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Concentration of Tritium in Liquid Samples by Electrolysis problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS 17 th Annual RETS – REMP Workshop.

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Presentation on theme: "Concentration of Tritium in Liquid Samples by Electrolysis problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS 17 th Annual RETS – REMP Workshop."— Presentation transcript:

1 Concentration of Tritium in Liquid Samples by Electrolysis problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS 17 th Annual RETS – REMP Workshop Stan Morton, Ph.D. June 27, 2007 Philadelphia, PA June 27, 2007

2 Tritium problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Heavy Isotope of Hydrogen 12.3 year half-life Beta Decays to Stable He-3 Low-energy Beta Particle –18.6 keV beta-max –5.7 keV beta-avg Hydrogen and Tritium interchangeable

3 Tritium Unit (TU) problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS TU Bq/L 3.19 pCi/L Or 1 Bq/L 8.47 TU 1TU Concentration of

4 Sources of Tritium problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Cosmogenic Nuclear Weapons – Atmospheric detonation By-Product Nuclear Power Reactors –Boron –Lithium Fission Process

5 Cosmogenic problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Spallation – Cosmic-rays interact with atomic nitrogen: 14 N (n, 3 H) 12 C Reaction altitude from 11 to 16 km Adds to Precipitation Level

6 Nuclear Weapons - Atmospheric problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Testing 1940s through 1970s Precipitation Levels peaked in 1963 Additional 52 X Bq to Global Inventory Estimated remnant of 100 – 400 pCi/L in precipitation

7 Precipitation Concentrations problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS

8 Tritium Production from Boron problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Boron-10 (19.9%) high thermal neutron cross section – 3835 barns Control rods for BWRs and PWRs Chemical shim and reactivity control in PWRs 10 B(n,2α) 3 H 10 B(n,α) 7 Li(n,nα) 3 H

9 Tritium Production from Lithium problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Most acceptable hydroxide for pH control in some PWR primary coolant 6 Li (7.5%) 940 barns Principle reactions: 7 Li(n,nα) 3 H 8 Li(n,α) 3 H

10 Tritium from Fission problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Lesser extent from fission Fission yield for 235 U is ~0.01%

11 Tritium Inventory problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Estimated normal releases 0.02 x Bq/year Estimated off-normal releases x Bq/year Steady-state buildup 0.4 x Bq globally Legacy release 0.4 x Bq/year Steady-state buildup 7.4 x Bq globally

12 Tritium Global Inventory problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Atmospheric detonations 50s & 60s: 185 to 240 X Bq Legacy today: 52 X Bq Combined natural and anthropogenic global inventory of approximately: 53 X Bq or ~ 10 Bq/L

13 Regulatory Limits problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Weak beta and rapid elimination produce a minor constituent in dose evaluation EPA 1976 Drinking Water Standard is 4 mrem/yr = 20,000 pCi/L mrem/yr = 60,900; retained 1976 limit.

14 Dose Considerations problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Human retention studies provide three- component half-lives –6 to 12 days – turnover of pool of body water –10 to 34 days – involved in carbon-tritium chemistry –130 to 550 days – organic molecules with slow turnover rates

15 Perception vs. Risk problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Braidwood – 1600 pCi/L 0.3 mrem/yr; Exelon Corporation bought the farm Decatur Daily headline: …TVA, NRC are flippant over tritium leaks Morris Daily Herald: Dresden leak levels 25 times the allowable drinking water limits Arizona Republic: Palo Verdes tritium leak may impact the groundwater. Harford Courant: Haddam a few gallons a day of tritium contaminated water breaches 6-foot thick concrete wall.

16 Concentration of Tritium by Electrolysis problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS 2006, GEL Labs recognized need Quantitative below 150 – 200 pCi/L Reliable method Well defined turn-around-times Quality driven Customer service

17 Concentration of Tritium by Electrolysis problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Exploits slight differences in physical properties between hydrogen and tritium Molecule of water containing hydrogen more likely to dissociate by electrolysis than molecule of water containing tritium.

18 Overview problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Aliquant of 500 mL sample screened for high levels of tritium and extraneous emitters Shipped to Richland Service Center (RSC) in Richland, Washington Enrichment process Returned in closed vial for LSC

19 Ambient and Environmental Considerations problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS All commercial analytical labs evaporate hundreds of liters of tritium laden water May produce elevated levels of ambient tritium Environmental concentrations vary by region –Eastern and Southern states highest levels –Mid-west and Western States lowest levels

20 Richland Service Center problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS

21 Electrolysis Instrumentation problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS

22 Electrolysis Cold-Water Bath problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS

23 RSC Tritium Laboratory problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS

24 Procedure problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS 300 mL distilled 250 mL concentrated by electrolysis for maximum sensitivity Batch size –12 samples –2 background –LCS containing NIST traceable tritium standard

25 Procedure (contd) problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Cold water bath (~ 5°C) Constant current until 25 mL remaining Reduce current until 12 – 15 ml Volume reduction and enrichment requires 12 – 14 days Vacuum distillation to remove NaOH

26 Procedure (contd) problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Volume determined by weight X = V i / V f Enrichment determined from LCSs Y = C f / C i Transferred to LSC vial Returned to Charleston for beta counting

27 MARLAP Approach problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Multi-Agency Radiological Laboratory Analytical Protocols (MARLAP) Manual Nationally consistent approach to producing analytical data Performance-based approach for selecting analytical protocol Project specific criteria

28 MARLAP Method Validation problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS

29 Newly Developed Methods problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Newly developed use Level D or E Increased number of replicates Best estimate of precision and bias Unique matrix

30 Determination of Uncertainty problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Method validation determines method uncertainty Sample uncertainty menu includes –Method uncertainty –Liquid-scintillation counting statistics –Background subtraction –NIST standards, decay time, half-life, etc.

31 Uncertainty Considerations problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Uncertainty increases as activity approaches detection limit Because of such effects, as analyte concentrations drop, the relative uncertainty associated with the result tends to increase, first to a substantial fraction of the result and finally to the point where the (symmetric) uncertainty interval includes zero. This region is typically associated with the practical limit of detection for a given method.

32 Questions & Contact Information problem solved HELPING OUR CLIENTS SOLVE COMPLEX PROBLEMS Contact Information: Stan Morton, Manager, Radiobioassay Programs Bob Wills, Manager, Nuclear Programs


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