HELIOS2: simple procedure for generating two-group homogenized parameters

The recent nodal reactor theory has improved the nodal reactor analyses to the point where accurate three-dimensional nodal methods can successfully replace the detailed pin-by pin calculations, provided adequate homogenized parameters are available. That has been the driving force behind the continuing development of transport methods and lattice codes from one side and homogenization techniques from the other. The introduction of heterogeneous factors by Koebke (1984) in the Equivalence Theory followed by the General Equivalent Theory and the definition of the discontinuity factors by Smith (1985), significantly improved the results from homogenized nodal calculations at the time and basically made possible the subsequent advances in the nodal methods and higher order homogenization and re homogenization techniques. The purpose of this paper is to demonstrate the applicability of HELIOS2 (3) and its post processor ZENITH in a simple, analytical procedure to derive and study homogenization parameters in a multi-assembly domain of fuel assemblies and non-multiplying assembly area. The two-group homogenized parameters are generated in the multi-assembly transport calculation by HELIOS and then used in one-dimensional, two-group homogeneous diffusion problem solved in ZENITH. The procedure is used to generate discontinuity factors and albedo matrices for non-multiplying domain and to verify their dependence on exposure and calculation conditions. (Authors)