05000263/LER-2024-002, Low Pressure Coolant Injection Inoperable Due to Motor Valve Failure

Low Pressure Coolant Injection Inoperable Due to Motor Valve Failure

ML24240A166
Person / Time
Site:	Monticello
Issue date:	08/27/2024
From:	Brown G Northern States Power Company, Minnesota, Xcel Energy
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
L-MT-24-024 LER 2024-002-00
Download: ML24240A166 (1)

LER-2024-002, Low Pressure Coolant Injection Inoperable Due to Motor Valve Failure

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function
2632024002R00 - NRC Website

text

Xcel Energy August 27, 2024 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket No. 50-263 Renewed Facility Operating License No. DPR-22 Monticello Nuclear Generating Plant Licensee Event Report 2024-002-00 2807 West County Road 75 Monticello, MN 55362 L-MT-24-024 10 CFR 50.73 Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), hereby submits Licensee Event Report (LER) 50-263/2024-002-00 per 10 CFR 50.73(a)(2)(v)(B) and 10 CFR 50.73(a)(2)(v)(D).

If you have any questions about this submittal, please contact Carrie Seipp, Senior Regulatory Engineer, at 612-330-5576.

Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.

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Greg D Brown Plant Manager, Monticello Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc:

Administrator, Region Ill, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC State of Minnesota

ENCLOSURE MONTICELLO NUCLEAR GENERATING PLANT LICENSEE EVENT REPORT 50-263/2024-002-00 3 pages follow

Abstract

On June 28, 2024 at 0110 CDT Monticello Nuclear Generating Plant was in Mode 1 at 100 percent power and performing OSP-RHR-0556 Residual Heat Removal (RHR) Water Fill Verification Technical Specification Surveillance Procedure. When the RHR Low Pressure Coolant Injection (LPCI) Motor Valve MO-2012 "RHR Division 1 LPCI Injection Outboard Valve" was attempted to be cycled, the Motor Valve opened approximately one inch then stopped. With the Motor Valve incapable of opening, the A LPCI injection path was inoperable for injection as an Emergency Core Cooling system; and due to the plant design of the LPCI Loop Select Logic, this rendered both subsystems of LPCI inoperable.

The cause of the event was that the Motor Valve's motor pinion was not secured to the motor shaft because an incorrect-sized set screw was installed. The shorter motor pinion set screw relaxed, allowing the motor pinion to move axially along the motor shaft until it no longer engaged the worm shaft clutch gear.

On June 29, 2024, the motor pinion was adjusted back into position on the motor shaft. On August 7, 2024, the incorrect motor pinion set screw was replaced with the correct set screw.

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3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.

052 050 ASSESSMENT OF SAFETY CONSEQUENCES Actual safety consequences of the event were minimal for both normal operation and design basis event operation based on the operability during this time of all High Pressure Emergency Core Cooling System (ECCS), as well as both loops of the Low Pressure ECCS subsystem of Core Spray. The remaining functions of RHR including Drywell Spray and Suppression Pool Cooling remained operable despite the loss of the LPCI subsystem ability to inject into A LPCI Injection Path. Based on the operability of these additional sources of coolant to the core, the consequences of this event were minimal. There was no impact on the health and safety of the public or plant personal. There were no radiological or industrial impacts associated with this event. The health and safety of the public and site personnel were not impacted during this event.

CAUSE OF THE EVENT The Motor Valve failed to operate because the motor pinion was not secured to the motor shaft because an incorrect-sized set screw was installed. The shorter motor pinion set screw relaxed, allowing the motor pinion to move axially along the motor shaft until it no longer engaged the worm shaft clutch gear.

CORRECTIVE ACTIONS On June 29, 2024, the Motor Valves motor pinion was adjusted back into position on the motor shaft. On August 7, 2024, the incorrect motor pinion set screw on the Motor Valve was replaced with the correct set screw.

PREVIOUS SIMILAR EVENTS There were no previous similar events in the past three years.

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