Approximate calculation of isotope ratio of a fast breeder reactor under self-sustaining mode of operation

The iteration method of isotope ratio calculations for a fast breeder type reactor under self-sustaining mode of operation, assuming the linear dependence of plutonium concentration on time and considering the reactor batch loading, is described. The results of calculation of the proper plutonium isotope ratio for the fast breeder reactor on dissociating N2O4 coolant are given. The method is intended for calculation of isotope ratio of the fast breeder type reactor with the batch loading taking into account the burnup in the reactor core and plutonium generating in the screens. The method uses the results of critical base version calculated on arbitrary isotope ratio of plutonium. Testing of this method shows its convergence and agreement with estimated data. The method has been verified by the direct calculation following SINVAR-2 program