Derivation of the Seismic Common Cause Parameter for a Multi-Unit Seismically Induced Loss of Coolant Accident. Annex II

In a multi-unit site, the potential exists for multiple large loss of coolant accidents (LOCAs) to occur simultaneously. The probability of this event could be large if the units are identical. This question of correlation between component failures has been identified as an important uncertainty in seismic probabilistic safety assessments. In this annex, the procedure in REED, J.W., McCANN, M.W., Jr., IIHARA, J., TAMJED, H.H., "Analytical techniques for performing probabilistic seismic risk assessment of nuclear power plants", Proceedings of the Fourth International Conference on Structural Safety and Reliability, Vol. III, New York (1985) 253–261 will be used to calculate the joint probability of two LOCAs occurring simultaneously, drawing from the seismic fragility analysis.