A design study of 900MWt lead cooled reactor cores for transmutation of TRUnuclides from LWR spent fuel is performed to assess the feasibility of the core design having a small burnup reactivity swing and a uniform fuel composition of the mono-nitride form. The reactor core is designed to be consisted of uniform composition fuel rods having mono-nitride fuel (U~(14)N-TRU~(14)N) by using the burnable absorber (B_(4)C) rods and vacancy rods for power flattening. A parametric study is performed by changing the fuel rod diameter, the boron enrichment and mass ratio of plutonium-to-minor actinide nuclides in the external feed to investigate the effects of these parameters on the core performances including the transmutation rate, fuel Doppler coefficient, coolant void reactivity, burnup reactivity swing and so on. From the results, it is shown that (1) the cores having B4C burnable absorber rods and moderator rods can be designed to have a supporting ratio of approx1.0, a burnup reactivity swing of approx900pcm, and a reasonable value of the fuel Doppler coefficient, (2) an adjustment of plutonium-to-minor actinide nuclides in the external feed is very effective way to reduce the burnup reactivity swing, the cores having 100(percent)MA in the external feed have nearly zero burnup reactivity swing (less than 1dollar) and supporting ratio larger than approx10 for MA transmutation, (3) these cores have negative reactivity coefficients except for the coolant expansion reactivity coefficient which can be effectively compensated by the other negative reactivity coefficients.
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