Experimental study on convectional heat transfer characteristics of argon space in the pool-type fast reactor vessel

Abstract

A large amount of sodium is used as coolant in the pool-type fast reactor, and argon is used as covering gas in the top part of main vessel. At the top of the main vessel, an annular cavity is formed between the rotating plug and its support, where natural convection of argon is formed. This kind of structure makes the heat transfer complicated at the top of main vessel. Excessive temperature or large temperature gradient at the top of main vessel may occur. Therefore, it is necessary to carry out analysis of the temperature distribution at the top of the main vessel. Many researches based on CFD have been carried out on the analysis of the top domain, but few of them are verified by experiment. In addition, a few experiments have been performed using simplified facility, which is not so similar to the real geometry. Therefore, a scaled-down Heat-transfer Experimental Facility for Argon space at the top of main vessel (HEFA) is established, which is much similar to the real geometry. In HEFA, the annular gap is kept, in addition, a heated stainless bottom plate is used to simulate the liquid sodium surface. Two conditions were set up, one for vacuum, the other for argon. The temperature of the facility was measured in the two conditions. By comparing the results of two condition, the results show that convection of the argon increases the overall temperature of the roof slab and reduces its temperature gradient of roof slab. The circumferential temperature difference at annular gap around rotating plug was observed in the argon condition. It is judged that the circumferential temperature difference is caused by natural convection in the annular gap with one side rising and the other falling. This phenomenon must be paid much attention in the design of SFR.