A CABLE TRAY FIRE AT A COMMERCIAL NUCLEAR POWER
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.
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.