A Study on Comparison of Seismic Capacities by Probabilistic Approach and Deterministic Approach

Seismic Performances of nuclear power plants are being performed by Seismic Probabilistic Safety Assessment (SPSA) and Seismic Margin Assessment (SMA). The major difference between these two methodologies is the approach, which of SPSA is based on the probabilistic approach, whereas which of SMA is based on the deterministic approach in evaluating capacities of structures and equipment. As for Korean nuclear power plants, SPSA has been used for new power plants but recently SMA has been taken for old power plants. This paper shows the quantitative correlation between the two methodologies by evaluating and comparing seismic capacities described as a HCLPF (High Confidence of Low Probability of Failure) on the same equipment using the two methodologies respectively. A model used for comparing and analyzing is a CCW surge Tank which is located on EL.165 ft in Auxiliary Building. A HCLPF value of SMA is about 1.33 times (0.64 g/0.48 g = 1.33) higher as that of SPSA and the value of 1.33 becomes a correlation factor of two methodologies in this study. (authors)