Nuclear reactor fuel element assemblies

Claim 1

A spacer grid for spacing apart a plurality of cylindrical nuclear fuel pins in a stream of coolant flowed over the surface of said pins parallel to the axis thereof, the grid comprising a plurality of cojointed, open ended, cylindrical ferrules, each ferrule having one rim defining part of the downstream face of the grid and its other rim defining part of the upstream face of the grid, positioning means for each ferrule positioning a fuel pin in spaced relation to the inner face of the ferrule said means including a pair of circumferentially spaced, co-planar rigid stop members extending inwardly from the inner face of the ferrule and a spring member also extending inwardly from the inner face of the ferrule with the line of action of the spring member being opposite to and extending between the stop members to urge a fuel pin into engagement with the rigid stop members, said spring member serving to position a fuel pin so that an annular clearance is defined between the pin and the inner wall of the ferrule whereby substantially uniform heat exchange between the fuel pin and the coolant may occur around the part of the circumference of the fuel pin lying within the grid, the said one rim of at least some ferrules being shaped to promote turbulence in the coolant leaving the downstream side of the grid and deflectors for deflecting coolant preferentially into the ferrules located on said other rim of the ferrules defining the upstream edge of the grid.