Precise gamma-ray thermal neutron capture cross sections have been measured at the Budapest Reactor for all elements with Z=1-83,92 except for He and Pm. These measurements and additional data from the literature been compiled to generate the Evaluated Gamma-ray Activation File (EGAF), which is disseminated by LBNL and the IAEA. These data are nearly complete for most isotopes with Z<20 so the total radiative thermal neutron capture cross sections can be determined directly from the decay scheme. For light isotopes agreement with the recommended values is generally satisfactory although large discrepancies exist for 11B, 12,13C, 15N, 28,30Si, 34S, 37Cl, and 40,41K. Neutron capture decay data for heavier isotopes are typically incomplete due to the contribution of unresolved continuum transitions so only partial radiative thermal neutron capture cross sections can be determined. The contribution of the continuum to theneutron capture decay scheme arises from a large number of unresolved levels and transitions and can be calculated by assuming that the fluctuations in level densities and transition probabilities are statistical. We have calculated the continuum contribution to neutron capture decay for the palladium isotopes with the Monte Carlo code DICEBOX. These calculations were normalized to the experimental cross sections deexciting low excitation levels to determine the total radiative thermal neutron capture cross section. The resulting palladium cross sections values were determined with a precision comparable to the recommended values even when only one gamma-ray cross section was measured. The calculated and experimental level feedings could also be compared to determine spin and parity assignments for low-lying levels.

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Recent Work (2018)

We describe the new ENDF/B-VIII.0 evaluated nuclear reaction data library. ENDF/B-VIII.0 fully incorporates the new IAEA standards, includes improved thermal neutron scattering data and uses new evaluated data from the CIELO project for neutron reactions on H, O, Fe, U, U and Pu described in companion papers in the present issue of Nuclear Data Sheets. The evaluations benefit from recent experimental data obtained in the U.S. and Europe, and improvements in theory and simulation. Notable advances include updated evaluated data for light nuclei, structural materials, actinides, fission energy release, prompt fission neutron and γ-ray spectra, thermal neutron scattering data, and charged-particle reactions. Integral validation testing is shown for a wide range of criticality, reaction rate, and neutron transmission benchmarks. In general, integral validation performance of the library is improved relative to the previous ENDF/B-VII.1 library. 1 16 56 235 238 239