  Radiation transport codes require accurate nuclear cross sections to compute
particle fluences inside shielding materials. The Tripathi semi-empirical
reaction cross section, which includes over 60 parameters tuned to
nucleon-nucleus (NA) and nucleus-nucleus (AA) data, has been used in many of
the world's best-known transport codes. Although this parameterization fits
well to reaction cross section data, the predictive capability of any
parameterization is questionable when it is used beyond the range of the data
to which it was tuned. Using uncertainty analysis, it is shown that a
relativistic Three-Dimensional Lippmann-Schwinger (LS3D) equation model based
on Multiple Scattering Theory (MST) that uses 5 parameterizations---3
fundamental parameterizations to nucleon-nucleon (NN) data and 2 nuclear charge
density parameterizations---predicts NA and AA reaction cross sections as well
as the Tripathi cross section parameterization for reactions in which the
kinetic energy of the projectile in the laboratory frame ($T_{\rm Lab}$) is
greater than 220 MeV/n. The relativistic LS3D model has the additional
advantage of being able to predict highly accurate total and elastic cross
sections. Consequently, it is recommended that the relativistic LS3D model be
used for space radiation applications in which $T_{\rm Lab}>$ 220 MeV/n.
