05000366/LER-2023-001, Primary Containment Penetration Exceeded Maximum Allowable Primary Containment Leakage Rate (La)
| ML23095A088 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 04/05/2023 |
| From: | Weissinger H Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NL-23-0232 LER 2023-001-00 | |
| Download: ML23095A088 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3662023001R00 - NRC Website | |
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A Southern Nuclear John H. Weissinger Hatch Nuclear Plant Vice President - Plant Hatch 11028 Hatch Parkway North Baxley, GA 31513 Date: April 5, 2023 Docket Nos.: 50-366 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant 912 537 5859 tel 912 366 2077 fax NL-23-0232 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)(ii)(A), 10 CFR 50.73(a)(2)(v)(C), and 1 O CFR 50.73(a)(2)(i)(B), 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,
~
John H. Weissinger Vice President - Hatch JMH Enclosure: LEA 2023-001-00 Cc:
Regional Administrator, Region II NRA Project Manager - Hatch Senior Resident Inspector-Hatch RTYPE: CHA02.004
U. S. Nuclear Regulatory Commission NL-23-0232 Page 2 Edwin I. Hatch Nuclear Plant Unit 1 and 2 Licensee Event Report 2023-001-00 Subject Primary Containment Penetration Exceeded Maximum Allowable Primary Containment Leakage Rate (La)
Enclosure LER 2023-001-00
Abstract
At 1738 EST on 02/07/2023, while in MODE 5 at 0% power, during planned Local Leak Rate Testing (LLRT) it was determined that the primary containment leakage rate exceeded the allowable limit, La, defined in 10CFR 50, Appendix J, "Primary Reactor Containment Leakage Testing for Water-Cooled Power Reactors" and specified in the Technical Specifications. Two primary containment isolation valves (PCIVs) in a single penetration failed LLRT which represents a failure to maintain primary containment integrity.
Troubleshooting and investigation efforts identified that the vendor supplied T-rings were manufactured incorrectly causing excessive LLRT leakage. As a corrective action correctly manufactured T-rings were installed in the affected valves, LLRTs were performed satisfactorily, and primary containment was restored to operable status.
EVENT DESCRIPTION
I
- 2. DOCKET NUMBER
- 3. LER NUMBER I y~
SEQUENTIAL REV NUMBER NO.
00366 12023 I -I 001 1-G At 1738 EST on 02/07/2023, while in MODE 5 at 0% power, during planned Local Leak Rate Testing (LLRT) it was determined that the primary containment leakage rate exceeded the allowable limit, La, defined in 1 OCFR 50, Appendix J, "Primary Reactor Containment Leakage Testing for Water-Cooled Power Reactors" and specified in the Technical Specifications. Two primary containment isolation valves (PCIVs) (EIIS: ISV) in a single penetration failed LLRT requirements which represents a failure to maintain primary containment integrity. This leakage also caused a failure of Integrated Leak Rate Testing {ILRT).
Failed Components Information
Master Parts List Number: 2T48F319 and 2T48F320 Manufacturer: Fisher Controls Company Model: Fisher Series 9200 Butterfly Valves Type: Isolation Valves This event is reportable per 10 CFR 50.73(a)(2)(ii)(A), 10 CFR 50.73(a)(2)(v)(C), 10 CFR 50.73(a)(2)(i)(B), and has been classified as a Safety System Functional Failure under NEI 99-02.
EVENT CAUSE ANALYSIS
These LLRT failures were caused by using a vendor supplied T-ring that was incorrectly manufactured, leading to the T-ring rotating away from the valve disc when in operation. All PCIVs of the same model that passed LLRTs had T-rings that did not have the manufacturing defect.
SAFETY ASSESSMENT
There were no actual safety consequences as a result of this event. Although the leakage rate through the degraded primary containment penetration for the as-found condition exceeded La, the exposure time of the penetration inoperability can reasonably be limited to just prior to shutting down the Unit 2 reactor for the refueling outage. Additionally, any leakage past the degraded PCIVs during an actual event would have been filtered through Standby Gas Treatment and released through the main stack.
CORRECTIVE ACTIONS
Correctly manufactured T-rings were obtained and installed in the affected valves, LLRTs were performed satisfactorily, and primary containment was restored to operable status.
PREVIOUS SIMILAR EVENTS
On January 4, 2020, it was determined that the maximum allowable primary containment leakage rate (La) as defined in 10CFR50, Appendix J, "Primary Reactor Containment Leakage Testing for Water-Cooled Power Reactors" had been exceeded under postulated accident conditions. Troubleshooting efforts identified the degraded primary containment penetration and noted that leakage past two PCIVs was causing La to be exceeded. The cause was that the set screws that support the T-ring inside the PCIVs were backing out. The root cause corrective action to prevent recurrence was to add to the maintenance procedure to apply Loctite 222 to each set screw threads. This prevented the set screws that support the T-ring from backing out (LER 2020-001-00). The current issue did not involve repetitive failures from previous cycles; all previous corrective actions taken in response to previous LLRT failures of these valves have been effective. Page 2
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