05000458/LER-2025-001, Human Performance Error Results in Manual Reactor Trip
| ML25156A246 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 06/05/2025 |
| From: | Giddens J Entergy Operations |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| RBG-48363 LER 2025-001-00 | |
| Download: ML25156A246 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B), System Actuation |
| 4582025001R00 - NRC Website | |
text
- ) entergy RBG-48363 June 5, 2025 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 John Giddens Senior Manager - Regulatory Compliance (Acting Regulatory Assurance Manager)
River Bend Station 601-368-5756 10 CFR 50.73
Subject:
Licensee Event Report, 50-458/2025-001-00, Human Performance Error Results in Manual Reactor Trip River Bend Station - Unit 1 NRC Docket Nos. 50-458 Renewed Facility Operating License No. NPF-47 Entergy Operations, Inc. (Entergy) submits the enclosed Licensee Event Report (LER), 50-458/2025-001-00 for River Bend Station, Unit 1 (RBS). The events reported herein are reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A), any event or condition that resulted in manual or automatic actuation of any of the systems listed in 10 CFR 50.73(a)(2)(iv)(B).
This letter contains no new regulatory commitments.
Should you have any questions, please contact me at 601-368-5756.
Respectfully, JMG/ahv Digitally signed by John Giddens DN: cn=John Giddens, o=Entergy, ou=Regulatory Compliance, email=jgidden@entergy.com Date: 2025.06.05 12:28:52 -05'00' Enclosure: LER 50-458/2025-001-00 cc:
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 61N., St. Francisville, LA 70775
Enclosure RBG-48363 Licensee Event Report 50-458/2025-001-00
Abstract
At 1607 CDT on April 8, 2025, with River Bend Station, Unit 1 operating in Mode 1 at 81 % power, control room operators responded to alarms received for a total loss of normal service water. The control room operators entered AOP-0009, Loss of Normal Service Water, and subsequently inserted a manual reactor trip.
The direct cause of the loss of normal service water was the result of non-licensed operators failing to close SWP-MOV55A block valve, SWP-V3302, prior to post maintenance testing. Two causal factors were identified during the investigation: (1) Non-licensed operators did not appropriately apply human performance tools and verification practices when performing equipment protection tagout task; and, (2) Operations supervisor did not ensure adequate pre-job brief in accordance with EN-OP-102 and EN-HU-102 during briefing of equipment protection tagout installation
- - specifically, the risks involved if the work was performed incorrectly, stop-work criteria, and the key role of engagement by both performer and peer checker.
This event is reportable in accordance with 10 CFR 50.73 (a)(2)(iv)(A), any event or condition that resulted in manual or automatic actuation of any of the systems listed in 10 CFR 50.73 (a)(2)(iv)(B).
Event Description
- 2. DOCKET NUMBER YEAR 00458 2025
- 3. LERNUMBER SEQUENTIAL NUMBER 001 REV NO.
00 At 1607 CDT on April 8, 2025, with River Bend Station (RBS), Unit 1 operating in Mode 1 at 81 % power, control room operators responded to alarms received for a total loss of normal service water [Bl]. The control room operators entered AOP-0009, Loss of Normal Service Water and subsequently inserted a manual reactor trip.
The control room operators entered the appropriate post trip procedures and appropriately responded to the uncomplicated reactor trip.
This event was reported on April 8, 2025, at 1911 EDT in accordance with 10 CFR 50.72(b)(2)(iv)(B) for reactor protection system actuation and 10 CFR 50.72(b)(3)(iv)(A) due to an expected reactor water level 3 isolation signal (EN 57655).
Event Cause
The direct cause of a loss of normal service water was the result of non-licensed operators failing to close SWP-V3302 [Bl:SHV], SWP-MOV55A block valve, prior to post maintenance testing. During post maintenance testing, maintenance personnel requested Operations to open SWP-MOV55A [Bl:ISV], Standby Cooling Tower Division 1 Return Isolation Valve, as the valve opened all normal service water pumps [Bl:P] received a low-pressure lockout condition due to an open flow path to the Standby Cooling Tower.
Two causal factors were identified during the investigation: (1) Non-licensed operators did not appropriately apply human performance tools and verification practices when performing equipment protection tagout task; and, (2)
Operations supervisor did not ensure adequate pre-job brief in accordance with EN-OP-102, Protective and Caution Tagging, and EN-HU-102, Human Performance Traps and Tools, during briefing of equipment protection tagout installation - specifically, the risks involved if the work was performed incorrectly, stop-work criteria, and the key role of engagement by both performer and peer checker.
Safety Assessment
The actual consequence of this human performance error was a loss of normal service water and a subsequent manual plant trip. Standby Service Water initiated as expected and Normal Service Water was restored 37 minutes after loss. There were no other actual consequences to general safety of the public, nuclear safety, industrial safety and radiological safety for this event.
Corrective Actions
Completed:
Performance management actions were taken with the operators involved in the event.
In progress:
Operations Shift Managers perform standards reset blitz.
Create and implement verification challenge activity utilizing the simulator for non-licensed individuals.
Operations Management perform standards reset with Senior Reactor Operators on utilizing quizzing during reverse briefs/pre-job briefs to ensure operations clearly understand the risk, probability of one, all instructions, and components to be manipulated. The discussion will include "I own the risk" and risk presented by operator performance.
Previous Occurrences
No previous similar events at RBS have occurred within the past 5 years in which a component misposition results in a reactor trip. Page 2 of 2