ML18267A093

0900 Overview of Gap Report

ML18267A093
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Issue date:	09/24/2018
From:	Robert Tregoning NRC/RES/DE
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Overview of EPRI Updated Gap Report Gary L. Stevens Technical Executive, EPRI NRC Public Meeting on Environmentally Assisted Fatigue (EAF) Research and Related ASME Activities September 25, 2018 NRC Headquarters - Rockville, MD

© 2018 Electric Power Research Institute, Inc. All rights reserved.

2012 Gap Report Environmentally Assisted Fatigue Gap OLD KNOWLEDGE GAPS Analysis and Roadmap for Future Research, November 2012 (Product ID 1026724)

Gap prioritization performed by industry expert panel 21 gaps identified as high priority 7 hypotheses proposed to explain the apparent discrepancy between test data and field experience The intent of the report is to identify knowledge gaps that can be used to direct research efforts Report is publicly available 2

© 2018 Electric Power Research Institute, Inc. All rights reserved.

Updated Gap Report NEW KNOWLEDGE GAPS Environmentally-Assisted Fatigue; B: S-N DATA & C: LWR E: LWR A: GENERAL D: PLANT F1: PROTOTYPICAL Knowledge Gap Analysis - Update and ISSUES DESIGN CURVES EFFECTS ON FATIGUE DESIGN REALISTIC S-N DATA CRACK GROWTH

& COMPONENT TESTING Revision of the EAF Knowledge Gaps A1:Plant vs.

B1:Material Specific C1:Data for D1:Complex/

non-isothermal E1:SS Reference NRC Model Design Curves Fen (Product ID 3002013214) B2:Transference Thresholds data to support improved asst methods Curves A2:EAF E2:C/LAS Gaps were reviewed in the light of recent Factors on life Reference Database and stress C2:Transference D: Model Curves Factors in LWR validation data for other alloys &

research B3:Weld Material Data C3:Strain BWR E3:NBA Reference and Design Amplitude Curves

- Based on direction of industry R&D effect on Fen D3:Strain Gradient effects and Total Life assessment E4:Plant Relevant programs C4:Mean Stress/Strain effects Data to support assessment method development A revised and categorized list of gaps was Paper and presentation was given at developed: Fontevraud 9, September 17-20, 2018

- Remove overlap and increase ease of use

- Emphasize collaboration between testing and assessment

- Revised gaps direct research without constraining organizations requirements Publication expected by end of September 2018; report will be publicly available The EAF Knowledge Gaps were recently updated to reflect the most recent research and understanding 3

© 2018 Electric Power Research Institute, Inc. All rights reserved.

Conclusions of Updated Gap Report Since the 2012 EAF Knowledge Gap Report, there has been extensive progress in EAF research aimed at closing some of the key gaps and developing improved assessment methodologies for EAF in LWR environments The main focus has been on austenitic stainless steels in PWR coolant Some of the most significant and promising new assessment methods and supporting data are at differing stages of development:

- Recognition that transference factors differ between air and LWR environments so a proportion of Fen is already included in the ASME III design curve (Fen-integrated, Fen-threshold)

- Weighting models for assessing both fatigue life and crack growth for complex and non-isothermal transients (SNW, WKR)

- Consideration of using lower transference factors on stress and on life

- Use of effective K for crack growth calculation for transients with a compressive portion

- Recognition of strain gradient effects for thermal transients which support the development of a Total Life Assessment methodology A revision of the Knowledge Gap report includes a revised, condensed, and categorized listing of the remaining knowledge gaps

- This publicly available EPRI report is in final publication 4

© 2018 Electric Power Research Institute, Inc. All rights reserved.

TogetherShaping the Future of Electricity 5

© 2018 Electric Power Research Institute, Inc. All rights reserved.