ML24136A130
| ML24136A130 | |
| Person / Time | |
|---|---|
| Issue date: | 05/14/2024 |
| From: | V Sreenivas NRC/NRR/DORL/LPL1 |
| To: | Vistra Operating Co. (VistraOpCo) |
| References | |
| Download: ML24136A130 (1) | |
Text
VERBAL AUTHORIZATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR PROPOSED ALTERNATIVE NUMBER 1-TYP-5-RRP-1 ALTERNATIVE METHOD OF NONDESTRUCTIVE EXAMINATION FOR RIVER WATER OUTLET PIPING WELD REPAIR VISTRA OPERATIONS COMPANY, LLC BEAVER VALLEY POWER STATION, UNIT NO. 1 DOCKET NO. 50-334 MAY 14, 2024 Technical Evaluation read by Matthew Mitchell, Chief of the Piping and Head Penetrations Branch, Office of Nuclear Reactor Regulation By letter to the U.S. Nuclear Regulatory Commission (NRC) dated May 13, 2024, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24134A204), Vistra Operations Company, LLC (the licensee) proposed an alternative to certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),
Section III, Rules for Construction of Nuclear Facility Components, and Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, related to the repair of degraded River Water Outlet Piping for the 1RS-E-1A, A Recirculation Spray Heat Exchanger at Beaver Valley Power Station, Unit No. 1 (Beaver Valley, Unit 1). The licensee submitted proposed alternative 1-TYP-5-RRP-1 for the use of progressive magnetic particle testing, consistent with ASME Code,Section III requirements, in lieu of the ASME Code-required radiographic testing for the repair.
The licensee requested authorization for this alternative in accordance with the requirements of Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a(z)(1) on the basis that the proposed alternative would provide for an acceptable level of quality and safety.
During refueling and maintenance outage 1R29, a 30 drops-per-minute leak was identified on the river water outlet piping for 1RS-E-1A,A Recirculation Spray Heat Exchanger between metal expansion joint MEJ-1RW-1 and containment penetration X-83. The extent of the flawed area was confirmed using ultrasonic testing. The location of the flaw is directly adjacent to the containment wall and associated liner at the interface of the containment penetration and liner.
The through-wall flaw stops at the boundary of a nearby test channel with the thinned material continuing into the test channel.
ASME Code,Section XI, IWA-4520, Examination, requires the examination of repairs to be performed in accordance with the Construction Code identified in the licensees Repair/Replacement Plan. ASME Code,Section III, NC-2539.4, Examination of Repair Welds, requires radiographic testing when the depth of the repair cavity exceeds the lesser of 3/8 in.
(10 mm) or 10% of the section thickness. The flaw location and nearby geometry was documented in the submittal and demonstrated that radiographic testing of the repair would be challenging.
The licensee is proposing to perform progressive magnetic particle testing in lieu of the volumetric radiographic testing required by ASME Code,Section III, NC-2539.4. A base metal weld repair will be performed using Gas-Tungsten Arc Welding with ER70S-2 filler material. The first and subsequent weld layers will be progressively examined via magnetic particle testing to ensure weld quality. The repair will restore the pipe wall thickness to approximately 0.25 inches, which is 0.204 inches more than the 0.046-inch allowed minimum wall thickness. In
addition to magnetic particle testing, ultrasonic testing thickness measurements will be taken after the completion of the repair to validate expected results.
After the repair is completed, the section of piping will also be pressurized with air to 44.5 psi in accordance with a 10 CFR Part 50, Appendix J, Type B testing technique to find possible leaks.
A river water system alignment similar to design basis accident scenarios will also be used to perform an in-service leak test.
The River Water Outlet Piping 1RS-E-1A is a low-pressure pipe with a design pressure of 85 pounds per square inch gauge (PSIG) with an allowed minimum wall thickness of 0.046 inches.
While progressive magnetic particle testing is not as rigorous as radiographic testing, the repair will restore the wall thickness to approximately 0.25 inches, which provides a significant margin over the minimum required wall thickness. The degradation mechanism is general corrosion, so any possible small additional weld flaws left in the repair would not significantly affect the rate of future wall thinning. The final repair will be tested using ultrasonic testing to confirm the thickness of the repair. The air and water pressure testing that will be performed after the repair will determine if the repair is leak tight. The combination of these factors provides reasonable assurance of adequate safety for the repair.
Based on these considerations, the NRC staff has determined that complying with the alternative requirements described in the licensees request referenced above would result in an acceptable level of quality and safety.
NRC Staff Conclusion read by Hipólito J. González, Branch Chief, 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 Penetrations Branch.
The NRC staff concludes that the proposed alternative 1-TYP-5-RRP-1, to use magnetic particle testing in lieu of radiographic testing, at Beaver Valley, Unit 1 will provide reasonable assurance of adequate safety for the subject pipe repair. The NRC staff finds that complying with the alternative requirements described in the licensees request referenced above would result in an acceptable 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)(1).
Therefore, effective May 14, 2024, the NRC authorizes the use of the proposed alternative 1-TYP-5-RRP-1, at Beaver Valley, Unit 1 for the repair of the degraded River Water Outlet Piping for the 1RS-E-1A, A Recirculation Spray Heat Exchanger.
All other requirements in ASME Code,Section III and 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 questions and clarifications regarding proposed alternative 1-TYP-5-RRP-1 while preparing the subsequent written safety evaluation.