Nuclear reactor fuel element sub-assemblies

A fuel element sub-assembly for a liquid metal cooled fast reactor is described. It comprises a bundle of fuel pins enclosed by a tubular wrapper having a lower end journal for plugging into an aperture in an upper wall of a core support structure and a spike bar for plugging into an aperture in a lower wall of the core support structure. The spike bar has a loading disk rigidly attached to its free end for engaging the aperture in the lower wall of the core support structure, with means for sealing against entry of liquid metal from between the walls of the core support structure to the cylindrical engagement surfaces of the aperture and loading disk. The sealing means may comprise a sealing bush and a flexible bellows extruding between the bush and the spike bar, the sealing bush being laterally movable on the spike bar. The sealing bush may have scarfed metal rings for effecting a seal between the walls of the aperture in the lower-wall of the core support structure and the external surface of the sealing bush. The loading disk may have a tapered extension to provide a lead-in surface to facilitate engagement with the apertures in the walls of the core support structure. The construction lessens liability to rattling of the fuel element sub-assemblies and aids removal for replacement. (U.K.)