05000321/LER-2024-001, Primary Containment Penetration Exceeded Maximum Allowable Primary Containment Leakage Rate (La)

Primary Containment Penetration Exceeded Maximum Allowable Primary Containment Leakage Rate (La)

ML24100A863
Person / Time
Site:	Hatch
Issue date:	04/09/2024
From:	Busch M Southern Nuclear Operating Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
NL-24-0144 LER 2024-001-00
Download: ML24100A863 (1)

LER-2024-001, Primary Containment Penetration Exceeded Maximum Allowable Primary Containment Leakage Rate (La)

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(v), Loss of Safety Function
3212024001R00 - NRC Website

text

Matt Busch Hatch Nuclear Plant

~ Southern Nuclear Vice President - Plant Hatch 11028 Hatch Parkway North Baxley, GA 31513 Date: April 9, 2024 Docket No.:

50-321 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant - Unit 1 Licensee Event Report 2024-001-00 912 537 5859 tel 912 366 2077 fax NL-24-0144 Primary Containment Penetration Exceeded Maximum Allowable Primary Containment Leakage Rate (La)

Ladies and Gentlemen:

In accordance with the requirements of 10 CFR 50.73 (a)(2)(i)(B), 10 CFR 50.73 (a)(2)(ii)(A), and 10 CFR 50.73(a)(2)(v)(C), Southern Nuclear Operating Company hereby submits the enclosed Licensee Event Report.

This letter contains no NRC commitments. If you have any questions, please contact the Hatch Licensing Manager, Jimmy Collins, at 912.453.2342.

Respectfully submitted, M.S. Busch Vice President - Hatch MSB/JMH Enclosure: LER 2024-001-00 Cc:

Regional Administrator, Region II NRR Project Manager - Hatch Senior Resident Inspector - Hatch RTYPE: CHA02.004

U.S. Nuclear Regulatory Commission NL-24-0144 Page 2 Edwin I. Hatch Nuclear Plant Unit 1 Licensee Event Report 2024-001-00 Primary Containment Penetration Exceeded Maximum Allowable Primary Containment Leakage Rate (La)

Enclosure LER 2024-001-00

Abstract

At 10:11 EST on 02/11/2024 while Unit 1 was at 0% power in Mode 5, planned local leak rate testing (LLRT) of feedwater check valves were being performed. The test resulted in determining the primary containment leakage rate exceeded the allowable limit, La, defined in 10 CFR 50, Appendix J, "Primary Reactor Containment Leakage Testing for Water-Cooled Power Reactors" and specified in Technical Specifications 5.5.12. Two primary containment feedwater isolation check valves in a single penetration failed LLRT which represents a failure to maintain primary containment integrity.

Following the completion of valve maintenance, which included machining of the in-body seats, disc, and adjustment or replacement of the hinge pins (as needed), a successful as-left LLRT was performed on each feedwater check valve and primary containment was restored to operable status.

EVENT DESCRIPTION I

2. DOCKET NUMBER 00321 I

YEAR 8-1

3. LER NUMBER SEQUENTIAL NUMBER 001 REV NO.

1-G On 02/11/2024, while Unit 1 was at 0% power in Mode 5, planned local leak rate testing (LLRT) of the feedwater check valves were being performed. At 10:11 EST, it was determined that the primary containment leakage rate exceeded the allowable limit, La, defined in 10 CFR 50, Appendix J, "Primary Reactor Containment Leakage Testing for Water-Cooled Power Reactors" and specified in Technical Specifications 5.5.12. Two primary containment feedwater (EIIS Code: SJ) isolation check valves (EIIS Code: ISV) in a single penetration failed LLRT which represents a failure to maintain primary containment integrity.

FAILED COMPONENTS INFORMATION Master Parts List Number: 1 B21 F01 0A, 1 B21 F032A Manufacturer: Edward Valves Model Number: Vendor P/N 415595 Type: Isolation Valves EVENT CAUSE ANALYSIS Causal analysis was performed to determine the reasons the feedwater check valves leaked excessively. It was determined that the valve disc was mis-aligned to its in-body seats which resulted in leakage through the valves exceeding allowable limits.

SAFETY ASSESSMENT There were no actual safety consequences as a result of this event. The feedwater line containing these check valves is postulated to remain filled with water post-LOCA. With the leakage rate higher than allowable through this line, there is a potential pathway failure via this line. The leakage through this primary containment penetration for the as-found condition was determined to exceed La under postulated accident condtions. However, the primary containment leakage rate was below the level required to significantly impact the Core Damage Frequency and Large Early Release Frequency and was of low safety consequence. Additionally, the event was within the analysis of the UFSAR Chapter 15.

This event is reportable per 10 CFR 50.73 (a)(2)(ii)(A) because it resulted in one of the plant's principal safety barriers being seriously degraded. This event is also reportable per 10 CFR 50.73 (a)(2)(i)(B) because this is a condition prohibited by Technical Specifications because primary containment was inoperable in excess of the allotted Limited Condition of Operation (LCO) timeframe. Additionally, this event is reportable per 10 CFR 50.73 (a)(2)(v)(C) because it is an event that could have prevented fulfillment of a safety function that is needed to control the release of radioactive material.

CORRECTIVE ACTIONS Maintenance was performed on the isolation valves which included machining of the in-body seats, disc, and adjustment or replacement of the hinge pins (as needed). Following the completion of valve maintenance a successful as-left LLRT was performed on each feedwater check valve and primary containment was restored to operable status.

PREVIOUS SIMILAR EVENTS None. Page 2

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