In-house capability for deterministic neutron and gamma transport analyses has been implemented at Yankee Atomic Electric Company (YAEC). A detailed R-Theta (R-θ) calculational model of Maine 4ankee was developed to help in validation of the methods and to establish appropriate models for support of the ongoing Maine Yankee pressure vessel surveillance program. Several data and modeling sensitivity studies were performed and comparisons to measured dosimetry capsule data were emphasized. The calculated results establish confidence in the YAEC in-house computational methodology for general pressure vessel fluence analyses.