ML25317A633
| ML25317A633 | |
| Person / Time | |
|---|---|
| Issue date: | 09/30/2025 |
| From: | Delosreyes J Division of Operating Reactor Licensing |
| To: | Muftuoglu K, Smith F Electric Power Research Institute |
| References | |
| MRP-480, RAI-1 | |
| Download: ML25317A633 (1) | |
Text
From:
James Delosreyes To:
"Smith, Fred"; "Muftuoglu, Kurshad" Cc:
Lois James; Jennie Rankin; Aida Rivera-Varona; Ravi Penmetsa; Angie Buford; "CSONTOS, Aladar"; David Rudland; David Dijamco; Robert Tregoning
Subject:
Revised Summary of NRC Suggested Feedback to MRP-480 Topical Report RAI-1 Date:
Tuesday, September 30, 2025 1:10:00 PM Attachments:
Revised Seismic Impact Items for ALS MRP-480.docx Good afternoon Fred and Kurshad,
Attached is the revised summary of NRC suggested feedback to the MRP-480 RAI response based on the discussion during the RAI clarification call on 9/29 which is copied below. This email will be made publicly available in ADAMS and referenced in the meeting summary for the workshop conducted on 9/18-19.
For all plants applicable to ALS:
- 1. Demonstration that the seismically induced LOCA risk is low:
- a. Includes referenced statement on the impact of PLP failure on the overall seismic risk.
- b. Impacts of degradation addressed in 2.) on the seismic fragility and summary of practices used to mitigate seismic risk (e.g., walkdowns, maintenance, testing).
- 2. Demonstration that the plant-specific seismic impacts on PLP failure frequencies are acceptable with a focus on acceptable risk associated with break-before-leak. The following list provides options that may be used to demonstrate that these impacts are minimal:
- a. Plant-specific LBB analyses - flaw analysis demonstrates impacts of SSE loading on flawed piping with degraded material properties, i.e., thermal embrittlement, and screening criteria demonstrates that no active degradation exists in the piping system.
- b. LBB in PWSCC piping reports (both RES and EPRI) - xLPR analyses demonstrate that for these dissimilar metal welds the seismic impacts on the failure frequencies are minimal. Discussions on (a) the conservatism associated with the non-probabilistic treatment of seismic loads in the PFM LBB analyses and (b) the effect of the probabilistic treatment of seismic loads on failure frequencies, if any.
- c. MRP-480 + ALS report - analyses and sensitivity studies that demonstrate that for these piping welds and non-piping components the seismic impacts on the failure frequencies are minimal.
- d. NUREG-1829, NUREG-1903, and white papers on continued adequacy of NUREG-1829 and NUREG-1903 - analyses that demonstrate that for these welds that the seismic impacts on the failure frequencies are minimal.
- e. Recent work on CASS - PFM analyses that demonstrate that for these thermally embrittled components, the seismic impacts on the failure frequencies are
minimal.
- f. Plant-specific aging management programs - programs in place to monitor and mitigate aging in these PLP systems.
- 3. Demonstration that performance monitoring of the welds in the PLP will continue to occur:
- a. RI-ISI programs and the similar metal circumferential welds inspected in the PLP as identified in the recent plant survey to support ALS. Provide information broken down by plants collected in the survey; discuss rationale used for current PLP inspection locations; identify other surrogate inspection locations to support 3b.
- b. Identify and provide a basis for using other similar RCPB welds that may be used as a leading indicator of degradation (e.g., thermal fatigue and SCC) in the PLP.
James Delosreyes U.S. Nuclear Regulatory Commission