On November 21, 1998 while performing refuelling, at the time of unloading the core and lifting a spent fuel assembly, a failure occurred affecting the refuelling machine which caused the spent fuel assembly to slump to the reactor core. The fuel assembly was taken to a safe condition. Reactor vessel water and refuelling floor atmosphere were monitored without finding any abnormal changes.
Basis for rating this event: Event initiator - drop of a fuel assembly; frequency - Low/unlikely; Safety function availability - full. From Table II, column 3, Row A of INES user's Manual, the classification is 2.