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This report presents the results of the Task 4, defined in working program as: evaluation of reactivity feedback coefficients. Three main parameters of the Fertile-Free Fuel (FFF) lattices were evaluated: Moderator Temperature Coefficient (MTC), Fuel Temperature Coefficient due to Doppler Effect (DC), and soluble Boron reactivity worth (BW).

One of the major design challenges associated with utilization of FFF is deterioration of the temperature coefficients and control materials reactivity worth caused by high thermal cross-section of Pu and consequent hardening of the neutron spectrum. The purpose of the investigation reported in this section is to estimate the potential of addition of different burnable poison (BP) materials to improve reactivity feedback coefficients without significant deterioration of control materials worth. Therefore, each parameter was evaluated for all BP design options. For each design option, i.e. BP material and geometrical arrangement, one design was selected, that with sufficient loading of BP material to ensure operationally acceptable maximum soluble boron concentration. These BP loading values were determined in Task 3 of the current project.

List of calculated cases is presented in the following section, the case identification and associated design parameters are detailed in the previous progress report.


Mixed oxide fuels (Nuclear engineering); Nuclear chemistry; Nuclear fuel elements; Nuclear fuels; Nuclear reactors – Reactivity; Solid oxide fuel cells


Nuclear | Nuclear Engineering | Oil, Gas, and Energy | Radiochemistry