On Approximations to the Neutron Escape Probability from an Absorbing Body

The mathematical problem of approximating the neutron escape probability junction is studied through an analysis of the moment expansion of the junction. The problem with possible divergence of the expansion is identified and avoided by devising an alternative based on physical arguments. An approximation of general validity for any convex geometry is thus deduced that is simple, accurate, and convenient for use. As examples, numerical results are presented for three geometries: a sphere, a cylinder, and a slab.