On the Treatment of First- and Last-Collision Effects in Neutron Age Theory

One limitation of conventional neutron age theory is that the first collision made by a particle when emitted by a source occurs right at the source. If a first-collision source is used explicitly, one no longer obtains an analytical solution, a principal advantage of age theory. In this Note, an approximate form that permits analytical solution is used for the distribution of first collisions in plane geometry. Substantial improvement over age theory results.