Energy degradation matrix for inelastic scattering of neutrons

A new formulation is obtained for energy kernel, used in calculation of energy distribution of inelastic neutrons in shields, by taking account of successive emissions of neutrons. The formulated energy kernel is named ''Probability Density Matrix'' for energy degradation of inelastic neutrons because the kernel helps visualize cascade of energy degradation of neutrons through inelastic process as a form of probability of energy distribution. Contributions from discrete part and from continuum part of energy levels of residual nuclei are taken into account in calculation of matrix elements. As an example, the formulated probability density matrix is applied to calculate energy distributions of inelastic neutrons in Iron shield and compared with energy distribution obtained by ENDF/B-III data. As a result, it is found that ENDF/B-III data for energy distribution of inelastic neutrons in Iron are inadequate for application to shielding calculation because of contradiction of the energy distribution to experimental nuclear temperature. (auth.)