Addressing Uncertainty in Radiochemistry Measurements

1. Addressing Uncertainty in Radiochemistry Measurements M. C. Nichols, CHP mcnichols@vzw.blackberry.net 404-819-5118 RETS-REMP meeting

2. Guidelines for Using Quality Control and Performance Testing (PT) Data • USNRC regulatory guide 4.15 revision 1, performance testing • Specification in 6.3.2 for performance testing • Acceptance criteria • Uncertainty estimates from PT data • Revision 2, based on MARLAP • Total propagated uncertainty RETS-REMP meeting

3. USNRC Regulatory Guide 4.15, Rev. 1 • Performance testing - 6.3.2 • Measure accuracy (normalized deviation) • Measure precision (normalized range) • Basis: “Environmental Radioactivity Laboratory Intercomparison Program”, EPA 600/4-07-001, January 1977 RETS-REMP meeting

4. Acceptance Criteria • Confidence interval estimates • Normalized deviation and normalized ranged in the EPA cross check program • Ratio and resolution based on US NRC Inspection Procedure-84750 RETS-REMP meeting

5. Confidence Limit RETS-REMP meeting

6. EPA Cross Check - Accuracy RETS-REMP meeting

7. EPA Cross Check - Precision RETS-REMP meeting

8. NRC IP-84750 • Resolution - divide each NRC result by its associated uncertainty • Uncertainty defined as the relative uncertainty, 1S, of NRC results calculated from counting statistics • Ratio - licensee result / NRC result • Criteria - gives a range of acceptable ratios as a function of resolution RETS-REMP meeting

9. Single Laboratory Precision • Counting uncertainty • Providers specification • Use performance testing history • Construct an uncertainty budget • May be available for specific procedures (gamma spectroscopy) • Build on existing quality control data RETS-REMP meeting

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12. Variance - Future Prediction RETS-REMP meeting

13. Prediction Intervals for Sr-90 RETS-REMP meeting

14. Suggestions for Performance Testing Data • Two components to the evaluation of performance data • Uncertainty of the known value • Uncertainty of the measured value • Regression - use replicate measurements for each performance testing round • Uncertainties from performance testing results are limited to the range of testing RETS-REMP meeting

15. Uncertainty Budget • Define the process including components of the activity estimate • Identify uncertainty estimates for each component • Use software tools to create uncertainty budgets (e.g. Gumcalc) RETS-REMP meeting

16. Efficiency

17. Example - Uncertainty for Balance Measurement RETS-REMP meeting

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19. Strontium-89 Uncertainty at 18.5 mg cm-2, Efficiency 0.453 ± 0.012 (95% CL). RETS-REMP meeting

20. Summary • All performance testing evaluation is based on an estimate of measurement uncertainty • Performance testing data will provide an estimate of total measurement uncertainty • Measurements outside the range of PT data and new program requirements will require assessment of measurement uncertainty • Laboratories currently have sufficient data to construct these estimates RETS-REMP meeting

21. References • Ellison, S.L.R., M. Rosslein, and A. Williams, 2000. EURACHEM/CITAC guide CG 4: quantifying uncertainty in analytical measurement, 2nd edition • MARLAP, 2004. Multi-agency radiological laboratory analytical protocols manual (final) volume i (epa 402-b-04-001a), volume ii (epa 402-b-04-001b), volume iii (epa 402-b-04-001c) • Mccroan, K. D., 2005. Gumcalc v 1.0. Freeware developed for the MARLAP project. Http://mccroan.Com/gumcalc.Htm • USEPA, 1977. Environmental radioactivity laboratory intercomparison program”, EPA 600/4-07-001 • USNRC, 2007 Quality assurance for radiological monitoring programs (inception through normal operations to license termination) -- effluent streams and the environment, revision 2, ML071790506, July, 2007 • USNRC, 1994. NRC inspection manual procedure 84750 for radioactive waste treatment, effluent, and environmental monitoring RETS-REMP meeting