Two-group Monte Carlo perturbation theory and applications in fixed-source problems

Abstract

The collision estimator is used in a second-order derivative sampling scheme for fixed-source problems involving a perturbation in the material density. The analytical formulation of a one-group problem in a finite slab with forward scattering is demonstrated to obtain exact expressions for the collision density and its derivatives. The track length estimator is also used for comparisons in some cases. Results are presented for a two-group multi-region problem using the MORSE code. The predicted collision densities in zones close to the source are found to be in excellent agreement with those obtained in full ‘re-runs’.