Sensitivity coefficients of the neutron and physical reactor parameters to the fuel inventory parameters

Required properties of fast reactor core with nitride fuel are reached only if the fuel it is loaded with is plutonium-based and has strictly determined (equilibrium) isotopic composition and strictly determined plutonium mass fraction (plutonium enrichment). It is suggested to use fuel composition representing mixture of nitrides of uranium and plutonium (U-Pu)N with power generation grade composition as the starting reactor core fuel load. It is known that at present extracted plutonium is stored in Russia at the “MAYAK” PA where it is kept packed in containers. It is not possible to predict exactly isotopic composition of plutonium which will be obtained after blending different batches of plutonium. Therefore, measures must be anticipated allowing compensating for the deviations of fuel isotopic composition and enrichment from the designed values. Algorithm accounting for such deviations is required for the purpose. Such algorithm can be built by calculating sensitivity of physical characteristics to the deviations of reactor fuel load. Two approaches to the calculation of sensitivities of reactor parameters to the variation of plutonium isotopic composition are examined. Numerical illustrations are presented as applied to fast nuclear reactor of BREST-300 type.