Abstract: A grid for supporting and spacing nuclear fuel rods, particularly at the nodes of a triangular array, has a peripheral frame of regular polygonal, typically hexagonal, shape and at least two beds of wires spaced in the longitudinal direction of the fuel assembly. Each bed has at least two series of mutually parallel wires secured to said frame at the end thereof, the wires of a same one of said series being parallel to two opposed side of said frame and all said wires defining passages for said fuel elements.

Abstract: A sipping test for detecting defective sheaths in a nuclear fuel assembly is carried out by increasing the pressure of the gases within the sheaths by increasing the temperature. The fission products are released in case of sheath failure. A mixture of water and inert gas is introduced into a hood containing the fuel assembly. Gas and water are separated at the upper portion of the hood and are circulated in distinct loops for continuous detection of the water-soluble fission products and the gas-driven fission products.

Abstract: A nuclear reactor has a stationary horizontal core plate and a plurality of upright nuclear fuel assemblies all having the same cross-section and located side by side in a regular polygonal network. Each fuel assembly either has two locations for elongated plug elements or is adjacent a fuel assembly having such locations. A device for holding down the fuel assemblies comprises a plurality of locking sets each having at least one deformable locking member and a rigid member one of which is carried by a fuel assembly and the other by the core plate. The deformable locking member is so located with respect to a location and with the associated rigid member that insertion of an elongated element into the location forces the deformable locking member into positive engagement with the associated rigid member.

Abstract: The assembly comprises fuel elements carried and retained by a structure comprising tie rods and end parts. Dismantable holding devices for the plug of at least one element are provided at one end part and comprise a threaded connection. They are actuatable without applying a high torque to the sheath of the fuel element and enable the element to be extracted across an end part.