beta Alpha Ratio Lo Limit 1 50 Shoe Beta Aipha Ratio Lo Limit 1 50 Hi Limit Hi Limit Hi Limit Hi Limit Hi Limit 1 80 1 80 rm 1 80 1 80 1 80 If Radon is Detected Beta Aipha Ratio within limits Apply during Alarm Test Apply to Gamma Detectors Don t allow Sum Zones to Alarm on Use CTP instead of ATP on Use Multipliers on Enable Disable No Detectors No Detectors No Detectors F6 Set Factory Defautt Ctri F6 Set All Factory Defaults Ctri F7 Recall Previous Settings lt gt Y Enter Select item Change Value Ctrl Fast Change Esc Return to Setup Menu FACTORY DEFAULT SETTINGS WHEN REJECTION IS ENASLED F6 Set Factory Default Ctri F6 Set All Factory Defaults Ctri F7 Recall Previous Settings 4 lt gt Y Enter Select item Change Value Ctri Fast Change Esc Return to Setup Menu How does the monitor determine if Radon Progeny is detected Using the basic premise that we discussed at the beginning of the Application Note the Monitor software makes this decision based upon the Beta Alpha Ratio The Ratio is calculated in one of two ways One being the Net Rate in cps of the Beta Alpha count rate and the second or the Activity being the beta count rate efficiency divided by the aloha count rate efficiency ii Radon Rejection Radon Rejectior oot
13. Recall Previous Settings 4 4 gt V Enter Select item Change Value Source Activity dpm Ctri Fast Change Ctri E Edit Date Esc Return to Setup Detection Zones Menu Alarm Test Source Dimension cm Calibration Source Source Activity dpm Date Dimension cm A PRACTICAL DEMONSTRATION The easiest way to demonstrate how this all works in practice is to use some actual preliminary files settings from a monitor at a facility with significant radon progeny levels At this facility the beta activity levels on some clothing polyester blend pants and hardhats were in excess of 15 000 dpm as reported by the monitor The typical alarm level settings for this facility are as follows Alarm Level settings 1 Beta 4500 dpm 4r 2 Alpha 1000 dpm 4r Radon Progeny Rejection settings as seen below can be seen in the SETUP TXT file and a screen capture from the Monitor program Note that you would typically not use both the CTP and multipliers at the same time as the monitor determines the CTP first and then applies the multiplier value More exact control can be achieved by adjusting the multiplier alone and not use both the CTP and multipliers combined SETUP TXT File SETUP TXT Notepad File Edit Format View Help F3 setup F10 Radon rejection Radon Rejection Enable Ratio Net Rate Ratio Sum Zones Enable Hand Beta Alpha Ratio Le Limit 0 60 H Limit 6
14. a Ratio Zone TRadon Detected Zone 9 Beta Aiph Radon De BetaiAlph Radon Di Be 11 5774 ng 11 0672 x0 Once all the data associated with the collection of volunteer personnel is collected the RADON CSV file can be analyzed by body area and the average ratio s selected Various analyses may be performed to determine the averages ranges and most appropriate ratios to be selected for trial in the monitors Fil RadonProgenRatioAnalysis xisx A B D E F G H l J K 1 Monitor ID Location IE Serial Num Date Time YYYY Position Beta Alpha R Radon Dete Beta Alphz Radon Det Beta Alphz Radon Det 1939 1940 Max 1690 4084 2013 1941 Min 0 01 0 01 0 07 1942 AVG Not 0 lt 15 gt 0 5 3 5 2 5 7 1943 AVG Not 0 lt 50 gt 0 8 5 8 7 9 8 1944 i AVG Not 0425 20 eat 5 9 74 1945 Cells Zone beta alpha beta alpha beta alpha 1946 BBtoDB 25to 51 B 5 6 9 7 7 4 1947 ENtoER 70 to 72 lead 5 8 9 7 7 4 1948 DD to DT 52 to 60 5 1 8 2 6 4 1949 DV to EF 61 to 66 3 5 0 77 6 3 1950 FioP 1to6 00 5 5 9 1 7 0 1951 ETtoEX 73to75 6 4 12 0 8 4 1952 RtoAZ 7to24 Le 5 6 9 6 7 3 1953 Hi 67 to 69 i 5 4 8 6 8 14 Collection and Analysis of data Setting up to perform and document the collection of radon progeny data by considering the inclusion of the following elements Outline a test plan and the steps needed to complete the testing Determine a location within your facility that you have identified as a source of radon prog
