OE Review by MRP Thermal Fatigue Focus Group (TFFG)– Reviewed on conference calls and at last week’s MRP meeting Determine if Interim Guidance is needed – Initial review of OE

© 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


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


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)


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)


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


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


BACKUP SLIDES

Background and Reference Information


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


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)


MRP Thermal Fatigue Program


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)


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


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


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


Together…Shaping the Future of Electricity

Documents

OE Review by MRP Thermal Fatigue Focus Group (TFFG)– Reviewed on conference calls and at last week’s MRP meeting Determine if Interim Guidance is needed – Initial review of OE