The Determination Of 226 Ra In Soil Samples Lawrence D. Morris General Engineering Laboratories, Inc. Anil H. Thakkar Eichrom Technologies, Inc

The Determination Of The Determination Of 226226RaRaIn Soil SamplesIn Soil Samples

Lawrence D. Morris

General Engineering Laboratories, Inc.

Anil H. Thakkar

Eichrom Technologies, Inc.

General Engineering Laboratories, Inc.Charleston, SC

Objective: Design a reliable method to measure 226Ra in soil samples by Alpha Spectroscopy thus meeting the current need of our clients.

Faster Turn Around Times than current methods This procedure utilizes Cation and Eichrom’s Ln Resin Achieve Peak Resolution (FWHM) of less than 100keV


Anil Thakkar visited GEL in April

Discussed the Radium in Water procedure– Ran some test samples


Spectrum from Testing Water Procedure


This brought up the question about how well the procedure would work with soils?

Spectrum from Testing Water Procedure


Highlights of the Procedure:Radium in Water (RAW03)Eichrom Technologies, Inc.

Digest the sample Dissolve the residue with dilute HNO3

Pass sample through Cation resin column Elute Ra and Ba with 8M HNO3

Evaporate eluate to dryness Dissolve residue with 0.095M HNO3


Pass through Ln Column collecting the eluate for determination of 226Ra

Perform Barium Sulfate micro-precipitation Filter Count on Gamma for Tracer Recovery

(133Ba) Count on Alpha for 226Ra determination

Highlights of the Procedure:Radium in Water (RAW03)Eichrom Technologies, Inc.


Test #1 Results

Sample Volume

(g)

% Yield

(133Ba)

Activity

(pCi/g)

Uncertainty

2-Sigma

(pCi/g)

MDA

(pCi/g)

FWHM

(keV)

%

Recovery

1(Sample)

1.01 96.6 3.70 0.41 0.05 142

2(Sample)

0.59 101.1 3.56 0.46 0.07 172

3(Sample)

1.07 92.6 3.55 0.40 0.04 417

4(Blank)

1.00 98.2 -0.01 0.02 0.07 3

5(Matrix Spike)

0.58 98.8 21.20 1.82 0.09 300 92.6

6(Lab Control Sample)

1.00 100.6 11.00 0.95 0.05 80 100.9


Test #1 SpectraSample 1




Test #1 SpectraSample 6 (LCS)


Problem with initial testing:

Resolution exceeded 100keV– Suspected cause was from natural Barium in the

soil.


Proposed solutions:

Use less sampleUse less Barium Carrier

– 100L of 0.75 mg/mL Barium Carrier was used for Test #1

Use less Seeding Suspension


Test #2

Analyze 3 samples with No Barium CarrierAnalyze 3 samples with 50 L of Barium

CarrierVary aliquot size from 0.1g to 0.5g


Test #2 Results

Sample Volume

(g)

% Yield

(133Ba)

Activity (pCi/g)

Uncertainty

2-Sigma

(pCi/g)

MDA (pCi/g)

FWHM (keV)

1No Barium

0.47 93.2 3.84 0.08 0.09 177

2No Barium

0.25 99.1 4.04 0.43 0.06 105

3No Barium

0.16 92.5 3.68 0.55 0.15 96

450µL Barium

0.48 97.9 3.79 0.36 0.01 129

550µL Barium

0.25 95.4 3.78 0.44 0.12 172

650µL Barium

0.10 96.6 3.85 0.58 0.26 104


Problem with Test #2:

Resolution on samples with reduced Barium Carrier continue to exceed 100keV






Test #3

Used 0.1mL of the seeding suspension• 0.2mL used previously

No Barium Carrier was used


Test #3

No Barium Yields

FAILUREFAILURE


Test #4

Comparison of Alpha Spec vs. EmanationAlpha Spec

– Used 0.2g of sample– 50L of Barium Carrier

Emanation used 0.5g of sample


Test #4 Results

Sample Volume (g)

% Yield

(133Ba)

Activity (pCi/g)

Uncertainty

2-Sigma

(pCi/g)

MDA (pCi/g)

FWHM (keV)

Alpha Spec Run

1 0.20 61.7 5.04 1.12 0.48 172

2 0.20 45.5 3.31 1.08 0.60 99

Emanation Run

1 0.51 4.25 0.84 0.31

2 0.51 4.53 0.96 0.59






Update to the Objective

Further discussions with the client revealed they were never able to achieve resolution <100keV– They re-set their requirement to <250keV

Current testing Average FWHM– 149keV– Consistently <200keV


Changes to 226Ra Water Procedure

Ensure that 0.5g or less of soil used– Minimizes natural Barium introduced

Reduce Barium carrier used– 50µL 0.75mg/mL


In Conclusion

Original FWHM Goal (<100keV) not achieved– Client changed their requirement to <250keV

• Average FWHM for soils 149keV

Faster Turn Around Times accomplished– Soils can be run in 2 days

• Emanation 3 day minimum

• Gamma 7-30 day minimum

– Waters can be run in 1 day

Documents

The Determination Of 226 Ra In Soil Samples Lawrence D. Morris General Engineering Laboratories, Inc. Anil H. Thakkar Eichrom Technologies, Inc