Research and Application of Software Reliability Analysis Method for Safety I&C System in NPPs

With the extensive application of digital equipment in nuclear power plants (NPPs), computer software plays an increasingly important role in the digital instrumentation and control (I&C) systems of NPPs. However, with the increase of software scale, defect density increases geometrically. Therefore, the reliability of the software must be considered before the digital equipment is put into practical use of the safety I&C systems in NPPs. This research firstly introduces the advantages and disadvantages of software failure modes and effects analysis (FMEA) and software fault tree analysis (FTA), adopts FMEA and FTA comprehensive analysis method for qualitative analysis of software reliability, and establishes the analysis steps and comprehensive analysis principles. On this basis, taking the application software of safety instrumentation and control (I&C) system of nuclear power plant as the analysis object, the analysis model is established, and the key causes of function failure are found out by solving the minimum cut set to make improvement measures. At last, the technical characteristics of FMEA and FTA comprehensive analysis method are summarized to provide reference for the software reliability analysis of I&C systems in NPPs.