The Determination of 226Ra in Water Samples

1
The Determination of 226Ra in Water Samples

• Anil H. 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
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
Ln Resin Column Separation
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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 11
  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
133Ba Via Gamma Counter
eichrom

• 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
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226Ra Alpha Spectrum
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133Ba Gamma Spectrum
16
226Ra, 224Ra, and Daughters
224Ra
226 Ra
220Rn
218Po
222Rn
17
226Ra Recoveries in Tap water
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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

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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

• lt1.0 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