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© 2017 Electric Power Research Institute, Inc. All rights reserved.
Materials R&D Tech Exchange Meeting
May 23, 2018
OE Review by MRP Thermal Fatigue Focus
Group (TFFG)
2© 2018 Electric Power Research Institute, Inc. All rights reserved.
Scope
2017 – Review and discuss potential for cross-flow (out-flow) as cause of
thermal fatigue – MRP letter issued to member utilities in December 2017 to ensure
awareness of cross-flow and how it may result in thermal fatigue2018
– Proceed with review of recent OE to:Determine if current guidance should be revised, i.e., issue
interim guidanceDetermine if research roadmap and program should be revised
3© 2018 Electric Power Research Institute, Inc. All rights reserved.
Recent Operating Experience
Date Component Flaw Depth Method of Detection
March 2016 Drain Line 58% Part-wall Extent of Condition*
March 2016 Charging Line 44% Part-wall MRP-146 Inspection
May 2016 RHR Suction Line 24% Part-wall Section XI Program
February 2017 Safety Injection Line Through-wall N/A
March 2017 Safety Injection Line 21% Part-wall MRP-146 Inspection
April 2017 RHR Suction Line 14% Part-wall Extent of Condition*
* Inspection methods consistent with MRP-146 inspection guidance.
- All this OE was discussed at last year’s NRC-EPRI Tech Exchange Meeting- No additional thermal fatigue OE observed
4© 2018 Electric Power Research Institute, Inc. All rights reserved.
Type of OE Committee Actions and Current Focus
Safety Injection 2017 - Issued MRP information letter on cross-flow and how it may result in thermal fatigue
2018 - Initial action to confirm factors that may result in check valve leakage
Drain Line 2018 - Technical Committee developing guidance- Final decision this year
RHR Suction Line 2018 - Technical Committee developing guidance- Final decision this year
2017-2018 Actions and Guidance Revision Considerations(since 2017 NRC-EPRI Technical Exchange Meeting)
5© 2018 Electric Power Research Institute, Inc. All rights reserved.
Next Steps to Complete OE Review
Complete review of OE– Reviewed on conference calls and at last week’s MRP meeting
Determine if Interim Guidance is needed– Initial review of OE complete – Guidance revisions under consideration
Determine if R&D program needs revision– Review and revise of 2019-2020 R&D strategic plan process– Review and revise of thermal/vibration fatigue R&D roadmap
Issue Interim Guidance (if needed)
6© 2018 Electric Power Research Institute, Inc. All rights reserved.
MRP Thermal Fatigue R&D in Strategic Plan Title
Fatigue ResearchEvaluation Criteria for Craze CrackingExperiments and Computational Fluid Dynamics Thermal Fatigue Model DevelopmentReducing High Vibration FatigueNDE for Thermal Fatigue Damage in Small Bore PipingThermal Fatigue Virtual Mockups for Computer Based TrainingInvestigate and Define Mixing Tee Conditions for Upstream Thermal Fatigue CrackingDevelopment of Mitigation ConceptsSupport for Thermal Fatigue OE InvestigationsSupport for SLR-Focused Aging ManagementMRP and NEI-03-08 Standards and GuidanceThermal Fatigue Guidance Maintenance and Revisions
7© 2018 Electric Power Research Institute, Inc. All rights reserved.
Conclusions
Program successful in detecting flaws before leakage occurs in many instances; however, opportunities for improvement identifiedTFFG continues to actively disposition OE and adjust
guidance documents as necessary Industry is investing a significant amount of effort to better
understand thermal fatigue mechanisms and develop improved guidance
8© 2018 Electric Power Research Institute, Inc. All rights reserved.
BACKUP SLIDES
Background and Reference Information
9© 2018 Electric Power Research Institute, Inc. All rights reserved.
MRP Thermal Fatigue Program Evolution
Original plant designs and inspection programs did not conceive of all potential thermal fatigue vulnerabilities– Thermal stratification– Thermal mixingPWR OE during the mid 1980s alerted Industry to the need
for management of thermal fatigue Industry responded - collaborative research led to a better
understanding of system behaviorMRP strategy focuses on component identification,
inspection and mitigation
10© 2018 Electric Power Research Institute, Inc. All rights reserved.
MRP Thermal Fatigue Program Evolution (2)
MRP thermal fatigue management under NEI 03-08 is implemented by:– MRP-146 Cyclic stratification in non-isolable RCS branch lines
(“Needed” item)– MRP-192 Thermal mixing tees in RHR systems
(“Good Practice” item)
11© 2018 Electric Power Research Institute, Inc. All rights reserved.
MRP Thermal Fatigue Program
12© 2018 Electric Power Research Institute, Inc. All rights reserved.
Operating Experience History
5 Events leading into NRC Bulletin 88-08– All through-wall (2 US plants)6 Events subsequent to Bulletin thru 2000 (12 years)
– All through-wall (2 US plants)3 Events after industry guidance thru 2012 (12 years)
– All part-wall (2 US plants, cracking discovered during planned MRP-146/192 program examinations)
10 Events in US between 2013 and 2015 (2 years)– 3 through-wall– 7 part-wall (cracking discovered during planned MRP-146/192
examinations or extent of condition examinations)
13© 2018 Electric Power Research Institute, Inc. All rights reserved.
MRP Response Program successful in detecting flaws before leakage occurs in many
instances; however, opportunities for improvement identified EPRI Thermal Fatigue Focus Group (TFFG) established to assess
impact of OE and recommend corrective actions TFFG objectives:
– Publish Interim Guidance to prevent thermal fatigue degradation from exceeding Regulatory limits
– Identify actions for program improvement TFFG process:
– Review each event– Identify specific program failures– Identify potential causes and determine mitigation alternatives– Develop Interim Guidance to detect cracks at an early stage– Identify knowledge gaps and propose specific research to close gaps &
improve program
14© 2018 Electric Power Research Institute, Inc. All rights reserved.
MRP Response (2)
TFFG major findings:– Certain screening criteria found suspect – population of susceptible
piping to increase– Need for expansion of MRP-146/192 inspection zones– Newer NDE techniques and procedures are better in detecting cracking Interim Guidance issued in May 2015
– 2 “Good Practice” requirements– 8 “Needed” requirementsEDF and Japanese thermal fatigue program benchmarking effort
initiated and completed (MRP-408/409)Additional NDE mock-ups created to aid in examiner training
15© 2018 Electric Power Research Institute, Inc. All rights reserved.
MRP Response (3)
Maintain plant staff expertise– EPRI Fatigue Management Handbook updated (MRP-235)– Fatigue management training conducted and recordedMRP-146 Revision 2 published in September 2016
incorporating Interim GuidanceMRP-192 Revision 3 under development and to be published
in 2018 incorporating Interim Guidance
16© 2018 Electric Power Research Institute, Inc. All rights reserved.
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