Sampling Airborne Radioactivity Generic Soil Sampling

Transcription

1 Sampling Airborne Radioactivity Generic Soil Sampling 15 th Annual OSC Readiness Training Program

2 Air Sampling Primary Tasks 1. Collect 2. Count 3. Calculate 15 th Annual OSC Readiness Training Program 1

3 Air Monitoring Air monitors Alpha Isotope specific Sensitive to dust Low sensitivity Beta Complex Not Isotope Specific Gamma Particulate Size important Chemistry important Not a stand alone field instrument because additional analysis is required. 15 th Annual OSC Readiness Training Program 2

4 Purpose of Sampling Protect workers Normally have respiratory protection Work close to scene, changing radiological conditions Personal or representative sampling Protect public No respiratory protection More stable radiological conditions Lower thresholds larger samples 15 th Annual OSC Readiness Training Program 3

5 Air Sampling Considerations Sampler power, exhaust, location Filter type Collection time Interferences Atmospheric conditions Labeling Handling Disposition 15 th Annual OSC Readiness Training Program 4

6 Air Sampling Considerations Airborne alpha radioactivity at 1 DAC that falls out and deposits on flat surfaces may only attain 10% of the criteria for removable contamination. Alpha contamination in excess of 100 times the criteria for removable contamination may only generate 10% of a DAC when walking through. CONCLUSION: DACs are not a good indicator of surface contamination, and vice versa; but SHOULD be considered. 15 th Annual OSC Readiness Training Program 5

7 Air Sampler Calibration Calibrate annually. Calibration is filter media specific changing filter type invalidates calibration. Follow steps in H-810 quick start procedure. 15 th Annual OSC Readiness Training Program 6

8 Air Sampler Calibration 15 th Annual OSC Readiness Training Program 7

9 Collecting Sample(s) Equipment needed: H-810 air sampler Glass fiber particulate filters Glassine envelope Sharpie Tweezers Generator or AC power H-810 sensitive to power quality, check for generator/air sampler compatibility before deploying. Quick Start Guide for Radeco High Volume Air Sampler -Model H th Annual OSC Readiness Training Program 8

10 H-810 Air Sampler 15 th Annual OSC Readiness Training Program 9

11 Safety Precautions Use GFCI electrical cables/ cords to reduce potential shock hazard. Be careful of potential static electricity. Do not allow interior of air sampler to get wet or allow other materials in. Keep electrical cords up off the ground. Securely fasten sampler to tripod or other working surface. Use hearing protection and eye safety. 15 th Annual OSC Readiness Training Program 10

12 Air Sampling Procedure Place samplers. Up/down wind, source & receptor site. Install glass fiber filter, type LB-5211, rough side out, marked with an X on the rim of the filter. Turn on power, 5 10 sec warm up. Press CLEAR and then START twice. 15 th Annual OSC Readiness Training Program 11

13 Air Sampling Procedure (cont.) Adjust flow rate (4 cfm suggested). Press STOP and then press CLEAR key twice. Press SET key, set total air volume to sample, minimum of 120 ft 3 (30 min sample time), longer (8+ hours) is better. Press START key, sampler will stop when target volume is reached. 15 th Annual OSC Readiness Training Program 12

14 Air Sampling Procedure (cont.) Record the sample location, start time and flow rate in field logbook. Sampler will run until target volume has been sampled. Collect upwind/background air sample in same manner. 15 th Annual OSC Readiness Training Program 13

15 Retrieving Air Sample Put on Nitrile or similar gloves for contamination control. Record the ending time and flow volume in the logbook. Remove filter from the sampler with tweezers and place in glassine envelope. Record on envelope: sample location, sample number, sample start time, sample volume, sample collection time. 15 th Annual OSC Readiness Training Program 14

16 Retrieving Air Sample Wipe sampling ring and filter holder with moist paper towel. Repeat procedure for other samples. Start second round of sample collection as directed. Bring air filter media back to command post for counting. 15 th Annual OSC Readiness Training Program 15

17 Counting Samples Equipment needed: Model 3030 Alpha/Beta sample counter Alpha and Beta QC disc sources BPA No. B NTLX Th-230, 1 disc, $425 Sr-90, 2 disc, $425 Nitrile gloves, tweezers, planchets Quick Start Guide for Ludlum Alpha/Beta Sample Counter - Model th Annual OSC Readiness Training Program 16

