Effect of correlations of component failures and cross-connections of EDGs on seismically induced core damages of a multi-unit site

Muramatsu, Ken; Liu, Q.; Uchiyama, Tomoaki*

A preliminary seismic PSA study was conducted for a two-unit site to examine core damage frequency (CDF) and core damage sequences with consideration of the effect of correlation of component failures. In addition, the effectiveness of cross-connection of emergency diesel generators (EDGs) between adjacent units was also examined. The results showed that calculated CDF depends on the assumptions on component correlations and when the rules for assigning correlation coefficients defined in NUREG-1150 program was adopted, the CDF of a single unit, the CDF of this site and the frequency of simultaneous core damage of both units increased. Besides, it might be possible that simultaneous core damage of both units was caused by different accident sequence pairs. When cross-connection of EDGs between two units was available, the CDF of a single unit, the CDF of this site and the frequency of simultaneous core damage of both units decreased.