05000354/LER-2013-001
| Hope Creek Generating Station | |
| Event date: | 04-08-2013 |
|---|---|
| Report date: | 06-05-2013 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
| 3542013001R00 - NRC Website | |
- Energy Industry Identification System (EllS) codes and component function identifier codes appear as {SS/CCC}
IDENTIFICATION OF EVENT
Event Date: April 8, 2013 Discovery Date: April 8, 2013
CONDITIONS PRIOR TO EVENT
Hope Creek was in Operational Condition 1 at 100 percent rated thermal power (RTP). No structures, systems, or components were INOPERABLE at the start of this event or contributed to the event.
DESCRIPTION OF EVENT
At 11:15 a.m., on April 8, 2013, the High Pressure Coolant Injection (HPCI) system {BJ} was declared INOPERABLE during the performance of HC.IC-FT.BJ-0007 "Logic System Function Test - Containment High Pressure/Low Water Level/Reactor High Water Level HPCI Actuation." The functional test is performed every 18 months to partially satisfy the surveillance requirements of Technical Specification 4.3.3.2, which is to simulate automatic operation of the emergency core cooling system logic channels. Specifically, the test inserts initiation signals to generate an auto-start to the HPCI Auxiliary Oil Pump (HPCI AOP)(10-P-213) and HPCI Gland Seal Vacuum Pump (10-P-216). The test directs the operators to open the breaker for the HPCI Steam Isolation Valve (HV-F001) to remove power from the valve's motor operator. This ensures the valve remains closed because starting the HPCI AOP opens the HPCI Stop Valve (FV-4880).
During the test, l&C technicians inserted a reactor low water level initiation (Level 2) signal to generate an auto-start of the HPCI AOP {BJ/P} and HPCI Gland Seal Vacuum Pump. The operator noted that the HPCI Gland Seal Vacuum Pump started, but the HPCI Stop Valve (FV-4880) did not open as expected. The operator identified that the HPCI AOP failed to start. Upon recognizing the HPCI AOP failure to start, the Shift Manager declared the HPCI system INOPERABLE. This condition was reported to the NRC via the Emergency Notification System (ENS) under 10 CFR 50.72(b)(3)(v)(D) for a condition that could have prevented fulfillment of a safety function of structures or systems that are needed to mitigate the consequences of an accident.
Troubleshooting of the HPCI AOP failure identified that the control relay, H1BJ-1BJYY-K056-E41A (K056){BJ/RLY}, a normally de-energized relay, had failed. Relay K056 starts the HPCI AOP when a reactor low water level or containment high pressure start signal is received. The relay was replaced and the HPCI AOP start signal was successfully retested. On April 8, 2013, at 6:18 p.m., upon completion of the functional test, the Shift Manager declared the HPCI system OPERABLE. The HPCI system was inoperable for seven hours and three minutes. HPCI was capable of being manually started during the period of inoperability.
Exelon PowerLabs inspected the HPCI AOP control relay (K056) and found an "open" in the coil that was most likely due to corrosion. This is an age-related failure. The HPCI AOP relay failure prevented the HPCI AOP from automatically starting on demand. The failed relay is an Amerace (TYCO) Model FGPDC750 control relay.
The apparent cause evaluation (Notification #20602498) for this event identified that in 2007, the Preventive Maintenance (PM) replacement activity periodicity was extended from 22 years to 40 years. The change, however, did not consider all applicable references or failure mechanisms.
SAFETY CONSEQUENCES AND IMPLICATIONS
The HPCI system was declared INOPERABLE because of the failure of the control relay (K056), which prevented the HPCI AOP from automatically starting on demand. This is a condition that could have prevented the fulfillment of a safety function of structures or systems that are needed to mitigate the consequences of an accident. No other safety systems were INOPERABLE during the time the HPCI system was INOPERABLE, and the HPCI AOP was capable of being started manually. This event is a Safety System Functional Failure (SSFF) as defined in Nuclear Energy Institute (NEI) 99-02.
PREVIOUS OCCURRENCES
A review of Licensee Event Reports for the past three years at Hope Creek was performed to determine if a similar event had occurred. One event occurred in July 2012 involving the failure of a normally energized relay that provided indication in the Remote Shutdown Panel (LER 2012-005).
CORRECTIVE ACTIONS
1. Control relay (K056) for the HPCI AOP was replaced and the HPCI system was satisfactorily retested and declared OPERABLE.
2. The relay was inspected by Exelon PowerLabs.
3. An Equipment Apparent Cause Evaluation was completed to determine the cause of failure.
4. Completed a re-evaluation of the PM replacement periodicities for the normally energized and de- energized relays.
5. Developed a strategy, based on plant function, to replace the population of relays which had their PM replacement periodicities extended in 2007.
COMMITMENTS
This LER contains no regulatory commitments.