05000374/LER-2023-001, Standby Liquid Control Valve Inoperable Due to Failed Motor Starter Contactor
| ML23107A190 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 04/17/2023 |
| From: | Van Fleet J Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| RA23-024 LER 2023-001-00 | |
| Download: ML23107A190 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3742023001R00 - NRC Website | |
text
Constellation.
RA23-024 April 17, 2023 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 LaSalle County Station, Unit 2 Renewed Facility Operating License No. NPF-11 NRC Docket No. 50-37 4 LaSalle County Station 2601 North 21 " Road Marseilles, IL 61341 815-415-2000 Telephone 10 CFR 50.73
Subject:
Licensee Event Report 2023-001-00, Standby Liquid Control valve Inoperable due to failed motor starter contactor In accordance with 10 CFR 50.73(a)(2)(i)(B), Exelon Generation Company, LLC (EGC) is submitting Licensee Event Report (LER) Number 2023-001-00 for LaSalle County Station, Unit 2.
There are no regulatory commitments in this letter. Should you have any questions concerning this report, please contact Mr. Dan Mearhoff, Regulatory Assurance Manager, at (815) 415-2800.
Respectfully, fr i/4 ::;f,W--
John Van Fleet Jr Acting Site Vice President LaSalle County Station
Enclosure:
Licensee Event Report cc:
Regional Administrator - NRC Region Ill NRC Senior Resident Inspector - LaSalle County Station
Abstract
On 2/17/2023, during performance of outage surveillances, the A Standby Liquid Control (SLC) storage tank outlet valve, 2C41-F001A, failed to open. The failure was due to binding of the Motor Operated Valve (MOV) full voltage reversing (FVR) contactor mechanical interlock. Failure analysis revealed that the mechanical interlock would have become bound the previous time the contactor picked up to close the MOV during the 2021 refueling outage. This established firm evidence that a past inoperability condition existed.
Failure of this valve to open results in inoperability of the A SLC system required by LCO 3.1. 7 (SLC System). At the time of discovery of the breaker failure the unit was in Mode 5, and LCO 3. 1. 7 was not in the mode of applicability. There were no reportability thresholds applicable to this issue at the time of the event, and there was no loss of safety function. The condition is reportable in accordance with 10 CFR 50. 73(a)(2)(i)(B) for operation or condition prohibited by Technical Specifications.
Corrective actions were taken to replace the failed component and restore the associated train to operable prior to entering Mode 3.
Plant and System Identification
- 2. DOCKET NUMBER YEAR 374 2023 -
- 3. LER NUMBER SEQUENTIAL NUMBER 001 REV NO.
00 LaSalle County Station Unit 2 is a General Electric Boiling Water Reactor with 3546 Megawatts Thermal Rated Core Power. The affected system was the Standby Liquid Control (SLC) system. The affected component is the breaker for the A SLC storage tank outlet valve.
Condition Prior to Event
Unit(s): 2 Reactor Mode(s): 5
Description
Date:
Mode(s) Name:
February 17, 2023 Cold Shutdown Time:
1544 CST Power Level: 0 percent On 2/17/2023, during performance of outage surveillances, the A Standby Liquid Control (SLC) storage tank outlet valve, 2C41-F001A, failed to open. The valve is normally closed and opens upon manual SLC initiation. The failure was due to binding of the contactor mechanical interlock resulting failure of the contactor to operate. Failure analysis revealed that the mechanical interlock would have become bound the previous time the contactor picked up to close the Motor Operated Valve (MOV). This established firm evidence that a past inoperability condition existed.
Cause
The cause of the breaker failing to operate is binding of the full voltage reversing (FVR) contactor mechanical interlock.
The FVR mechanical interlock is designed to return to the neutral position following contactor de-energization. When the mechanical interlock binds, it does not return to the center position, preventing one of the two contactors from closing. The FVR mechanical interlock became bound the previous time the contactor picked up when operated in L2R 18. As such, the MOV would have failed to open from manual operation from the valve control switch or automatic actuation after initiation of the SLC system.
This failure mode was identified in a Part 21 issued by Westinghouse on April 11, 2022. (ML22140A208)
Reportability and Safety Analysis
Failure of the A SLC storage tank outlet valve to open results in inoperability of the A SLC system required by LCO 3.1.7 (SLC System). At the time of discovery the Unit was in Mode 5 and not in the mode of applicability for LCO 3.1.7. There were no reportability thresholds applicable to this issue at the time of the event, and there was no loss of safety function.
Failure analysis revealed that the mechanical interlock would have become bound the previous time the contactor picked up to close the Motor Operated Valve (MOV). This established firm evidence that a past inoperability condition existed.
The last time the valve was operated was two years prior during refueling outage L2R 18. Therefore, it is assumed that the valve was inoperable and unable to open for the entire operating cycle. The event is reportable in accordance with 1 O CFR 50. 73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.
LCO 3.1. 7 requires two trains of SLC to be operable in Modes 1, 2 and 3. Condition A is entered when one SLC subsystem is inoperable and requires the SLC subsystem to be restored to Operable in 7 days or in accordance with Risk Informed Completion Time. If this Action is not met, Condition C is entered and requires the unit to be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
- 2. DOCKET NUMBER
- 3. LER NUMBER SEQUENTIAL REV YEAR NUMBER NO.
374 2023 -
001 00 The SLC system is composed of two safety related trains, A and 8. The A train is powered from Division 1 and 8 train is powered from Division 2. With the A train of SLC being inoperable, LCO 3.8.1 (AC Sources-Operating) actions also apply to the 8 train of SLC. LCO 3.8.1.b requires three diesel generators (DG) to be Operable. Condition 8 is entered when a required Division 1 or 2 DG is inoperable. Action 8.2 states to declare required feature(s), supported by the inoperable DG(s), inoperable with the redundant required feature(s) are inoperable within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of discovery of the concurrently inoperability of redundant required feature(s). If this action is not complete, action H is entered requiring the unit to be in mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
With the A train of SLC inoperable, any time the Unit 2 division 2 DG is inoperable, LCO 3.8.1 8.2 requires declaring the 8 train of SLC inoperable. lnoperability of both SLC trains requires entry into 3.1. 7 RA 8.1 to restore one subsystem to operable in 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. If this action is not complete Condition C is entered and requires the unit to be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. Over the past operating cycle, the Unit 2 Division 2 DG was declared inoperable two times for greater than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and four times for greater than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, with required actions not taken.
Corrective Actions
A work order was completed to replace the failed contactor mechanical interlock with the recommended updated mechanical interlock. The valve was restored to Operable prior to entering Mode 3.
Previous Occurrences
On 4/11/2022, Westinghouse issued a Part 21 notification identifying that Eaton FVR contactors sporadically failed to electrically close on demand due to the mechanical interlock pawl failing to consistently return to its neutral position following contactor energization.
Component Failure Data
Manufacturer: Eaton Device: Breaker Component ID: 2AP75E-C2, Breaker, A SLC storage tank outlet valve Page_3_ of _3_