Role of Reliability in the Safety Analysis of Nuclear Power Plants for Public Risk

The safe operation of nuclear power plants is of utmost importance as their compact core contains a very large quantity of radioactivity which is very harmful to the public. Any accident which spreads out this reactivity in the public domain must be avoided. It is practically impossible to safeguard against all possible accidents which could occur in a plant. Safety designers take advantage of proven reliability if its components and probabilities of failure of components and systems. Engineered safeguard systems are provided wherever components and systems are expected to fail during the lifetime of an NPP. The purpose of engineered systems is to limit the spread of radioactivity to an extent that risk to the public is of the same order as that due to natural and other sources. The risk is interpreted as the probability of the occurrence of an accident multiplied by its consequences. This paper explains the reliability and probabilities of accident aspects of the design and analysis of Nuclear Power Plants. The key aspects discussed in this talk will cover characteristics of nuclear power plants, reliability aspects of principles of operating systems, reliability aspects of systems and components, role of probabilities in the selection and analysis of the accidents which are considered possible, role of reliability in the engineered safeguard systems for limiting the risk due to possible accidents within permissible limits and role of reliability and probability for accidents in safety design of systems for accidents which are least likely to occur.