Fort Calhoun (USA)
PWR 480 MW constructed by CE; grid connection in 1973
Facilities in Fort Calhoun
| plant | reactor typ | construction start | operation start | shut down |
|---|---|---|---|---|
| Fort Calhoun-1 | PWR | 1968 | 1973 |
Failure of a pressurizer safety valve initiated a LOCA with potential to degrade the reactor coolant pressure boundary. A pressure spike in the RCS led to the opening of the safety relief valve, coolant flow through the valve into the holding tank, But when the valve did not reseat properly the tank overflowed -> about 80.000 liters of reactor coolant spilled onto containment building floor. HPCI and LPCI start. -> scram. Inspection revealed that the valve which malfunctioned was seriously damaged by chattering.
station batteries developed cracks in the cell casings CAUSED BY STRESSES FROM CORROSION BUILDUP AT THE POSITIVE POST SEAL AREA.
EDGS: radiator exhaust dampers had cracked pins in their couplings, Could have prevented both EDGS from performing their design functions
containment spray and containment coolers were outside design basis for post accident containment cooling, condition existed since startup
original design error: potential common mode failure of both EDGs existed since startup; the static voltage regulator cabinet reached temperatures high enough to cause solid state component malfunction
beause of design fault, in the event of a main steam line break or a LOCA, the auxiliary feed water piping inside the containment would be overpressurized due to thermal expansion of fluid between closed valves
all 4 wide range nuclear instsrumentation cables found to be in same fire area
Excessive leakage past 4 check valves in the instrument air system could cause premature switching to a dry containment sump, potential loss of SI and containment spray