15. any files need to be evaluated Once radon progeny rejection has been enabled on the monitor the monitor will collect the beta alpha ratio data for each and every zone of the monitor for every individual monitored in the RADON CSV file The Radon Detected flag may be NO in these trials since you are collecting data to determine the beta alpha ratio and if the ratio does not agree with your settings then the NO flag will be set CONTAM CSV 1 Monitor ID Location ID Serial Nur Date Time YYYY MM DD hh mm ss 00 Beta UTP Beta BKG 9 2 20224 XXX 11 17 10 9 50 AM 3 20224 XXX XXX 11 17 10 9 50 AM 4 4 5 4 6 7 8 9 RADON CSV ms a M 0 E 1 Monitor IC Location ID Serial Nut Date Time YYYY MM DD hh mm ss 00 Positio 2 20224 0X0 11 17 10 9 50 AM TS 20225 11 17 10 9 50 AM 4 5 Here a RADON CSV file has been copied from the DATA LOG folder of an Argos 5AB Monitor Note that for all contaminated results a corresponding data and time stamped entry will also be made in the CONTAM CSV file These are results extracted for a single individual who was determined to have radon progeny on the legs of his pants in zone 9 and zone 16 these zones correlate to detector sections 3c and 6a as seen in the zone pictorial below Only the data from zone 9 is displayed in the Excel sheets w x a z Beta NET9 Beta UTP9 Beta BKG Beta NET Beta Alpha Ratio Radon Detected Zone 9 13 11 5774 no 11 0672 no 7426 dpm y wW R T U beta Alph
16. application note A number of pictorial representations can be seen in Figures 1 2 3 4 5 and 6 showing single detector zones and what different series of a sum zones are comprised of zones are shown by cross hatching Grayed out detectors indicate that those detector sum zone combinations are not possible These sum zones can also be used to determine the beta alpha ratio present to drive radon rejection actions of the monitor Figure 1 Single Zone Figure 2 Intra Pair Sum Zone Figure 3 Inter Pair 9 3 MES St mei i a aa BER BLE BLE ICE Gc Figure 4 Inter Pair Figure 5 Quad Zone Figure 6 Another Quad Zone a El GER FEN WEE TCE ELE ECE Ee BE ES ICE SES SLE z k p7 THE f eA la f ja Le ES BWCE ECE ECE pee fats NEE EGT SOW FZE AEN AE The Argos Monitor Software The monitor software includes data collection results files and archiving capabilities which enable the easy collection of monitoring data related to establishing your beta to alpha ratios for radon progeny rejection or radon rejection It is possible to enable radon rejection in the software and capture data to tune your beta alpha ratios and settings Let s look at the data files present on the Argos monitor and see what radon progeny rejection related data and settings are available The basic settings are available only if radon progeny rejection is enabled So from the Service Menu of the monitor availabl
17. ar way to immediately and positively identify the cause as activity from radon progeny without some type of spectroscopy While this spectroscopy is practical using very close and constant geometry as is done using CANBERRA s iSolo and iCAM products this method isn t possible using either gas flow or solid scintillation based alpha beta detectors due to variable and potentially significant distances relative to the range of the alpha particle from the detectors and the lack of sufficient spectroscopic capabilities of these detectors In a typical nuclear power situation the personnel or equipment such as hard hats which were determined to be contaminated at the RCA exit point and thought to be so from radon progeny would sit off to the side and wait for the short lived radon progeny to decay Once decay had occurred personnel would make additional attempts at passing through the monitors to achieve a Clean determination On days where radon and thus radon progeny concentrations may be high it may not be uncommon to have a handful or up to a dozen or more personnel and objects waiting to decay prior to exiting the RCA Many personnel waiting is costly to the utility facility because personnel are still on the clock sometimes collecting overtime pay as well as stressful annoying to the employees who cannot leave the RCA for home meals or other engagements In addition the possibility of true contamin
