05000395/LER-2024-002, Loss of Control Room Emergency Filtration System

Loss of Control Room Emergency Filtration System

ML24290A087
Person / Time
Site:	Summer
Issue date:	10/15/2024
From:	Ryan Justice Dominion Energy South Carolina
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
24-310, VCS-LIC/JB RO LER 2024-002-00
Download: ML24290A087 (1)

LER-2024-002, Loss of Control Room Emergency Filtration System

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v), Loss of Safety Function
3952024002R00 - NRC Website

text

Dominion Energy South Carolina, Inc Virgil C. Summer Nuclear Station Bradham Boulevard & Highway 215, Jenkinsville, SC 29065 Mailing Address :

P.O. Box 88, Jenkinsville, SC 29065 Dominion Energy.com Document Control Desk October 15, 2024 U.S. Nuclear Regulatory Commission Washington, DC 20555

~

Dominion P" Energy 8

Serial No.: 24-310 VCS-LIC/JB RO Docket No. 50-395 License No. NPF-12 DOMINION ENERGY SOUTH CAROLINA, INC. (DESC)

VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT 1 LICENSEE EVENT REPORT 2024-002-00 LOSS OF CONTROL ROOM EMERGENCY FILTRATION SYSTEM Dominion Energy South Carolina, Inc. hereby submits Licensee Event Report (LER) 2024-002-00, for VCSNS. This report provides updated information regarding the inoperability of Control Room Ventilation on August 20, 2024.

This event is currently being evaluated in accordance with the VCSNS Corrective Action Program. Submittal of a supplemental report based on the results of that evaluation is planned by December 20, 2024.

Should you have any questions, please call Mr. Justin Bouknight at (803) 941-9828.

Sincerely, Enclosure Commitments contained in this letter: None cc:

G. J. Lindamood - Santee Cooper L. Dudes - NRC Region II G. Miller - NRC Project Mgr.

NRC Resident Inspector J. N. Bassett-INPO Marsh USA, Inc.

Abstract

On August 20, 2024, at 2001 ET, V.C. Summer Nuclear Station (VCSNS) identified that both trains of Control Room Emergency Filtration System (CREFS) were inoperable. The CREFS consists of the 'A' and

• B' trains of the Control Room Ventilation System (CRVS). The ' B' train CRVS had been removed from service earlier in the day for planned maintenance and testing activities. At 1015 ET, 'A' CRVS Inlet Control Damper failed to close under its own power, when required to do so to support retest of the

• B' CRVS. As a result, the CREFS would have been unable to perform the emergency filtration function.

At 2107 ET, the 'A' CRVS was restored to OPERABLE status and available to perform its safety function. Reactor power remained at 100% throughout the event.

This event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) and 10 CFR 50.73(a)(2)(v).

1.0 DESCRIPTION OF THE EVENT

2. DOCKET NUMBER I

395

3. LER NUMBER

~ NUMBER I

~-I 002 REV NO.

1-0 On August 20, 2024, V.C. Summer Nuclear Station (VCSNS) removed 'B' train of its Control Room Ventilation System (CRVS) from service for planned maintenance activities. Following maintenance, the 'B' CRVS was to be retested per STP 454.002, "Control Room Emergency Air Cleanup System Performance Test."

To support performance of STP 454.002, the Control Room Air Handling Unit A Inlet Control Damper (XDP0022A) had to be closed. At 1015 ET, XDP0022A failed to close upon demand. With the Unit A Inlet Control Damper unable to close on demand, the 'A' CRVS was no longer OPERABLE, while the 'B' CRVS was removed from service for maintenance. As a result, the control room did not have emergency filtration capability, which is a safety function needed to mitigate the consequences of an accident.

At 2107 ET, the 'A' train CRVS returned to OPERABLE status, following cleaning, lubrication, and retest of XDP0022A.

Reactor power remained at 100% throughout the event. This event is being reported in accordance with 10 CFR 50.73(a)

(2)(i)(B) and 10 CFR 50.73(a)(2)(v).

2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS

With both trains of CRVS inoperable, the Control Room Emergency Filtration System (CREFS) would have been unable to perform its safety function needed to mitigate the consequences of a postulated accident.

3.0 CAUSE OF THE EVENT

This event is currently being evaluated, in accordance with the VCSNS Corrective Action Program (CAP). The cause will be provided in a future LER supplement.

4.0 CORRECTIVE ACTIONS

XDP0022A was inspected, cleaned, and lubricated, prior to being retested. At 2107 ET, the 'A' train CRVS was declared OPERABLE.

On August 23, 2024 at 0849 ET, the 'B' CRVS was returned to OPERABLE status following completion of its planned maintenance activities.

This event is currently being evaluated, in accordance with the VCSNS Corrective Action Program (CAP). Corrective actions will be provided in a future supplement, based on the ongoing cause evaluation.

5.0 SIMILAR EVENTS

No similar events were identified within the last three years.

6.0 COMPONENT I

2. DOCKET NUMBER

3. LER NUMBER I

YEAR SEQUENTIAL REV I 2024 I NUMBER NO.

395

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