A Study of Several Methods for Analysis of Critical Assembly Heterogeneity

The methods for nonresonant cell homogenization in plate-type fast reactor critical assemblies are discussed and tested against high order S_n transport calculations in one-dimensional geometry. The methods tested show satisfactory agreement with transport calculations. The TESS calculations with bilinear flux-adjoint weighting are slightly preferred over flux weighting with either TESS or CALHET fluxes. Two different treatments of the leakage in the cell calculation lead to slightly different heterogeneity effects when calculated by flux weighting, but very little difference when calculated by bilinear weighting. A two-dimen-sional test problem gave some surprising results (negative heterogeneity factor) and has raised some unanswered questions.