05000458/LER-2025-003, Turbine Control Valve Closure Results in Loss of Safety Function
| ML25226A231 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 08/14/2025 |
| From: | Mccoy J Entergy Operations |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| RBG-48371 LER 2025-003-00 | |
| Download: ML25226A231 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 4582025003R00 - NRC Website | |
text
Jack McCoy Manager Regulatory and Emergency Planning 225-378-3310 Entergy Operations, Inc., 5485 U.S. Highway 61N. St. Francisville, LA 70775 RBG-48371 10 CFR 50.73 August 14, 2025 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Licensee Event Report 50-458 / 2025-003-00, Turbine Control Valve Closure Results in Loss of Safety Function River Bend Station - Unit 1 NRC Docket Nos. 50-458 Renewed Facility Operating License No. NPF-47 In accordance with 10 CFR 50.73, enclosed is the subject Licensee Event Report.
This document contains no commitments.
Should you have any questions, please contact Mr. Jack McCoy, Regulatory and Emergency Planning Manager, at 225-378-3310.
Respectfully, JM/jdb
Enclosure:
LER 50-458 / 2025-003-00, Turbine Control Valve Closure Results in Loss of Safety Function cc:
NRC Region IV Regional Administrator - Region IV NRC Senior Resident Inspector - River Bend Station
Enclosure RBG-48371 Licensee Event Report 50-458/2025-003-00
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 10 CFR Part 20 20.2203(a)(2)(vi) 10 CFR Part 50 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 73.1200(a) 20.2201(b) 20.2203(a)(3)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 73.1200(b) 20.2201(d) 20.2203(a)(3)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 73.1200(c) 20.2203(a)(1) 20.2203(a)(4) 50.36(c)(2) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 73.1200(d) 20.2203(a)(2)(i) 10 CFR Part 21 50.46(a)(3)(ii) 50.73(a)(2)(v)(A) 10 CFR Part 73 73.1200(e) 20.2203(a)(2)(ii) 21.2(c) 50.69(g) 50.73(a)(2)(v)(B) 73.77(a)(1)(i) 73.1200(f) 20.2203(a)(2)(iii) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C) 73.77(a)(2)(i) 73.1200(g) 20.2203(a)(2)(iv) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D) 73.77(a)(2)(ii) 73.1200(h) 20.2203(a)(2)(v) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii)
Other (Specify here, in abstract, or in NRC 366A).
Abstract
On June 18, 2025, at 0553 CDT, with River Bend Station (RBS), Unit 1 operating in Mode 1 at 100% power, High Pressure Turbine Main Steam Supply Line D Control Valve (MSS-HYVCV3) closed causing both Turbine Bypass Valves to open. Reactor power was lowered to approximately 95% and the Bypass Valves Closed. At 0646 CDT, MSS-HYVCV3 was observed opening and all other Turbine Control Valves intermittently changing position causing the Bypass Valves to open again. Reactor power was lowered to approximately 90% and the Bypass Valves closed. The Bypass Valves were open for approximately one minute for each of the two occurrences.
With the Bypass Valves open, Technical Specification (TS) required instrumentation that utilize turbine first stage pressure were declared inoperable.
The direct cause of this event was a failure of the Redundant Valve Positioner B (RVP-B) for MSS-HYVCV3. The RVP-B was replaced on June 19, 2025.
This event is reportable in accordance with 10 CFR 50.73(a)(2)(v)(A) and 10 CFR 50.73(a)(2)(v)(D) as an event or condition that could have prevented fulfillment of the safety function of structures or systems that are needed to: (A) shut down the reactor and maintain it in a safe shutdown condition and (D) mitigate the consequences of an accident.
Event Description
On June 18, 2025, at 0553 CDT, with River Bend Station (RBS), Unit 1 operating in Mode 1 at 100% power, the High-Pressure Turbine Main Steam Supply Line D Control Valve (MSS-HYVCV3) [TG:VLV] closed causing both Turbine Bypass Valves [JI:V] to open. Control room operators entered appropriate procedures and began to lower reactor power.
Reactor power was lowered to approximately 95% and the Turbine Bypass Valves closed. At 0646 CDT, MSS-HYVCV3 was observed opening and all other High-Pressure Turbine Main Steam Supply Line Control Valves were observed intermittently changing positions causing the Turbine Bypass Valves to open again. Reactor power was lowered to approximately 90% and the Bypass Valves closed.
During the time the Turbine Bypass Valves were open, Technical Specification (TS) required instrumentation that utilizes turbine first stage pressure were declared inoperable. Safety Related Functions of TS 3.3.1.1 (RPS Instrumentation), TS 3.3.2.1 (Control Rod Block Instrumentation) and TS 3.3.4.1 (End of Cycle Recirculation Pump Trip) were declared inoperable.
This event was reported on June 18, 2025, at 1126 CDT in accordance with 10 CFR 50.72(b)(3)(v)(A) and 10 CFR 50.72(b)(3)(v)(D) as an event or condition that at the time of discovery could have prevented fulfillment of a safety function of structures or systems that are needed to: (A) shut down the reactor and maintain it in a safe shutdown condition and (D) mitigate the consequences of an accident. (EN 57767)
Event Cause
The direct cause of this event was a failure of the Redundant Valve Positioner B (RVP-B) for MSS-HYVCV3. This failure resulted in the closing of MSS-HYVCV3 resulting in the opening of the Turbine Bypass Valves to maintain reactor pressure at the selected setpoint. The RVP-B was replaced on June 19, 2025.
Safety Assessment
During the transient there were no radiological impacts and therefore no actual impact to the health and safety of the public. The event is considered of small safety significance from the Probabilistic Risk Assessment (PRA) perspective as no PRA related mitigative components or strategies were affected by this event. While the corresponding functions were declared inoperable from a Technical Specification perspective, functionality was maintained, therefore this is not considered a safety system functional failure.
Corrective Actions
Planned:
Perform a vendor analysis for the failed RVP module.
Investigate a possible solution to mitigate or eliminate similar failures of the RVP modules.
Previous Occurrences
None Energy Industry Identification System (EIIS) codes are identified in the text as [XX]. River Bend equipment codes are identified as (XX).