Research on the effect of heat pipe temperature oscillation on heat pipe cooled reactor operation

Heat pipes have been recognized as the unique equipment of heat absorption for heat pipe cooled reactor. The operating characteristics of heat pipe have the direct effect on the operation of the reactor system. In accordance with the results of the theoretical analysis and the experimental research, it has been confirmed that the heat pipe will have the temperature oscillation whether it has the horizontal operation or the inclined operation. In this study, the effect of temperature oscillation on heat pipe cooled reactor was preliminary investigated. The typical heat pipe cooled reactor named Kilowatt Reactor Using Stirling TechnologY (KRUSTY) was chosen for study. To simplify the analysis, the operating characteristics of heat pipe were approximated by setting the wall temperature change of condenser. As revealed by the simulated results, when the temperature of heat pipe oscillated, the fuel temperature would oscillate with the similar period leading to the significant periodic change of reactor power. Besides, the heat absorption of heat pipes would be significantly affected. Meanwhile, The longer the period and the larger the amplitude, the more obvious the effect on the reactor operation. For the KRUSTY reactor, even if the fuel temperature oscillation was only 8.0 K, there would be nearly 560 W change of reactor power which is about 12 % of the fission power. Moreover, the mitigation effect using the buffer layer was discussed. The simulated results suggested that the buffer layer with a smaller thermal diffusion coefficient could effectively reduce the temperature oscillation and the power oscillation, whereas it would lead to the higher reactor operating temperature, which might reduce the safety of the reactor system. All the discussions and analyses could contribute to the design of the heat pipe cooled reactor system and to the understanding of the real operating characteristics of this reactor system.