2. 1 Analytical Technique for Tritium in Soil Richard Conatser Calvert Cliffs Constellation Energy Group June 2007

3. 2 Outline u Introduction u Objectives for the method u Soil sampling u Analytical Method u Calculations u LLDs and Reporting Levels u Regulations and Use of Soil Results u Conclusion

4. 3 Method’s Objectives u Rapid analytical technique u Minimal impact on Chem Techs/Staff u Collect samples from small areas u Want results to be pCi/kg soil u Results should be simple to report u Results should be easy to interpret

5. 4 Types of Soil Sampling u Sample soil vapors u Solar still u Direct soil sample u Direct reading instrument

6. 5 CCNPP Analytical Method u Sample soil u Measure %moisture (w/w%) u Quantitatively add soil to “container” u Add carrier DI water to dry samples u Allow soil-water to equilibrate u Distill, and Count on LSC u Calculate the results

7. 6 Method Assumptions u Soil sample is representative u All tritium originates from the soil u All tritium is in the water fraction u If DI water (carrier) is added, all tritium enters the liquid phase u Vapor pressure H-3 & H 2 O are equal

8. 7 Calculations A S = A W * [M % + (V DI / M S )] Where, A S = Activity in soil, pCi/kg soil A W = Activity in water, pCi/l distillate M % = Moisture fraction in soil sample V DI = Mass of DI water, grams M S = Mass of soil sample, grams

10. 9 LLD (no carrier) u CCNPP LLD for water is ~ 350 pCi/l u Assume distillate is 350 pCi/l u Assume the soil moisture is 5% u Convert water LLD to soil LLD A S = A W * [M % +(V DI / M S )] A S = 350 pCi/l * 0.05 A S = 18 pCi/kg

12. 11 % Moisture in Soil u If M % is unknown u a bias will exist u Soil tritium will be mis-reported u If M % is assumed 15%, reduce bias u Determine moisture analytically u gravimetrically u moisture tester

13. 12 Low Soil Moisture u Some samples may be “dry.” u DI water can be added as a carrier u This is necessary IF analysis is needed u Water added dilutes sample’s H-3

14. 13 Just Add Water u As water is added, soil is diluted u Adding water required for dry soil u If no water is added, LLD=350 pCi/l u As water is added, LLD suffers u Can natural soil moisture be ignored? u Use the calculation model to test u The following graph demonstrates effect

19. 18 Limitations of the Model u Previous example was one case: u 15% moisture u Took 46 ml DI water to be <LLD u LLD will be dependent on M % u Graph shows family of lines

22. 21 LLD u The LLD with respect to soil: u As good as 18 pCi/kg of soil u Up to 350 pCi/kg of soil u The LLD with respect to soil vapor: u As good as 350 pCi/liter of vapor u May be over 18,000 pCi/liter of vapor

23. 22 Regulations and Use u No regulatory LLDs for H-3 in soil u No NRC regulatory reporting level u NEI guidance to report spill results u What does this mean to managers? u Use soil H-3 as remediation criteria?

24. 23 Potential Enhancements u Microwave digestion of soil u Oxidizer or reducer (permanganate) u Use more than 100 g soil u Use DI water carrier sparingly u Combine with other methods u Solar Still u Tritium in soil vapor

25. 24 Conclusions u Tritium in soil can be an easy analysis u The method can get more complex u The focus needs to be on using the results u Using the results can be problematic u Tritium in soil needs to be tailored to the site u At Waterford 3, it may not make sense u For coastal sites on hillsides with no drinking water, it may not make sense u Best use may be for remediation criteria

26. 25 Questions?