The next-event estimator in the MORSE multigroup Monte Carlo code has been extended to include Klein-Nishina scattering and annihilation radiation from pair production for both the forward and adjoint modes of calculation. A formulation for the solid angle subtended at a point by a cylinder has also been used in the estimator. These procedures have been included in the investigation of the gamma-ray environment of a remote fuel reprocessing facility. Calculational results are presented which indicate the validity and efficiency of the developed methods as compared to those in standard use.