Abstract: The fuel assembly comprises a bundle of fuel pins spaced in parallel relation in a uniform lattice by means of support grids resiliently applied against the fuel pins and a rigid independent structure formed by two parallel end plates. Tie-rods extending between the end plates are disposed at uniform intervals at the lattice nodes. The bundle of fuel pins is supported by the first grid on a series of tubular spacer members which surround the lower ends of at least a number of tie-rods with provision for a clearance space. The tubular spacer members extend between the bottom end plate and the first grid, the tie-rods being permitted to pass freely through each grid by means of guide sleeves.

Abstract: The spacer grid for a nuclear reactor fuel assembly has an open structure constituted by an array of flat sheet metal members in interfitting relation and defining compartments. Narrow corrugated strips project into the interior of the compartments and form separations between openings of substantial width in the surface of the sheet metal members and an outer frame surrounds the structure. The sheet metal members are joined to the corrugated strips by means of a zone having lower mechanical strength so as to increase the deflection of each strip in respect of the same applied force.

Abstract: The plate-type element is made up of a fuel core consisting of ceramic fuel wafers inserted in a lattice formed by a wire grid having low neutron-absorption characteristics, the shape and dimensions of each mesh of the grid being intended to correspond to those of each wafer. The grid is fitted in an outer frame and the fuel element is completed by top and bottom cladding plates.

Abstract: A stack of clad fuel plates disposed vertically in uniformly spaced and parallel relation constitutes the fuel assembly. The fuel plates are connected together in rigidly fixed relation by coupling means extending at right angles to the plane of the fuel plates and mounted at intervals in the vertical direction on the lateral edges of the plates. Hollow sleeves are rigidly fixed to at least a certain number of fuel plates and extend vertically in the plane of these latter, the sleeves being uniformly spaced in the transverse direction of the plates.

Abstract: A fuel assembly for a light-water or heavy-water reactor or for a fast reactor comprises a bundle of clad fuel pins disposed on a uniform lattice and maintained in parallel relation by means of separate spacer grids fitted with resilient members for applying the grids against the fuel pins. A rigid support structure is formed by two parallel end-plates braced by tie-rods having the same diameter as the fuel pins and disposed at uniform intervals at the lattice nodes. The fuel-pin bundle is associated with a single support grid rigidly fixed at the mid-point of the tie-rods, the other grids being uniformly spaced in the vertical direction on each side so that elongation of the fuel pins takes place upwards and downwards from the support grid.

Abstract: The casing is made up of a number of identical compartments of prismatic shape in which are placed vertically either one or a number of fuel element bundles which are not secured to the casing, the casing walls being provided with means for guiding control rods, supplying emergency coolant and positioning measuring devices. At least some of the casing walls are constituted by two parallel thin metal sheets welded at intervals to stiffening webs which extend between the two metal sheets to the full height of the casing and parallel to the axis of the reactor.

Abstract: The fuel element comprises a core having a base of ceramic fuel material enclosed between two metallic cladding plates and constituted by the juxtaposed array of a plurality of ceramic fuel wafers. At least a number of wafers are provided with individual metallic protection which performs a contributory function in the cladding of the wafers and in the division of the fuel element into compartments.

Abstract: A nuclear fuel assembly comprises a cluster of elongated fuel, retained parallel and at the nodal points of a square network by a bottom supporting plate and by spacing grids. The supporting plate is connected to a top end plate via tie-rods which replace fuel pins at certain of the nodal points of the netword. The diameter of the tie-rods is equal to that of the pins and both are slidably received in the grids.