Abstract: A nuclear reactor having a penetration seal ring interposed between the reactor vessel flange and a mating flange on the reactor vessel head. Radial ports through the flange provide passage into the interior of the reactor vessel for utility conduits that can be used to convey signal cables, power cables or hydraulic lines to the components within the interior of the pressure vessel. A double o-ring seal is provided on both sides of the penetration flange and partial J-welds on the inside diameter of the flange between the flange and the utility conduits secure the pressure boundary.

Abstract: A nuclear fuel assembly having improved dimensional stability to support aggressive fuel management wherein the fuel skeleton lateral stiffness is enhanced by the addition of a second joint attachment between the control rod guide thimble and spacer grid support sleeve.

Abstract: A fuel assembly for a boiling water reactor has a bundle of fuel rods consisting of a top tie plate and a bottom part which, together with a plurality of fuel rods, constitutes a rigid unit. The fuel rod bundle is surrounded by a fuel channel (1), to which there is attached a fixing member (2) cast in stainless steel. The fixing member (2) is attached to a vertical projection (3), extending from the top tie plate, by means of a bolt (4) which is loaded with a tensile force and a sleeve (10) which is loaded with a compressive force and which surrounds the bolt and is arranged in the fixing member, the coefficients of thermal expansion of the bolt and the sleeve being less than that of the fixing member.

Abstract: A nuclear fuel assembly has fuel rods connected to the lower end plate of the assembly. The connecting structure comprises an attachment plate which is superimposed on the lower end plate and which is formed with openings corresponding to the rods. The openings lead out into parallel grooves machined on the lower surface of the plate. Each rod comprises a lower part having three radial branches at 120.degree., each formed with an end extension projecting radially outwardly from the outline of the rod. The extensions engaged in a groove have a height substantially equal to the depth of the groove. Axial fixing and locking against rotation of the rods are thus ensured.

Abstract: A hold down device for a nuclear reactor of the type in which a plurality of assemblies are disposed between an upper plate and a lower plate, which hold down device comprises a member having at least two resilient means, for example leaf springs which, when the device is placed between the top of a first fuel assembly and the upper plate, and downward pressure is applied to the member, are applied against fuel assemblies adjacent the first fuel assembly.