05000458/LER-2003-004

LER-2003-004,

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation
4582003004R00 - NRC Website

REPORTED EVENT

On March 28, 2003, at approximately 3:48 p.m., with the plant in cold shutdown for a refueling outage, the Division 2 standby service water (SSW) system automatically initiated. The cause of this event was an error during system realignment using the system operating procedure. This event is being reported in accordance with 10CFR50.73(a)(2)(iv) as an event that caused the automatic initiation of an emergency service water system.

INVESTIGATION and CAUSAL ANALYSIS The error occurred during the realignment of the "B" loop of the CCP system. The CCP system normally serves the spent fuel pool cooling (SFC) system heat exchangers (**CLR**) in addition to other loads. The SFC heat exchangers can be isolated from the CCP system and supplied by either the normal service water (SWP) system or the safety-related SSW system. At the start of the realignment, the "B" SFC heat exchanger was being supplied by the SWP system. It was planned to restore the alignment to being supplied by CCP.

The system operating procedure for the CCP system is written such that the desired realignment can be performed while maintaining pressure in both the CCP and SWP systems above the trip setpoint of pressure switches designed to automatically initiate the SSW system. The format of the procedure directs sequential operation of the valves (i.e., the SWP return valve is closed first, followed by closure of the SWP supply valve). However, an inappropriate decision was made to start the supply valve (**V**) moving in the closed direction before a fully closed indication was received on the return valve. This resulted in a system configuration that caused the CCP header pressure to decrease to the SSW automatic initiation setpoint.

The root cause of this event was determined to be an inadequate peer check by the Control Room Supervisor (CRS). With the many tasks being completed in the Control Room, the CRS did not afford his concentrated attention to the sensitive task of re- aligning the Service Water System. Factors contributing to the procedure implementation error were investigated. A contributing cause of this event is the loss of the oversight function by the Senior Reactor Operator assigned as CRS. The CRS stepped out of his oversight role when he became a peer-checker for the service water realignment. There was no other oversight or peer checker available due to the outage workload. The team did not regard this evolution as sensitive or risky, and decided to continue the task to completion. This led to the procedural non-compliance that directly caused the initiation of SSW. Additional causal factors were, (1) the pre-job brief was not conducted with the personnel conducting the task, and, (2) procedural place keeping was less than adequate, in that the CRS directed the operator to continue to the next step in the procedure prior to ensuring the SWP return valve indicated fully closed.

The SSW system responded to the CCP low pressure signal as designed. Subsequent procedure steps were performed shortly thereafter to open the CCP valves supplying the SFC heat exchangers. Using the appropriate abnormal operating procedures, the SSW system was shut down and returned to its standby configuration approximately 74 minutes after the event.

CORRECTIVE ACTION TO PREVENT RECURRENCE

1. A briefing on the event, including a discussion of the human performance aspects, was held during subsequent control room shift turnovers.

2. A simulator training scenario for this event will be developed for licensed operator requalification training.

PREVIOUS OCCURRENCE EVALUATION

Inadvertent actuations of the standby service water system have been previously reported in LER 50-458/01-003-00 (event date 9/24/01) and LER 50-458/99-006-00 (event date 4/6/99). Both these events involved test procedures not related to the operation being conducted on 3/28/03, thus, they are not considered events of similar cause.

SAFETY SIGNIFICANCE

The SSW system responded as designed to the low pressure signal. CCP cooling water flow was restored to the SFC heat exchangers shortly after the initiation of the event.

Thus, this event was of minimal significance.

(NOTE: Energy Industry Component Identification codes are annotated as (**XX**).)