Nuclear reactor using pressurised water coolant - has elastically supported columns holding fuel assemblies in place between grids

摘要

An internal structure for a nuclear reactor, with a core comprising a number of fuel assemblies and a number of movable control rods, incorporates a lower, an intermediate and an upper grid, all joined to the reactor vessel, and a number of vertical support columns. The fuel assemblies are fixed on the lower grid. The support columns extend between the upper and intermediate grids. Each column is joined at its upper end to the upper grid by an elastic system, deformable in the vertical direction. Each column has at its lower end, above the intermediate grid, a pair of centering pins, symmetrical about the axis. These pins pass through the holes in the grid into holes in the upper end-piece of the fuel assembly, supporting the end of the column on the end of the assembly. Faults of current methods are obviated in which the elastic systems consist usually of four leaf springs joined to the upper end-piece of the core assembly by screws. These faults are the limited strength of the springs because of the small space available to them, their nearness to the fuel, weakening the, through irradiation, and inconvenience during charging and discharging the reactor.