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|  DOE-HDBK-1116-98
APPENDIX B
about the effects of grounds and shorts on
reactor. While this was being done, the
plant operation and also the potential
recirculating pumps tripped off. The reactor
personnel hazards associated with fighting
was scrammed by the operator 30 minutes
fire in electrical cabling with water.
after the fire started.
Operators confirmed that the reactor control
Effects on Plant Operation
rods were fully inserted. Thirty-five minutes
after the fire started the turbine-generator
The first indication of the fire's effect on Unit
was manually tripped. One minute later, all
1 operation came 20 minutes after the fire
capability to monitor core power was lost as
started with the almost simultaneous
the vital power supply electrical boards were
annunciation of several alarms:
lost. In addition, all emergency core cooling
systems were lost because their
" ESIDUAL HEAT REMOVAL OR CORE
R
motor-operated valves lost power and could
SPRAY AUTOMATIC BLOWDOWN
not be operated remotely. All of the
PERMISSIVE,"" EACTOR WATER LEVEL
R
outboard main steam isolation valves shut,
LOW-AUTOMATIC BLOWDOWN,"and
isolating one main condenser as a heat sink.
" ORE COOLING SYSTEM/DIESEL
C
Because reactor pressure increased rapidly
INITIATE."
to 1100 psig, the control room operators
took manual control of the main steam relief
The control room operators observed that
valves to reduce pressure by cycling
normal conditions of reactor water level,
pressure between 850 and 1080 psig.
reactor steam pressure, and drywell
atmosphere pressure existed, so they were
Owing to the almost constant blowdown of
confused by the alarms. Over the next 8
reactor pressure that added heat to the
minutes, several events occurred, including
suppression pool, suppression pool cooling
the automatic starting of residual heat
became essential 40 minutes after the fire
removal and core spray pumps, the
started, but the residual heat removal
high-pressure coolant-injection pump, and
system, which is normally used, was
the reactor core isolation coolant pump. In
unavailable because of the electrical board
addition, control board indicating lights were
losses.
randomly glowing brightly, dimming, and
going out; numerous alarms occurred; and
The next 30 minutes were spent trying to get
smoke came from beneath Panel 9-3, which
the shutdown buses powered either by the
is the control panel for emergency core
running diesel generators or from Unit 2.
cooling systems. The operators shut down
During this period, the reactor water level
equipment that was not needed, such as the
dropped from its normal 201 inches to 48
residual heat removal and core spray
inches above the top of the active fuel. To
pumps, only to have them restart again
recover water level, water was added to the
automatically.
reactor through the feedwater bypass valve
from the condensate booster pump. Water
When reactor power was affected by an
level went too high because control of the
unexplained runback of the reactor
bypass valve had been lost, so an auxiliary
recirculating pumps, the shift engineer
unit operator was sent to manually throttle
instructed the operator to reduce
the valve.
recirculating pump loading and scram the
B-8
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