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The Determination of 224 Ra, 226 Ra, & 228 Ra in Water Samples PowerPoint PPT Presentation


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The Determination of 224 Ra, 226 Ra, & 228 Ra in Water Samples. Michael Fern Eichrom Technologies, Inc. Background. EPA monitoring of radium in water in US Ra-224 found in drinking water in New Jersey Need for faster method to measure Ra-224 ASTM + US Geological Survey.

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The Determination of 224 Ra, 226 Ra, & 228 Ra in Water Samples

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The Determination of 224Ra, 226Ra, & 228Ra in Water Samples

Michael Fern

Eichrom Technologies, Inc.


Background

  • EPA monitoring of radium in water in US

  • Ra-224 found in drinking water in New Jersey

  • Need for faster method to measure Ra-224

  • ASTM + US Geological Survey


Original Method – Eichrom RAW01(Burnett, et al., 1995)

1

2

0.5-2 L acidified sample

Ba-133

3

Load sample in 0.095M HNO3

1

Ln

BaSO4 ppt

Rinse 0.095M HNO3

2

0.35M HNO3

3

Resin

Conversion to BaCO3

226Ra via Rn emanation

223,224Ra via a-spectrometry

1

2

3

0.095M HNO3

228Ra via 228Ac

{proportional or HPGe counter}

{hold for ~30 hrs.}

g-ray measurement Ba-133


228Ra Results Burnett, et al. 1995


Limitations of Original Method

  • α-emitters determined by Rn emanation: too long

  • Need fast method to measure 224Ra (t1/2 = 3.66 days)

  • 30 hour ingrowth for 228Ac

  • Conversion of SO42- to CO32- is tedious


1

1

2

2

3

3

1

2

3

New Approach - RAW03

Load sample at pH 2 (0.5 – 1 L)

Evaporate and re-dissolve in 0.095M HNO3

Rinse 50 mL 0.1M HNO3

50 mL 8M HNO3

1

2

3

Load sample in 0.095M HNO3

Cation

1

Ln

Ln

Rinse 0.095M HNO3

2

0.35M HNO3

3

Resin

Resin

Resin

224, 226Ra via a-spectrometry

1

2

3

To waste

228Ra via 228Ac

{proportional or HPGe counter}


Advantages of New Method

  • No need for 228Ac ingrowth

  • Eliminate dangerous and inconsistent carbonate conversion

  • Rapid measurement of α-emitting isotopes

  • Same day measurement of 224Ra


226Ra % Recoveries-0.5L DI Water

Eichrom data


226Ra Alpha Spectrum


226Ra, 224Ra, and Daughters

224Ra

226 Ra

220Rn

218Po

222Rn


226Ra % Recoveries in Tap water

Eichrom data


226Ra in EPA SampleSept.18, 1998

Eichrom data


226Ra in NJ Sample

Eichrom data


226Ra in Georgia Inst. Of Tech. Sample# S8933

Eichrom data


226Ra in Georgia Inst. Of Tech. Sample# WS 14776

Eichrom data


Sample

Chemical recovery

(Ba-133)

Spiked

pCi/L

(mBq/L)

Found

pCi/L

(mBq/L)

A

92.8%

1.16

(42.9)

1.22

(45.1)

B

87.1%

5.80

(215)

5.73

(212)

C

84.3%

11.6

(429)

11.7

(433)

226Ra ResultsHerbert, USEPA 2002


Sample

Chemical recovery

(Ba-133)

Spiked

pCi/L

(mBq/L)

Found

pCi/L

(mBq/L)

A

92.8%

32.8

(1210)

32.0

(1180)

B

87.1%

10.9

(403)

11.9

(440)

C

84.3%

4.37

(162)

4.54

(168)

228Ra ResultsHerbert, USEPA 2002


Ca and Mg Interference in 500 mL Samples

Eichrom data


Ca Interference in 100 mL of Sample

Eichrom data


Detection Limits – 226RaUS EPA Requires: 37 mBq/L


Summary

  • <37 mBq/L detection limits achievable

  • Eliminates inconsistent carbonate conversion

  • Faster measurement of 224Ra

  • High amounts of Ca and Mg interferences handled well with 100 mL samples

  • Acceptable 226Ra and 228Ra recoveries


  • Special thanks to:

    • Anil Thakkar, Eichrom Technologies

    • David McCurdy & Ann Cleveland, ASTM

    • Dr. B. Parsa, New Jersey department of health, NJDr. B. Kahn, Georgia Institute of Technology, GA

  • References:

    • Burnett, W.C., Cable, P.H., & Moser, R.; Determination of Ra-228 in Natural Waters Using Extraction Chromatography, Radioactivity & Radiochemistry, vol. 6, no. 3 (1995)

    • Herbert, V., USEPA NAREL, Single Operator Test Report, ASTM Test Method: Ra in Water; presented at RRMC, Knoxville, TN 11/2002.


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