The findings of Kalambokas and Henry, about the representation of light water reactor reflectors by boundary conditions, are the basis for the development of a practical scheme for the elimination of the reflector from two-group diffusion calculations of a pressurized water reactor. Boundary conditions are generated once, from a full-sweep diffusion calculation of the core and reflector, then used in short core sweeps to calculate power distributions and criticality for any change in core properties.