Energy spectrums of slowed neutrons in heterogeneous uranium-carbon and thorium-carbon fission media
Using the Geant4 and OpenMC Monte Carlo codes, the energy spectra of moderated neutrons were studied in homogeneous uranium dicarbide and uranium dioxide media, as well as in heterogeneous uranium and carbon and thorium and carbon channel type fission structures with various compositions and lattice parameters. In homogeneous uranium dicarbide the spectral maximum lies in the from 20 to 50 keV range, which is important for the design of a prototype fast single channel reactor operating in the traveling wave fission mode with a soft fast neutron spectrum. A heterogeneous thorium and carbon medium that forms a thermal neutron spectrum has been identified, enabling the realization of a traveling wave mode of neutron nuclear fission on thermal neutrons. By varying channel lattice parameters and introducing burnable absorbers (Cd, In), the possibility of forming a super thermal neutron spectrum (from 1 to 20 eV) in a heterogeneous uranium and carbon medium was demonstrated. The results are useful for the development of nuclear transmutation reactors and next generation reactors operating in the traveling wave mode.