INES-event
INES 2

UNIT SHUTDOWN DUE TO BREACH OF NORMAL OPERATION CONDITIONS

The unit was shut down by operating personnel due to breach of normal operation condition, namely, the time of safety system (SS) train 3 DG being removed from service in excess of that specified by procedure. DG-3 tripping occurred during routine test of SS train 3 components immediately after connection to the bus. The cause of DG-3 trip is breaker defect. During replacement of the DG's faulty breaker the subsitute breaker designed for transformer switchings was erroneously installed. The closure of this breaker resulted in the damage to DG-3 exciter.
BASIS FOR RATING: Event - postulated, expected (failure of one SS train while routine testing). Safety funciton availability - adequate. According to Table A1 - level 1/2 (C-1P). Level 2 has been chosen since the event revals safety culture deficiencies.
DIFFICULTIES IN RATING:

Location: ZAPOROZHE-1
Event date: Wed, 23-01-1991
Nuclear event report
Legenda & explanation