ML24271A098
| ML24271A098 | |
| Person / Time | |
|---|---|
| Issue date: | 09/30/2024 |
| From: | Leslie Terry NRC/NRR/DNRL/NCSG |
| To: | |
| Shared Package | |
| ML24271A085 | List: |
| References | |
| Download: ML24271A098 (1) | |
Text
U.S. Nuclear Regulatory Commission Public Meeting Summary
Title:
Meeting with the Industry Steam Generator Task Force Meeting Identifier: 20240974 Date of Meeting: September 5, 2024 Location: Webinar Type of Meeting: Observation Meeting Purpose of the Meeting: The purpose of this meeting was for the U.S. Nuclear Regulatory Commission (NRC) staff to discuss steam generator (SG) issues with the industry Steam Generator Task Force (SGTF).
General Details: The industry SGTF met with NRC staff on September 5, 2024, by webinar.
The purpose of the meeting was to discuss a variety of SG issues. The NRC and industry slides are available in (Agencywide Documents Access and Management System (ADAMS)
Accession Nos. ML24241A012 and ML24241A023), respectively. This meeting was noticed as a public meeting and the agenda is available in ML24211A022.
CONTACT:
Leslie Terry, NRR/DNRL (301) 415-1167 September 30, 2024 LISTING OF ATTENDEES U.S. NRC MEETING WITH THE INDUSTRY STEAM GENERATOR TASK FORCE September 5, 2024 Participant Affiliation Participant Affiliation Isaac Anchondo-Lopez NRC Craig Kelley Framatome Sasan Bakhtiari ANL Mitchell Krinock Westinghouse James Benson EPRI Sean Kil EPRI Cotasha Blackburn Southern Company Paul Klein NRC Steven Bloom NRC Greg Makar NRC Michael Bodak Constellation Dan Mayes Duke Energy Jasmyn Bone Entergy Ingrid Nordby Steve Brown Entergy Paul Rittenhouse DEV Generation - 3 Brent Capell EPRI Miranda Ross NRC Robert Chappo Westinghouse Phil Rush MPR Associates Russ Cipolla Intertek Jay Smith Westinghouse James Cirilli EPRI Mike Stark Dominion Energy Helen Cothron EPRI Leslie Terry NRC Bill Cullen EPRI Kester Thompson FPL Michael Frotscher Entergy Tim Thulien Duke Rich Guill EPRI Nicole Vitale Westinghouse Joel Jenkins NRC Bill Wiltsey Intertek Andrew Johnson NRC Summary of Presentations: Industry representatives made presentations on recently published Electric Power Research Institute (EPRI) reports, the status of revisions to industry guidelines, an information letter related to in situ pressure test guidelines, and recent domestic operating experience.
The NRC staff presented their perspective on loss of SG tube integrity from wear at tube support plates (TSPs).
Additional details of the information exchanged during the meeting is provided below.
Recently published EPRI reports on the following topics were discussed:
o Sourcebook on industry experience and best practices for tube pulls and laboratory examination of pulled tubes.
o Framework for storage of SG digital twin data.
o Technical basis for secondary-side hydrazine concentration limits.
o White paper regarding EPRI Steam Generator Management Program (SGMP) research related to secondary-side deposit management.
o Degradation examples relative to SG design and industry survey results related to secondary-side inspection frequency, scope, and results.
o Secondary-side hydrogen injection.
Industry explained that a small group will determine whether the Steam Generator Management Program: Steam Generator Integrity Assessment Guidelines (Integrity Assessment Guidelines) should be updated based on recent domestic operating experience related to loss of SG tube integrity at TSPs. A revision to the Steam Generator Management Program: In Situ Pressure Test Guidelines (In Situ Pressure Test Guidelines) and Steam Generator Management Program: Pressurized Water Reactor Steam Generator Examination Guidelines (Examination Guidelines) are in progress (tentative for first quarter of 2025 with a 12-month implementation date).
An industry representative discussed that until recently, the In Situ Pressure Test Guidelines included a 3-volt initial screen for structural and leakage integrity for volumetric flaws at SG tube supports. Following recent in situ pressure tests, where one flaw that was close to the 3-volt initial screen failed the pressure test at three times normal operating pressure differential (3xNOPD), the SGMP found that condition monitoring (CM) limits are preferentially being used as the initial screen for volumetric flaws instead of the voltage initial screen. The In Situ Pressure Test Guidelines were revised to delete the initial volumetric flaw screen and industry was notified of the change. As previously stated, a revision to the In Situ Pressure Test Guidelines is in progress, including a committee gathering the latest inspection data for wear at TSPs to potentially change the initial screen for volumetric flaws.
Industry discussed SGMP actions related to recent domestic operating experience with loss of SG tube integrity at TSPs. It was stated that the flaws may have been undersized in the 2017 inspection; therefore, the SGMP is discussing changes to the Integrity Assessment Guidelines related to sizing wear flaws. In addition, the SGMP is determining the need for additional guidance and tools to assist with operational assessment reviews by utility engineers. Utility engineers review operational assessments (OAs) provided by a vendor.
An industry representative discussed experience related to longer operating intervals. It was stated that four plants have inspected after four cycles of operation and two plants have inspected after five cycles of operation, all with no unexpected results. In addition, three plants plan to inspect in fall 2024 after five cycles of operation.
The NRC staff presented their perspective on the recent domestic operating experience related to loss of SG tube integrity at TSPs. In November 2023, nine flaws in four thermally treated Alloy 690 SG tubes did not satisfy CM analytically and required in situ pressure testing. Two of the four tubes failed to meet the technical specification structural integrity performance criterion (i.e., 3xNOPD). The unit had skipped a planned third refueling outage SG tube inspection after adopting Technical Specifications Task Force, TSTF-577, Revised Frequencies for Steam Generator Tube Inspections, Final Traveler Safety Evaluation (ML21098A188) and revising their OA. The staffs perspective is that the recent operating experience is due to an inadequate OA and non-destructive examination calibration/sizing error, and not due to adopting TSTF-577. Specifically, the revised operational assessment was nonconservative because it did not recognize a sub-population of locations with aggressive wear and assumed a tapered wear shape instead of a flat wear shape. The staff reiterated that loss of tube integrity due to wear at support structures should not happen.
The staff questioned whether generic changes are needed related to tube wear calibration standards and sizing techniques, and OA techniques. In addition, for situations where licensees are using longer inspection intervals or have challenging CM and OA reports (CMOAs), the staff asked whether the technique parameters and assumptions that are most sensitive to changing the time between inspections should be highlighted in the CMOA. The staff also asked when a third-party review of CMOAs may be warranted (e.g., licensees internal expertise, OA approaching acceptance criteria).
An NRC staff member identified that Section 1.5, Contractor Oversight, in Revision 5 of the Integrity Assessment Guidelines appears to be missing information in the last sentence that was contained in the previous revision.
If you have any questions regarding this meeting summary, please feel free to contact Leslie Terry by phone at 301-415-1167, or by e-mail at Leslie.Terry@nrc.gov.
Attachments:
1.
Meeting Notice: ML24211A022 2.
NRC Slides: ML24241A012 3.
Industry Slides: ML24241A023 4.
Meeting Summary: ML24271A098 5.
Package: ML24271A085
Package: ML24271A085 Meeting Summary: ML24271A098 Meeting Notice: ML24211A022 NRC Slides: ML24241A012 Industry Slides: ML24241A023 OFFICE NRR/DNRL/NCSG NRR/DNRL/NRLB/LA NRR/DNRL/NCSG/BC NAME LTerry SGreen SBloom DATE 9/26/2024 09/30/2024