静止和摇摆条件下浮动式核电站一二回路PRHRS特性分析

浮动式核电站长期在海洋环境中运行，各系统都会受到海洋运动条件的影响。非能动余热排出系统（PRHRS）可在核电站发生全厂断电事故的情况下带出堆芯衰变余热，防止堆芯熔化，是重要的反应堆辅助系统。本文以一种采用海水作为最终热阱的浮动式核电站作为研究对象，分别设计了一回路和二回路PRHRS，开展了静止和摇摆条件下反应堆系统发生全厂断电事故的计算，对两种PRHRS在静止和摇摆条件下的运行特性进行了分析。研究表明，静止条件二回路PRHRS具有更强的带热能力，摇摆条件下一回路PRHRS的带热能力更加稳定。

Performance Analysis of PRHRS in Primary and Secondary Circuits for OFNP under Static and Rolling Conditions

As offshore floating nuclear plant (OFNP) operates in the marine environment for a long time, all systems will be affected by the ocean motion conditions. Therefore, it is necessary to consider the influence of ocean motion conditions in the design, operation and accident safety analysis of OFNP. Station blackout (SBO) accident has been an essential part of nuclear power plant accident safety analysis after the Fukushima nuclear accident and necessary safety systems must be established in nuclear power plant to mitigate or delay fuel degradation during SBO accident. The passive residual heat removal system (PRHRS) is an important auxiliary system in nuclear power plant, which can bring out the residual heat and prevent the core melting after the SBO accident. However, current researches focus on the following aspects: 1) the development of system analysis code suitable for ocean motion conditions; 2) the analysis of natural circulation characteristics under ocean motion conditions; 3) the computation and analysis of single kind of PRHRS operation characteristics. While little research work has been carried out to compare the performance of PRHRS in primary and secondary circuits under static and motion conditions. In this paper, a system analysis code applicable to OFNP was developed by adding motion condition model to existing code and validated by comparing to experimental data, furthermore an OFNP system model with PRHRS in primary and secondary circuits was established and SBO accident simulation and safety analysis were conducted under static and rolling conditions with PRHRS in primary and secondary circuits operating respectively to compare the performance of the two PRHRS. The results show that the modified code shows great accuracy and feasibility by conducting simulation of a two loop single phase circulation system and comparison of simulation results and experimental data. The heat removal capability of PRHRS in secondary circuit is better than that in primary circuit under static condition while both of the two PRHRS can effectively extract the residual heat from reactor core after the SBO accident. The volume of secondary PRHRS heat exchanger can be smaller when the heat removal capability of the two PRHRS is the same. Rolling motion condition has little influence on both of the two PRHRS, and PRHRS in the secondary circuit is more susceptible to pitching motion condition. Since secondary PRHRS is more susceptible to motion conditions, it needs to be selected carefully when reactor system operating in motion environment is designed and evaluated.