05000364/LER-2004-001

LER-2004-001,

Docket Number
Event date:	3-30-2004
Report date:	05-28-2004
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3642004001R00 - NRC Website

Westinghouse -- Pressurized Water Reactor Energy Industry Identification Codes are identified in the text as [XX]

Description of Event

On March 30, 2004, with the unit defueled, the 2E Service Water Pump [BI] failed to start on a Safety Injection Signal during routine surveillance testing.

It was determined that a splice in the wire carrying the auto start signal [EA] had corroded and failed.

The affected cable splice included an insulating sleeve over each of four conductor splices, and an insulating jacket over the entire cable splice. Water was found inside the splice when the outer jacket was removed from the cable. Individual sleeves were found to be installed with less than the vendor's current recommended seal length, or to not be fully shrunk around the wire. Failure of the jacket to be fully shrunk around the wire allowed water to enter the cable and corrode the splice over time. The four splices in the cable containing the one failed conductor were inspected. Other conductors in this cable, at the location of the failed splice, also showed some signs of corrosion. Possible sources of water were rainwater, or condensation from the high humidity environment of the pull box. The installed pull box drain system was noted to be functioning properly.

Corrosion of this splice resulted in failure of the auto start signal to the 2E Service Water Pump. This failure occurred some time after the last satisfactory surveillance test performed during the fall 2002 refueling outage. There is no firm evidence of when the failure occurred. However, due to the slow degradation rate assumed for the failed conductor, it is likely that the length of time the failure existed exceeded the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed outage time for the B Train of Service Water. The manual start function of the pump was unaffected by this failure.

The entire cable splice was repaired and insulated properly. An additional splice in the affected cable in another pull box was inspected satisfactorily. The pump was satisfactorily retested to verify proper auto start function.

Cause of Event

This event was due to incorrect assembly of splice insulation in a cable pull box during initial construction. Lack of proper sealing of the insulation sleeves over the spliced conductor allowed water intrusion to corrode the conductor.

Safety Assessment The manual start function of the pump was unaffected by this failure. Plant procedures direct operator verification of auto start functions. Had an auto start been demanded and failed, the pump would have been promptly recovered by operator action from the control room. Therefore, the health and safety of the public were unaffected by this event.

This event does not represent a Safety System Functional Failure.

Corrective Action The splice in the affected cable was repaired and the autostart function of the 2E Service Water pump was tested satisfactorily.

The preventive maintenance task for pull box inspection and water removal has been revised to include a visual inspection of insulation sleeves on cable splices in the pull boxes.

This type of degradation is a long term phenomenon; therefore, a sample of cable splices in pull boxes on both units will be disassembled and inspected to identify the onset of degradation prior to failure. If degradation is identified in the sample, appropriate preventive maintenance tasks will be developed and implemented. This action will be completed by the end of the next refueling outage on each unit.

Additional Information

No similar LERs have been submitted in the past two years.