 INES 0 |
FLOODING IN BASEMENT AND SUB BASEMENT OF TURBINE BUILDING |
Unit-1 of the Kakrapar Atomic Power Project was remaining shutdown from 6.2.1994 and since 0620 hrs. of 16.6.94 the supply to the emergency equipment was from Diesel Generators as outside power supply was lost due to bus fault in switch yard.
Water level of Moticher lake (supplying water to station) increased due to heavy rain fall in the catchment areas during 15.6.94 and 16.6.94. Water started entering Turbine Building (TB) through Raw Water Pump House, switchyard cable trenches and pipe tunnels since morning of 16.6.94. As the level in the TB started rising, control room staff switched off the main equipments in the TB. By 0900 hrs. Process Cooling Water Pumps (PCW), Auxiliary Boiler feed pumps and all other control panels and equipments in basement and sub-basement (at 91 m and 95 m elevation) of Turbine Building started getting submerged in water. As process water pumps got submerged, fire water was supplied to shut down cooling heat exchangers and moderator heat exchangers.
Since rising water level made threat to class III power supplies (DGs) located in Turbine Building at 103m, plant emergency was declared at 1100 hrs. The water level continued to rise at a steady rate and reached around 98.5 m elevation at about 1500 hrs. By 1700 hrs rainfall had stopped and further ingress of water to Turbine Building stopped. There was no ingress of water to the Reactor Building. Plant emergency was terminated as water level had come down due to discharge of water from lake to other areas and also because rain had stopped. The event has been rated at level 0 on INES.
Justification of Rating:
On the day of the incident, the reactor was remaining shutdown for over four months. The decay heat was very small and there was no interruption in core cooling. The event is a below scale event. (Ref. clause III-3.1.1, degradation of reactor core cooling during reactor shutdown).
Event date: Thu, 16-06-1994
