05000325/LER-2023-001, Loss of Redundant Power Supply Operation Causes Turbine Trip and Subsequent Reactor Scram

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Loss of Redundant Power Supply Operation Causes Turbine Trip and Subsequent Reactor Scram
ML23166A081
Person / Time
Site: Brunswick Duke Energy icon.png
Issue date: 06/15/2023
From: Krakuszeski J
Duke Energy Progress
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
RA-23-0116 LER 2023-001-00
Download: ML23166A081 (1)


LER-2023-001, Loss of Redundant Power Supply Operation Causes Turbine Trip and Subsequent Reactor Scram
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(iv)(A), System Actuation
3252023001R00 - NRC Website

text

J._-, DUKE

~ ENERGY June 15, 2023 Serial: RA-23-0116 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Subject:

Brunswick Steam Electric Plant, Unit No. 1 Renewed Facility Operating License No. DPR-71 Docket No. 50-325 Licensee Event Report 1-2023-001 John A. Krakuszeski Vice President Brunswick Nuclear Plant 8470 River Rd SE Southport, NC 28461 o: 910.832.3698 10 CFR 50.73 In accordance with the Code of Federal Regulations, Title 10, Part 50.73, Duke Energy Progress, LLC, is submitting the enclosed Licensee Event Report (LER). This report fulfills the requirement for a written report within sixty (60) days of a reportable occurrence.

This document contains no regulatory commitments.

Please refer any questions regarding this submittal to Mr. Mark DeWire, Manager - Nuclear Support Services, at (910) 832-6641.

Sincerely, John A. Krakuszeski

Enclosure:

Licensee Event Report

U.S. Nuclear Regulatory Commission Page 2 of 2 cc (with enclosure):

Ms. Laura Dudes, NRC Regional Administrator, Region II Mr. Luke Haeg, NRC Project Manager Mr. Gale Smith, NRC Senior Resident Inspector

Abstract

At 01:48 Eastern Daylight Time (EDT) on April 20, 2023, with Unit 1 in Mode 1 at approximately 100% power, an automatic reactor scram occurred due to a turbine trip. All control rods inserted as expected. Turbine bypass valves did not open on the scram; Safety Relief Valves (SRVs) opened automatically to control reactor pressure. Reactor Pressure reached approximately 1100 psig on the scram, exceeding the Reactor Protection System (RPS) setpoint. Reactor water level reached low level 1 following the scram resulting in automatic actuation of Primary Containment Isolation System (PCIS) Group 2, 6, and 8 isolation valves, by design.

Operations responded and stabilized the plant. Operations transitioned pressure control from SRVs to main steam line drains to the condenser. Following the scram, reactor water level was maintained via the condensate and feedwater systems.

The turbine trip and subsequent inoperative turbine bypass valves resulted from a complete loss of 24 Vdc power to the Turbine Protection system. The power supplies were replaced prior to restart.

There was no impact on the health and safety of the public or plant personnel. This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A) due to valid actuation of the RPS and PCIS.

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

(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/)

Page 3 of 3 Prior to this event the power supplies had operated successfully with no indication of deficiencies for approximately five years.

Safety Assessment

There was no adverse impact on the health and safety of the public or plant personnel. The safety significance of this event is minimal. The condenser remained available for pressure control. The condensate and feedwater systems remained available for level control.

Corrective Actions

Prior to restart from this event, the 24 Vdc Turbine Protection system power supplies were replaced.

The site is planning to implement changes to the current 24Vdc power supply functionality that will prevent a power supply internal failure from impacting the redundant power supply.

Any changes to corrective actions or completion schedules will be made in accordance with the sites corrective action program.

Previous Similar Events

No previous similar events have occurred within the past three years in which inadequate vendor design resulted in a turbine trip and reactor scram.

Commitments

No regulatory commitments are contained in this report.