Collision probabilities in spatially stochastic media II

An improved model for calculating collision probabilities in spatially stochastic media is described based upon a method developed by Cassell and Williams [Cassell, J.S., Williams, M.M.R., in press. An approximate method for solving radiation and neutron transport problems in spatially stochastic media. Annals of Nuclear Energy] and is applicable to three-dimensional problems. We shall show how to evaluate the collision probability in an arbitrarily shaped non-re-entrant lump, consisting of a random dispersal of two phases, for any form of autocorrelation function. Specific examples, with numerical values, are given for a sphere and a slab. In the case of the slab we allow the material to have different stochastic properties in the x, y and z directions.