05000325/LER-2024-001, Primary Containment Penetration Local Leak Rate Testing Failure

Primary Containment Penetration Local Leak Rate Testing Failure

ML24102A123
Person / Time
Site:	Brunswick
Issue date:	04/10/2024
From:	Krakuszeski J Duke Energy Progress
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
RA-24-0074 LER 2024-001-00
Download: ML24102A123 (1)

LER-2024-001, Primary Containment Penetration Local Leak Rate Testing Failure

Event date:
Report date:
3252024001R00 - NRC Website

text

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 approximately 08:37 Eastern Standard Time (EST), on February 17, 2024, with Unit 1 in Mode 5 at 0% power during a planned refueling outage, it was determined that the Unit 1 primary containment leakage rate did not meet the 10 CFR 50, Appendix J, requirements, as specified in Technical Specification 5.5.12, due to the as-found Local Leak Rate Testing (LLRT) results of the Reactor Core Isolation Cooling (RCIC) turbine steam supply line penetration (part of the containment boundary).

Both the inboard and outboard primary containment isolation valves in this line would not pressurize during LLRT.

The inboard and outboard RCIC turbine steam supply line primary containment isolation valves were repaired during the refueling outage. Subsequent LLRT of this containment penetration was satisfactory.

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)(ii)(A) due to a degraded primary containment is olation boundary, and 10 CFR 50.73(a)(2)(v)(C) since this event could have prevented the fulfillment of the safety function of primary containment.

Energy Industry Identification System (EIIS) codes are identified in the text as [XX].

Background

Initial Conditions

At the time of the event, Unit 1 was in Mode 5 (i.e., Refueling), at 0 percent rated thermal power.

Reportability Criteria

This event is being reported in accordance with 10 CFR 50.73(a)(2)(ii)(A) due to a degraded primary containment [NH]

isolation boundary discovered by as-found Local Leak Rate Testing (LLRT) of the inboard and outboard primary containment isolation valves [BD] in the Reactor Core Isolation Cooling (RCIC) [BN] turbine steam supply line. In addition, this event is being reported in accordance with 10 CFR 50.73(a)(2)(v)(C) since this event could have prevented the fulfillment of the safety function of primary containment [NH].

The NRC was notified of this event per 10 CFR 50.72(b)(3)(ii)(A) via Event Notification 56974 at 14:07 Eastern Standard Time (EST) on February 17, 2024.

Event Description

At 08:37 EST, on February 17, 2024, with Unit 1 in Mode 5 at 0% power during a planned refueling outage, it was determined that the Unit 1 primary containment leakage rate did not meet the 10 CFR 50, Appendix J, requirements, as specified in Technical Specification (TS) 5.5.12. The RCIC turbine steam supply line penetration inboard and outboard primary containment isolation valves did not pressurize during LLRT resulting in a leak rate greater than the acceptance criteria.

This condition occurred during an Integrated Leak Rate Test (ILRT) outage. Therefore, it is also considered an as-found ILRT failure.

Event Cause

The direct cause of the primary containment leakage rate exceeding the 10 CFR 50, Appendix J, requirements specified in TS 5.5.12 was the RCIC turbine steam supply line penetration inboard and outboard primary containment isolation valves not maintaining test pressure during LLRT. The subject valves are double disc gate valves.

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. Unit 1 was shutdown at the time, and operation was aligned with TS required actions.

Corrective Actions

The inboard and outboard RCIC turbine steam supply line primary containment isolation valves were repaired during the refueling outage. Subsequent LLRT of this containment penetration was satisfactory. In addition, the as-left ILRT was satisfactory.

The subject valves are double disc gate valves that are planned to be replaced with a new design. The current plan is to replace these valves prior to startup from the 2028 refueling outage.

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

Previous Similar Events

No previous similar events have occurred within the past 20 years in which the inboard and outboard containment isolation valves in the same containment penetration would not pressurize during LLRT.

Commitments

No regulatory commitments are contained in this report.