05000333/LER-2024-002, Reactor Protection System Electric Power Monitoring System Trip Caused Primary Containment Isolation

Reactor Protection System Electric Power Monitoring System Trip Caused Primary Containment Isolation

ML24249A254
Person / Time
Site:	FitzPatrick
Issue date:	09/04/2024
From:	Sterio A Constellation Energy Generation
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
JAFP-24-0042 LER 2024-002-00
Download: ML24249A254 (1)

LER-2024-002, Reactor Protection System Electric Power Monitoring System Trip Caused Primary Containment Isolation

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
3332024002R00 - NRC Website

text

Constellation.

JAFP-24-0042 September 4, 2024 United States Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001 James A. FitzPatrick NPP P.O. Box 110 Lycoming, NY 13093 Alexander Sterio Site Vice President-JAF James A. FitzPatrick Nuclear Power Plant Renewed Facility Operating License No. DPR-059 NRC Docket No. 50-333 Subject:

Dear Sir or Madam:

LEA: 2024-002-00, Reactor Protection System Electric Power Monitoring System Trip Caused Primary Containment Isolation This report is being submitted pursuant to 1 O CFR 50.73(a)(2)(iv)(A).

There are no new regulatory commitments contained in this report.

Questions concerning this report may be addressed to Mr. Mark Hawes, Regulatory Assurance, at (315) 349-6659.

Sincerely,

,~,~

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Alexander Sterio Site Vice President ADS/MH Enclosure:

LER: 2024-002-00, Reactor Protection System Electric Power Monitoring System Trip Caused Primary Containment Isolation cc:

USNRC, Region I Administrator USNRC, Project Manager USNRC, Resident Inspector INPO Records Center (IRIS)

Abstract

On July 8, 2024, at 1927, James A. FitzPatrick Nuclear Power Plant (JAF) received annunciators and indication of a half-scram on the B side Reactor Protection System (RPS). The cause was determined to be an overvoltage condition that tripped the Electrical Protection Assembly (EPA) for the B RPS Motor Generator (MG) Set. This event caused invalid primary containment isolation signals in multiple systems, reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A). The investigation into the cause of the event is ongoing. A supplement to this report will be submitted when the investigation is complete.

(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)

(See Page 2 for required number of digits/characters for each block)

LICENSEE EVENT REPORT (LER)

=

Background===

Reactor Protection System (RPS) [EIIS: JE] Electric Power Monitoring System is provided to isolate the RPS bus from the motor generator (MG) set or an alternate power supply in the event of overvoltage, undervoltage, or underfrequency. This system protects the loads connected to the RPS bus against unacceptable voltage and frequency conditions and forms an important part of the primary success path of the essential safety circuits. Some of the essential equipment powered from the RPS buses includes the RPS logic, scram pilot valve solenoids, and various valve isolation logic.

RPS electric power monitoring assembly will detect any abnormal high or low voltage or low frequency condition in the outputs of the two MG sets or the alternate power supply and will de-energize its respective RPS bus, thereby causing all safety functions normally powered by this bus to de-energize. (Safety functions powered by the RPS buses deenergize to actuate.)

Two redundant Class IE circuit breakers are connected in series between each RPS bus and its MG set, and between each RPS bus and its alternate power supply. Each of these circuit breakers has an associated independent set of Class IE overvoltage, undervoltage, and under frequency sensing logic. Together, a circuit breaker and its sensing logic constitute an electric power monitoring assembly. If the output of the inservice MG set or alternate power supply exceeds predetermined limits of overvoltage, undervoltage, or underfrequency, a trip coil driven by this logic circuitry opens the circuit breaker, which removes the associated power supply from service.

Event Description On July 8, 2024, at 1927 when James A. FitzPatrick Nuclear Power Plant (JAF) at 100% power, annunciators were received with indication of a half-scram on B side RPS. AOP-60, Loss of RPS Bus B Power, was entered and the cause was determined to be a trip of the B RPS MG set due to an overvoltage condition.

The direct cause of the output breaker tripping was due to an Electric Power Monitoring System overvoltage trip on 71EPA-RPS1B1G, Electrical Protection Assembly (EPA).

The condition was corrected when the RPS Bus was placed on the alternate power supply.

The event resulted in invalid system actuations of "B" side half scram and Primary Containment Isolation System (PCIS) [JM] isolations. The following systems isolated as a result of the loss of B RPS bus: Reactor Water Cleanup [CE], Reactor Building ventilation [NG], B Containment Atmosphere Dilution [BB], Torus Vent and Purge, Drywell Equipment and Floor Drain Sumps [WK], B Drywell Containment Atmospheric Monitors

[IP], Recirculation System Sample Line, and Main Steam Line Drains [SB]. B Standby Gas Treatment System [BH] started as designed. These system actuations were not initiated by signals in response to actual plant conditions or parameters satisfying the requirements for initiation of the system.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A). U.S. NUCLEAR REGULATORY COMMISSION (04-02-2024)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET APPROVED BY OMB: NO. 3150-0104 EXPIRES: 04/30/2027

1. FACILITY NAME 050

2. DOCKET NUMBER

3. LER NUMBER James A. FitzPatrick Nuclear Power Plant 05000333 YEAR SEQUENTIAL NUMBER REV NO.

052 2024

- 002

- 00 Page 3 of 3 (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)

Event Analysis At the time of this report, the investigation into the cause of the event is ongoing. A supplement to this report will be submitted by November 22, 2024.

Corrective Actions Completed Actions RPS Bus was placed on the alternate power supply after the event.

Safety Significance There were no actual nuclear consequences. RPS Electric Power Monitoring System responded as designed to an overvoltage condition to protect the electrical power systems. Then system actuations responded to the loss of power condition as expected without any issue. There was no loss of any safety functions during this event.

References Issue Report - IR 04785661, AOP-60 entry due to B side half scram, dated July 8, 2024