Abstract

In recent years SMRs have received a lot of attention due to their small size and portability, as well as some nuclear propulsion. In this research, VVER-1000 fuel assembly has been used as a basis and has been compacted and reduced by special methods and arguments. In this paper, a hexagonal fuel assembly without soluble boron and rely on suitable burnable absorbers has been designed and proposed for use in the SMRs. The objectives of this research are elimination of boric acid from the coolant, determine the number of fuel rods and guide channels inside the fuel assembly, determine the optimal arrangement of fuel rods and guide channels inside the fuel assembly, keeping the fuel to moderator ratio and determine the appropriate dimensions Boron-free hexagonal fuel assembly for use in SMR reactors. Also, one of the challenges of this design was to keeping the ratio of fuel volume to moderator of the VVER-1000 reactor fuel assemblies for SMR reactor, which was solved with neutronics and safety considerations. Due to the maintenance of the fuel volume to moderator ratio, pitch of fuel rods of the VVER-1000 reactor is also intended for the boron-free fuel assembly. Also the desired cycle length for the designed fuel assembly is about 40 month, for which the fuel enrichment has been set at 6.6%. According to increase in fuel enrichment in the SMR cores, the reactivity at the beginning of the cycle is very high, therefore, this reactivity needs to be compensated. One of the most important challenges and concerns in this research is the control of reactivity at the beginning of the cycle, during the cycle and the reduction of the radial power distribution In the absence of boric acid, the burnable absorber of gadolinium was solved problem with proper design. The designed boron-free fuel assembly has 156 fuel rods, 12 guide channels and 1 central tube. It should be noted that MCNP and WIMS codes have been used to simulate fuel assembly and also to ensure the correct design process.