Optimal design of a Small Modular Reactor core with dual cooled annular fuel based on the neutronics and natural circulation parameters

Abstract

Small Modular Reactors (SMRs) are the creative design of nuclear reactors that have received considerable attention in recent years. Since there is insufficient operational experience in SMRs, extensive research on these types of reactors may be needed to improve the current level of these systems performance. Also, one of the approaches which can help the enhancement of a reactor power is changing its fuel geometry. For this purpose, as well as decreasing the maximum fuel temperature in the reactors, the technology of annular fuels with the ability of internal and external cooling shows its importance. The nuclear SMRs with annular fuel which is cooled internally and externally has the potential to increase high power density while maintaining a sufficient safety margin. The benefit of the dual cooled annular fuel design is that heat can be transferred to the coolant at both the outer and inner channels. Hence, in this study, for the first time, dual cooled annular fuel in the Small Modular Reactors is considered and studied thoroughly. In this paper, neutronics and natural circulation parameters are calculated for an SMR with Annular Fuel which is cooled internally and externally, with changes of the internal radius. By analyzing the fuel internal radius changes in a specific range via the neutronics and computational fluid dynamics (CFD) simulation codes, the effects of power peaking factor, effective multiplication coefficient and natural circulation parameters are investigated. For the purpose of data fitting, an artificial neural network is trained using the observed data. The input consists of different internal radiuses which yields to output consisting effective multiplication factor, power peaking factor and natural circulation parameters. The Optimal geometry of annular fuel is determined using the neural network by implementing the genetic algorithms based on these neutronics and natural circulation parameters. Finally, using a simulated optimal geometry in the hot channel by neutronics and CFD simulations, thermal–hydraulic and neutronics calculations are accomplished, and these parameters are compared with the conventional SMR which uses solid (conventional) fuel. One of the main results of the evaluation is that optimal internally and externally cooled fuel in the presented SMR has a satisfactory margin for the departure from nucleate boiling (DNB) and maximum fuel rod temperature relative to the solid fuel which is used in the conventional SMRs. Indeed, fuel center temperature of conventional SMR is much more than that of presented optimal SMR. Also, presented optimal geometry increases the core effective multiplication coefficient which leads to increase in the excess reactivity. Also, reduces total power peaking factor and improves natural circulation parameters compared to the conventional SMR.