Design of Common Cause Failure Prevention for Priority Actuation and Control System in VVER-1200 Nuclear Power Plant

In the Vodo-Vodyanoi Energetichesky Reactor (VVER-1200) nuclear power plants, an independent priority actuation and control system is used to realize the control function of safety actuators with different levels of defense in depth and safety classes from different systems/equipment. During the design of PACS, it is necessary to adopt corresponding measures to mitigate the impact of common cause failure on the performance of safety functions. Based on the domestically developed platform of the main instrumentation and control system for VVER-1200 nuclear power plants, the design principles and methods of PACS for preventing common-cause failures are introduced, and the feasible schemes to reduce the probability of common-cause failure occurrence and the probability of simultaneous triggering or propagation of common-cause failures are proposed. Various means such as diversity, testability and independence are combined to improve the level of common-cause failure prevention of the system, and these measures have been successfully applied in engineering projects. This design approach holds significant reference value for the development, research, and improvement of common-cause failure prevention strategies in PACS for various reactor types.