under Interagency Agreement DOE 1886-C000-9B

Vol. 2, Rev. 6F7.iii ORIGEN-S computes time-dependent concentrations and source terms of a large number of isotopes, which are simultaneously generated or d pleted through neutronic transmutation, fission, radioactive decay, input feed rates, and physical or chemical removal rates. The calculations may pert in to fuel irradiation within nuclear reactors, or the storage, management, transportation, or subsequent chemical processing of removed fuel elements. The matrix exponential expansion model of the ORIGEN code is unaltered in ORIGEN-S. Essentially all features of ORIGEN were retained, expanded, or supplemented within new computations. The primary objective of ORIGEN-S is to make it possible for the calculations to utilize the multi-energy-group cross sections from any currently processed standardized ENDF/B data base. This purpose has been implemented through the prior execution of codes within either the SCALE system or the AMPX system, developed at Oak Ridge National Laboratory (ORNL). These codes compute flux-weighted cross sections, simulating conditions within any given reactor fuel assembly, and convert the data into a library that can be input to ORIGEN-S. Time-dependent libraries may be produced, reflecting fuel composition variations during irradiation. Some of the other objectives included in ORIGEN-S are the convenience of free-form input