05000260/LER-2021-002, Main Steam Relief Valves Lift Settings Outside of Technical Specifications Required Setpoints
| ML21214A128 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/02/2021 |
| From: | Rasmussen M Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 2021-002-00 | |
| Download: ML21214A128 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2602021002R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 August 2, 2021 10 CFR 50.73 10 CFR 50.4(a)
ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 2 Renewed Facility Operating License No. DPR-52 NRC Docket No. 50-260
Subject:
Licensee Event Report 50-260/2021-002 Main Steam Relief Valves Lift Settings Outside of Technical Specifications Required Setpoints The enclosed Licensee Event Report provides details of the inoperability of Main Steam Relief Valves for longer than allowed by plant Technical Specifications. The Tennessee Valley Authority is submitting this report in accordance with Title 10 of the Code of Federal Regulations 50.73(a)(2)(i)(B), as any operation or condition which was prohibited by the plants Technical Specifications.
There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact Michael W. Oliver, Interim Site Licensing Manager, at (256) 337-6803.
Respectfully, Matthew Rasmussen Site Vice President Enclosure: Licensee Event Report 50-260/2021-002 Main Steam Relief Valves Lift Settings Outside of Technical Specifications Required Setpoints p
y, Matthew Rasmussen
U.S. Nuclear Regulatory Commission Page 2 August 2, 2021
cc (w/ Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant NRC Project Manager - Browns Ferry Nuclear Plant
Abstract
On June 3, 2021, the Tennessee Valley Authority was notified of As-Found testing results that five Main Steam Relief Valves (MSRVs) from Unit 2 were outside the +/- 3 percent set-point band required for operability.
More than the one allowed MSRV was considered to be inoperable during the entire operating cycle and longer than permitted by Technical Specifications. During this time, BFN Unit 2 made entries into Modes of Operation that were not allowed under this condition. The affected valves remained capable of maintaining reactor pressure within the American Society of Mechanical Engineers code limits.
It was determined that one MSRV failed due to corrosion bonding between the pilot valve disc and seat, and the other four failed due to setpoint spring relaxation. As a corrective action, the MSRV maintenance procedure will be revised to include stricter testing and acceptance criteria for pilot setpoint spring parameters based on industry best-practices. This stricter testing criteria will drive spring replacement prior to a point of relaxation which results in as-found setpoint testing failures. Additionally, all thirteen of the MSRV pilot valves were replaced during the Unit 2 Spring 2021, refueling outage with pilot discs coated in platinum utilizing the Plasma Enhanced Magnetron Sputtering (PEMS) deposition method. PEMS provides a more consistent finish on the pilot valve seating surface and gives the platinum more inherent ductility than what the previous deposition method provided. BFN began using the PEMS method in 2019, so the valves involved in this event did not receive PEMS deposited platinum coatings during their last rebuild. The PEMS method was used for the pilot discs of the rebuilt valves installed during the Unit 2 Spring 2021 refueling outage, and will be used for all pilot discs going forward.
Page 8 of 8 Procedure MCI-0-001-VLV002, Main Steam Relief Valves Target Rock Model 7567 Disassembly, Inspection, Repair and Reassembly, will be revised to include stricter acceptance criteria for pilot setpoint spring parameters based on recommendations provided by the Exelon Corporation Fleet SRV owner via the Target Rock SRV BWROG. The recommendations are based on three primary parameters and four secondary parameters.
For the most reliable setpoint performance, all of the primary parameters must be within tolerance and only one secondary parameter can be outside of tolerance. If two secondary parameters are outside of tolerance, only one cycle is allowable before retest. The stricter criteria during testing will drive spring replacement prior to the point of significant relaxation that results in as-found setpoint testing failures.
VII. Previous Similar Events at the Same Site
A search of BFN Units 1, 2, and 3 LERs for the last five years identified eight LERs associated with MSRV lift settings outside of TS required setpoints:
LER 50-259/2020-003-01, for Unit 1 Cycle 13 LER 50-296/2020-002-00, for Unit 3 Cycle 19 LER 50-260/2019 002 00, for Unit 2 Cycle 20 LER 50-259/2018 007 00, for Unit 1 Cycle 12 LER 50-296/2018 004 00, for Unit 3 Cycle 18 LER 50-260/2017 004 00, for Unit 2 Cycle 19 LER 50-259/2016 005 00, for Unit 1 Cycle 11 LER 50-296/2016 004 00, for Unit 3 Cycle 17
VIII. Additional Information
There is no additional information.
IX.
Commitments
There are no new commitments.