EFFECT OF THE SEISMIC CAPACITY OF EQUIPMENT ON THE COREDAMAGE FREQUENCY IN NUCLEAR POWER PLANTS

摘要

The effects of the seismic capacity of equipment on the core damage frequency (CDF) in nuclear powerplants are investigated through a case study for the Younggwang Nuclear Units 5&6, which are operatingpressurized water reactors in Korea. A probabilistic safety assessment for a seismic event (seismic PSA) isperformed for the plant and then the equipment important for the CDF are selected. Then the seismic PSA isperformed using different seismic capacities of the selected equipment for the investigation of the effect of theirseismic capacity on the CDF. The results of the case study show that an increase of the seismic capacity of theequipment reduces the CDF significantly. This indicates that the seismic safety of the operating nuclear powerplants can be significantly improved by increasing the equipment seismic capacity. When the Diesel Generator orCondensate Storage Tank has an increased seismic capacity, the CDF will decrease significantly, while in the caseof the Battery Rack the CDF does not decrease significantly. When all of the selected equipment items have a25%, 50%, and 75% increased seismic capacity, the core damage frequency will decrease by 45.8%, 64.5%, and67%, respectively. The effective HCLPF values for the Diesel Generator, Offsite Power, Condensate Storage Tank,and Battery Rack are determined as 0.84g, 0.35g, 0.63g, and 0.63g, respectively.