Bryntrn: A Baryon transport model

This report describes the development of an interaction data base and a numerical solution to the transport of baryons through an arbitrary shield material based on a straight ahead approximation of the Boltzmann equation. The code is most accurate for continuous-energy boundary values but gives reasonable results for discrete spectra at the boundary using even a relatively coarse energy grid (30 points) and large spatial increments (1 cm in H₂O). The resulting computer code is self-contained, efficient, and easy to use. The code requires only a very small fraction of the computer resources required for Monte Carlo codes.