Interpretation and Evaluation of the TS Criteria - Development of a Guidance Document

摘要

A nuclear power plant's Technical Specifications (TS) define the limits and conditions for plant operation. The original TS were based on deterministic analyses and engineering judgments, but as the Probabilistic Safety Assessment (PSA) has developed it has shown to constitute a useful tool for evaluating many aspects of the TS from a risk point of view. The US NRC has fully adopted a risk informed decision process, in which PSA plays an important role. In the Nordic countries the use of risk informed methods has been discussed since the early nineties, but on the whole the methods have only been applied on a case by case basis. It is however expected that the use of risk informed decision making will increase significantly in the coming years with on-going modernization and power uprate projects, which require TS to be updated. Within a co-operation project between Nordic Nuclear Safety Research (NKS) and the Nordic PSA Group (NPSAG) the different aspects that must be taken into account in a risk based evaluation process of TS changes have been studied. The aim has been to produce a guidance document covering the most important issues to consider, but not to point out a single method as the only acceptable one.