Analysis on the real-time performance of digital computer systems used in nuclear power plant safety systems

As digital computer systems used in the safety systems of nuclear power plants should be responded within timing requirements to accident situations, strict performance requirements (e.g., response time) are imposed upon the design of the computer systems. Especially, with respect to system response time, digital systems are largely different from analog systems. This paper analyzed the differences, performed the timing and scheduling analyses of digital computers used in shutdown system no. 2 at Wolsong nuclear power plants, and evaluated whether the system response time and real-time performance are complied with. We analyzed the operation model, execution algorithm and execution timing diagram of a scheduler for execution modules, and assessed their timing deadlines qualitatively. We concluded the digital computer systems are capable of scheduling on demand and evaluated the real-time performance of the systems has the timing margin of more than 50% as compared with performance timing requirement (100ms), since the response time for each trip parameter measured through validation tests was less than 50ms