Fission rate measurements were performed in the Purdue Fast Breeder Blanket Facility (FBBF) and compared with two-dimensional 50-group diffusion calculations on an absolute basis. Fission rates in 239Pu, 235U, 237Np, 238U, and 232Th were measured using fused quartz fission track recorders. Calculations using the 1DX and 2DB codes, and the LIB-IV nuclear data library were compared with the measurements in the form of reaction rate calculated-to-experiment (C/E) trajectories. The investigations were aimed at providing an improved understanding and description of the high-energy neutron fluxes and reaction rate distributions. Also investigated were previously reported C/E reaction rate discrepancies in the blanket. Detailed analysis of the fine structure in the fission rate C/E trajectories, which drop off with increasing radius similar to previously reported C/E deviations, indicates that the transmission of neutrons through the blanket is being underpredicted to a greater degree at higher energies. Different C/E trajectories were found for different blanket configurations of the FBBF. Special computational studies, allowing fast neutron transmission and in situ effects to be separated, provided information on the sources of discrepancies.