High-flux lead reactors with average neutron energies up to 1 MeV

Abstract

The paper is devoted to the physics and technology of special nuclear reactor operating on hard neutrons. As is known, a fast neutron spectrum is realized in sodium fast reactors (SFR) at neutron flux densities up to 8⋅1015 neutrons / cm2⋅ s. In SFRs the coolant and fuel limit the average neutron energy by a value of not more than 0.5 MeV, with a relatively small fraction,15%, of hard neutrons, En>0.8 MeV. Future high-flux reactors on hard neutrons, with an average neutron energy up to 1 MeV and neutron flux densities on the order of (3-5)⋅1015 neutrons / cm2⋅s, may be constructed and claimed in the medium term as multipurpose reactors that combine the functions of reactors - transmutators of minor actinides (MA), as well as isotope and research reactors. The requirements for obtaining a hard neutron spectrum in the core of the reactor lead to the need to use nuclear fuel and a coolant that slow moderate neutrons. Metallic fuel should be used as a fuel, and as a coolant - natural lead, whose isotopic composition accounts for the fraction of the slow-moderating 208Pb isotope a value of 52.3%. An even more harder neutron spectrum can be obtained in the case of using a coolant based on enriched at gas centrifuges 208Pb or radiogenic 208Pb extracted from lead-rich thorium ores. The next condition leading to a hard neutron spectrum is the small dimensions of core, D × H ≈ 0.5 × 0.5 meters, in which the initial neutron fission spectra of 235U, 239 Pu, 241Pu are not strongly changed. This requirement means that reactors on hard neutrons should be classified as small power or research reactors, within which their thermal capacity does not exceed a value of the order of 200-300 MW.