18. ation may also be on the workers minds The potentially contaminated personnel objects clothing such as hard hats can become a distraction as well as an additional source of unnecessary work surveys for radiation protection personnel who may already be short staffed This is often likely the case If the monitor does not have the ability to account for radon have procedures in place to evaluate alarms for short lived or natural radioactivity INPO 05 008 Thus procedures and personnel must be available to deal with radon progeny if an automated system is not available The Basic Method The method used by CANBERRA involves the use of the beta to alpha activity over a range of body locations to trigger monitor actions and settings dependent upon the appropriate selection of the ratio In selecting this ratio one must consider several factors to avoid the identification of contamination resulting from plant operations as radon related Typical plants without failed fuel have beta to alpha activity ratios that are in the 100 s of thousands to millions to one Thus the typical expected presence of any alpha related activity would not be due to normal plant operation but most likely from radon related decay products If sufficient alpha activity is present due to facility conditions source term then this method must be used with extreme caution conservatism restricted to personnel who are not working in areas of potentially
19. e by using the USB keyboard plugged into the computer of the monitor press the escape key Once in the Service Menu press the CTRL F10 key combination this is a hidden key combination which will place you in the Factory Setup Menu from the Factory Setup Menu select F1 Model Selection Care should be used in this menu as it is possible to change the monitor type and other configurations that may cause you to lose your original monitor settings Please see the user s manual to make sure you have backed up your settings prior to entering this menu F1 Place in Normal Service F2 Test Menu Shift F 2 Additonal Test Menu F3 Setup Menu F4 Faults F5 Information Menu F6 Printout Menu F7 Demonstration Display Menu F8 Maintenance Log F9 Recent Event Log Alt F4 Exit Program actory Setup Menu F1 Model Selection F2 Operation Configuration F3 Badge Configuration F4 Access Configuration FS Head Configuration F6 Access Level Settings F7 Dosimeter Reader Configuration Esc Return to Service Menu Using the keyboard down arrow to the bottom of the menu and highlight the Radon Rejection Support and toggle the key to set this to YES Press the ESC key twice to retain your settings and return to the Service Menu Note that your menu may appear different for other settings as these screen captures have been produced on a demonstration software version of th
20. e monitor Model Selection ME GERTE E Sanar F Set Factory Defautt Grief 6 Set All Factory Defaults Chief Recall Prewous Settings Model Argos 5 48 Zeus Demanstration Seip Language English _ EN dll Font AR LAL A db F Enter Select term Change Value Aumiary Sensor Board insmlied NO Access Compra Cii Fest Change Head Meter Corral Board aataled YES Meweabie Head Detector Esc Return to Fectory Setup Manu Hid Detector bretalied Alpha Gata iter Detector 30 installed NO Built in ar Side Maum item Detector J1 imsialed NG Built in or Sids Maim Shoe Detector inaiallied Alpha Bata Body Detectors iasialied 3 Tote Gamma Activity Suppor MO Detector O1 installed Alpha Beta Detector Od installed Alpha Beta Detector 37 instalied MO Enskar Oetector lasialan NO Aipha Deiechan Mode Channel 2 Bete Detection Meade Channa 1 Gamma Deteccion Mode Channa 3 Darmonsiraton YES Simulator MG Have Progam Siart Clear All Pula MO Aow Condiionai Barace YES Aiow Gamma Oniy Condionai Semere YES Radon Rejecbon Supocet s Krypton Mode Suppor YES Now that your monitor has been enabled at the Model Selection Level it is time to proceed to enabling the rejection settings within the Setup Menu The Setup Menu is selected by pressing F3 on the Service Menu then select F10 Radon Rejection to enter the radon progeny rejection setup screen ervice Menu F1 Place in Normal Service F2 Test Menu