18 Ludlum 3030 Alpha/Beta Sample Counter 15 th Annual OSC Readiness Training Program 17

19 Counter QC Procedure Perform while air samples are being collected. Plug in system, turn on, press QC CHECK. Set count time for 1 minute. Insert alpha calibration source, close/latch tray, and press COUNT. When alpha count is finished, replace alpha source with beta calibration source, close/latch tray, and press COUNT. 15 th Annual OSC Readiness Training Program 18

20 Counter QC Procedure When beta count is finished, remove source, insert clean planchet, close/latch tray, and press COUNT - a background count is performed. When background count is finished, the QC light should go out, instrument is ready for sample counting. If QC light does not go out, conduct QC check again and/or check operating parameters. 15 th Annual OSC Readiness Training Program 19

21 Counting Samples 1. Allow sample to decay for 3 hours Counts Alpha Beta Time (min) 15 th Annual OSC Readiness Training Program 20

22 Counting Samples Select count time, longer count time leads to lower MDA, 3030 software provides MDA estimate. Place background sample on planchet, position on sample tray, close/latch tray. Apply contamination control techniques. Press the COUNT key and adjust volume to desired level. Colon symbol on the display indicate the count is in process. 15 th Annual OSC Readiness Training Program 21

23 Counting Samples CPM or DPM. Establish during Model 3030 set up. Record time of sample count and alpha-beta count data, note units (CPM or DPM). Count and record other samples. Contamination control Recount samples, 20+ hours after collection. 15 th Annual OSC Readiness Training Program 22

24 Calculate and Evaluate Compare incident scene samples to upwind/background sample. Expect air samples from all locations to show significant alpha and beta activity from radon daughters. If sample < background results, then airborne contaminant unlikely. If sample > twice background results, then airborne contamination exists. 15 th Annual OSC Readiness Training Program 23

25 Calculate and Evaluate If background < sample < twice background grey area. Use field gamma spectrometry (SAM-935 or GR- 135) to identify (if possible) the radionuclide detected on the air filters. Capture/record spectrum. Expect to see gammas from radon daughters. 15 th Annual OSC Readiness Training Program 24

26 Calculate DAC Level Health Physics assistance recommended at this point. Radon and daughter products complicate the calculation and interpretation of air sample results. Can mask the presence of a contaminant. Continue to wear respiratory protection until sample analysis and data interpretation are complete. 15 th Annual OSC Readiness Training Program 25

27 Calculate DAC DAC: Derived Air Concentration 10 CFR 20 Appendix B Inhalation of 1 DAC for 1 year (2000 hrs) leads to a dose of 5 rem. Varies by radionuclide and chemical form D, W, Y clearance class. Sum of fractions rule for multiple radionuclides. 15 th Annual OSC Readiness Training Program 26

28 Calculate DAC Fraction Quantify amount of radionuclide on air filterspectrometer, lab analysis, assumptions, experience, etc. Calculate airborne concentration C x (µci/cc). Consult reference 10 CFR 20, App B, Table 1 C x / DAC x = DAC fraction 15 th Annual OSC Readiness Training Program 27

29 DAC(s) and Dose Inhalation dose is tabulated/tracked by DAC hrs: 4 hours at 50% DAC = 2 DAC-hrs 1 DAC-hr = 2.5 mrem Respirator protection factors reduce or eliminate inhalation dose. 15 th Annual OSC Readiness Training Program 28

30 Demonstration Set up an H-810 air sampler. Program the unit to collect a 120 cubic foot sample of potential Am-241 in air. Operate the air sampler. Retrieve the sample when sampling is completed. Package sample, submit for analysis. Take air sampler unit down. Count the sample, calculate the fraction of the DAC (assume Am-241). 15 th Annual OSC Readiness Training Program 29

31 Soil Sampling Considerations Current Rad Playbook, FRMAC, etc., call for 10 x 10 cm sampler at 1. Use the scoop. Depending on time in response larger or deeper sample may be required. Sampling in open areas best. Vegetation and rocks in sample not a good idea. Decon of tools is really important. Care is needed in collection in bagging, tagging, etc. 15 th Annual OSC Readiness Training Program 30

32 Soil Sampling Considerations Frozen ground a problem! Wet ground potentially a problem! Sandy ground potentially a problem! It may not scoop! Bottom line: use your common sense Note special circumstances on sample form Note radiation readings on samples from surface of bag and handle accordingly. 15 th Annual OSC Readiness Training Program 31

33 Questions? 15 th Annual OSC Readiness Training Program 32