Transient Analysis of Active Cooling Procedure of HTR Reactor Core

It is crucial to design a proper cooling strategy for the high temperature gas-cooled reactor (HTR) reactor core after the HTR emergency shutdown in order to achieve safety and efficiency and prepare for the restart. A numerical model was set up for the transient simulation of heat and mass transfer during cooling process. Firstly the direct cooling strategy used in thorium high-temperature nuclear reactor (THTR) was analyzed and the results show that this strategy is too risky because of the inevitable hot or cold shock introduced to the equipment. Then a new strategy was presented, which is suitable to Chinese high temperature gas-cooled reactor and includes four steps: Discharging the steam generator, depressurizing, pre-cooling, and cooling the core. The transient simulations show that this new strategy is safer than the direct cooling strategy, by eliminating the hot and cold shock. Meanwhile the time consumed by the cooling process using the new strategy is acceptable.