MARKED POINT PROCESS FRAMEWORK FOR LIVING PROBABILISTIC SAFETY ASSESSMENT AND RISK FOLLOW-UP

We construct a model for living probabilistic safety assessment (PSA) by applying the general framework of marked point processes. The frame work provides a theoretically rigorous approach for considering risk f ollow-up of posterior hazards. In risk follow-up, the hazard of core d amage is evaluated synthetically at time points in the past, by using some observed events as logged history and combining it with re-evalua ted potential hazards. There are several alternatives for doing this, of which we consider three here, calling them initiating event approac h, hazard rate approach, and safety system approach. In addition, for a comparison, we consider a core damage hazard arising in risk monitor ing. Each of these four definitions draws attention to a particular as pect in risk assessment, and this is reflected in the behaviour of the consequent risk importance measures. Several alternative measures are again considered. The concepts and definitions are illustrated by a n umerical example.