Improvements to the photon-production data for radiative capture in ENDF

High-quality photon-production data from thermal-neutron-capture reactions are important for many applications, including oil-well logging, planetary gamma-ray spectroscopy, and environmental techniques. Radiation transport codes usually access photon-production data from the national U.S. nuclear database, ENDF/B. To improve the photon-production data for thermal-neutron capture, we have compiled and evaluated the energies and yields of gamma rays for most naturally occurring isotopes with Z<31 and for a few heavier isotopes. The impact of improved photon-production cross sections for thermal-neutron capture in Cl is illustrated by comparing MCNP simulations and experimental measurements for a pulsed neutron oil-well logging instrument. The new compilation of photon-production data is being incorporated into the latest ENDF/B evaluations for each isotope and will be provided for future releases of the ENDF/B database.