05000348/LER-2002-004

LER-2002-004,

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
3482002004R00 - NRC Website

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

Description of Event

On December 10, 2002 at 0824, with the reactor at 100% power, Unit 1 was manually tripped due to loss of both Steam Generator Feed Pumps (SGFP's)[SJ]. On the previous day, December 9, facilities personnel had been removing catch bags from areas in which leaks were no longer present. The individual assigned routine housekeeping activities in the turbine building on December 10 remembered that not all catch bag removal work was complete. A few feet outside the SGFP barrier, and directly behind the local control panel for the 120/208 Volt Miscellaneous Bus, a catch bag required removal.

The individual did not discuss this activity with his supervision nor with Operations prior to commencing the work. He did not have the proper tools for tie-wrap removal, and decided to apply force to break a tie-wrap which had been used to support the catch bag. He stood on a narrow raised step immediately to the side of the control panel, and reached behind it to pull the tie wrap apart. When the tie-wrap broke, the individual momentarily lost his balance, reached out to steady himself, and inadvertently struck the main feeder breaker trip pushbutton on the local control panel for the 120/208 Volt Miscellaneous Bus[EC] with his hand. This button was raised above the panel surface, but not equipped with a protective guard. Striking the button tripped the main feeder breaker causing deenergization of the Miscellaneous Bus.

The SGFP control cabinet has primary and backup power supplies fed from separate distribution panels, but both panels are powered from the same 120/208 Volt Miscellaneous Bus. Therefore, loss of the Miscellaneous Bus resulted in loss of control power to both SGFP's. Upon loss of control power, all SGFP control valves closed and main control room SGFP indication was also lost. Loss of all main feedwater to the steam generators followed.

Operators manually tripped the reactor in accordance with Abnormal Operating Procedures. All safeguards equipment functioned as designed following the trip.

In addition to the loss of the SGFPs, non safety related components which contain a thermal overload relay powered from the affected Miscellaneous Bus ceased operating or did not start as designed. When the Miscellaneous Bus was reenergized, the equipment was restarted with no further problems.

Cause of Event

This event was caused by personnel error — a lack of awareness of the sensitivity of surrounding equipment and the consequences of inadvertent contact with such equipment and lack of situational awareness that the pushbuttons on breaker control panels can affect operations.

Contributing causes were failure to consider the consequences of actions prior to the event and failure to use the proper tool to safely remove the tie wrap.

Safety Assessment The health and safety of the public were not affected by this event.

This event does not represent a Safety System Functional Failure.

Corrective Action A protective barrier has been installed over the Unit 1 Miscellaneous Bus control panel pushbuttons to prevent inadvertent contact. Access to the corresponding Unit 2 panel has been barricaded until plant conditions allow installation of a protective barrier over the pushbuttons.

The individuals directly and indirectly involved have been coached on the specifics of this event including station expectations for situational awareness, use of proper tools, communications with Operations, and prejob briefings.

A stand down meeting of facilities personnel was held to reinforce station expectations concerning human performance related to this event, including tool use, situational awareness, communications with Operations personnel prior to the start of activities near sensitive equipment, and prejob briefings.

Additional Information

A walkdown of the turbine building to identify other non recessed pushbuttons that could directly lead to a plant trip was conducted. None were identified.

The following LERs have been submitted in the past two years on reactor trips involving personnel error:

Maintenance