Functional Safety of Software Systems Important for NPP Safety

Designing systems important for NPP safety is basing on fulfilling the demands of normative documents and ensuring the quality of soft- and hardware systems throughout the entire life cycle. The most critical tasks in ensuring the quality of soft- and hardware complex are the phase for the formation of demands for a designed or modifiable system and their consequent verification. An increase in demands for the quality of software (SW) for systems important for NPP safety at all phases of the life-cycle is associated with an increase in the complicity and functionality of the software and has led to the need to develop methods to justify the safety of the systems themselves and the software included in them. The paper discusses a method based on the construction of "safety functions," the implementation of which subsequently verified. This method is using in SW verification for upper-level systems of APCS and can be used to analyze cybersecurity, information, and fault tolerance of soft- and hardware systems.