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This paper presents the results of a numerical calculation of beryllium poisoning of an IRT-T reactor and its effect on the excess reactivity and neutron flux density in the beam ports. Also, the prediction of 6Li and 3He poison concentrations in the beryllium reflectors of the IRT-T reactor is presented. The results are based on MCU Monte Carlo calculations. The part of reactor history was taken into account to predict reliable values of parasitic isotope concentrations. The impact of shut-down time and operating time on the excess reactivity is shown. The results presented in this paper could be used to perform the safety analysis of an IRT-T reactor.

The results of simulation of IRT-T reactor conversion from highly enriched fuel to new perspective low enriched fuel based on uranium-molybdenum alloy are given. Main characteristics of reacting core with the use of highly enriched and low enriched fuel are calculated. It is shown that impact of using new materials in fuel composition remains neutronic and thermal hydraulic characteristics of the core at an acceptable level.