Np, Am, Cm transmutation efficiency parameters taking account of neutron reaction rates

Abstract

Np, Am, and Cm transmutation efficiency parameters, taking account of the neutron reaction rates on all transuranium isotopes in all transformation chains initiated by introducing Np, Am, and Cm, are proposed for specialized transmutation facilities. These parameters can be helpful when comparing the efficiencies of different types of transmutation facilities and analyzing possible ways to increase the Np, Am, and Cm transmutation efficiency. The efficacy of including the parameters in the definition of transmutation efficiency is shown for a specialized transmutation facility. The possibility of evaluating the efficiency of Np, Am, and Cm transmutation in fast power reactors is examined taking account of the proposed parameters.As a rule, the efficiency of Np, Am, and Cm transmutation facilities is characterized by stationary parameters, specifically, the rate of equilibrium makeup by the transmuted isotopes and the number neutrons required to transmute one nucleus of an isotope. It is noted in [1] that additional parameters taking account of the rates of the radiative capture and fission reactions on all transuranium isotopes in all transformation chains initiated by introducing Np, Am, and Cm into the facility's fuel cycle must be included in order to evaluate the transmutation efficiency correctly.The present article proposes efficiency parameters that take account of neutron reaction rates. The efficacy of including such parameters in the evaluation of the transmutation efficiency is shown for a specialized transmutation facility. The possibility of determining Np, Am, and Cm transmutation efficiency in fast power reactors taking account of the proposed parameters is examined.For Np, Am, and Cm transmutation in a closed fuel cycle, it is desirable to introduce the concept of "initial isotopes," i.e., Np, Am, and Cm introduced into the facility's cycle from outside, i.e., from VVER. During refueling, this makes it possible to distinguish Np, Am, and Cm loaded from outside into the facility's transmutation cycle from the isotopes Np, Am, and Cm returned into the cycle from a preceding run. The transmutation of the initial Np, Am, and Cm signifies their conversion into fission products [2]. An act of transmutation of an initial isotope is an act of fission of the initial isotope itself and any isotope in the transformation chain of the initial isotope. All transuranium isotopes in the transformation chains of the initial Np, Am, and Cm (including plutonium isotopes) are viewed as non-transmuted initial Np, Am, and Cm isotopes. In what follows, transmutation applies to the initial Np, Am, and Cm isotopes proper.The approach proposed here is based on an analysis of the irradiation of a mass of initial isotopes, starting with the introduction of the mass into the facility's cycle. The mass (mixture) of the initial Np, Am, and Cm with a prescribed isotopic composition expressed as the number N 0 of nuclei is introduced into the facility's cycle at the time t = 0. The function ω(t) defined as ω(t) = q tr (t)/N 0 ,