Data library and method of economizing radiation shielding calculations for laminar shields

A multigroup method of current synthesis with a short calculation time is described for those neutrons which are reflected from and transmitted through a slab shiels or a pipe-like cylindrical shield, composed of layers of different materials. In this method, one needs informations about energy dependence and geometry dependence of energy spectra to the currents of neutrons reflected from and transmitted through each constituent of layers. A set of equations is derived for description of the energy dependence so that one can generate all data for geometry dependence of energy spectra from fundamental quantities such as shield thickness in unit of mean free path for incident neutrons, cross section ratio Σsub(s)/Σsub(tot) for the incident neutrons, and ratio of inner radius to outer radius for the pipe-like cylindrical geometry. Values of all parameters included in these equations make a data library along with data on incident energy dependence of energy spectra for response currents to constituent materials. Synthesized energy spectra for currents agree fairly well with those calculated directly by ANISN code and MORSE-CG code. The current synthesis method is extended to gamma rays by incorporating gamma-ray data into the library, and is applied to the calculation of dose distributions for neutrons and gamma rays around spent fuel shipping casks. Dose values obtained by the current synthesis method agree with measured values within experimental error. (author)