What is Sparsity

The accurate availability and safety assessment of a reactor trip system for nuclear power plants instrumentation and control systems (NPP I&C) application is an important task in the development and certification process. It can be conducted through probabilistic model-based evaluation with variety of tools and techniques (T&T). As each T&T is bounded by its application area, the careful selection of the appropriate one is highly important. This chapter presents the gap-analysis of well-known modeling approach—Markov modeling (MM), mainly for T&T selection and application procedures—and how one of the leading safety standards, IEC 61508, tracks those gaps. The authors discuss how main assessment risks can be eliminated or minimized using metric-based approach and present the safety assessment of typical NPP I&C system. The results analysis determines the feasibility of introducing new regulatory requirements for selection and application of T&T, which are used for MM-based assessment of availability and safety.