EPRI Radiation Management Program: Review of Radiation Field Reduction Strategies

1. EPRI Radiation Management Program:Review of Radiation Field Reduction Strategies HPS Power Reactor SessionJuly 12th, 2009 Dennis HusseySr. Project Manager Radiation Management, Chemistry, LLW, Fuel Reliability

2. Overview EPRI Support of RP2020 Radiation Source Term Fundamentals • Overview of Radiation Transport Mechanisms • Activity Generation Boiling Water Reactor Highlights • Elemental cobalt measurements • BWR Shutdown Calculations Pressurized Water Reactor Highlights • Crud Bursts • Dose Rate Trends

3. RP2020 Mission Reshape radiological protection at nuclear power plants to achieve significant improvements in safety performance and cost-effectiveness.

4. RP2020 Strategies and EPRI Status • Reduce radiation fields—EPRI • Improve technologies utilization—EPRI • Standardize RP criteria & practices—ALL • Redefine RP roles/responsibilities—NEI/INPO/EPRI • Influence RP regulations—NEI

5. Partners in CreatingRP 2020 Radiation Protection Managers Chief Nuclear Officers NEI EPRI INPO NEI = Policy INPO = Performance EPRI = Research

6. Source Term Reduction Program Strategy • EPRI Source Term Reduction Program focuses on four areas Operations Analysis-Shutdown benchmarking-Radiation data correlation-In-depth case studies Data Collection/Analysis-Collect and organize available data(BWRVIP, SRMP, FRP, SGDD, Chemistry)-Blocking analysis Plant Specific Recommendations Technology Review-Investigate candidates-Evaluate promising candidates-Report results Theoretical Review-Materials Analysis-Chemistry/Operations Interactions-Transport Mechanisms

7. Source Term Activation and Transport Activation of 60Co and 58Co as a function of time • Ex-core radiation fields are dominated by two nuclides • 60Co (Cobalt-60)—Requires years to saturate and decay • 58Co (Cobalt-58)—Saturates and decays in one cycle • Cobalt is a transition metal • Low solubility at high temperatures • Precipitates with iron and nickel • Incorporates into corrosion layers • Difficult to remove from corrosion film

8. Source Term Activation and Transport • Ex-core radiation field mechanism • Corrosion of the parent nuclide from surfaces • Transport of the parent nuclide to the fuel surface • Activation of the parent nuclide to activated nuclide • Transport of the activated nuclide to ex-core surface • Incorporation of the activated nuclide into the surface • Source Term Reduction involves reducing all of these mechanisms

9. Source Term Activation and Transport Water Fuel in Reactor Corrosion Product Sources(tubing, valves, components) Shutdown Cleanup Refuel Normal Operations Ex-core Surfaces (piping, valves) 59Co 60Co 58Ni 58Co

10. Source Term Magnitude By LocationPWR Example

11. BWR Source Term Reduction Project • BWR Source Term Reduction – Estimating Cobalt Transport to the Reactor (Report #1018371) • Goals of Project • Identify how plants measure cobalt • Target cobalt sources • Benchmark cobalt transport to reactor • Quantify removal and releases during shutdown and normal operations

12. BRAC Radiation Fields (June 2008)Mitigation Strategy

13. Elemental Cobalt Measurements • 19 plants of the 45 BWRs sample and analyze for elemental cobalt in • condensate, • feedwater, • reactor coolant • Results vary widely depending upon • sample point, • sample volume collected (LLD), • analytical method (ICP, XRF, ICP-MS), • source term

14. BWR Benchmarking/Source Term Ranking • Co-60 Categories and BRAC

15. Impact of Control Rod Blade Replacement on Reactor Water Cobalt

16. BWR Summary and Recommendations • Recommendations • Plants should update cobalt source term reduction status (CRBs, turbine components, valves, etc.) • Conduct industry survey to see if plants have performed NP-2263 source identification evaluations • Conduct a further evaluation on elemental cobalt sampling with focus on sample collection, preparation and analytical methods

17. PWR Source Term ReductionTechnology Evaluations—Report 1016767 • Key Results • Activity release magnitude has correlation to core duty and surface area • Tubing manufacturing method impact is less clear • Zinc continues to show significant radiation benefits • pH effects noticed when comparing before and after PWR Primary Guidelines • Ringhals, San Onofre report benefits of elevated pH • Comanche Peak 1 and 2 do not show clear benefits • Long term benefits of electropolishing are noted

18. SRMP: PWR Center Channel Head Hot Leg Most Recent Available Cycle

19. SRMP: PWR Loop Piping Cold Leg Most Recent Available Cycle

20. Zinc Injection Impact on Radiation Fields Several examples of positive impact of zinc Diablo Canyon 1 is most striking Cobalt-60 decay curve is followed Implies no additional activity deposition For Diablo Canyon 1, since zinc injection, Cobalt-60 surface loading follows Co-60 decay curve at Diablo Canyon 1

21. Impacts of PWR Primary Chemistry Guidelines on Dose Rates

22. PWR Summary/Conclusions • Tubing manufacturing impact is uncertain, but still under review • Impacts of core design need to be studied more rigorously • Zinc appears to be the strongest option to reduce ex-core dose rates • pH has an impact, but mechanism is under investigation