sampling airborne radioactivity generic soil sampling › osc2012 › uploads › 528 › 11_air...

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15th Annual OSC Readiness Training Program

Sampling Airborne Radioactivity

Generic Soil Sampling

15th Annual OSC Readiness Training Program www.oscreadiness.org 1

Air Sampling Primary Tasks

1. Collect

2. Count

3. Calculate


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.


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


Air Sampling Considerations

Sampler power, exhaust, location Filter type Collection time Interferences Atmospheric conditions Labeling Handling Disposition


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.


Air Sampler Calibration

Calibrate annually.

Calibration is filter media specific – changing filter type invalidates calibration.

Follow steps in H-810 quick start procedure.


Air Sampler Calibration


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-810


H-810 Air Sampler


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.


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.


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 ft3 (30 min sample time), longer (8+ hours) is better.

Press ‘ START’ key, sampler will stop when target volume is reached.


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.


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.


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.


Counting Samples

Equipment needed: Model 3030 Alpha/Beta sample counter Alpha and Beta QC disc sources

• BPA No. B3-1102-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 3030


Ludlum 3030

Alpha/Beta Sample Counter


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”.


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.


Counting Samples

1. Allow sample to decay for 3 hours

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 30 60 90 120 150 180 210 240 270

Time (min)

Cou

nts Alpha

Beta


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.


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.


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.


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.


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.


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.


Calculate DAC Fraction

Quantify amount of radionuclide on air filter-spectrometer, lab analysis, assumptions, experience, … etc.

Calculate airborne concentration Cx(µCi/cc).

Consult reference 10 CFR 20, App B, Table 1 Cx / DACx = DAC fraction


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.


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).


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.


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.


Questions?

sampling airborne radioactivity generic soil sampling › osc2012 › uploads › 528 › 11_air...

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