Safety case of digital protection systems focusing on safety-critical software failures in NPP

Abstract

Nuclear power plants has safety functions to prevent the release of radioactive materials to manage accidents. The safety functions consist of various components, which are monitored and controlled by the instrumentation and control (I&C) system. Analog-based I&C systems are being replaced by microprocessor-based digital systems, so the risks of digital systems that may emerge need to be analyzed and integrated into existing probabilistic safety analysis. In this study, the safety case focusing on the failure of software is developed. The causes of software failure are categorized into three types and the safety case is developed for each type. The result of the proposed test method can be utilized as the evidence of each safety case.