EPRI Radiation Management Program: Review of Radiation Field Reduction Strategies HPS Power Reactor Session July 12 th, 2009 Dennis Hussey Sr. Project Manager Radiation Management, Chemistry, LLW, Fuel Reliability

2 © 2009 Electric Power Research Institute, Inc. All rights reserved. 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 © 2009 Electric Power Research Institute, Inc. All rights reserved. RP2020 Mission Reshape radiological protection at nuclear power plants to achieve significant improvements in safety performance and cost-effectiveness.

4 © 2009 Electric Power Research Institute, Inc. All rights reserved. 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 © 2009 Electric Power Research Institute, Inc. All rights reserved. Partners in Creating RP 2020 NEI EPRIINPO NEI = Policy INPO = Performance EPRI = Research Radiation Protection ManagersChief Nuclear Officers

6 © 2009 Electric Power Research Institute, Inc. All rights reserved. Source Term Reduction Program Strategy EPRI Source Term Reduction Program focuses on four areas Data Collection/Analysis -Collect and organize available data (BWRVIP, SRMP, FRP, SGDD, Chemistry) -Blocking analysis Theoretical Review -Materials Analysis -Chemistry/Operations Interactions -Transport Mechanisms Operations Analysis -Shutdown benchmarking -Radiation data correlation -In-depth case studies Technology Review -Investigate candidates -Evaluate promising candidates -Report results Plant Specific Recommendations

7 © 2009 Electric Power Research Institute, Inc. All rights reserved. Source Term Activation and Transport Ex-core radiation fields are dominated by two nuclides – 60 Co (Cobalt-60)—Requires years to saturate and decay – 58 Co (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 Parameter 60 Co 58 Co Activation Reaction 59 Co(n,  ) 60 Co 58 Ni(n,p) 58 Co Disintegration Energy (keV) E  = E  = E  = 811 Half-life, t 1/2 5.3 years71 days Activation of 60 Co and 58 Co as a function of time

8 © 2009 Electric Power Research Institute, Inc. All rights reserved. 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 © 2009 Electric Power Research Institute, Inc. All rights reserved. Source Term Activation and Transport Corrosion Product Sources (tubing, valves, components) 59 Co 58 Ni Fuel in Reactor 60 Co 58 Co Ex-core Surfaces (piping, valves) Water Normal Operations Shutdown Cleanup Refuel

10 © 2009 Electric Power Research Institute, Inc. All rights reserved. Source Term Magnitude By Location PWR Example LocationSurface Loading (uCi/cm 2 ) Total Curies FuelCo-58 = 250 Co-60 = 12 ~10,000-15,000 Ci Co-58 ~ Ci Co-60 Removal During Shutdown N/A Ci Co Ci Co-60 Ex-core Surfaces (including tubing, piping, channel heads) Co-58 = 8 Co-60 = 3 ~ Ci Co-58 ~ 70 Ci Co-60

11 © 2009 Electric Power Research Institute, Inc. All rights reserved. BWR Source Term Reduction Project BWR Source Term Reduction – Estimating Cobalt Transport to the Reactor (Report # ) 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 © 2009 Electric Power Research Institute, Inc. All rights reserved. BRAC Radiation Fields (June 2008) Mitigation Strategy

13 © 2009 Electric Power Research Institute, Inc. All rights reserved. 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 © 2009 Electric Power Research Institute, Inc. All rights reserved. BWR Benchmarking/Source Term Ranking  Co-60 Categories and BRAC ParameterLow Co-60 Plants (≤ 1E-4 µCi/ml) Moderate Co-60 Plants (>1E-4 µCi/ml, < 2E-4 µCi/ml) High Co-60 Plants (≥ 2E-4 µCi/ml) Average Co-60; µCi/ml 7.95E-51.38E-44.13E-4 Median Co-60; µCi/ml 6.48E-51.40E-42.79E-4 Co-60 Range; µCi/ml 1.94E-5 to 2.74E-45.98E-5 to 3.29E-49.42E-5 to 1.83E-3 Average BRAC; mR/hr Median BRAC; mR/hr BRAC Range; mR/hr

15 © 2009 Electric Power Research Institute, Inc. All rights reserved. Impact of Control Rod Blade Replacement on Reactor Water Cobalt

16 © 2009 Electric Power Research Institute, Inc. All rights reserved. BWR Summary and Recommendations  Recommendations 1.Plants should update cobalt source term reduction status (CRBs, turbine components, valves, etc.) 2.Conduct industry survey to see if plants have performed NP-2263 source identification evaluations 3.Conduct a further evaluation on elemental cobalt sampling with focus on sample collection, preparation and analytical methods

17 © 2009 Electric Power Research Institute, Inc. All rights reserved. PWR Source Term Reduction Technology Evaluations—Report 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 © 2009 Electric Power Research Institute, Inc. All rights reserved. SRMP: PWR Center Channel Head Hot Leg Most Recent Available Cycle

19 © 2009 Electric Power Research Institute, Inc. All rights reserved. SRMP: PWR Loop Piping Cold Leg Most Recent Available Cycle

20 © 2009 Electric Power Research Institute, Inc. All rights reserved. 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 © 2009 Electric Power Research Institute, Inc. All rights reserved. Impacts of PWR Primary Chemistry Guidelines on Dose Rates

22 © 2009 Electric Power Research Institute, Inc. All rights reserved. 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