05000354/LER-2013-008
| Hope Creek Generating Station | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| Initial Reporting | |
| ENS 49592 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation |
| 3542013008R01 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric — Boiling Water Reactor {BWR/4} Main Turbine — EllS Identifier (TATTRB)* Moisture Separator — EllS Identifier {SB/MSR}* Moisture Separator Dump Valve (SB/LCV) Reactor Protection System — EllS Identifier {JC}* Reactor Recirculation Pumps — EllS Identifier {AD/P} Safety Relief Valves - EllS Identifier (SB/RV) * Energy Industry Identification System (EllS) codes and component function identifier codes appear as {SS/CCC}
IDENTIFICATION OF EVENT
Event Date: December 1, 2013 Discovery Date: December 1, 2013
CONDITIONS PRIOR TO EVENT
Hope Creek was in Operational Condition (OPCON) 1 operating at approximately 100 percent rated thermal power. No other structures, systems or components were inoperable at the time of the event.
DESCRIPTION OF EVENT
On December 1, 2013, at 06:13 EST, Hope Creek Unit 1 automatically scrammed from 100 percent rated thermal power due to a trip of the main turbine (TA/TRB). The main turbine trip was due to a high level in the 'A' moisture separator {SB/MSR}. The main turbine trip caused an actuation of the reactor protection system (RPS){JC} resulting in an automatic reactor scram. Both reactor recirculation pumps {AD/P} tripped per design and three safety relief valves (SRV){SB/RV} lifted. The plant was stabilized in hot shutdown (OPCON 3). All control rods inserted as required and no automatic emergency core cooling system (ECCS) or reactor core isolation cooling (RCIC) system initiations occurred.
A four-hour NRC Emergency Notification System (ENS) notification was required by 10 CFR 50.72(b)(2XivXB) for an actuation of RPS when the reactor was critical. The ENS notification (#49592) was completed on December 1, 2013, at 10:02 EST. This event involved an automatic actuation of RPS; therefore, this LER is being submitted pursuant to the requirements of 10 CFR 50.73(aX2Xiv)(A).
CAUSE OF EVENT
The MS normal level controller failed due to a ruptured bellows causing the MS drain valves to close. The MS dump valve {SB/LCV) controller attempted to maintain level by cycling the MS dump valve as required; however, after 15 cycles, the dump valve failed in the closed position. This caused MS level to increase above the high level setpoint, resulting in the main turbine trip and the subsequent automatic reactor scram.
A causal evaluation determined the failure of the MS dump valve was due to thermal binding. The valve dimensional clearances were based on analysis performed at thermal equilibrium; however, the assumption of thermal equilibrium is not valid for all thermal events when temperature rise is not uniform throughout the valve.
SAFETY CONSEQUENCES AND IMPLICATIONS
There was no safety consequence associated with this event. The high moisture level in the 'A' MS resulted in a main turbine trip and subsequent automatic reactor scram. All reactor protection systems functioned as designed. All control rods inserted. All systems responded as expected to the turbine trip. No ECCS or RCIC initiation setpoints were reached. The plant was stabilized in hot shutdown (OPCON 3).
SAFETY SYSTEM FUNCTIONAL FAILURE
A review of this event determined that a Safety System Functional Failure (SSFF) did not occur as defined in Nuclear Energy Institute (NEI) 99-02, "Regulatory Assessment Performance Indicator Guideline." This event did not prevent the ability of a system to fulfill its safety function to either shutdown the reactor, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident.
PREVIOUS EVENTS
A review of events for the past three years at Hope Creek was performed to determine if a similar event had occurred. No occurrences were identified.
CORRECTIVE ACTIONS
1. The MS normal level controller, which failed due to a ruptured bellows, was replaced.
2. The MS dump valves will be modified during the next refueling outage to prevent thermal binding.
COMMITMENTS
This LER contains no commitments.