Toshifumi Hayashi

A verification and validation method and its application to digital safety systems in ABWR nuclear power plants

A verification and validation (V&V) method has been developed and applied to newly developed digital safety systems for the first ABWR plant, Kashiwazaki–Kariwa unit No. 6 of the Tokyo Electric Power Company. This paper describes the method and experience gained from its application. The method was developed on the basis of domestic and foreign standards and guidelines, and covers the more concrete procedures required for actual V&V. The application of problem oriented language (POL) helps make the V&V feasible and reliable. A personal-computer-based automatic test tool for the validation test has been developed and utilized. This tool is used to carry out the pre-defined validation test procedure automatically and produce a test report, and it was found to be effective in reducing the time and manpower required for the validation test. The validation test covers dynamic transient tests in which the response of the digital safety system against the simulated design based transients are tested. The tool enables automatic execution of the dynamic test.

A post trip operational guidance system for BWR plants

Abstract A post trip operational guidance system (PTOG) for BWR power plants was developed to support the operators in achieving safe plant shutdown after a scram. The objective of PTOG is to support the operators in collecting plant information, in diagnosing plant status and in deciding corrective actions. To achieve this objective, PTOG has three main functions, i.e., the diagnosis of plant subsystems performance, the identification of safety functions status and the dynamic synthesis of operating procedures. The main advantage of PTOG is that it provides operating procedures irrespective of the transients initiating event and evolutional history. The results of verification and validation tests showed that PTOG was a useful, effective and trustworthy vehicle in coping with abnormal plant conditions.

Application of FPGA to Nuclear Power Plant I&C Systems

This paper presents a Field Programmable Gate Array (FPGA) application for nuclear power plants, and introduces Toshiba FPGA-based Instrumentation and Control (I&C) systems as typical examples. An FPGA is a semiconductor device including more than thousands of logic gates which can be connected to constitute application specific circuits. A notable feature of FPGA is its simplicity. Thanks to this feature, several companies including Toshiba have developed FPGA based-systems for nuclear power plants recently. The simplicity of FPGAs is one of the most notable advantages to provide cost-effective options for I&C systems, ensuring reliable and safe operation of nuclear power plants.

Next Generation Technologies in the Digital I&C Systems for Nuclear Power Plants

In this chapter, overviews of digital technologies for instrumentation and control (I&C) systems and the main control room (MCR) of boiling water reactor nuclear power plants (BWR NPPs) are explained. Then, cutting edge fundamental technologies and future possibilities for the next generation I&C systems are described.

Application of Algebraic Specification to Verify the Design of Safety Logic in Nuclear Power Plants

A formal verification method using an algebraic specification technique is proposed, and its effectiveness is studied. A computerized automatic verification system, which utilizes an algebraic specification to describe system requirements and to prove an inductive theorem based on a term-rewriting technique for verification, is built and evaluated through experimentally verifying the logic design of a digital reactor protection system in boiling water reactors. The results show that the proposed method can mathematically correctly verify the logic design in a limited time, thereby improving accuracy and reducing person-hours for the verification.