Funtional Assignment And Segment For Safety I&C System In Nuclear Plant

With the great increasing of China’s economic development and people’s living standards, China’s per capita electricity consumption increased rapidly, while on the other hand, "haze Besieged City" is becoming a nightmare in many cities. Thus, more safety, clean nuclear power alternative to coal, breaking the current environmental predicament is the main direction of achieving national energy transformation and environmental improvement. In the current context, how to continuously improve nuclear safety of nuclear power has become the target of continuous efforts of practitioners. The research content of this paper is functional allocation and segment for safety I&C system in nuclear power plant(NPP), the main purpose is to improve nuclear safety level which is the basic objectives of NPP, I&C systems is the central nervous of NPPs shouldering the normal operation of NPPs and incident handling mission, and ensuring safe and reliable operation of nuclear power plants in any conditions. Safety I&C system is nuclear safety related I&C system, mainly used to deal with the design basis accident conditions and some severe accident conditions, to ensure that in the event of an accident, the safety system will maintain the station and brought to a safe state, and continuous monitoring of critical parameters. Since the 21 st century, new construction NPPs at home and abroad widely used digital control systems(DCS). With the development of industrial technology, I&C systems design and applications in NPPs has different characteristics at different stages, replacing the technology which uses analog modular instrumentation implementing analog control and relay rack implementing logical control, DCS has inherent advantages in many aspects compared to the previous generation of I&C technology(analog modular + relay), such as processing capability, high reliability, self-diagnostics, design and configuration flexibility, etc., but there also have some concerns, such as too centralized function caused by high processing performance, common mode failure due to software using. The target of I&C system functional allocation and segment study is to avoid the risk reason by excessive concentration of function, designed the allocation and segment solution both to meet the economy demand, but also to maximize the safety level. Base on the traditional principles of design methods, this paper apply probabilistic safety assessment(PSA) technologies to verify and evaluate the reliability of the I&C system allocation solution, finally to optimize it. This is an emerging field of design engineering technology research, can effectively ensure and enhance DCS reliability. There are three innovation of this paper: firstly, combine the reliability theory(PSA) with the safety I&C system functional allocation and segment, apply PSA technology to optimize design solution; secondly, on the basis of deterministic design, process quantitative validation using PSA to improve nuclear safety level and avoid safety weaknesses; thirdly, the research achievement first applied to three generations of NPP(ACPR1000) design to improve the safety of nuclear power plants.