Three-dimensional transmission coefficients for neutrons and photons in amorphous materials

We use Boltzmann’s transport equation to calculate the 3D incoherent Landauer equation for neutrons and photons diffusing in a slab of amorphous material. We use the P1 approximation to calculate the multiple-scattering transmission coefficient as a function of the diffusion coefficient. The 3D transmission coefficient obtained is smaller than the 1D case. The P1 result, valid only for thick slabs, is proved to be an excellent approximation to the exact solution.