Calculation and comparison of xenon and samarium reactivities of the HEU, LEU core in the low power research reactor

摘要

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 and GETERA codes. The precise calculations of Xe-135 and Sm-149 concentrations and reactivities were carried out and compared during the MNSR operation time and after shutdown for the existing HEU fuel (UAl4-Al, 90% enriched) and the potential LEU fuels (U3Si2-Al, U3Si-Al, U9Mo-Al, 19.75% enriched and UO2, 12.6% enriched) in this paper using the MCNP4C and GETERA codes. It was found that the Xe-135 and Sm-149 reactivities did not reach their equilibrium reactivities during the daily operating time of the reactor. The Sm-149 reactivities could be neglected compared to Xe-135 reactivities during the reactor operating time and after shutdown. The calculations for the UAl4-Al produced the highest Xe-135 reactivity in all the studied fuel group during the reactor operation (0.39 mk) and after the reactor shutdown (0.735 mk), It followed by U3Si-Al (0.34 mk, 0.653 mk), U3Si2-Al (033 mk, 0.634 mk), U9Mo-Al (0.3 mk, 0.568 mk) and UO2 (0.24 mk, 0.448 mk) fuels, respectively. Finally, the results showed that the UO2 was the best candidate for fuel conversion to LEU in the MNSR since it gave the lowest Xe-135 reactivity during the reactor operation and after shutdown. (C) 2015 Elsevier Ltd. All rights reserved.