05000382/LER-2024-001-01, Manual Reactor Trip Due to Engineered Safety Features Actuation System Relay Failure

Manual Reactor Trip Due to Engineered Safety Features Actuation System Relay Failure

ML24312A174
Person / Time
Site:	Waterford
Issue date:	11/07/2024
From:	Twarog J Entergy Operations
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
W3F1-2024-0050 LER 2024-001-01
Download: ML24312A174 (1)

LER-2024-001, Manual Reactor Trip Due to Engineered Safety Features Actuation System Relay Failure

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
3822024001R01 - NRC Website

text

S) entergy W3F1-2024-0050 November 7, 2024 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 John Twarog Manager Regulatory Assurance 504-739-6747 10 CFR 50.73 Subject:

Licensee Event Report 50-382/2024-001-01, Manual Reactor Trip Due to Engineered Safety Features Actuation System Relay Failure Waterford Steam Electric Station, Unit 3 NRC Docket No. 50-382 Renewed Facility Operating License No. NPF-38 Entergy Operations, Inc. (Entergy) submits the enclosed Licensee Event Report (LER) supplement 50-382/2024-001-01 for Waterford Steam Electric Station, Unit 3 (Waterford 3).

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 paragraph (a)(2)(iv)(B); Reactor protection system (RPS) including: reactor scram or reactor trip and PWR auxiliary or emergency feedwater system actuation.

The LER supplement provides an update to the cause of the event and corrective actions.

This letter contains no new commitments.

Should you have any questions concerning this issue, please contact me at 504-739-6747.

Respectfully, John R.

Twarog John Twarog JRT/mrp 0191tally signed by John R Twarog DN cn=John R Twarog, c=US, o=Entergy, ou=Waterford 3 Regulatory Assurance, emall=jtwarog@entergy com Date 2024 11 06 07 57 50 --06'00' Entergy Operations, Inc., 17265 River Road, Killona, LA 70057

W3F 1-2024-0050 Page 2 of 2 Enclosure: Licensee Event Report 50-382/2024-001-01 cc:

NRC Region IV Regional Administrator NRC Senior Resident Inspector - Waterford Steam Electric Station, Unit 3 NRC Project Manager - Waterford Steam Electric Station, Unit 3 Louisiana Department of Environmental Quality

Enclosure W3F1-2024-0050 Licensee Event Report 50-382/2024-001-01

Abstract

At 1449 CDT on March 16, 2024, with Waterford Steam Electric Station, Unit 3 (WF3), operating in Mode 1 at approximately 100% power, Main Feedwater Isolation Valve #2, FW-184B, and Main Steam Isolation Valve #2, MS-124B, began closing resulting in steam generator levels lowering. As a result of these indications, control room operators initiated a manual reactor trip. All control element assemblies properly inserted in response to the reactor trip. All safety systems, including the Emergency Feedwater System, performed as designed and there were no complications with the trip.

The cause of the event was a failure of the Steam Generator #2 and Main Steam Line #2 Valves Main Steam Isolation Signal Actuation Relay, K313-A, resulting in the unexpected closing of MS-124B and FW-184B. The vendor analysis determined the failed relay was due to a manufacturing defect of the relay coil. The failed relay was replaced, and the remaining Engineered Safeguard Features Actuation System relays were verified to be from a different batch.

This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A), as an actuation of the Reactor Protection System and Emergency Feedwater System.

Event Description

2. DOCKET NUMBER

3. LER NUMBER I

00382 NUMBER NO.

I YEAR SEQUENTIAL REV

- 1 001 1-0 At 1449 CDT on March 16, 2024, with Waterford Steam Electric Station, Unit 3 (WF3), operating in Mode 1 at 100% power, Main Feedwater Isolation Valve #2 [SJ: ISV], FW-184B, and Main Steam Isolation Valve #2 [SB: ISV], MS-124B, began closing resulting in steam generator levels lowering. As a result of these indications, control room operators initiated a manual reactor trip. All control element assemblies properly inserted in response to the reactor trip. All safety systems, including the Emergency Feedwater System (EFW) [BA], performed as designed and there were no complications with the trip. The condition was reported on March 16, 2024, at 1836 EDT (Event Number 57032) in accordance with 10 CFR 50.72 (b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A) for a valid Reactor Protection System (RPS) actuation and EFW system actuation.

Following the reactor trip, an acrid odor was detected in the rear of relay cabinet, 3AS Bay 3. The investigation identified that the Tyco, MDR-7034, K313-A relay had failed.

Event Cause The cause of FW-184B and MS-124B failing closed was due to a degraded relay coil. The K313-A relay, Steam Generator

1. 2 and Main Steam Line #2 Valves Main Steam Isolation Signal Actuation Relay, is part of the Engineered Safeguard Features Actuation System (ESFAS). The vendor analysis determined the failed relay was due to a manufacturing defect of the relay coil. The failed relay was screened for 10 CFR 21 reportability and determined to not be reportable.

ESFAS relays were previously identified as Single Point Vulnerabilities (SPV). Elimination of this SPV was scheduled to be completed in WF3's most recent outage (Refuel Outage [RF] 25) however due to a design discrepancy with the Engineering Change the modification was removed from the RF-25 scope.

Safety Assessment The actual consequence for the relay failure was a reactor trip. The relay failure challenged the ESFAS and Reactor Protection System. Following the manual reactor trip, plant equipment performed as designed. There were no other structures, systems, or components out of service that contributed to this event. EFW responded and provided normal post trip heat removal via the Steam Generators [SG] such that there were no actual consequences to general safety of the public, nuclear safety, industrial safety, or radiological safety for this event.

Corrective Actions (1) K313-A relay was replaced, and post maintenance testing was completed.

(2) Validated the remaining ESFAS relays are not from the same batch as the failed K313-A relay.

(3) Determined the ESFAS spare relays in stock are from a different batch as the failed K313-A relay.

(4) The Engineering Modification to eliminate the ESFAS relays as SPVs has been scoped for RF-26.

(5) Create a preventative maintenance task (PM) to perform MDR Relay Coil Inductance testing at all available opportunities including Forced Outages and Refuel Outages.

Previous Similar Events

2. DOCKET NUMBER I

00382

3. LER NUMBER SEQUENTIAL NUMBER 001 REV NO.

1-0 LER-2022-005-00, documents the opposite train failure ESFAS relay, K313-B that resulted in a reactor trip on June 24, 2022. The direct cause of the relay failure was a short in the relay coil. After the failure of the relay on June 24, 2022, the site replaced all six Main Steam Isolation Valve and Main Feed Isolation Valve ESFAS relays. Vendor analysis determined the relay coil failed due to a manufacturing defect. Page 3

of 3