Process for the control of the core of a pressurized nuclear water reactor

Abstract From the Canadian patent

The core of a pressurized water nuclear reactor is partly formed from dismantlable assemblies (10) whereof, the rods contain mixed UO2-PuO2 oxide pellets said, assemblies (10) being subdivided into concentric zones (12,14,16) with a plutonium concentration decreasing from the inside to the outside. At the end of each irradiation cycle, the rods (C3) located in peripheral zone (16) are discharged and the rods (C2,C1) located in the other zones (12,14) are transferred towards the outside of assembly (10) into zone (14,16) adjacent to that which they previously occupied. New rods C4) with a single enrichment are then introduced into the thus freed central zone (12). Figure lb.