Physical characteristics of fast power reactor fuel and their effect on the fuel cycle

In the paper, the influence of higher plutonium isotopes on the inherent fuel activity and radiation situation when fabricating fuel elements and handling plutonium fuel is analyzed. Contribution from AM-241 and Pu 236 decay products build-up to the total activity is evaluated as a function of time elapsed from fuel reprocessing, till reloading a reactor. Main physical characteristics of spent fuel from fast power reactors, i.e. fuel isotopic composition, residual heat release and activity values, are presented. Data are given on transuranium elements build-up values in the discharged fuel as a function of the fuel isotopic composition, on the transuranium elements build-up effect upon the activity and residual heat release in the discharged fuel. On the basis of the fuel, inherent activity requirements for the degree of fast reactor fuel fission-products decontamination by chemical reprocessing are determined. In the paper, the dynamics of the fuel residual heat release and activity variations are considered under conditions of reduced cooling times. The effect of the fuel delay time before its charging into the reactor upon the residual heat release value and neutron activity of the discharged fuel is evaluated. Engineering problems connected with the above mentioned fuel properties and arising from the spent fuel cooling time reduction in the external fuel-cycle systems are discussed on the basis of the material presented. In conclusion, the relations between different fuel-cycle steps and the influence of the external fuel-cycle time upon fast reactor power system development rates are considered