05000397/LER-2003-010
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| 3972003000R00 - NRC Website | |
Event Description
At 1231 on October 7, 2003, with the plant in mode 1, a depressurization of the High Pressure Core Spray (HPCS) system [BG] occurred while the HPCS system waterleg piping was isolated during an unscheduled maintenance activity to replace the power frame on the waterleg pump motor. System pressure unexpectedly decreased to below the low pressure alarm point requiring plant operators to remove fuses for the main HPCS pump and perform a system fill and vent procedure. These actions rendered the single train HPCS system inoperable.
Immediate Corrective Action With the HPCS system inoperable, the action required by Technical Specifications Limiting Condition for Operation (LCO) 3.5.1.B to verify operability of the Reactor Core Isolation Cooling (RCIC) system [BN] and restore HPCS within 14 days was taken. Approximately three hours later at 1538, after verifying the system was filled and vented, and the pump fuses reinstalled, the HPCS system was operable and all requirements of LCO 3.5.1 were met. As an additional measure, control room operators have been instructed to maintain an oversight role of maintenance activities and be less involved in the work planning process.
Root Cause
The cause of this event is attributed to the judgment of control room operators who allowed the unscheduled maintenance to proceed when contingency actions to be taken in the event of unexpected system conditions had not been pre-planned. Currently, development of contingency plans is included in the work planning process only for higher risk maintenance activities. In this case, plant operators developed the contingency plan during a pre-job briefing that was conducted just prior to performance of the maintenance activity. The operator's plan was to start the main HPCS pump (HPCS-P-1) if system pressure decreased significantly (to below — 80 psi) from the initial pressure of approximately 105 psi while the power frame was being replaced. However, the system pressure decreased more rapidly than expected and HPCS-P-1 could not be started before the low-pressure alarm actuated.
Alternatives to the operator's contingency plan that would not have resulted in a reportable event would be to run HPCS-P-1 during the power frame replacement to maintain system pressure or remove the HPCS system from service in accordance with approved procedures and Technical Specifications prior to maintenance.
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Assessment of Safety Consequences
There were no safety consequences associated with this event and the HPCS system was not inoperable for greater than the 14-day outage time allowed by Technical Specifications.
Additionally, the independent RCIC system was available to perform the safety function of high-pressure injection during the time HPCS was inoperable.
Similar Events There have been no previous similar events in which a condition reportable pursuant to 10 CFR 10 CFR 50.73(a)(2)(v)(D) existed due to allowing maintenance to be conducted without pre-planned contingency actions.