Some remarks on the neutron elastic—And inelastic—Scattering cross sections of palladium

Abstract

The cross sections for the elastic-scattering of 5.9, 7.1 and 8 MeV neutrons from elemental Pd were measured at 40 scattering angles distributed between ≈15 and 160°. The inelastic-scattering cross sections for the excitation of Pd levels at energies of 260–560 keV were measured with high resolution at the same energies, and at a scattering angle of 80°. The experimental results were combined with lower-energy values previously obtained by this group to provide a comprehensive data base extending from near the inelastic-scattering threshold to 8 MeV. That data base was interpreted in terms of a coupled-channels model, including the inelastic excitation of one- and two-phonon vibrational levels of the even isotopes of Pd. It was concluded that the Pd inelastic-scattering cross sections, at the low energies of interest in assessment of fast-fission-reactor performance are large (≈50% greater than given in widely-used evaluated fission-product data files). They primarily involve compound-nucleus processes, with only a small direct-reaction component attributable to the excitation of the one-phonon 2 + vibrational levels of the even isotopes of Pd.