Isotope separation methods for self-consistent nuclear energy system

Abstract

It is known that for transmutation of fission products(FPs) in the concept of self-consistent nuclear energy system(SCNES) based on fast neutron reactor it is necessary to apply isotope separation of some FPs to keep neutron balance (to decrease parasitic capture of neutrons by stable isotopes). It is a question whether such FPs isotope separation can be feasible or not within amount of nuclear fission energy production. So it is necessary to consider isotopic content of FPs after fast reactor and to choose energetically appropriate isotope separation method for each radioactive FPs taking into account safe radioactivity level of FPs. In this paper we discuss about isotope separation method for SCNES. Isotopic composition of FPs was calculated using tables of fission yields from 239Pu fission. It isshown that concentrations of radioactive isotope in the main FPs to be isotopically separated are significant and vary from 2% in ruthenium up to 74% in iodine. We consider new isotope separation methods developed recently such as plasma separation process (PSP) based on selective ion cyclotron resonance heating and atomic vapor laser isotope separation (AVLIS) as a possible candidates. It seems to be energetically profitable to combine various methods to achieve desired separation characteristics. Since the most of FPs have a high initial concentration of radioactive isotope, PSP method seems to be a good candidate for first stages of separation process. We consider the main parts of energy expenditure in one PSP module and its separation characteristics. Estimations of energy consumption in multistage isotope separation process of FPs give maximum value 100keV/fiss. using PSP only and 3MeV/fiss. using AVLIS only. We can significantly decrease these values using AVLIS after PSP when concentration of target isotope in separation cascade will become sufficiently low. We can affirm that energy consumption in isotope separation of FPs is less than 60 MeV of electricity per one fission in nuclear reactor.