On Integration of Probabilistic and Deterministic Safety Analysis

The paper presents the case study on probabilistic and deterministic safety analysis of Engineered Safety Features Actuation System. The Fault Tree as a Probabilistic Safety Assessment tool is developed and analysed. The same Fault Tree is specified in a formal way. When formalized, it has a possibility to include (he time requirements of the analysed system, which can not be included in a probabilistic approach to Fault Tree Analysis. The feature of inclusion of lime is the main advantage of formalized Fault Tree, which extends it to a dynamic tool. Its results are Minimal Cut Sets with time relations, which are the base for the definition of safety requirements. Definition of safely requirements is one of early phases of software lifecycle and it is of special importance designing safety-related computer systems.