MCNP and CFD Modeling for Potential High-Power Configuration of Missouri S&T Reactor

Abstract

Utilization of nuclear research reactors is of high importance for education and training, research and development, and many other applications. However, less effective utilization encountered in research reactors is mainly due to limitations in power levels and related experimental facilities. Such limitations, however, have led different global owners of research reactors to consider upgrading the power levels of their reactors to accommodate the increase in utilization demands. To consider upgrading the power levels of research reactors without replacing major components, a pair of essential analyses must be performed, namely the neutronic evaluation of nuclear fission and thermal-hydraulic evaluation for heat removal from the reactor core. In this work, a conceptual upgrade to the core design and configuration of MSTR, or Missouri University of Science and Technology Reactor (200 kilowatts (kW)), is demonstrated. The conceptual design of the MSTR high-power configuration (MSTR-HPC) aims to achieve high neutron flux and demonstrate the power level and core configuration with greater flexibility and adaptability while not exceeding safety limits. The conceptual design of the MSTR-HPC involves uprating the power level to 2 megawatts (MW), reconfiguring the core, changing the fuel meat type, inclusion of a flux trap (FT) facility, and others. In addition, the conceptual design of MSTR-HPC includes three in-core irradiation facilities, namely FT, bare rabbit tube (BRT), and cadmium rabbit tube (CRT). The neutronic evaluation of the MSTR-HPC was carried out using the Monte Carlo N-particle Code (MCNP), version 6. In addition, the thermal-hydraulic behavior of MSTR-HPCs’ hot-channel has been assessed by means of ANSYS Fluent to evaluate the satisfaction of thermal-hydraulic safety requirements of the conceptual design. The results obtained have shown that the conceptual MSTR-HPC has demonstrated a maximum neutron flux obtained higher than that obtained in the current MSTR core by two orders of magnitude. The conceptual design of MSTR-HPC with composite BeO/graphite reflector blocks was able to sustain critically and operate continuously at full power for 61 days. In regards to the hottest fuel plate of MSTR-HPC, the results have shown that the determined temperature for the fuel plate regions was below the safety limits. In addition, at full operation power of the MSTR-HPC, the mass flow rate of 39.86 kg/s (10.644 gallon/s) was sufficient for removing the generated heat. In conclusion, the conceptual design of the MSTR-HPC has demonstrated its flux enhancement capabilities while maintaining safety limits, which are of high importance in enhancing reactor utilization for a larger window of time.