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The Determination of 226 Ra in Water Samples

The Determination of 226 Ra in Water Samples. Anil H . Thakkar & Michael Fern Eichrom Technologies, Inc. David McCurdy Duke Engineering & Services. Objectives. To design a procedure for radium in water which would: be a simple, short and quick procedure

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The Determination of 226 Ra in Water Samples

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  1. The Determination of 226Ra in Water Samples AnilH. Thakkar & Michael Fern Eichrom Technologies, Inc. David McCurdy Duke Engineering & Services

  2. Objectives • To design a procedure for radium in water which would: • be a simple, short and quick procedure • allow to measure Ra-226 and Ra-224 via alpha spectroscopy and Ra-228 via Ac-228 measurements • eliminate the tedious steps of precipitation and metathesis

  3. Current Procedure Used • Barium sulfate precipitation • Conversion to BaCO3- tedious and time consuming

  4. Current Procedure Used Sample + Ba carrier + Ba-133 + Conc.H2SO4_+ Heat BaSO4 Precipitate allowed to settle for several hours or overnight Precipitate collected and converted to BaCO3

  5. Water samples Cation exchange resin column Eichrom Ln Resin column New Approach

  6. Preparation of Water Samples • 0.5 L / 1.0 L water samples • Acidified to pH 2 • Add 133Ba as a tracer

  7. Eichrom Cation Exchange Column • Load solution: 0.5 L/ 1.0 L of sample • Rinse with 50 mL of 0.1M HNO3 • Strip Ra and Ba with 50 mL of 8M HNO3

  8. Preparation of Load Solution for Ln Resin Column • Evaporate eluent from cation exchange column to dryness • Dissolve residue in 10 ml of 0.095M HNO3 acid • Load on Eichrom Ln Resin column

  9. (1) Load: 10 mL of 0.095M HNO3, Collect (1) and (2) for Ba & 226Ra (2) Rinse: 15 mL of 0.095M HNO3 (3) Strip: 10 mL of 0.35M HNO3 collect (3) for 228Ac Ln Resin Column Separation

  10. 226Ra Via Alpha Spectrometry • Evaporate 226Ra/133Ba fraction to 10 mL volume • Add 0.1 ml of 0.75 mg/ml barium carrier • Add 3 mL of 40% sodium sulfate, 4 drops of 1:1 acetic acid. Swirl • Add 0.2 mL of seeding suspension. Mix • Place tubes in cold water bath for 30 minutes • Filter on 0.1 micron filters, count via alpha spectrometry

  11. eichrom 133Ba Via Gamma Counter • Count 133Ba tracer yield via gamma spectrometry

  12. 228Ac Via Gas-Flow Proportional Counter • Add 50 micrograms of cerium carrier • Add 1.0 mL of HF • Filter on 0.1 micron filters • Measure for beta radiation

  13. 226Ra % Recoveries-0.5L DI Water

  14. 226Ra Alpha Spectrum

  15. 133Ba Gamma Spectrum

  16. 226Ra, 224Ra, and Daughters 224Ra 226 Ra 220Rn 218Po 222Rn

  17. 226Ra % Recoveries in Tap water

  18. 226Ra in EPA SampleSept.18, 1998

  19. 226Ra in NJ Sample

  20. 226Ra in Georgia Inst. Of Tech. Sample# S8933

  21. 226Ra in Georgia Inst. Of Tech. Sample# WS 14776

  22. Ca and Mg Interference • 50, 100, 200, 400 and 500 ppm of Ca and Mg solutions were tested • 500 mL and 100 mL volumes tested

  23. Ca and Mg Interference in 500 mL Samples

  24. Ca Interference in 100 mL of Sample

  25. Detection Limits

  26. Summary • <1.0 pCi/L detection limits achievable • A good replacement for BaSO4 precipitation • Eliminates inconsistent metathesis steps • Reduces usage of chemicals/reagents • Provides consistency and saves time • High amounts of Ca and Mg interferences handled well with 100 mL samples • Acceptable 226Ra recoveries

  27. Acknowledgements • Special thanks to • Dr. B. Parsa, New Jersey department of health, NJ • Dr. B. Kahn, Georgia Institute of Technology, GA

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