Gamma-Rays of some Principal Fuel Nuclei Excited by Monochromatic Neutrons

Abstract

Gamma-ray spectra in the interactions of ²³²Th, ²³⁶U, and ²³⁸U with neutrons of energies 0.7–2.0 MeV, 3.0 MeV, and 14.9 MeV have been measured. Above 300 gamma-transitions have been revealed. The neutron flux was determined using small fission chambers, activation foils, and scintillation counters. Gamma-ray excitation cross sections of the ²³²Th(n, nδ)-, and ²³⁸U(n, nδ)reactions obtained at neutron energies of 0.7–2.0 MeV and 3.0 MeV were transformed to the partial neutron scattering cross sections. The data indicate an appreciable level population by unobserved gamma-transitions from unknown high lying levels. Fission fragment gamma-ray intensities were determined at neutron energies of 3.0 MeV and 14.9 MeV in a time gate of 25 ns. The coincidence within experimental errors was found between 2⁺ – 0⁺ transition yields and independent yields of corresponding even-even fission fragments.