SAS2 Depletion and Source Term Sequence

SAS2 is a control module that processes fuel assembly cross sections, computes photon and neutron source spectra and evaluates dose rates from spent fuel casks using a one-dimensional transport shielding analysis. The execution includes: repeated passes through BONAMI, NITAWL, XSDRNPM, COUPLE, and ORIGEN-S for cross-section processing and fuel burnup; radiation source computations; the radial shipping cask shielding analysis applying the calculated spent-fuel composition and sources; and the final determination of dose rates by XSDOSE from the angular flux leakage. The neutron flux used to update the cross sections during the depletion is based on a one-dimensional model of the fuel assembly. Typically, SAS2H is used only for the depletion/decay portion of the analysis and SAS1 or SAS4 is used for the shielding evaluation.

The SAS2 module (also known as SAS2H) was originally developed to perform a depletion/decay calculation to obtain spent fuel radiation source terms that were subsequently input automatically to a 1-D, radial shielding analysis in a cylindrical geometry. Over time the depletion/decay portion of the SAS2 module has been significantly enhanced and its use for spent fuel isotopic characterization and radiation source term generation has increased. Interfacing to the other shielding modules has been provided so that radiation source terms calculated with SAS2 can be used in the other SCALE shielding sequences.