NPSAG/SAFIR/NKS project DIGREL : Digital I&C reliability

The OECD/NEA CSNI Working Group on Risk Assessment (WGRisk) has set up a task group called DIGREL to develop a taxonomy of failure modes of digital components for the purposes of probabilistic safety assessment (PSA). The taxonomy is aimed to be the basis of future modelling and quantification efforts. It will also help define a structure for data collection and to review of PRA studies. A parallel Nordic activity carried out a pre-study where a comparison of Nordic experiences and a literature review were performed. The study showed a wide range of approaches and solutions to the challenges given by digital I&C. In order to study the effect of I&C design features and modelling approaches, an existing simplified PSA model has been complemented with fault tree models for a distributed reactor protection system. The paper summarises the failure modes taxonomy work.