Effects Assessment for Requirements Faults of Safety Critical Software in Nuclear Industry

In a context where software has been pervasive in safety critical applications, trust in software safety is challenged by software complexity and lack of systematic methods to assess the effects of remaining faults. To expand the use of digital technology in the nuclear industry, systematic methods are required to assess the effects of remaining faults for software-based Instrumentation & Control (I& C) systems in safety critical applications. In this paper, the effects of the remaining requirements faults are assessed using a probability density function (PDF) of their hazard rates. A hazard-based effect analysis (HEA) method is developed to obtain the probability distribution of the hazard rates of a remaining requirements fault. The HEA method is applied to a Reactor Protection System (RPS) in the case study. The probability density functions for the introduced faults, detected faults and remaining faults in the requirements phase of the RPS system on the domain of hazard degree are obtained.