ML25111A024
| ML25111A024 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 04/21/2025 |
| From: | Hipolito Gonzalez NRC/NRR/DORL/LPL1 |
| To: | Blair B Energy Harbor Nuclear Corp |
| Sreenivas, V | |
| References | |
| EPID L-2024-LLR-0004, BV-ISI-2025-01 BV-ISI-2025-01 | |
| Download: ML25111A024 (1) | |
Text
April 21, 2025 Barry N. Blair Vistra Operations Company LLC Beaver Valley Power Station Mail Stop P-BV-SSB P.O. Box 4, Route 168 Shippingport, PA 15077-0004
SUBJECT:
BEAVER VALLEY POWER STATION, UNIT 1, ALTERNATIVE METHODOLOGY TO DEMONSTRATE STRUCTURAL INTEGRITY OF MODERATE ENERGY CLASS 3 POPING-ALTERNATIVE REQUEST BV-ISI-2025-01 (EPID L-2024-LLR-0004)
Dear Mr. Blair:
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).
On January 18, 2025 (ML25021A022), the U.S. Nuclear Regulatory Commision (NRC) staff communicated its verbal authorization of Alternative Request BV-ISI-2025-01 to the licensee in accordance with Office of Nuclear Reactor Regulation Office Instruction LIC-102, Revision 3, Review of Relief Requests, Proposed Alternatives, and Requests to Use Later Code Editions and Addenda. This letter documents the NRC staffs safety evaluation.
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 Title 10 of the Code of Federal Regulations 50.55a(z)(2).
Therefore, the NRC authorizes the use of the proposed alternative BV-ISI-2025-01, at BVPS-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.
B. Blair If you have any questions, please contact the Project Manager, V. Sreenivas, at 301-415-2597 or V.Sreenivas@nrc.gov.
Sincerely, Hipólito González, Branch Chief Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-334
Enclosure:
Safety Evaluation cc: Listserv HIPOLITO GONZALEZ Digitally signed by HIPOLITO GONZALEZ Date: 2025.04.21 15:01:08 -04'00'
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR ALTERNATIVE REQUEST BV-ISI-2025-01 FIFTH 10-YEAR INSERVICE INSPECTION INTERVAL VISTRA OPERATIONS COMPANY, LLC BEAVER VALLEY POWER STATION, UNIT 1 DOCKET NO. 50-334
1.0 INTRODUCTION
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 U.S. Nuclear Regulatory Commission (NRC) approval of a proposed alternative to demonstrate that the 12 inch quench spray system piping, line QS-1-153B-Q3, with a 140°Fahrenheit (F) design temperature and 30 pounds per square inch gauge (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 QS 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 of the licensees proposed analysis.
On January 18, 2025 (ML25021A022), the NRC staff communicated its verbal authorization of Alternative Request BV-ISI-2025-01 to the licensee in accordance with Office of Nuclear Reactor Regulation (NRR) Office Instruction LIC-102, Revision 3, Review of Relief Requests, Proposed Alternatives, and Requests to Use Later Code Editions and Addenda. This letter documents the NRC staffs safety evaluation.
2.0 REGULATORY EVALUATION
2.1 Regulations Adherence to Section XI of the ASME BPV Code is mandated by 10 CFR 50.55a(g)(4), which states, in part, that ASME BPV Code Class 1, 2, and 3 components must meet the requirements, except the design and access provisions and the pre-service examination requirements, set forth in the ASME BPV Code,Section XI.
The regulations in 10 CFR 50.55a(z) state, in part, that alternatives to the requirements of 10 CFR 50.55a(b)-(h) may be used, when authorized by the NRR Director if (1) the proposed alternatives would provide an acceptable level of quality and safety or (2) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
2.2 ASME Code Applicable Code Edition The Code of record for BVPS-1s fifth 10-year ISI program interval is the 2013 Edition of ASME Code,Section XI. The fifth 10-year ISI interval for BVPS-1 began on August 29, 2018, and is currently scheduled to end on August 28, 2028.
