Simulation, digital system validation and reliability

In the past nuclear power plant (NPP) instrumentation and control (I and C) systems are mostly based on analog technology. With the advancement of commercially available digital systems such as Programmable Logic Controllers (PLC) and Distributed Control Systems (DCS), digital technology has been widely used in new installations and in replacement of existing installations. Validation and reliability assessment of digital systems in nuclear power plant applications are both important and challenging. The challenges are on how to perform dynamic, integrated and interactive testing of digital systems and how to quantify reliability assessment. In both areas an engineering simulator can play a role. In order to be able to play a role in validation testing and reliability assessment, the engineering simulator must satisfy the following criteria. The reactor core modeling should be based on advanced best estimate core modeling codes. The simulator should be a full scope simulator, i.e. it should include all the plant systems and the process and logic modeling should be the same as the actual plant. A V and V program should be implemented to assure that the implementation of the plant process and logic modeling are correct. In this paper a methodology on how to use simulation to perform validation and quantify assessment of digital systems are discussed and preliminary results for a specific application are also presented. (author)