05200025/LER-2024-004, Condition Prohibited by Technical Specification Due to Main Steam Safety Valve Lift Pressure Setpoint Drift
| ML24344A153 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 12/09/2024 |
| From: | Martino P Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NL-24-0416 LER 2024-004-00 | |
| Download: ML24344A153 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 0252024004R00 - NRC Website | |
text
._ Southern Nuclear December 9, 2024 Docket No.:
52-025 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Patrick Martino Site Vice President, Vogtle Units 3 & 4 Vogtle Electric Generating Plant (VEGP) - Unit 3 Licensee Event Report 2024-004-00 Condition Prohibited by Technical Specification 7825 River Road Waynesboro, Georgia 30830 (706) 848-6602 tel NL-24-0416 Due to Main Steam Safety Valve Lift Pressure Setpoint Drift Ladies and Gentlemen:
In accordance with the requirements of 10 CFR 50.73(a)(2)(i)(B), Southern Nuclear Operating Company is submitting the enclosed Licensee Event Report for VEGP Unit 3.
This letter contains no regulatory commitments. If you have questions regarding the enclosed information, please contact Will Garrett at (706) 848-7154.
Respectfully submitted, O:>>;z,1-Patrick A. Martino Site Vice President Vogtle Units 3 & 4 PAM/kjd/cbg
Enclosure:
Unit 3 Licensee Event Report 2024-004-00 CC:
Regional Administrator, Region II VPO Project Manager Senior Resident Inspector - Vogtle Units 3 & 4 Director, Environmental Protection Division - State of Georgia
Vogtle Electric Generating Plant - Unit 3 Licensee Event Report 2024-004-00 Condition Prohibited by Technical Specification Due to Main Steam Safety Valve Lift Pressure Setpoint Drift Enclosure Unit 3 Licensee Event Report 2024-004-00
Abstract
During a Technical Specification (TS) 3.7.1 surveillance beginning on October 9, 2024 and completing on October 10, 2024, four steam generator main steam safety valves (MSSVs) were sequentially tested and adjusted with Vogtle Electric Generating Plant (VEGP) Unit 3 in Mode 1 at approximately 99 percent power. Three MSSVs failed the as found lift pressure test because the setpoints were outside the TS limits; however, the setpoint values met the +/-3 percent ASME OM Code criteria. Setpoint drift is the most likely cause of the MSSVs' lift setpoint test failure. It is likely that the setpoint for each of the three MSSVs was outside the TS limit for longer than the allowed completion times for the associated required action statements during the operating cycle in all applicable modes of operation. The three MSSVs' lift setpoint were immediately adjusted to within the TS limits as required by the surveillance test and returned to service restoring compliance.
This condition is reportable under 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS. VEGP Units 1, 2 and 4 were unaffected by this event.
EVENT DESCRIPTION
I
- 2. DOCKET NUMBER 00025 I
YEAR 8-1
- 3. LER NUMBER SEQUENTIAL NUMBER 004 REV NO.
1-G During a technical specification (TS} 3.7.1 surveillance beginning on October 9, 2024, and completing on October 10, 2024, four steam generator main steam safety valves (MSSVs) [EIIS: SB/RV] were sequentially tested and adjusted to verify the lift pressure settings with Vogtle Electric Generating Plant (VEGP) Unit 3 in Mode 1 at approximately 99 percent power.
Three MSSVs failed the as-found lift pressure test because the setpoints were outside the +/-1 percent tolerance specified in TS 3. 7.1. The MSSVs' lift pressure settings were likely outside the TS limits for longer than the completion times for the applicable required action statements. During the test, MSSVs, 3-SGS-V030A and 3-SGS-V031A, as-found lift settings were 1.97 percent higher and 1.89 percent higher, respectively, and MSSV, 3-SGS-V031 B, was 1.32 percent lower than the TS limit.
EVENT CAUSE ANALYSIS
The cause of the event was most likely due to setpoint drift. The TS requirement of maintaining the MSSV lift settings to within +/-1 percent of the setpoint is conservative relative to design basis/ transient accident analysis which demonstrates up to +/-3 percent tolerance in the setpoints will ensure system pressure is maintained within 110 percent of the design pressures and ASME Code allowable stresses.
SAFETY ASSESSMENT AND REPORTABILITY
There were no safety consequences as a result of this event. Each of the three MSSV's as-found lift pressures were within
+/-3 percent of the setpoints allowed by the system design basis accident analysis to ensure the MSSVs function to prevent the main steam system from exceeding 110 percent of the system design pressure.
There were no other safety-related structures, systems, or components that were inoperable that contributed to the event.
This event is reportable per 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS. All safety systems functioned as expected as a result of the event. VEGP Units 1, 2, and 4 were unaffected by this event.
CORRECTIVE ACTIONS
The three MSSV's setpoints were immediately adjusted to within the +/-1 percent tolerance from the setpoints specified the TS 3.7.1 as part of the surveillance test and returned to service.
PREVIOUS SIMILAR EVENTS
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