05000324/LER-2023-001, Two Main Steam Line Safety Relief Valves Inoperable
| ML23199A224 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 07/17/2023 |
| From: | Krakuszeski J Duke Energy Progress |
| To: | Document Control Desk |
| References | |
| RA-23-0138 LER 2023-001-00 | |
| Download: ML23199A224 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3242023001R00 - NRC Website | |
text
U.S. Nuclear Regulatory Commission Page 2 of 2 cc (with enclosure):
Ms. Laura Dudes, NRC Regional Administrator, Region II Mr. Luke Haeg, NRC Project Manager Mr. Gale Smith, NRC Senior Resident Inspector
Abstract
On May 23, 2023, BSEP received test results for the eleven main steam line safety relief valves (SRVs) removed from Unit 2 during the spring 2023 refuel outage (RFO). Two of the eleven valves were found to have as found pilot valve lift setpoints outside the +/-3 percent tolerance required by Technical Specification (TS) 3.4.3, which requires ten of the eleven installed SRVs to be operable. All eleven of the SRV pilot valves were replaced with certified spares before Unit 2 startup from the spring 2023 RFO. At the time the test results were received, Unit 2 was operating in Mode 1 at approximately 100% power.
Corrosion bonding of the SRV pilot disc to the pilot seat likely caused one of the out of tolerance as-found lift setpoints. The other out of tolerance lift setpoint was likely a result of a combination of degraded pilot valve assembly sub-components.
Since less than ten SRVs were operable and the failure modes likely arose over a period of time during Unit 2 operation, this event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plants TS.
There was no impact on the health and safety of the public or plant personnel.
(See Page 2 for required number of digits/characters for each block)
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
Previous Similar Events
A review of LERs for the past three years identified the following previous similar event associated with SRVs with as-found lift setpoints outside of TS allowable limits.
LER 1-2020-004, dated September 29, 2020, reported Unit 1 operation prohibited by TSs due to three of the eleven valves found with lift setpoints of their pilot valves outside the +/-3 percent tolerance required by TS SR 3.4.3.1.
The direct cause of this event was corrosion bonding. The root cause was attributed to the procedures in place at the time these valves were refurbished lacking sufficient detail to ensure consistent surface preparation and proper quality checks of surface condition prior to Platinum coating. The procedures were revised and utilized during the rebuild process for the subject pilot valves.
Commitments
No regulatory commitments are contained in this report.