A Cable Tray Fire At a Commercial Nuclear Power Plant

DOE-STD-1058-93

A CABLE TRAY FIRE AT A COMMERCIAL NUCLEAR POWER

PLANT

A commercial nuclear power plant experienced a serious inplant cable tray fire.

The fire was started by an engineer who was using a candle to check for air leaks through

a fire wall penetration seal. The fire spread and was fought on both sides of the reactor

building and cable spreading room wall by plant and local community fire fighting

personnel. Efforts to put out the fire were made difficult by several factors: delay in

notifying personnel of the exact location of the fire, physical location of the fire in the cable

trays, and the high differential pressure between the cable spreading room and the reactor

building that resulted in high air flow rates through the wall.

The effects of the fire on the plant were almost immediate. All Unit 1 emergency

core cooling systems were lost, as well as the capability to monitor core power. To remove

decay heat, low pressure water from the condensate pumps and manual operation of

primary relief valves were used until normal decay heat removal systems could be made

operational. Control power to motor operators and pump controls was established using

temporary jumpers allowing the plant to be brought to a stable shutdown condition. There

was no release of radioactivity.

Lessons Learned

The inability to put out the fire was caused, in part, by the large air flow through

the penetration that prevented the carbon dioxide and dry chemicals from

smothering the fire. Compounding this were the fire fighters' difficulty in seeing

exactly what was burning and working in the confined spaces, which made

access to the affected areas difficult.

The use of water at an early stage would have extinguished this fire and

prevented the loss of circuits not already affected. Although the suggestion to

use water was made repeatedly by the local community fire chief, plant

personnel were concerned about the effects of grounds and shorts on plant

operation and potential personnel hazards.

Community fire fighting personnel did not arrive at the scene until approximately

45 minutes after they were called. Part of the delay was the need to process

temporary radiation monitoring badges.

B-15