ML25021A022
| ML25021A022 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 01/21/2025 |
| From: | V Sreenivas NRC/NRR/DORL/LPL1 |
| To: | Energy Harbor Nuclear Corp |
| Sreenivas, V | |
| References | |
| Download: ML25021A022 (1) | |
Text
1 VERBAL AUTHORIZATION BY THE OFFICE NUCLEAR REACTOR REGULATION REQUEST TO USE ALTERNATIVE METHODOLOGY TO DEMONSTRATE STRUCTURAL INTEGRITY OF MODERATE ENERGY CLASS 3 PIPING VISTRA OPERATIONS COMPANY, LLC.
BEAVER VALLEY POWER STATION, UNIT 1 DOCKET NO. 50-334 January 18, 2025 Technical Evaluation read by Matthew Mitchell, Chief of the Piping and Head Penetration Branch, Office of Nuclear Reactor Regulation By letter dated January 17, 2025 and supplemented by letter dated January 18, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession Nos.
ML25017A395 and ML25018A001, respectively), Vistra Operations Company, LLC (VistraOps, the licensee), proposed an alternative to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, paragraph IWA-4421 that requires defects be removed or mitigated in accordance with the requirements of IWA-4411, IWA-4461 or IWA-4462, for Beaver Valley Power Station, Unit 1 (BVPS-1).
Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee submitted Alternative Request, BV-ISI-2025-01, requesting NRC approval of a proposed alternative to demonstrate that the 12 moderate-energy quench spray system piping, line QS-1-153B-Q3, with a 140°F design temperature and 30 psig design pressure, will maintain its structural integrity without repair or replacement in accordance with ASME Code,Section XI until the units next refueling outage, currently scheduled to begin in October 2025. The licensee has concluded that complying with the specified ASME Code requirement to repair or replace the quench spray system piping would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety, noting that unnecessary plant shutdown activities result in additional plant risk. The licensee requested approval of the proposed alternative until the next scheduled refueling outage scheduled for October 2025, or until such time that the flaw exceeds the critical surface flaw size of 0.125-inches which is within the bounds the licensees proposed analysis.
The NRC staff finds the licensees identified hardship meets the requirements of 10 CFR 50.55a(z)(2) and reviewed the proposed alternative to determine if it provided an adequate level of quality and safety given this hardship.
On January 16, 2025, the licensee discovered a minor leak (weepage) from a through-wall flaw in the weld toe of a 12-inch stainless steel socket weld on the quench spray system piping. The licensee evaluated the flaw to be approximately 1/32 of an inch. The area of the leak was observed weeping with no measurable drops of water. Currently, there is no water spray from the pinhole leak and no equipment in the area would be damaged due to spray from the leak. The allowable leak for the piping is bounded by the allowable surface flaw size of 0.125-inches. Augmented ultrasonic testing (UT) will be completed per GL 90-05 on five
2 additional accessible locations deemed most susceptible to a similar flaw. The licensee identified no active degradation mechanism for the weld material at operating conditions.
Therefore, since the flaw appears to be at the stop-start interface of the socket weld, the licensees assessment is that the leakage is the result of a lack of fusion or other defect at this location during installation and could be a result of poor work practices or workmanship.
In lieu of an ASME Code repair, the licensee chose to use NRC Generic Letter (GL) 90-05, Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping, which contains a through-wall flaw evaluation method for flaw stability. The licensee was not able to volumetrically size the flaw in accordance with GL 90-05. However, through analysis, the licensee determined that a surface examination would provide a reasonable flaw evaluation technique for the total flaw length allowed by the GL 90-05 analysis. Given the weld material, apparent cause for the defect, and no known active degradation mechanism, the NRC staff finds the licensees proposed acceptance criteria of 0.125-inch at the surface to be an acceptable alternative to volumetric sizing for evaluating the structural integrity of the weld. Therefore, the NRC staff found the licensees GL 90-05 evaluation to be acceptable and that the results showed reasonable margins for this low pressure system for short term operability when combined with leakage and flaw size monitoring measures.
In order to meet the GL 90-05 examination guidelines, the licensee proposes to implement augmented inspections on a 30-day frequency, not to exceed the 3-month frequency required by GL 90-05, to detect changes in the condition of the identified defect. The licensee will use an acceptance criteria of 0.125-inch for the flaw on the surface. This testing will use suitable nondestructive examination methods, including UT. Additionally, the licensee intends to perform a daily qualitative assessment of leakage, not to exceed the weekly requirement by GL 90-05, to determine if there is evidence of additional degradation of structural integrity. If the daily qualitative assessment of leakage determines there is potential additional degradation of structural integrity, the licensee will measure the flaw on the surface of the pipe and compare it to their acceptance criteria. The NRC staff finds the licensees proposed qualitative leakage monitoring will be able to detect increased leakage well before the licensees makeup capacity for the quench spray system is reached based on the GL 90-05 flaw analysis. Therefore, the NRC staff finds the licensees leakage monitoring and flaw examinations meet the GL 90-05 guidance and are acceptable.
Given the licensees identified hardship and based on the review of the information provided above, the NRC staff finds that the licensees proposed alternative to use a modified version of GL 90-05 guidance provides reasonable assurance of adequate protection based on (1) adequate margin in the flaw stability evaluation of the subject location in the quench spray system piping at Beaver Valley, Unit 1, (2) the licensees performance of qualitative daily leakage monitoring and action plan to measure the flaw size if the daily qualitative assessment of leakage determines there is potential additional degradation, (3) the licensees performance of augmented inspection, every 30 days to verify the flaw does not exceed the maximum acceptable surface flaw size of 0.125-inches (4) the apparent lack of increase in flaw/leak rate and the low operating pressure of the system, and (5) the allowable leak for the piping is bounded by the allowable surface flaw size of 0.125-inches.
The NRC finds that the proposed alternative will provide reasonable assurance that the structural integrity will be maintained until the next scheduled refueling outage in October 2025 when an ASME Code repair will be performed. If the observed flaw exceeds the critical surface flaw size of 0.125-inches, the basis for the licensees alternative ensuring
3 structural integrity will no longer be valid. The NRC staff also finds that plant system realignments cause operational risk as well as unnecessary plant shutdown activities result in additional plant risk and therefore is a valid basis for establishing hardship with respect to implementing an ASME Code repair prior to the October 2025 refueling outage.
Authorization read by Hipo Gonzalez, Chief of the Plant Licensing Branch I, Office of Nuclear Reactor Regulation As Chief of the Plant Licensing Branch I, Office of Nuclear Reactor Regulation, I agree with the conclusions of the Piping and Head Penetration Branch.
The NRC staff concludes that the proposed alternative will provide reasonable assurance that the structural integrity will be maintained until the next scheduled refueling outage in October 2025 when an ASME Code repair will be performed. The NRC staff finds that complying with the requirements of the ASME Code,Section XI would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(2).
Therefore, effective January 18, 2025, the NRC authorizes the use of the proposed alternative BV-ISI-2025-01, at Beaver Valley, Unit 1, until completion of the next scheduled refueling outage, scheduled for October 2025.
All other requirements in ASME Code,Section XI for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
This verbal authorization does not preclude the NRC staff from asking additional clarification questions regarding the proposed alternative while subsequently preparing the written safety evaluation.