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The transmutation of minor actinides in a fast reactor is investigated by a new method to investigate the transmutation behavior of individual minor actinides. It is found that Np-237 and Am-241 mainly contributes to the transmutation rate though the transmutation behaviors are very different.

The purpose of this paper is to apply our improved method for calculating sensitivities and uncertainties of reactivity responses for UO2 and MOX fueled pressurized water reactor cells. The improved method has been used to calculate sensitivity coefficients relative to infinite dilution cross-sections, where the self-shielding effect is taken into account. Two types of reactivities are considered: Doppler reactivity and coolant void reactivity, for each type of reactivity, the sensitivities are calculated for small and large perturbations. The results have demonstrated that the reactivity responses have larger relative uncertainty than eigenvalue responses. In addition, the uncertainty of coolant void reactivity is much greater than Doppler reactivity especially for large perturbations. The sensitivity coefficients and uncertainties of both reactivities were verified by comparing with SCALE code results using ENDF/B-VII library and good agreements have been found.

The effect of anisotropic scattering has been studied in UO2 and MOX fueled LWR cells and cores. The effect is negligibly small for UO2 fueled cells, but the effect is remarkable for the MOX fueled cells and cores. For the MOX fuel cells, the anisotropic effect decreases kinf by 0.15 ∼ 0.23% Δk/k depending on the moderator to fuel volume ratio. For small UO2 and MOX cores, the anisotropic scattering leads to the flux peaking in water reflectors, and the increase of neutron absorption in the reflector decreases keff remarkably.