Evaluations of LEU Conversion Impact on the High Temperature Experiment Performance at the MIT Reactor

摘要

The LEU conversion impact on the high temperature experiment performance at the MIT Reactor has been investigated in this study, with focuses being placed on reactivity worth and nuclear heating capability. The major conclusions can be summarized as follows: 1. The reactivity penalty of the HTIF experiment is less significant in the LEU core than that in the HEU core by ～ 30%, due to the harder neutron spectrum in the former. This implies a generally larger reactivity margin for in-core experiments with use of LEU fuel. 2. The overall impact on the HTIF nuclear heating due to LEU conversion is a 14% reduction, since U-Mo (LEU) fuel is more dense than U-Alx (HEU) fuel. This is because the gamma attenuation effect in the former is significantly stronger. 3. Based on thermal analysis, the average and maximum HTIF temperature in the 7 MW LEU core is lower than that in the 6 MW HEU core by no more than 50℃. This implies that the nuclear heating capability influence on the high temperature experiment performance is insignificant. 4. Compensating the reduced nuclear heating may be feasible by adding irradiation materials (e.g. by increasing the size of tungsten sample holder), since there is sufficient reactivity margin with LEU fuel as compared with that of the reference HEU core.