Study of more efficient models for reactor vessel fluence calculations

In support of the plant life extension program it is necessary to determine the reactor vessel fluence. In this determination transport calculations for the fast neutrons (> 0.1 MeV) are performed over the life of the reactor. This study reevaluates the appropriateness of the assumptions commonly used in such analyses. A review of this depth is generally too costly to perform for every series of calculations, but it is seen as useful for calculations that will be needed to evaluate the ex-vessel cavity dosimetry. The results of this study reinforces that the standard approach used is adequate, but additional savings may be observed by simplifying the problem. Limiting the range of neutron energies to only those required can reduce the computation cost by a factor of two. Additionally the use of specific lower order quadrature sets can yield results comparable to those of higher orders