Determination of the LEU core safety parameters of the MNSR reactor using the MCNP4C code

Comparative studies for the conversion of the fuel from HEU to LEU in the Miniature Neutron Source Reactor (MNSR) have been performed using the MCNP4C code. The safety parameters like: the effective multiplication factor (keff), excess reactivity (ρex), control rod worth (CRW), shutdown margin (SDM), safety reactivity factor (SRF) and delayed neutron fraction (βeff) for the existing HEU fuel (UAl4-Al, 90% enriched) and the potential LEU fuels (U3Si2-Al, U3Si-Al and the U9Mo-Al, 19.75% enriched) were investigated in this paper for the MNSR using the MCNP4C code. The results showed for the existing HEU fuel and the potential LEU fuels that the control rod shutdown margins were: 2.587, 2.295, 2.325 and 2.165 mk. The control rod worths were: 6.54, 6.16, 6.09 and 6.05 mk. The safety reactivity factors were: 1.648, 1.588, 1.611 and 1.551. The delayed neutron fractions were calculated to be: 7.54×10-3, 7.48×10-3, 7.29×10-3 and 7.57×10-3 for the UAl4-Al, U3Si2-Al, U3Si-Al and the U9Mo-Al fuels respectively. Finally, the safety parameters of the LEU fuels are in good agreements with HEU results and all types of the LEU fuels can be suitable candidates for the fuel conversion in the future.