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Study of Neutron Spectra Near the Surfaces of Iron and Water Spheres with 252Cf Sources at Their Centers

“…Hence, the neutron spectrum at the point under study near the sphere surface must contain a partial component with the spectrum of fission neutrons. It is known that the spectrum of instantaneous fission neutrons from 252 Cf nuclei includes three partial Weisskopf evaporation spectra with mean neutron spectral energies of 0.4, 2.0, and 2.8 MeV [22]. Therefore, the other neutrons, with the spectrum of instantaneous fission neutrons, i.e., predominantly neutrons with energies of <1 MeV in each of the above three partial Weisskopf evaporation spectra, are transformed into thermal and epithermal neutrons as a result of multiple elastic neutron scattering by hydrogen nuclei.…”

Studying Neutron Spectra at the Centers of the Metal Cores of Fast Research Reactors

“…Using these partial spectra, we simulated the spectra of prompt fission neutrons from 235 U nuclei and the spectra of fission neutrons scattered both elastically and inelastically by U and Mo nuclei incorporated in the nuclear fuel; by the U, Pb, and Cu nuclei constituting the material of the reactor core reflectors; and by the Pb nuclei constituting the material of the hollow cylinder at the center of the BR-K1 reactor core. When a component of the fission-neutron partial spectrum was formed in the neutron spectrum at the center of a reactor's metal core, we also used a representation of the spectrum of prompt fission neutrons from 235 U nuclei in the form of three Weisskopf evaporation spectra with mean energies of 2.8 (with a constant α = 0.69), 2.0 ( α = 0.97) , and 0.4 MeV ( α = 5) [11,12].…”

“…This table contains information on certain characteristics of the cores and their reflectors for the reactors under study. For purposes of comparison, the results from reconstructing the standard fission spectrum of 235 U nuclei exposed to thermal neutrons are given in the first row in both the Maxwellian form and in the form of a superposition of three Weisskopf evaporation spectra [11,12]. Table 3 presents the results from comparing the experimental and calculated cross sections for nuclear reactions in the neutron fields studied at the centers of the metal cores of fast reactors.…”

Experimental Study of the Deformation of Instantaneous Neutron Spectra from the Fission of 235U Nuclei in Fast-Reactor Core Materials

“…For the first time in the making of neutron measurements based on the physics of nuclear fission and experimental investigations of the energy spectra inside the cores of fast reactors, the spectrum of instantaneous nuclear fission neutrons F ( E ) was presented in an analytical form in [2,3] as a superposition of three similar Weisskopf evaporation spectra (2) where A W i is the contribution of the i th evaporation spectrum, and α W i are the constants of partial evaporation spectra.…”