The development of high temperature heat-pipe transient model for system analysis of heat pipe cooled microreactor

Abstract

The miniaturization of nuclear reactor power is the direction of nuclear energy development in the future. A nuclear power system with a small solid core and cooled by a high-temperature alkali metal heat pipe has excellent safety performance. The start-up of the heat pipe cooled reactor depends on the heat pipe start-up characteristics from the frozen state, so transient analysis models of high-temperature heat pipe from the frozen state are established in this paper for the system characteristics analysis of the heat pipe cooled microreactor. The models include three stages of high-temperature heat pipe start-up from the frozen state: the molecular diffusion model of the free molecular stage, the flat-front model of the transitional flow process, and the 2-D thermal resistance network model of continuous flow. The energy conservation model is also used to consider the phase transition between solid, liquid, and gas. And The heat transfer limit model of heat pipe has been also coupled in the model. The models have been verified by the start-up experimental dates of the sodium heat pipe and the transient experimental dates of the water heat pipe. Then the models are applied to the system analysis code of the heat pipe reactor to analyze the transient experiment characteristics of a typical heat pipe reactor system. The results show that the predicted trend by HPMR system code is reasonable and the deviation with experimental data is less than 2%, which further demonstrates the applicability and effectiveness of the heat pipe transient models.