The Situation and Suggestion of Diversity Actuation System Applied in China

Digital control system has been widely used in nuclear power plant. It brings some obvious advantages in system design and application. Meanwhile the accompanying common cause failures (CCFs) problem becomes one of the most concerned issues. To deal with this problem, many regulations and methods are proposed. NUREG 6303 describes a method for analyzing computer-based nuclear reactor protection systems to discover design vulnerabilities with common-mode failure (US NRC. NUREG/CR6303-1994 in Method for Performing Diversity and Defense-in-Depth Analyses of Reactor Protection Systems, [1]). NUREG 7007 considers that diversity in a safety system is needed for mitigating the consequences of potential CCFs and provides guidance to the staff and nuclear industry for evaluation (US NRC. NUREG/CR7007-2010 in Diversity Strategies for Nuclear Power Plant Instrumentation and Control Systems, [2]). In this paper, the diversity actuation system (DAS) has been described in detail and the functions of DAS system have been introduced. Then several representative different reactor type in China is selected (including M310 model, Second generation plus based on M310 model, AP1000 model and EPR model), and made some comparison between these DAS systems. At the end of this paper some suggestions are proposed to the third generation nuclear power technology in China to reduce the common cause failures and enhance the reliability.