Experimental And Simulation Research On Leakage And Solidification Characteristics Of High Temperature Molten Salt

Molten salt reactors have received extensive attention and research,due to the advantages such as continuous refueling and online processing of fission products,high-temperature and low-pressure operation,and inherent safety.During the design and operation of molten salt reactors,the problem of molten salt leakage is an unavoidable safety issue in the safety of molten salt reactors.Therefore,mastering the phenomenon of molten salt leakage accidents,the development process and the containment method of leaked molten salt(LMS)are technical problems that need to be solved in the development of molten salt reactors.Based on the above objectives,this thesis carried out experimental and simulation research on molten salt leakage.First,the molten salt leakage experiment device was designed and built,and the leakage experiment of nitrate molten salt(HTS)leaking to the aluminum silicate fiber(ASF)insulation cotton was carried out,and the research on the penetration characteristics of molten salt in the insulation layer was completed.The research results show that the LMS flowing onto the ASF penetrates and diffuses in it,and cannot form an obvious temperature gradient,that is,the LMS in the ASF cannot be solidified during the leakage stage.As the leakage rate increases,LMS will penetrate and seep out from the bottom surface of the ASF.The greater the LMS flow rate,the shorter the time for LMS to penetrate the ASF,and the lower the quality of molten salt consumed.At a lower LMS flow rate,as the LMS temperature and the ASF thickness increases,the time for the molten salt to penetrate the ASF and the amount of the LMS consumed increase significantly;while at a larger LMS flow rate,the time to penetrate the ASF and the amount of the LMS consumed will decline rapidly,and will hardly change as the LMS temperature and the LMS flow rate increase.Secondly,the CFD method was used to study the diffusion,penetration and solidification and melting phenomena of fluoride salt leaking onto the quartz sand layer.The research results show that after the molten salt leaks into the sand layer,it diffuses and penetrates on the surface and inside the sand layer.Due to the cooling of the environment and the temperature distribution of the sand layer,the bottom area of the leaked molten salt will gradually solidify,making the axial penetration depth of molten salt in the sand layer gradually stable,the LMS only spreads radially near the surface of the sand layer.For molten salt leakage in a certain time span,as the LMS temperature and flow rate increase,its radial diffusion radius and axial penetration depth also increase.Finally,based on the research results,a new solution for the collection and heat insulation of molten salt under the fluorine salt leakage accident of molten salt reactors is proposed,which provides a new idea for mitigation measures after the accident.