05000461/LER-2020-002, Simultaneous Lnoperability of Main Control Room Ventilation Subsystems a and B
| ML21063A252 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 01/15/2021 |
| From: | Chalmers T Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| U-604598 LER 2020-002-00 | |
| Download: ML21063A252 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 4612020002R00 - NRC Website | |
text
Clinton Power Station 8401 Power Road Clinton, IL 61727 U-604598 January 15, 2021 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRC Docket No. 50-461 Subject: Licensee Event Report 2020-002-00 Exelon Generation 10 CFR 50.73 SRRS 5A.108 Enclosed is Licensee Event Report (LER) 2020-002-00: Simultaneous lnoperability of Main Control Room Ventilation Subsystems A and B. This report is being submitted in accordance with the requirements of 10 CFR 50.73.
There are no regulatory commitments contained in this report.
Should you have any questions concerning this report, please contact Mr. Dale Shelton, Regulatory Assurance Manager, at (217) 937-2800.
Respectfully,
~0,:
Site Vice President Clinton Power Station
Attachment:
Licensee Event Report 2020-002-00 cc:
Regional Administrator - Region Ill NRC Senior Resident Inspector - Clinton Power Station Office of Nuclear Facility Safety - Illinois Emergency Man~gement Agency
Abstract
The Main Control Room (MCR) Ventilation and Air Conditioning System (VC) subsystem A was removed from service for planned maintenance and declared inoperable on 11 /16/20. At 1918 on 11/16/20, MCR VC subsystem 8 supply air isolation dampers 0VC21YB, 0VC24YB and OVC27YB lost power and failed closed. Technical Specification (TS) 3.7.3, Control Room Ventilation System, Action F.1 and TS 3.7.4, Control Room AC System, Actions 8.1 and 8.2 were entered. VC subsystem A ventilation was restored to OPERABLE status and at 2036, TS 3.7.3 Action F.1 was exited.
At 0350 on 11 /17 /20, VC subsystem A chiller was restored to OPERABLE status and TS 3. 7.4 Actions 8.1 and 8.2 were exited. Investigation determined that a shorted coil in breaker cubicle 0AP25E-48 motor starter caused fuse 0AP25E4A-F01 to blow, which resulted in dampers 0VC21YB, 0VC24YB and 0VC27Y8 losing power and failing closed. The failed motor starter coil and fuse were replaced and successfully tested. The condition where both required VC subsystems were simultaneously inoperable is reportable under 10 CFR 50.73(a)(2)(v)(D), any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. However, there was no impact to the health and safety of the public or plant personnel, as subsequent post-maintenance testing demonstrated VC subsystem A remained capable of performing its safety functions throughout the event.
PLANT AND SYSTEM IDENTIFICATION
SEQUENTIAL NUMBER 002 REV NO.
00 General Electric -- Boiling Water Reactor, 3473 Megawatts Thermal Rated Core Power Energy Industry Identification System (EIIS) codes are identified in text as [XX].
EVENT IDENTIFICATION Divisions 1 and 2 Main Control Room Ventilation and Air Conditioning Systems Simultaneously Inoperable A.
Plant Operating Conditions Before the Event
Unit: 1 Mode: 1 Event Date: November 16, 2020 Mode Name: Power Operation B.
Description of Event
Event Time: 1918 Reactor Power: 098 On November 16, 2020 at 0153 CDT, Main Control Room (MCR) Ventilation [VI] and Air Conditioning [KM] System (VC) subsystem A was removed from service and declared inoperable for scheduled maintenance. At 1918 CDT, MCR VC subsystem B supply air isolation dampers [DMP]
0VC21 YB, 0VC24YB and 0VC27YB lost power and failed closed. Technical Specification (TS) 3.7.3, Control Room Ventilation System, Action F.1 and TS 3.7.4, Control Room Air Conditioning (AC) System Actions 8.1 and 8.2 were entered. TS 3.7.3 Action F.1 directs the plant 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 />. TS 3. 7.4 Action 8.1 requires verification of MCR temperature to be less than or equal to 86 degrees F and Action B.2 requires one VC subsystem to be restored to OPERABLE status within 7 days. VC subsystem A ventilation was restored to OPERABLE status at 2036 CDT and TS 3.7.3 Action F.1 was exited. At 0350 CDT on November 17, 2020, VC subsystem A chiller was restored to OPERABLE status and TS 3.7.4 Actions 8.1 and 8.2 were exited. At 1737 CDT on November 17, 2020, VC subsystem 8 was restored to OPERABLE and TS 3.7.3 and TS 3.7.4, Action A.1, were exited.
Simultaneous inoperability of VC subsystems A and B resulted in a condition that could have prevented fulfillment of a safety function. Therefore, this condition was reported to the NRC Operations Center via ENS Notification 55002 on November 17, 2020, at 0340 CDT, in accordance with the reporting requirements of 10 CFR 50. 72(b)(3)(v)(D), any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident.
NRG FORM 3EEA (C8-2C20)
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C.
Cause of the Event
Investigation determined that a shorted coil [CL] in breaker cubicle 0AP25E-48 motor starter [MSTR]
caused fuse [FU] 0AP25E4A-F01 to blow, which resulted in dampers 0VC21YB, 0VC24YB and 0VC27YB losing power and failing closed. Based on the visual evidence and electrical testing, the motor starter coil failed due to electrical overheating. The motor starter coil is a high duty cycle component and cycles frequently when either of the two VC subsystems is in service. The failed motor starter coil was installed in July 2005 and failed after approximately fifteen years of service.
D.
Safety Consequences
The condition where both required VC subsystems were simultaneously inoperable described in this LER is reportable under 10 CFR 50. 73(a)(2)(v)(D), any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. There was no impact to the health and safety of the public or plant personnel, as subsequent post-maintenance testing demonstrated VC subsystem A remained capable of performing the safety functions of the VC system throughout this event. Engineering analysis has determined that this event does not meet the criteria for a Safety System Functional Failure.
E.
Corrective Actions
The failed 0AP25E-48 motor starter coil and fuse 0AP25E4A-F01 were replaced and successfully post-maintenance tested on November 17, 2020.
F.
Previous Similar Occurrences There were no previous events identified involving failed motor starter coils similar to the condition described in this LER.
G.
Component Failure Data
GE, Magnetic Pickup (Motor Starter) Coil, Part 55-5372898002 Series A, VA1498, 115-120V, 60Hz MR:: FOR/,! 3EA (08-2020)
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