Reliability evaluation of nuclear power plants

The reliability and safety analysis of complex systems, such as nuclear power stations are considered using the event tree methodology. A computational technique which develops the system event tree and relates each branch of this tree to its qualitative and quantitative impact on specified system outcomes following an abnormal operating condition is assessed. The critical failure modes of complex systems are deduced by a new technique for finding the minimal cut or tie of various system outcomes. Potential common mode failures and cut or tie sets containing dependent failures of some components are identified. Two methods for calculating the probability of a component being either in the failure or in the partial failure state are introduced. The first deals with revealed faults and makes use of the concept of Markov processes. The second deals with unrevealed faults and can be used to calculate the relevant probability of a component taking into account its inspection and replacement process. The quantitative data obtained by using these methods is used to quantify the event tree and the cut or tie set analyses. (author)