General study on new MA burner concept being capable of flexible control of Plutonium inventory

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In the study done in the first year, a new concept of ultra-long life core loaded with minor actinide(MA) and metal diluent was examined, and the feasibility from the neutronic characteristics point of view was proved. Several parametric surveys were performed for the two core concepts! MOX fuel- sodium cooled core, and metal fuel-Pb cooled core, for burnup characteristics in order to clarify the effect of neutron spectrum. The comparison was done using three parameters that describe the process of nuclear reactions' direct fission, indirect fission, and capture. In the study done in the second year, a new semi-theoretical method was introduced to describe the effect of MA on burnup characteristics. The method was applied to an ultra-long life core, and the optimized initial MA loading was evaluated As the conclusions, the followings are obtained; 1) Np-237 shows bad effect on bumup in high neutron flux level So, it is desirable to load in low neutron flux level. 2) Blanket loaded with large amount of Np-237(57%,remainder is U-238) may drastically reduce the power distribution change due to Pu buildup. In the study done in the last year, neutronic characteristics of several candidates for metal diluent, Nb, Cr, W, Pb were measured in the KUCA B-assembly. The sample reactivity was successfully measured through the period method after determining the proper amount of sample loaded in the core. The most important issue of this kind of experiment is the error of reactivity due to the loading and unloading of the sample. Through the five trials, it was found that the error was negligibly small except the first measurement.