05000354/LER-2013-002
| Hope Creek Generating Station | |
| Event date: | 06-12-2013 |
|---|---|
| Report date: | 10-12-2013 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| Initial Reporting | |
| ENS 49108 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation |
| 3542013002R01 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric — Boiling Water Reactor (BWR/4) Condenser System — Circulating Water Pump — (SG/P)* - EllS Identifier Condenser System — Circulating Water Discharge Valve — {SG/V}* - EllS Identifier Reactor Protection System — {JC/NA}* - EllS Identifier *Energy Industry Identification System (EllS) codes and component function identifier codes appear as {SS/CCC}
IDENTIFICATION OF EVENT
Event Date: June 12, 2013 Discovery Date: June 12, 2013
CONDITIONS PRIOR TO EVENT
Hope Creek was in Operational Condition 1 at 100 percent rated thermal power (RTP). The 'C' service water pump was inoperable for planned maintenance and the reactor core isolation cooling (RCIC) system was in service for quarterly inservice testing. The status of these two systems did not contribute to the event.
The plant was operating with the 'B' circulating water discharge valve stuck in the full-open position. This condition did contribute to this event.
DESCRIPTION OF EVENT
On June 12, 2013, at 13:32 EDT, the 'B' circulating water (CW) pump {SG/P} tripped with the 'B' CW discharge valve {SG/V} stuck in the full-open position resulting in a degrading vacuum. In accordance with plant procedures, the operators lowered reactor power from 100 percent in an effort to stabilize condenser vacuum. When vacuum reached 6.5 inches of mercury absolute (HgA), the operators initiated a manual reactor scram {JC/NA} at 13:33, in accordance with plant procedures. All control rods inserted as required and all systems functioned as expected following the scram. The 'A' reactor feed pump turbine (RFPT) was in service for reactor pressure vessel (RPV) inventory control. No automatic emergency core cooling system (ECCS) or reactor core injection cooling (RCIC) system initiations occurred. No primary or secondary containment isolations occurred. At the time of the event, a RCIC quarterly inservice test was in progress, but did not contribute to the event. Operators secured the RCIC pump and restored it to a standby lineup. At approximately 14:00, the main condenser vacuum further degraded due to two redundant sealing steam supply valves failing to reposition as designed causing the RFPT to trip. The RFPT could not be recovered and as a result, the operators manually placed RCIC in service for RPV inventory control. At 14:50, operators secured RCIC and controlled reactor level with the secondary condensate pumps. Operators completed the scram response procedures and placed the plant in a stabilized hot shutdown condition.
At 16:59 EDT, on June 12, 2013, Hope Creek made a 4-hour notification to the NRC under 10 CFR 50.72(b)(2)(iv)(B) for an actuation of the reactor protection system (RPS), and an 8-hour notification under 10 CFR 50.72(b)(3)(iv)(A) for a valid manual initiation of the RCIC system (Event Number 49108).
This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) and manual initiation of the RCIC system.
Additional Background On May 7, 2013, the 'B' CW discharge valve failed to attempting to remove the 'B' CW pump from service for Triton XR-70, 84 inch, butterfly valves manufactured by hydraulic power unit. Initial troubleshooting revealed the Operational and Technical Decision Making (OTDM) document operation with the degraded discharge valve until it could evaluation acknowledged the risk of a reactor scram on
CAUSE OF EVENT
summer months.
as a valid manual actuation of RPS stroke from OPEN- FULL to OPEN-MID while maintenance. The CW discharge valves are model PRATT. The valves are operated hydraulically by a valve was unable to be stroked closed. An determined the acceptability of continued be repaired in the fall refueling outage. The low condenser vacuum, especially during the filament growth that bridged across two solder and generating a CW pump trip signal. Conductive In this phenomenon, minute "whiskers" grow The failure analysis on the auxiliary relay card of conductive filaments and a burn mark was across two contacts that could have Previous to the identification of conductive filament cause a normally de-energized relay to activate.
to this event.
a conductive filaments or metallic whiskers on the Bailey auxiliary relay cards was sufficient or predictive maintenance program for the CW with this event. All control rods fully inserted were no automatic initiations of safety systems, adequate and appropriate in placing and maintaining vacuum classified the event as an unplanned however, it is concluded that the safety significance to the health and safety of the public or plant The cause of the 'B' CW pump trip was due to conductive traces on auxiliary relay card, creating a short circuit, filaments are a phenomenon similar to "metallic whiskers.
between circuit card solder traces causing a short circuit.
conducted by an external vendor identified the presence associated with a short circuit. The burn mark on the card energized the relay to provide a trip signal to the pump.
growth, there was no identified failure mode that would Two root causes were determined to have contributed The first root cause is that Hope Creek has not implemented inspection program. The presence of conductive filaments to produce the trip signal for the pump.
The second root cause is the station's lack of a preventative pump Bailey auxiliary relay cards.
SAFETY CONSEQUENCES AND IMPLICATIONS
There were no nuclear safety consequences associated following the initiation of the manual reactor scram. There and immediate actions performed by the operators were the reactor in a safe shutdown condition. The loss of condenser scram with complications in accordance with NEI 99-02; of this event was low and the event did not pose a threat personnel.
SAFETY SYSTEM FUNCTIONAL FAILURE
Functional Failure (SSFF) as defined in NEI 99-02, did not occur. This event did not prevent the the reactor, remove residual heat, control the of an accident.
to 2006 identified the following previous occurrences; vacuum and reactor scram.
Inspection of the area did not identify any breaker or to be failed and was replaced. The corrective actions the current event from occurring.
The corrective action included replacing the 50G vendor for metallic whiskers, and none were found.
relay card in September 2013 found evidence of Failure analysis of the removed 50G relay from the identified. The corrective actions were specific to from occurring.
during the forced outage.
and the 'A' CW pump during the forced outage.
"metallic whisker" evaluations, and trending of circuit replacement of the Bailey auxiliary relay cards.
action program.
A review of this event determined that a Safety System "Regulatory Assessment Performance Indicator Guidelines," ability of a system to fulfill its safety function to either shutdown release of radioactive material, or mitigate the consequences
PREVIOUS EVENTS
A review of similar events at Hope Creek dating back however, none of these events resulted in a degraded June 6, 2006 — The 'B' CW pump tripped unexpectedly.
relay flags picked up. A Bailey logic module was found were specific to this event and would not have prevented January 8, 2008 — The 'A' CW pump tripped unexpectedly.
ground relay. The relay was inspected by an external However, a subsequent inspection of the Bailey auxiliary conductive filaments.
May 18, 2011 — The 'B' CW pump unexpectedly tripped.
'B' CW pump was completed with no degraded component this event and would not have prevented the current event
CORRECTIVE ACTIONS
1. The 'B' circulating water discharge valve was replaced 2. Replaced the auxiliary relay card for the 'B' CW pump 3. Establish a program for performing failure analysis, card failures in accordance with INPO and EPRI recommendations.
4. Establish a preventative maintenance program for Additional corrective actions are being tracked in the corrective
COMMITMENTS
This LER contains no regulatory commitments.