Power reactor core with fuel shuffling between cycles - has elements of lower reactivity in regions remote from flux gradient

摘要

A nuclear reactor core for power generation comprises fuel element assemblies which are shuffled from one region of the core in one operating cycle to a different region in the next operating cycle. The assemblies at positions remote from the neutron flux gradient have lower reactivity than the remaining element assemblies. Pref. individual fuel rods of an assembly have reduced reactivity compared with the other rods. In polygonal core where the assemblies are square in plan, the fuel element assemblies near the periphery in the first operating cycle contain fuel rods of reduced reactivity. Pref. these rods are located at the outer corners of the fuel assemblies. The arrangement is intended for improved utilisation of the rod for a given peak temperature in the core. The reduced reactivity may be obtd. by incorporating a neutron poison, pref. a poison which becomes consumed. A rod may contain only neutron poison and no fissile material.