Gamma-rays of some principal fuel nuclei excited by monochromatic neutrons

Gamma-ray spectra in the interactions of 232Th, 235U, 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, n'γ)-, and 238U(n, n'γ)-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. (orig.)