Abstract: In a device for coupling a tooth onto an adaptor nose with a key, the tooth includes a skirt shrouding the adapter nose beyond the key passage zone and having a configuration connected to a return wall, comprising a bordering ridge. The wall is provided in the width of the skirt and corresponds to the passage and positioning of the key. Proximate the ends of the wall, and in the thickness of the skirt, are provided passage openings for the key devoid of abutting function in operation and ensuring a guiding and stopping function only when the key is inserted or removed. The key comprises two components transversely mobile relative to each other.

Abstract: A grid for a nuclear fuel assembly comprises a common frame having an axis and a plurality of beds of plates distributed along the axis. Each bed has a plurality of plates which are mutually parallel and are directed transversely to the plates of the adjacent beds. All plates are secured to the common frame. The plates having a same direction are distributed between a plurality of said beds interleaved with other ones of said beds consisting of plates having another direction, and the plates of the beds placed in an upstream portion of the grid have fins oriented so as to deflect coolant inwardly whereas the plates placed in a downstream portion of the grid have fins oriented so as to deflect the flow coolant outwardly.

Abstract: A grid for use in a PWR assembly includes a peripheral girdle and at least two sets of parallel plates. The plates of one set are at an angle with respect to those of the other set so that the sets defined cells for the fuel rods. The parallel plates are distributed in at least two beds spaced apart in the longitudinal direction of the assembly. In a fuel assembly having a triangular array of fuel rods, three successive beds of mutually parallel plates are provided.

Abstract: A spacing grid is provided for a nuclear fuel assembly comprising two sets of intersecting metal plates having fins and defining fuel element receiving pockets. The plates comprise solely half-fins each associated with a single pocket of the grid, disposed in opposed pairs at the angles of the pockets, the half-fins of one pocket being placed at 90.degree. from the half-fins of adjacent pockets.