VARIANT - variational anisotropic nodal transport

VARIANT solves the multigroup steady-state neutron diffusion and transport equations in two- and three-dimensional Cartesian and hexagonal geometries using variational nodal methods. The transport approximations involve complete spherical harmonic expansions up to order P{sub 5}. Eigenvalue, adjoint, fixed source, gamma heating, and criticality (concentration) search problems are permitted. Anisotropic scattering is treated, and although primarily designed for fast reactor problems, upscattering options are also included. Variational nodal methods incorporate a number of attractive features. These include a standard hierarchy of space-angle approximation, well behaved small mesh limits, and the absence of both ray effects and artificial diagonal streaming depressions. Dimensionless parts of the response matrices involving integrals in space and angle are pre-computed once using MATHEMATICA for each geometry option. The results are stored in FORTRAN data statements and used to generate response matrix sets for unique nodes (defined by cross section and dimension data) prior to fission source iteration. Anisotropic scattering (up to order P{sub 5}) is also available. VARIANT achieves near Monte Carlo accuracy at a fraction of the cost.