Gamma-Ray Production Cross Sections of Neutron-Induced Uranium-238 Reactions

The gamma-ray spectra produced by neutron-induced ²³⁸U reactions are analyzed, primarily using the statistical model, to provide the data for gamma-ray heating and shielding in the nuclear reactor. The gamma-ray spectra in the low energy neutron capture were calculated by taking into account the discrete and the continuous energy levels, and E1, M1, E2, and M2 electromagnetic transitions. The transition probabilities for primary gamma rays were taken from the data of Price et al. The calculated data are compared with John’s experimental data and Yost’s calculations. To calculate the gamma-ray spectra due to inelastic neutron scattering, the E2 and M1 transitions of the lowest 13 discrete levels of ²³⁸U were calculated by using the rotational vibrational model of Bohr-Mottelson. The gamma production cross section due to fast-neutron reactions (E_n > 2 MeV) and the prompt gamma-ray spectrum due to fission were calculated by taking into account the yrast levels in the cascade process, as proposed by Thomas and Grover. The calculated prompt gamma-ray spectrum and the total gamma-ray production cross section are discussed in comparison with the experimental data.