Ken Sejkora Entergy Nuclear Northeast – Pilgrim Station

1. Dose Consequence of Environmental Water LLD Values and Implications to Derivation of Revised Values Ken Sejkora Entergy Nuclear Northeast – Pilgrim Station Presented at the 19th Annual RETS-REMP Workshop South Bend, IN / 22-24 June 2009

2. REMP LLDs - General • Specified in Table 4.12-1 of NUREG-1302/1302 • Derived in late 1960s to early 1970s… limited documentation of pedigree, “gray-hair” phenomenon • Loosely based on dose consequence and assumption of “reasonable survey” • Nuclide list based on major nuclides anticipated to be seen in radwaste source term • Values are likely outdated when compared to “modern” standards

3. REMP LLDs - Dose • Original dose factors based on ICRP-2, circa 1950s • Dose coefficients have undergone several revisions… ICRP-26/30, ICRP-68/72, newer. Newer factors used throughout international community, limited endorsement by EPA in Federal Guidance Report series. • Concept of ‘risk’ based dose consequence based on effective dose equivalent… basis of effluent control limits in 10CFR20 Appendix B, Table 2

4. REMP LLDs – Reasonable Survey • Based on “state-of-the-art” in 1960s • What is a “reasonable survey”? • Length of counting time – 1hr? Over-night? • Analyze as-is, or process? Separation required? • Underlying assumptions not documented • Function of sample volume, sample geometry, detector efficiency, interfering nuclides (including natural activity) • Significant improvements in detector efficiencies and nuclide identification algorithms since 1960s • Caveat – just because we can “see” tritium down to 150 pCi/L doesn’t mean we have to set the LLD at 150 pCi/L!

5. REMP LLDs – Critical Nuclides • Origin of current list unknown… GALE source term? • How does list compare to what has been seen in 30+ years of power reactor operation? • Assuming 100 reactors operating for an average of 20 years, over 2000 “reactor-years” of REMP and effluent data are available for analysis; these are REMP LLDs – emphasis should be on historical REMP sample results • Is current list based on activity levels anticipated, or dose impact anticipated? • Should some nuclides be removed, and others added? • Largely gamma emitters… what about hard-to-detects?

6. Reason For Concern - 1 • Current list of nuclides and LLD values is nearly 40 years old, poorly documented • Current list may not reflect modern standards or past operating experience • Current list was proposed for inclusion in DG-4013, the new revision to Regulatory Guide 4.1 • Do we want to incorporate LLD values from 40 years ago, with undocumented pedigree, into new standards?

7. Reason For Concern - 2 • What rationale is to be used to derive required LLDs for nuclides and/or exposure pathways not in current list? • Need to have consistent approach for all licensees to apply if posed with deriving their own LLDs for a specific nuclide or pathway • LLDs chosen should result in a similar dose/risk consequence -- Dose-based LLDs!

8. Method of Approach • Evaluate dose impact of current LLD requirements • Age-specific dose coefficients; ICRP-2 and ICRP-72 • Age-specific media usage factors • Derive revised LLD values based on a normalized dose impact of 1 mrem/yr • I am NOT suggesting or endorsing 1 mrem/yr as the limiting dose for establishing LLDs! • “Normalized” factor allows easy scaling to any dose target deemed “acceptable”

9. Dose Impact – Current Water LLDs • Illustrate technique. Need to repeat for other exposure pathways and nuclides Dose = Concentration * Usage * Dose Factor mrem/yr pCi/L L/yr mrem/pCi • Usage factors for Adult, Teen, Child, Infant • Are Regulatory Guide 1.109 usage values valid or current? • Dose coefficients for Adult, Teen, Child, Infant • Reg Guide 1.109 (LADTAP) values – Outdated, but provide insight to what may have been used in derivation of original values • Avoid ICRP-30 factors… single age group (Adult), occupational • ICRP-72 factors… used 4 of 6 available age classes

10. Dose Consequence from Current LLD Requirement Concentrations

11. Derived Normalized LLDs – 1 mrem/yr Dose Consequence • Existing LLD concentration will yield corresponding dose consequence • Only accounts for drinking water ingestion. Other exposure pathways not included • If existing dose consequence is less than 1 mrem/yr, increase LLD proportionally • If existing dose consequence is greater than 1 mrem/yr, decrease LLD proportionally • How? -- Multiply arithmetic inverse of dose consequence by existing LLD concentration value

12. Derived Water Concentrations for 1 mrem/yr Dose Consequence

13. Limitations and Concerns -1 • Only addresses drinking water pathway • Data from 2007 RETS-REMP Presentation indicate including other pathways may increase dose by 2x to 600x over drinking water alone… nuclide dependent • However, the above effect is offset if analysis of other pathways (fish, shellfish, crops) shows buildup is not occurring and contributing to increasing total dose from all pathways • Approach assumes water concentration is at or above LLD 100% of the time • In reality, concentration is likely much less than LLD, and dose consequence is much less than 1 mrem/yr

14. Limitations and Concerns -2 • Calculated EDE dose from ICRP-72 dose factors is often much higher than “Total Body” dose calculated from ICRP-2 factors • Potential to grossly underestimate true “total body” dose used to demonstrate compliance with dose limits… NON-CONSERVATIVE • ICRP-72 factors are more modern and widely accepted and used by the international community

15. Where to from here… - 1 • Encourage NRC to derive new dose-based LLD targets for inclusion in revision to Regulatory Guide 4.1 • Based on use of ICRP-72 or newer dose coefficients • Provide guidance and methodology for deriving LLDs for nuclides of interest not addressed in table • Endorse application of stochastic, EDE-based dose/risk assumptions… eliminate need for non-stochastic, organ-specific dose calculations

16. Where to from here… - 2 • Encourage revision of list of critical nuclides included in LLD table • Primary emphasis should be on those nuclides yielding majority of dose; secondary consideration to activity • Consider data gleaned from review of historical REMP and effluent data from over 2000 reactor-years of operation to determine most-important nuclides; 1˚ emphasis on REMP sample data, 2˚ consideration on effluent data… EPRI? Industry working group? Graduate student research project?

17. Where to from here… - 3 • Encourage establishment of dose/risk based LLDs with risk commensurate with other regulatory programs • The same dose/risk value used to derive MARSSIM DCGLs should be considered for establishing dose-based LLDs; already accepted and endorsed by NRC, EPA, and DOE agreement • MARSSIM DCGL values may prove to be a viable alternative to dose-based LLDs

18. Summary - 1 • Current REMP LLD values are likely outdated, poorly documented, and may be non-conservative in some cases • The current list of critical nuclides may not be representative of those observed through 30+ years of commercial power reactor operations • Existing/current REMP LLD values are not “robust” enough for inclusion in new revisions to NRC guidance documents

19. Summary - 2 • Establishment of EDE-based LLDs would provide a consistent, uniform approach and risk-basis across various nuclides and pathways • Current ICRP-2 dose coefficients from Regulatory Guide 1.109 and LADTAP are likely underestimating total body dose; Reg Guide 1.109 dose coefficients need to be modernized

20. Questions?