A three-dimensional MCNP-based fluence computational software package is developed for accurate, BWR, three-dimensional, continuous-energy, neutron and gamma fluence and dose computation. The 3D MCNP model is established based on actual heterogeneous BWR core geometry rather than on conventional homogenized reactor core geometry. This software package will be a useful tool for computing accurate BWR fluence and for benchmarking existing, less precise methodologies.