Monitoring the Risk of Loss of Heat Sinks During Plant Shutdowns at Bruce Generating Station A

Abstract

A relatively simple Loss Of Shutdown Heat Sink Fault Tree mode/ has been developed and used during unit outages at Bruce Nuclear Generating Station "A " to assess. from a risk and reliability perspective, alternative hear sink strategies and to aid in decisions on allowable outage configurations. The model is adjusted 10 reflect the various unit configurations planned during a specific outage, and identifies events and event combinations leading to loss of fuel cooling. The calculated failure frequencies are compared to the limits consistent with corporate and international public safety goals. The Importance Measures generated by the interrogation of the Fault Tree model/or each outage configuration are also used to reschedule configurations with high Fuel Damage Frequency later into the outage and to control the configurations with relatively high probability of Fuel Damage to short intervals at the most appropriate time into the outage.