Safety design of instrumentation in nuclear power plant and its standards

As the nuclear power plants with light water reactors are in the stage of practical use, the fundamental design guides and standards for their safety design seem to have been established. In this report, the fundamental design guides and standards are described, which are considered for the design of the instrumentation for safety which requires high quality and reliability in design, manufacutre and operation. In general, independent redundancy is needed in the construction of safety protection system as the standard for single failure. The independency and maintenability of safety and protection system are also one of the purposes of safety design for nuclear instrumentation, and each channel must be independent and isolated in order to eliminate the correlative effects due to environmental factors and electrical and physical phenomena. Also the safety protection system and control system must, of course, be separated to avoid mutual interference. The safety protection system must be designed so as to be able to carry out test and calibration, and in-service inspection if necessary, to prove that their functions are sound. The reliability of the instrumentation in nuclear power plants is described on its analysis and evaluation. (Wakatsuki, Y.)