05000373/LER-2003-004

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LER-2003-004, High Pressure Core Spray Inoperable Due to Improperly Seated Fuse
Lasalle County Station, Unit 1
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3732003004R00 - NRC Website

PLANT AND SYSTEM IDENTIFICATION

General Electric - Boiling Water Reactor, 3489 Megawatts Thermal Rated Core Power

A. CONDITION PRIOR TO EVENT

Unit(s): 1. Event Date: 11/17/03 Event Time: 0110 Reactor MOde(S): 1 Power Level(s): 100 Mode(s) Name: Run

B. DESCRIPTION OF EVENT

At 0110 on 11/17/03, during the performance of a maintenance surveillance, fuse 11321A-F8, the power supply fuse for the High Pressure Core Spray System (HPCS)[BG] Low Level Initiation/High Level Trip was found not fully seated in its fuse clip. This fuse was not involved in the surveillance. The fuse was pushed back fully into the fuse clip at 0143.

An Engineering evaluation concluded that the fuse function might not have been retained during a seismic event, and continued operability could not be assured while in the as-found condition. Failure of this fuse would have prevented automatic actuation of HPCS on reactor vessel low level 2; and would prevent automatic closure of the HPCS discharge valve 1B21-F004 on reactor water high level 8. This might prevent the HPCS system, a single train system, from performing its design function during a loss of coolant accident subsequent to a seismic event.

Extent of condition walk downs in the Division 3 Control Panels (3.H13-P625 and 2H13-P625) found no similar conditions. A subsequent expanded extent of condition review was completed in the Auxiliary Electric Equipment Room and the Main Control Room. There were two other instances where fuses were not completely seated in their carriage. In both of cases, Engineering determined that this minor misalignment would not impact the ability of these fuses to perform their design function. The fuses were reseated properly.

This condition is reportable under 10 CFR 50.72(b)(3)(v)(D), and 50.73(a)(2)(v)(D) as an event or condition that could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident". An ENS call was made at 0835 CST on 11/17/03. It is also reportable under 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's Technical Specifications.

C. CAUSE OF EVENT

A review of the Passport work management system identified that this fuse was last manipulated as part of a clearance in March 2002. The operator who participated in the clearance had no specific recollection of installing this fuse, but was aware that fuse installation is always verified by pushing both ends of the fuse to ensure that it is fully engaged.

The cause of this event could not be determined. The most probable cause was a failure to fully seat the fuse during the last clearance order restoration in March 2002.

D. � SAFETY ANALYSIS The safety significance of this event was minimal. Failure of the fuse would have prevented automatic actuation of HPCS on reactor vessel low level, and would have prevented automatic closure of the HPCS discharge valve on reactor water high level. However, had fuse continuity not been maintained, control room operators would have been alerted by alarm 1H13-P625 "Rosemount Card File Trouble" on the 1H13-P601 panel, and would have responded to replace the fuse.

With the fuse open, HPCS could have been manually operated if required to mitigate the consequences of an accident. Additionally, RCIC provides alternate high-pressure injection, and Automatic Depressurization System and Low Pressure Core Spray were available to provide low pressure spray to the reactor.

This event constitutes a safety system functional failure.

E. � CORRECTIVE ACTIONS 1. An extent of condition review of the Division 3 Control Panels (1H13-P625 and 2H13-P625) was completed with no other improper fuse installations identified.

This action is complete.

2. An extent of condition review was completed in the Auxiliary Electric Equipment Room and the Main Control Room. This action is complete.

3. This event was reviewed with all Operations and Maintenance personnel, stressing the importance of ensuring fuses are fully seated in their clips, specifically for the purpose of maintaining seismic qualification and operability of equipment. This action is complete.

F. � PREVIOUS OCCURRENCES A search of the corrective action program database identified a similar, non- reportable event (CR# 125478) that occurred in October 2002. A loose fuse clip resulted in a "Drywall Equipment Drain Pump Failure to Start!' alarm, and a loss of indication for the Drywell Equipment Drain Sump pump suction valve. The corrective action was to replace the loose fuse clip. The corrective action would not have prevented this event.

C. � COMPONENT FAILURE DATA This is not applicable, as no component failures occurred.