Status of current PWR instrumentation and control system

The report outlines a study for improving the functions, reliability and maintainability of man-machine interface facilities, centering on control/protection systems and equipment in central control rooms in PWR power plants which have recently started operation or are currently in planning phase. In particular, systems used in the Takahama No.3 and No.4 reactors are described in detail. For the Takahama plant, failures and troubles as well as their effects on the operation of the plant were analyzed by the failure mode and effect analysis (FMEA)' and the reliability was evaluated by the 'fault tree analysis (FTA)' in order to make improvements for preventing reactor shutdown. Key measures for increasing the reliability include the improvement in the durability of individual components and incorporation of redundancy in major systems. For the No.3 and No.4 reactors, furthermore, human engineering factors were reexamined to reduce burdens on workers and to prevent judgement errors and misoperation. Advanced computer techniques are adopted actively to provide improved control panel configuration and accessories arrangement, making it possible to perform control and monitoring operations efficiently. The report further describes various improves made, or planned to be made, in PWR plants, citing examples of walk-through analysis and event tree analysis. (Nogami, K.)