05200025/LER-2022-001, Automatic Reactor Trip Signal Due to Inadequate Procedure Guidance Causing Incorrect Opening of Division B DC Supply Breaker

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Automatic Reactor Trip Signal Due to Inadequate Procedure Guidance Causing Incorrect Opening of Division B DC Supply Breaker
ML22336A125
Person / Time
Site: Vogtle Southern Nuclear icon.png
Issue date: 12/02/2022
From: Martino P
Southern Nuclear Operating Co
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
ND-22-0905 LER 2022-001-00
Download: ML22336A125 (1)
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LER-2022-001, Automatic Reactor Trip Signal Due to Inadequate Procedure Guidance Causing Incorrect Opening of Division B DC Supply Breaker
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(iv)(A), System Actuation
10 CFR 50.73(a)(2)(iv)(B), System Actuation
0252022001R00 - NRC Website
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text

A Southern Nuclear December 2, 2022 Patrick Martino Site Vice President, Vogtle Unit 3 7825 River Road Waynesboro, Georgia 30830 706 848 6602 tel ND-22-0905 10 CFR 50.73(a)(2)(iv)(A)

Docket No.:

52-025 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Southern Nuclear Operating Company Vogtle Electric Generating Plant (VEGP) - Unit 3 Licensee Event Report 2022-001-00 Automatic Reactor Trip Signal due to Inadequate Procedure Guidance Causing Incorrect Opening of Division B DC Supply Breaker Ladies and Gentlemen:

In accordance with the requirements of 1 O CFR 50. 73(a)(2)(iv)(A), Southern Nuclear Operating Company is submitting the enclosed Licensee Event Report for VEGP Unit 3.

This letter contains no regulatory commitments. If you have questions regarding the enclosed information, please contact Will Garrett at (706) 848-7154.

Respectfully submitted, Patrick A. Martino Site Vice President, Unit 3 PAM/KJD/sfr

Enclosure:

Unit 3 Licensee Event Report 2022-001-00 CC:

Regional Administrator, Region II VPO Project Manager Senior Resident Inspector - Vogtle 3 & 4 Director, Environmental Protection Division - State of Georgia

Vogtle Electric Generating Plant - Unit 3 Licensee Event Report 2022-001-00 Automatic Reactor Trip Signal due to Inadequate Procedure Guidance Causing Incorrect Opening of Division B DC Supply Breaker Enclosure Unit 3 Licensee Event Report 2022-001-00

Abstract

On October 6, 2022, at 0244 EDT with the Vogtle Electric Generating Plant (VEGP) Unit 3 defueled at O percent power, the Reactor Protection System automatically actuated during restoration of Division B Class 1 E DC and Un interruptible Power Supply system. The cause of the actuation was due to inadequate procedural guidance. During restoration of VEGP Unit 3 Division B 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> DC bus, the breaker for the Unit 3 Division B 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> DC distribution panel was opened while performing a lineup to establish initial conditions in accordance with the associated System Operating Procedure (SOP). This resulted in a loss of power to Division B powered safety related air-operated valves, causing the valves to reposition to their fail-safe, loss-of-power safety position. Due to 3-PXS-V108B (Passive Residual Heat Removal Heat Exchanger Outlet Flow Control Valve) failing open a Reactor Trip signal was generated. The operators responded with approved procedures and restored power to the Division B 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> DC distribution panel. As corrective action to address the cause of the event, procedure 3-IDSB-SOP-001 was revised to improve separation of the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> battery system alignments. This event is reportable under 10 CFR 50.73(a)(2)(iv)(A) due to the automatic actuation of the Reactor Protection System, which is one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). VEGP Unit 1, Unit 2, and Unit 4 were unaffected during this event.

EVENT DESCRIPTION

1-0 On October 6, 2022, at 0244 EDT with the Vogtle Electric Generating Plant (VEGP) Unit 3 defueled at O percent power, an actuation of the Reactor Protection System (RPS) [EIIS: JD] occurred during restoration of the Division B 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> DC bus [EIIS: EJ / BU) in the Class 1 E DC and Un interruptible Power Supply System [EIIS: EJ). During restoration, the breaker [El IS: EJ / 72) for the Unit 3 Division B 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> DC distribution panel (3-IDSB-DD-1) was opened by the system operator (non licensed). This resulted in a loss of power to Division B powered safety related air-operated valves, causing the valves to reposition to their fail-safe, loss-of-power safety position. The reason for the RPS actuation was due to the opening of the Division B Passive Residual Heat Removal (PRHR) Heat Exchanger Outlet Flow Control Valve (3-PXS-V108B) [EIIS: BP/ FCV]. The reactor trip breakers were in an open state at the time of the event when the RPS signal was received, therefore, the reactor trip breakers did not change state. The operators responded with approved procedures and restored power to the Division B 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> DC distribution panel.

EVENT ANALYSIS

All systems operated as expected even though the Unit was not in operation. The cause of this event was inadequate procedural guidance. Specifically, procedure 3-IDSB-SOP-001, "Class 1 E DC System-Division B," included instructions within the same attachment for both the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> battery subsystems and resulted in operation of an unintended component.

REPORTABILITY AND SAFETY ASSESSMENT

There were no safety consequences due to this event because the RPS signal was generated while the reactor was in a defueled condition and did not impact plant safety. Additionally, no radiological release occurred due to this event. This event is reportable under 10 CFR 50. 73(a)(2)(iv)(A) due to the automatic actuation of the RPS, which is one of the systems listed in 10 CFR 50. 73(a)(2)(iv)(B).

CORRECTIVE ACTIONS PLANNED OR COMPLETED

Procedure 3-IDSB-SOP-001 was revised to improve the separation of steps associated with the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> battery system and the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> battery system alignments by separating them into different attachments in the procedure.

PREVIOUS SIMILAR EVENTS

There were no events from the last three years with either the same or similar cause to this event. Page 2

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