An analytical procedure is described for the early-time asymptotic solution of a partial-differential integral equation of the parabolic type. Several applications to the analysis of the early stages of space-dependent nuclear reactor transients are presented. The one-energy-group diffusion model with a “Newton law of cooling” linear feedback is employed. Physical interpretations of the results are given. Comparisons with results obtained by different formulations of the point-kinetic method are performed.