Applicable Code Requirements Article IWA-4421, General Requirements, in Section XI of the 2013 Edition to the ASME Code requires that defects be removed or mitigated in accordance with code requirements IWA-4411, IWA-4461, or IWA-4462.
3.0 TECHNICAL EVALUATION
3.1 Proposed Alternative ASME Code Components Affected The component affected is the 12-inch stainless steel quench spray system piping, line QS-1-153B-Q3, with a 140°F design temperature and 30 psig design pressure. The QS system is designed to cool and depressurize containment following a design basis accident.
Proposed Alternative The licensees proposed alternative includes demonstrating that the 12-inch QS system piping, line QS-1-153B-Q3 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.
Licensees Basis for Use The licensee requested to use the alternative pursuant to 10 CFR 50.55a(z)(2), on the basis that compliance with the specified ASME Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The licensee has concluded that complying with the specified ASME Code requirement to repair or replace the QS 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 of the licensees proposed analysis.
Reason for the Proposed Alternative 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 QS piping that contains this flaw is between the refueling water storage tank and the A train QS pump. An accurate measurement of the pinhole diameter could not be obtained since the size of the pinhole leak is small enough that it cannot be accurately measured but is assumed 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 Generic Letter (GL) 90-05 on five 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.
3.2
NRC Staff Evaluation
In lieu of an ASME Code repair, the licensee chose to use NRC 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. In addition, UT measurements taken adjacent to the weld indicate nominal pipe/fitting thickness with a maximum thickness of 0.248 inches and a minimum thickness of 0.172 inches, demonstrates that there is no general wall thinning and the flaw does not extend into the base metal. The low design pressure and temperature of the pipe, along with low mechanical stress, minimizes the chance of primary water stress corrosion cracking as the degradation mechanism. Since the QS system is mostly in a static environment with little to no vibration, fatigue is not a likely failure mode, as is transgranular stress corrosion cracking not a likely failure mode because the weld is typically insulated and not exposed to outside contaminants. 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 examination will use suitable nondestructive examination methods, including ultrasonic testing. 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.
The licensee has determined that performing an ASME Code repair on the degraded portion of quench spray piping in accordance with ASME Code,Section XI, IWA-4000 represents a hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The hardship cited by the licensee would require a plant shutdown. Isolation of the affected quench spray piping is not practical given the location of the leak relative to the only drain location on the header. Repair will require removing the affected train of quench spray piping from service for the repair duration. The licensee is proposing to use GL 90-05, Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping, which allows a through-wall flaw to be evaluated using the criteria in Enclosure 1 to assess the structural integrity of the Class 3 piping. In addition, the licensee notes that GL 90-05 provides that repair of Class 3 piping that cannot be isolated without a plant shutdown is justified in some instances.
Based on the difficulty of isolating the affected area of quench spray piping and performing a code repair within the time period permitted by the limiting condition of operability, relief is being requested from ASME Code, Section Xl, 2013 Edition, Article IWA-4421, in accordance with 10 CFR 50.55a(z)(2) to prevent an unnecessary hardship caused by requiring a plant shutdown without a compensating increase in quality and safety.
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 QS system piping at BVPS-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 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.
4.0 CONCLUSION
The NRC staff concludes that the proposed alternative to defer an ASME Code repair on the 12-inch QS system piping, line QS-1-153B-Q3 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, the NRC authorizes the use of the proposed alternative BV-ISI-2025-01, at BVPS-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.
Principal Contributors: J. Honcharik, NRR J. Collins, NRR Dated: April 21, 2025
ML25111A024 OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LA NRR/DNRL/NPHP/BC NAME VSreenivas KEntz MMitchell DATE 04/18/2025 04/21/2025 04/18/2025 OFFICE NRR/DORL/LPL1/BC NRR/DORL/LPL1/PM NAME HGonzález VSreenivas DATE 04/21/2025 04/21/2025