05000389/LER-2024-003, Unplanned Reactor Scram

Unplanned Reactor Scram

ML24218A080
Person / Time
Site:	Saint Lucie
Issue date:	08/05/2024
From:	Rasmus P Florida Power & Light Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
L-2024-115 LER 2024-03-00
Download: ML24218A080 (1)

LER-2024-003, Unplanned Reactor Scram

Event date:
Report date:
3892024003R00 - NRC Website

text

August 5, 2024 L-2024-115 10 CFR 50.73

U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

Re: St. Lucie Unit 2 Docket No. 50-389 Reportable Event: 2024-03-00 Date of Event: June 4, 2024

Unplanned Reactor Scram

The attached Licensee Event Report, 2024-03, is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event.

Should you have any questions regarding this submission, please contact Mr. Kenneth Mack, Senior Manager Licensing and Reg Compliance - Nuclear Fleet, at 561-904-3635.

This letter contains no new or modified regulatory commitments.

Sincerely,

Paul Rasmus General Manager - Regulatory Affairs - Nuclear Fleet Florida Power & Light Company

Attachment

cc: St. Lucie NRC Senior Resident Inspector St. Lucie Station NRC Program Manager

Florida Power & Light Company

6501 S. Oc ea n Driv e, Jen se n Be ac h, FL 34957

Abstract

On June 4, 2024, at 1352 EDT, while in Mode 1 with Unit 2 at 92 percent power, the reactor was manually tripped due to a loss of condenser vacuum resulting from a circulating water pump (CWP) trip. The circulating water pump (282) trip was caused by the inability of the interlock circuit to provide the inhibiting function from the condenser outlet motor operated valve limit switch auxiliary contact. There were no Systems, Structures, or Components that were inoperable at the start of the event that contributed to the event. This event is being reported pursuant of 10 CFR 50.73(a)(2)(iv)(A), System Actuation.

Description of Event

On June 4, 2024, at 1352 EDT, while in Mode 1 with Unit 2 at 92 percent power, the reactor was manually tripped d ue to a loss of condenser vacuum resulting from a circulating wate r pump (CWP) trip. There were no Systems, Structures, or Components that were inoperable at the start of the event that contributed to the event. This event is being reported pu rsuant of 10 CFR 50. 73(a)(2)(iv)(A), System Actuation. *

Cause of Event

On June4, 2024, at 1345 EDT, St. Lucie Uni t 2 expe rienced a malfu nct ion of the condense r outlet valve (MV-21-5A2) limit sw itch. The ma lfunction resul ted in a trip of the 282 CWP that requ ired a manual reactor trip due to low condenser vacuum.

The 282 CWP trip was caused by the inability of the interlock circui t to prov ide the inh i bit ing fu nctio n f rom the condenser outlet motor operated valve limit switch auxiliary contac t. The lim it switch for the valves a re aux iliary contacts that do not provide indicat ion to the Control Room.

Safety Sign ificance :

This event did not prevent any safety systems from performing the i r safety related functions based on the m i ni mal amount of leakage identified.

Th is Licensee Event Report is being reported pursuant of 10 CFR 50.73(a)(2)(iv)(A), System Actuation.

Th is event did not result in a Safety System Functional Failure.

Correct ive Actions :

Operating procedu res we re revised to requ i re the re m oval of control fuses from the CWP breaker.

Simila r Events :

A rev iew of events over the past 5 years did not identify any unplanned reactor scrams as a result of a CWP trip.

N RC FORM 366 A (04-02-202 4) Page 2 of 2