We have extended our earlier calculations of steady-state space- and angle-dependent thermalneutron spectra in small beryllium assemblies to assemblies of much greater transverse dimensions and have studied neutron diffusion up to much greater distances from the source plane, with a view toward looking for a discrete mode of decay. We find that in the forward direction, neutron distribution fails to attain equilibrium inside 140-cm-thick assemblies with transverse dimensions of 150 × 150 cm2, whereas in the backward direction, equilibrium is reached even inside an assembly of transverse dimensions of 80 × 80 cm2. We show that in the forward direction, equilibrium is delayed by the presence of a penetrating beam of uncollided sub-Bragg neutrons of the source. Thus, an experimentalist can hardly hope to observe equilibrium in the forward direction. The calculated value of diffusion length is in excellent agreement with the observed as well as the theoretical values obtained by earlier workers.