An accurate evaluation of PWR pressure vessel fast neutron fluence is
essential to ensure pressure vessel integrity over the design lifetime. The
discrete ordinates method is one of the main methods to treat such problems.
In this paper, evaluations have been performed for three PWR benchmarks
described in NUREG/CR-6115 using ARES transport code. The calculated results
were compared to the reference values and a satisfactory agreement was
obtained. In addition, the effects of SN numeric and source distribution
modeling for pressure vessel fast neutron fluence calculation are
investigated. Based on the fine enough grids adopted, the different spatial
and angular discretization introduces derivations less than 3 %, and fix-up
for negative scattering source causes no noticeable effects when calculating
pressure vessel fast neutron fluence. However, the discrepancy of
assembly-wise and pin-wise source modeling for peripheral assemblies reaches
~20 %, which indicates that pin-wise modeling for peripheral assemblies is
essential. These results provide guidelines for pressure vessel fast neutron
fluence calculation and demonstrate that the ARES transport code is capable
of performing neutron transport calculations for evaluating PWR pressure
vessel fast neutron fluence.
Flux extrapolation models used in the DOT IV discrete ordinates neutron transport code
