Method for improving energy output of a nuclear reactor, method for determining natural uranium blanket for a fuel bundle, and a fuel bundle having a variable blanket layer

摘要

A method for improving the energy generating output of a nuclear reactor containing one or more fuel rods (100) in one or more fuel rod bundles (116) while satisfying a maximum subcritical banked withdrawal position (MSBWP) reactivity limit, enrichments of individual fuel rods in an axial cross-section of a lattice being evaluated at the top of the fuel bundle are ranked, and the fuel pins of the highest ranked rod location in the lattice are replaced with natural uranium pins. A core simulation is then performed to determine whether there is any margin to a MSBWP reactivity limit. For each lower ranked candidate rod position, the pin replacing and core simulation functions are repeated until no rod location violates the MSBWP reactivity limit, so as to achieve a desired lattice design for the top of the fuel bundle (116).