The Streaming of Neutrons in Shields

The streaming of neutrons in narrow channels through thick shields is treated theoretically, using one-velocity diffusion theory. Scattering by the channel walls is evaluated, and it is shown how the entrance and exit of a channel affects its streaming current. The cases examined are the straight duct, gap, and annulus, offsets for the gap and annulus, and bends for the duct and gap. In all cases simple, approximate formulas are obtained.