Gamma heating in LMFBR media

State-of-the-art approaches for the calculation of gamma heating in LMFBR core, blanket and reflector regions have been evaluated, with particular emphasis on coupled neutron-gamma methods/cross section sets. The major source of calculational error was found to be the apparent failure to impose a mass-energy balance on total gamma energy yield from neutron capture and other interactions in the preparation of representative neutron-gamma cross section sets. The applicability of many simplifying assumptions was demonstrated, including: volume-weighted homogenization, insensitivity to the shape of the gamma-source-spectrum, gamma energy deposition equal to gamma energy source more than 10 cm inside large zones of uniform composition, and the negligible effect of bremsstrahlung. A simple one-group method was developed to permit rapid, accurate estimation of the large (factor of 2) changes in the gamma energy deposition-to-source ratio possible near region interfaces. The approach, which also ensures conservation of mass-energy, was used in conjunction with coupled neutron-gamma computations to verify that previous experimental measurements of gamma heating in an LMFBR blanket mockup at M. I. T. were in accord with theoretical expectations within the experimental precision of +-10%