Safety behaviour of a material testing reactor using U ₃ Si ₂ fuel during reactivity insertion accident

Abstract The performance of the nuclear reactor responding to any unexpected variation in reactivity is very important for reactor safety. Positive reactivity insertion causes power excursion and could have a destructive impact on the reactor core. Uranium silicide is considered to be well known accident tolerant fuel for the light water reactors due to their high metal density and high thermal conductivity. The aim of this study is to examine the thermal-hydraulic behavior of material testing reactor using U 3 Si 2 fuel during reactivity insertion accident. The analysis is done for MTR-22 MW reactor with the U 3 O 8 original fuel and the U 3 Si 2 fuel using PARET; a neutronics-hydrodynamics-heat transfer code. The calculated parameters are the reactor power and the temperatures of clad and fuel as a function of time for the hot channel. The calculations show that a direct replacement of U 3 O 8 by U 3 Si 2 will not have effect on the reactor safety. The results show that in both cases the fuel integrity is maintained during the accident demonstrating the inherent safety features of the MTR reactor. Moreover, the maximum fuel temperature for U 3 Si 2 during the accident is lower than that of U 3 O 8 due to its higher thermal conductivity confirmed that it will perform better in severe accidents.