A Brief Introduction to Several Important Design Optimizations of Passive Nuclear Power Plants in China

Abstract Passive nuclear power technology was developed by Westinghouse in the United States and introduced to China around 2005. Currently, four passive nuclear power plants have been operating safely and stably in China for about 20 reactor years. However, some design defects have also been exposed. Therefore, a series of design optimizations have been carried out to improve the reliability and ease of operation and maintenance in passive nuclear power plants. This paper briefly introduces the several important design optimizations implemented and planed in Chinese passive nuclear power plants. We hope it can provide useful reference for other countries in the construction and operation of the passive nuclear power plants. (1) A gate has been added in refueling cavity. It creates conditions for equipment maintenance during refueling operations, which require the water level in the Reactor Pool to be lower than the level of flange of the Reactor Vessel. (2) A spare Variable Frequency Drive (VFD) has been added to solve the problem of unreliable long-term operation of the VFD for Reactor Coolant Pump (RCP). A 50Hz RCP has been selected for the plants under construction. (3) The anchor point of the support for Main Stream Pipelines has been adjusted from the Auxiliary Building in Nuclear Island to the adjacent wall of the First Bay so as to control Main Control Room (MCR) noise. The noise source has been also reduced by reducing the main stream flow rate. (4) A Spare Glove Box has been added, which is standby with the Grab Sample Panel. According to the characteristics of the sampling object, the sampling pipeline shall be reasonably separated to reduce or avoid the mixing of the sampling liquid, so as to improve the sampling representativeness.