21. eny and the absence of licensed material Configure the monitor so it is ready to collect data Make sure all monitors are operational and have recently passed their routine performance alarm testing successfully Have volunteer personnel wear clothing materials such as micro fleece plastic hardhats and polyester synthetic blend materials If you have identified problem clothing make sure to include this in the testing Consider the use of some control personnel who DO NOT wear materials which accumulate radon progeny Monitor all personnel in an Argos unit and get a clean determination on each individual prior to putting them into the area of radon progeny It is possible for personnel to have radon progeny on them from their home environment which may still be present on their clothing depending upon the levels at home and the time it takes them to travel from home to work After the data has been collected and analyzed and the monitors have been setup for radon progeny rejection send personnel back through the monitors after accumulating radon progeny to judge the efficiency of the rejection settings Some typical reductions in radon related alarms range from approximately 60 to 75 Define an acceptance criteria goal for reduction of alarms Determine how aggressive you can be in reducing radon progeny alarms This will depend upon the range and the severity of your radon problem 15 Have a recent
22. eny rejection worked for these detectors still several detectors were considered contaminated and likely were due to radon progeny So why weren t these detectors caught by the radon progeny rejection Let s have a look at detector 16a on the front of the body which can be seen in the Contaminated image at being at 6 706 dpm If we look for detector 16a in the RESULT TXT file we see the following Monitor Contaminated Results 14 25 31 wednesday a oie 2010 CANBERRA Argos 5AB Zeus Version 8 01 100902 serial Number 1009 220 20224 EXELON NUCLEAR Position 1 Extended Count No Radon Detected Yes Count Time 4 9969 5 Beta Results K Alpha 3 000 K Betal 2 000 K Beta2 2 000 Zone Description Raw Live Gross ekg self Net uTP alarm Eff Result Counts Seconds cps cps shid cps cps ra 4 2a Foot 25 4 9968 5 003 4 277 1 00 0 7257 6 2 5 0 0 1277 R Clean 5 2b Foot 23 4 90968 4 603 4 284 1 00 0 3191 7 0 7 75 0 0 1387 R Clean 6 2c Foot 19 4 99608 3 803 3 989 1 00 T 73 0 0 1404 clean 45 15c Body 20 4 9968 4 003 3 523 0 98 0 550 75 0 0 0964 Clean 46 16a Body 69 4 9966 13 81 3 008 1 00 amp 10 8 10 J5 75 0 0 0967 CONT art lt q 47 16b Body 16 4 9968 3 603 2 982 0 98 0 68 aq 75 0 0 0917 Clean 43 16 Body 22 4 9968 4 402 3 211 1 00 1 191 4 0 75 00 0906 Clean Beta Alarm Test Point zone Description RE Tb ALS CTP ATP LLO 3 Equiv Used ale Sum Rador eps 5 eps eps cps eps Bq s 5 Ratio Ratio 45 15 Body 3 5 304 9 f
23. eria Argos Monitors and Software Determination of the Presence of Radon Progeny Specific Settings Practical Demonstration Example Data Collection and Analysis Summary Background the radiation and problem Radon is a colorless and odorless radioactive gas that is produced by the radioactive decay of radium Radium is a product of uranium decay and is found in trace amounts naturally in nearly all rocks soils and groundwater as well as building materials plants animals and the human body One of the known characteristics of radon related contamination events is that they are normally very close to release limits i e low activity Note the radon decay chain shown on the previous page Note the short lived alpha and beta emitters which are present as radon progeny Po 218 Pb 214 Bi 214 Po 214 which attach themselves to clothing and objects From the decay chain one might expect a certain fixed beta to alpha particle ratio if this chain was in equilibrium However in practice in air and particularly on objects the decay products are not in a set equilibrium Many factors can affect the measured ratio including e Attenuation of alpha in air i e distance from the detector e The type of ventilation system s e The concentration of progeny on the monitored object and in the air e The time elapsed from acquiring radon progeny on clothing to the monitoring point The problem also arises in that there is no cle
