The effect of cylindrical holes in a moderator on the passage of virgin neutrons from a point source

The mean free path and the mean square free path of 14 MeV neutrons, generated isotropically from a d-t point source located at the center of the moderator region of a square lattice composed of parallel circular cylindrical holes in water, are calculated for various void ratios. Very interesting inequalities between the axial and transversal components of the mean free path and the mean square free path are found, which contradict with the results of Behrens for homogeneous neutron sources. We may conclude that the effects on the free path lengths of the position of the point source located in an anisotropic and heterogeneous medium cannot be neglected. (author)