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:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
3892024003R00 - NRC Website

text

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 August 5, 2024 L-2024-115 10 CFR 50.73 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. Ocean Drive, Jensen Beach, 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

2. DOCKET NUMBER

3. LER NUMBER I

00389 D

NUMBER NO.

I YEAR SEQUENTIAL REV

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03 1-0 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. 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.

Cause of Event

On June4, 2024, at 1345 EDT, St. Lucie Unit 2 experienced a malfunction of the condenser outlet valve (MV-21-5A2) limit switch. The malfunction resulted in a trip of the 282 CWP that required a manual reactor trip due to low condenser vacuum.

The 282 CWP 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. The limit switch for the valves are auxiliary contacts that do not provide indication to the Control Room.

Safety Significance

This event did not prevent any safety systems from performing their safety related functions based on the minimal amount of leakage identified.

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

This event did not result in a Safety System Functional Failure.

Corrective Actions

Operating procedures were revised to require the removal of control fuses from the CWP breaker.

Similar Events

A review of events over the past 5 years did not identify any unplanned reactor scrams as a result of a CWP trip. Page 2

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