24. io Lo Limit 0 60 Hi Limit 6 00 If Radon is Detected Beta Aipha Ratio within limits Apply during Alarm Test EHH Apply to Gamma Detectors Disable Pe ere Tar une All Detectors if any show radon S Use CTP instead of ATP on No Detectors Use Multipliers on No Detectors More Aggressive 3 Sum Zone Alarms are turned off for only detectors that show radon ratio within limits but now the CTP definitely contaminated Alarm level is used Please see the definition of ALS ATP CTP and UTP in the Argos manual for further specifics Radon Rejection more Aggressive 3 Radon Rejection Enable Ratio Net Rate Ratio Sum Zones Enable Hand Beta Aipha Ratio Lo Limit 0 60 Hi Limit 6 00 Foot Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Body Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Head Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Shoe Beta Aipha Ratio Lo Limit 0 60 Hi Limit 6 00 if Radon is Detected Beta Alpha Ratio within limits Apply during Alarm Test Enable Apply to Gamma Detectors Disable Don t allow Sum Zones to Alarm on Detectors that show radon a_ Ory Benders hele aE Detectors that show radon 4 Use Multipliers on No Detectors More Aggressive 4 D Radon Rejection More Aggressive 4 Radon Rejection Enable Ratio Net Rate Ratio Sum Zones Enable Hand Beta Alpha Ratio Lo Limit 0 60 Hi Limit 6 00 Foot Beta Alpha Ratio Lo
25. l the potential actions by the Radon Progeny Rejection are overridden if the contamination level exceeds the levels set This value is set at 22 200 dom times the efficiency value of the detector for beta or alpha respectively For a nominal efficiency value of 10 the High Contamination Alarm would be triggered at a net count rate of 2 220 net cps The level can be set differently for various areas foot top of shoe body head and hand by using the F5 Group Settings ommon Values 7 O Mwl F6 Set Factory Defaut Ciri F6 Set All Factory Defaults Ctri F7 Recall Previous Settings Senal Number a 4 6 Enter Select item j t Change Value Count Rate Units Esc Return to Setup Menu Activity Units l Emission Rate Units Location ID Alarm Calibration Type Activity 417 High Contamination Alarm High Alarm Avctrity Efficiency Extend Count if Contaminated YES Count Feet in 2 Steps YES The High Contamination Count Gamma Body in 2 Steps YES Alarm Activity overrides Count Head in 2 Steps YES any Radon rejection setting Enable Krypton Mode Service NG Approach Sensor dunng Initialize Background Stay Back Measurement Variance Ratio Limit Exceeded Notify Background Change Detectors Numeric Notation Engineering h newer lobal Settings Beta High Alarm Activity Ve Alarm Activity 5000 dpm 41 F6 Set Factory Default High Alarm Activity domin Ctri F6 Set All Factory Defaults Ctri F7
26. ly prepared representative plant smear to test that the radon progeny rejection settings do not pass personnel with a plant smear on them as Clean This is needed to validate the radon progeny rejection settings Prepare a representative plant smear using methods outlined in the most recent INPO How To RP 1 4 documents available on the INPO web site Challenge the response and performance of the Monitor in the presence of Radon Progeny only Radon Progeny plus a representative plant smear and the performance of the monitor with Radon Progeny rejection enabled and disabled Determine your acceptance criteria for overall performance Does the radon rejection setting identify actual contamination at an acceptable level in the presence of radon progeny Does the monitor perform acceptably in the absence of radon progeny with radon progeny rejection enabled The monitor should pass the INPO How To RP 1 4 at 90 or better in the absence of radon progeny and ideally at the same rate with radon progeny present Determine the rate at which you will consider the rejection settings successful with significant radon progeny present Will greater than 80 be successful Consult the User Manual and the CANBERRA Services and Application Support Group ASG for assistance or services to complete testing Summary CANBERRA radon progeny rejection algorithm has been demonstrated to significantly reduce the number of false alarms due to radon
