Preliminary study on the use of the heat pipe to the passive decay heat removal system of the modular HTR

摘要

Passive decay heat removal (DHR) is one of the most important features of the modular HTR. It is performed by the cooling system installed outside the reactor pressure vessel. Decay heat of the core is transferred to the reactor pressure vessel and then to the decay heat removal system passively by conduction, radiation and convection.rnThe purpose of our study is to establish the concept of the fully passive and highly reliable decay heat removal system utilizing the separated type of heat pipe, which has the self-regulation characteristics to minimize the heat loss under the normal operation with maintaining the sufficient heat removal capability during the accidents.rnAs the first step of the preliminary study, the system concept of the Heat Pipe DHR system was studied and the core heatup behaviour during the depressurization accident was calculated. These results show that the Heat Pipe DHR System is applicable to the modular HTRs and its heat removal capability is sufficient. Especially, by applying the variable conductance heat pipe, possibility of the self-regulation characteristics to reduce the normal heat loss is suggested.rnThe experiments to obtain the fundamental characteristics data of the separated type of the variable conductance heat pipe were carried out under various conditions such as heat removal rate, cooling mode and initial pressure of the non-condensible gas. These results show that the variable conductance heat pipe has sufficient self-regulation characteristics. The numerical model for the experiments was developed and the numerical results were compared with the experimental results.rnThese studies show that, by utilizing the variable conductance heat pipe, it is possible to design a fully passive DHR system with the self-regulation characteristics which can reduce the heat loss under the normal operation and can be sufficiently capable to remove large decay heat during accidents.rnThis paper provides the outline of our study mentioned above.