Design And Research Of Basket-fuel-assembly Molten Salt Reactor

The Molten Salt Reactor,utilizing molten salt as coolant,is one of the six fourth generation candidate reactors?Gas-Cooled Fast Reactor?GFR?,Lead-Cooled Fast Reactor?LFR?,Molten Salt Reactor?MSR?,Sodium-Cooled Fast Reactor?SFR?,Supercritical-Water Reactor?SCWR?,Very-High-Temperature Reactor?VHTR??.The representatives of the modern MSR designs based on solid fuels include the Advanced High Temperature Reactor?AHTR?put forward by ORNL,the Pebble-bed Advanced High Temperature Reactor?PB-AHTR?put forward by UC Berkeley and Thorium based Molten Salt Reactor?TMSR?initiated by the Chinese Academy of Science through its Shanghai Institute of Applied Physics?SINAP?.Based on these three reactors designs,we have designed a new kind of solid fuel MSR,named Basket-FuelAssembly Molten Salt Reactor?BFAMSR?.It combines the advantages of assemblies,molten salt coolant and the TRISO coated particle fuel elements and can operate at high temperatures with good neutron economics and safety.The use of Basket-FuelAssembly in Molten Salt Reactor enables the utilization of mature fuel loading techniques similar to that of water cooled reactors.In this thesis,the fuel assembly is designed and its feasibility and behavior are investigated by analyzing the infinite multiplication factor k_inf,the Temperature Reactivity Coefficient?TRC?and the void reactivity?VR?of the FLi Be coolant as a function of the material composition,material density,the thickness of the fuel assembly container,the TRISO coated particles packing factor?PF?and the enrichment of ⁷Li in FLiBe salt.The results show that carbon-based container is significantly better than silicon-carbide-based container for the fuel assembly.Increasing the TRISO particle packing factor and the enrichment of ⁷Li helps to improve the neutron economy and security property of the reactor.Based on the design of fuel assembly,the thesis analysed the neutron feasibility of the BFAMSR from the point view of economics and security.Through the calculation of the neutron physical parameters such as keff by the MCNP code and the calculation of the burnup by the MCNPX code,the effects of the container thickness of the assembly and the packing factor of the TRISO particles on the maximum burnup attainable and the temperature reactivity coefficient of the reactor was investigated in detail.The result shows that the coolant temperature reactivity coefficient CTRC,the coolant void reactivity coefficient CVRC and the full void reactivity coefficient FVRC are not completely negative,only if the packing factor is greater than 5%-35%?depending on the container thickness?.According to the results of the feasibility study,the parameters for the BFAMSR is determined and the neutron physical parameters required for the whole reactor designs are calculated which includes neutron energy spectrum,neutron flux distribution,burnup,power distribution and temperature reactivity coefficients etc.In the end,four fuel loading patterns for the BFAMSR based on fuel management strategy of the water reactors are proposed and discussed in terms of the economy and security of the reactor.It is found that the in-out loading pattern has the highest burnup and duration time,the worst neutron-flux and power distribution,and the lowest neutron leakage.The out-in pattern possesses the most uniform neutron-flux distribution,the lowest burnup and the total duration time,and the highest neutron leakage.The out-in partition alternate pattern has slightly higher burnup,longer total duration time and smaller neutron leakage than that of the out-in loading pattern.Moreover,its alternative distribution of fuel elements cut down the refueling time.The low-leakage pattern has the second high burnup and the total duration time among the four loading patterns,and its neutron-flux and power distributions are the second only to the most uniform out-in loading pattern.