27. oisotopes as identified through decay counting isotopic analysis worker interview or knowledge verification of plant conditions such as leaks or environmental inversions then the article of clothing may be e Left in a designated area for decay and may be resurveyd later for release e Decontaminated and returned to the owner e Released based upon isotopic analysis So guidance exists from industry documents and recommendations acknowledging the problems of radon progeny and methods to deal with these problems using contamination monitors and methods The Monitor The ARGOS 5AB as typically configured at many nuclear power facilities includes up to twenty five 25 gas flow proportional detectors each detector having three 3 separate smaller detectors or zones per large detector These smaller zones may be configured combined as virtual detectors as sum zones The principle behind the use of a sum zone s is to be able to detect contamination which may be between detectors in the minimized areas of the frame which has no detector exposed also known as dead zones As a consequence of this assumption that the source is between zones the efficiency is lower and spread disperse activity which is characteristic of radon progeny deposition the sum zones normally tend to alarm more frequently for radon progeny However this has been addressed in how the monitor handles such contamination and will be discussed later on in this
28. sed The following screen captures will progress from the least aggressive to the most aggressive settings to reduce radon progeny false alarms This is often the way that the radon progeny rejection can be setup in an experimental fashion in real time while individuals whom are known to have radon progeny on them are available for testing Starting out with the least aggressive settings and continuing to take steps using settings until an acceptable level of clearance of individuals as clean is achieved Once the settings have been tweaked experimentally a freshly made representative plant smear should be created and placed on individuals passing through the monitors to ensure that actual contamination does not exit the RCA The idea is that the plant smear will should make the beta alpha ratio high enough so that it exceeds the upper level of the ratio setting Least Aggressive 1 Turn off Sum Zones Alarms for just those detectors that have the beta alpha ratio within the limits from 0 6 to 6 0 Don t allow Sum Zones to Alarm on Detectors that show radon progeny So any sum zone which would normally be considered contaminated nominally 5000 dpm or greater beta or 1000 dpm or greater alpha would not alarm and would give a Clean result Note that this happens ONLY for SUM ZONES combinations of individual detector sections where at least one of the detectors within the sum zone has a Radon Detected flag set to YES
29. sition 1 P1 Figure below we can see the beta alpha ratio for these detectors For detector 5c the Radon Ratio is 4 3 which is in between 0 6 and 9 0 beta alpha ratio Thus Radon Detected Yes in the header of the file Thus the monitor has taken the following actions If radon was detected the Alarm level was multiplied by 2 25 so we see the Alarm of 75 Bq times 2 25 is now set at 168 8 Bq Monitor Contaminated Results CANBERRA argos 5AB serial number Position 1 Extended Count No Radon Detected Yes Count Time 4 9969 Also in this case CTP will be used instead of CTP so the CTP for this new Alarm Level is 180 5 Bq This has been set on detectors in the Body section Note however that the multiplier for the Foot is set at 1 0 so the Alarm setting is unchanged However since we are using CTP instead of ATP on All Detectors if Any Show Radon the Used Trip Point for the Alarm is set at the value for CTP Thus all the actions that were to be taken were applied Beta Results K Alpha 3 000 K B tal 2 000 K Beta2 2 000 Fone Description Raw Live Gross Bkg self Met UTP Alarm Eff Result Counts seconds cps eps shld eps cps Bq 4 2a FOOT 25 4 9966 3 003 4 2 7 1 00 0 7297 12 9 75 0 0 1277 R Clean 3 26 Foot 23 4 9966 4 603 4 284 1 00 0 3191 13 8 75 0 0 1387 R Clean 6 2c Foot 19 4 9968 3 803 3 989 1 00 O 13 9 75 0 0 1404 Clean 7 3a Leg 22 4 99668 4 403 3 211 0 98 1 256 B T 73 0 0 0795 Clean 8 3b Leg
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