05000458/LER-2025-002-01, For River Bend Station, Unit 1, Unidentified Drywell Leakage Increase Results in Shutdown
| ML25293A384 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 10/20/2025 |
| From: | Mccoy J Entergy Operations |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| RBG-48379 LER 2025-002-01 | |
| Download: ML25293A384 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4582025002R01 - NRC Website | |
text
- ) entergy RBG-48379 October 20, 2025 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Jack McCoy Manager Regulatory and Emergency Planning 225-378-3310 10 CFR 50.73
Subject:
Licensee Event Report 50-458 / 2025-002-01, Unidentified Drywell Leakage Increase Results in Shutdown 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, Jack McCoy JM/jdb
Enclosure:
cc:
Digitally signed by Jack McCoy ON: cn=Jack McCoy, o=Manager Regulato,yandEmergencyPreparedness, ou=Entergy/RiverBend, email:jmccoy1@entergy.com Date:2025.10.2013:34:06-05'00' LER 50-458 / 2025-002-01, Unidentified Drywell Leakage Increase Results in Shutdown NRC Region IV Regional Administrator - Region IV NRC Senior Resident Inspector - River Bend Station NRC Office of Nuclear Security and Incident Response Entergy Operations, Inc., 5485 U.S. Highway 61 N. St. Francisville, LA 70775
Enclosure RBG-48379 Licensee Event Report 50-458/2025-002-01
Abstract
On May 21, 2025, at 0324 CDT, with River Bend Station (RBS), Unit 1 operating in Mode 1 at 100% power, unidentified drywell leakage experienced a greater than 2 gallon per minute change over a 24-hour period. Technical Specifications (TS) Limiting Condition of Operations (LCO) 3.4.5 Condition C was entered. The required action to verify the source of unidentified leakage increase could not be completed within the allowable completion time. As a result, a plant shutdown was initiated at 0656 CDT.
While investigating the unidentified leakage source, RBS determined that a degraded condition existed following the examination of the Residual Heat Removal (RHR) 'A' injection line testable check valve. The leakage from the RHR 'A' injection line testable check valve was determined to be Reactor Coolant System pressure boundary leakage.
The direct cause of the leakage past RHR 'A' injection line testable check valve was due to improper gasket seating.
This event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(A) as a Plant Shutdown Required by Technical Specifications, 10 CFR 50.73(a)(2)(ii)(A) as a Degraded or Unanalyzed Condition that resulted in the condition of the nuclear power plant, including its principal safety barriers being seriously degraded, and 10 CFR 50.73(a)(2)(i)(B) as an Operation or Condition Prohibited by Technical Specifications.
Event Description
- 2. DOCKET NUMBER YEAR 00458 2025
- 3. LER NUMBER SEQUENTIAL NUMBER 002 REV NO.
01 On May 21, 2025, at 0324 CDT, with River Bend Station (RBS), Unit 1 operating in Mode 1 at 100% power, unidentified drywell leakage experienced a greater than 2 gallon per minute change over a 24-hour period. Technical Specifications (TS) Limiting Condition of Operations (LCO) 3.4.5 Condition C was entered. The required action to verify the source of unidentified leakage increase is not service sensitive type 304, type 316 austenitic stainless steel,
or other inter-granular stress corrosion cracking susceptible material within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, could not be completed within the allowable completion time due to the drywell being inaccessible during plant operation. As a result, a controlled manual plant shutdown was initiated at 0656 CDT. At 1405 CDT, the control room operators placed the mode switch to Shutdown. The control room operators entered the appropriate post scram procedures and appropriately responded to the reactor scram.
This event was reported on May 21, 2025, at 0950 CDT in accordance with 10 CFR 50.72(b)(2)(i), as an event or condition that results in a TS required plant shutdown. (EN 57725)
During the investigation of the unidentified leakage following the shutdown, RBS determined that a degraded condition existed following the performance of a visual examination of E12-AOVF041A (Residual Heat Removal 'A' Injection Line Testable Check Valve) [BO:V]. This examination was conducted on May 22, 2025, at 2358 CDT.
This event was reported on May 23, 2025, at 0121 CDT in accordance with 10 CFR 50.72(a)(2)(ii)(A), as Degraded or Unanalyzed Condition that resulted in the condition of the nuclear power plant, including its principal safety barriers being seriously degraded. (EN 57731)
The elevated drywell leakage was determined to be Reactor Coolant System (RCS) [AB] pressure boundary leakage and required actions were not completed within the completion time as required by TS LCO 3.4.5. Therefore, this event is also being reported under 10 CFR 50.73(a)(2)(i)(B) as an Operation or Condition Prohibited by TS.
Event Cause
The direct cause of this event was improper gasket seating, resulting from erosion of the gasket seating surface. The erosion was caused by steam cutting to the base metal of the gasket seat surface. In this degraded state, the base metal did not provide the required support as designed. Two causal factors were identified; (1) The organization did not fully understand the degraded condition of E12-AOVF041A valve body due to steam cutting; therefore, an adequate repair strategy was not formulated or executed and (2) Required VT-3 inspections were not added to the Job Plan as the plan was in Approved status and therefore not routed for additional reviews. In addition, the inspectors failed to realize the need for an inspection as it was not listed in the Job Plan description.
Safety Assessment
The actual consequence of these events was the initiation of a controlled manual plant shutdown. Following the controlled manual plant shutdown, reactor pressure was maintained by the Turbine Steam Drains [TF] and reactor water level was maintained by the Feedwater [SJ] system. Page 2 of 3 (04-02-2024)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 04/30/2027 LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form https:/lwww.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 1. FACILITY NAME River Bend Station, Unit 1
Corrective Actions
In Progress:
1:2]
050 052
- 2. DOCKET NUMBER YEAR 00458 2025
- 3. LER NUMBER SEQUENTIAL NUMBER 002 REV NO.
01 IT to resolve the discrepancies identified within the action tracking program.
Completed:
Completed a work order to repair and restore E12-AOVF041A to pre-steam cut conditions.
Revise job plans to include Operational Experience from this event.
Reinforce requirements of ASME Section XI inspections required for Class 1 pumps and valves with engineering.
Previous Occurrences
None Energy Industry Identification System (EIIS) codes are identified in the text as [XX]. River Bend equipment codes are identified as (XX). Page 3 of 3