A Quantification Framework for Software Safety in the Requirements Phase: Application to Nuclear Power Plants

With the increasing dependence on digital instrumentation and control (I&C) systems in nuclear power plants, software has become a significant determinant of system safety assurance. To expand the use of digital technology in the nuclear industry, systematic methods are required for quantifying the safety of software-based I&C systems in safety critical applications. A software safety quantification model limited to the requirements phase is built in this paper based on the causal mechanisms that challenge safety. A preliminary mathematical method was developed to assess the number of requirements faults and their sub-types. A case study is conducted on a function of a reactor protection system to verify the validity of the quantification model.