GB1350665A - Nuclear reactor fuel elements - Google Patents

Abstract

1350665 Fuel elements UNITED KINGDOM ATOMIC ENERGY AUTHORITY 20 June 1972 [7 July 1971] 32006/71 Heading G6C A cellular fuel assembly spacer grid provides for resilient bracing of fuel pins in the cells of the grid by bow spring locating members projecting inside the cells to hold the fuel pins against opposed rigid stops also projecting inside the cells, the grid comprising upper and lower tiers 2, 3 each formed from intersecting strip members 4, 5 and arranged parallel to one another but spaced apart. In one embodiment, shown in Fig. 2, the strip members 4 running in one direction across the grid are dimpled to form rigid locating stops 7 for the fuel pins, the fuel pins being held against the stops 7 by bow springs 8 extending between the grid tiers 2, 3. The bow springs 8 are located in oppositely acting pairs between adjacent fuel pins, and the springs in each pair are connected at their ends by ferrules 9 of flattened tubular form. The distance between the ferrules 9 in the relaxed condition of the springs 8 is greater than the spacing between the grid tiers 2, 3 and the springs 8 are compressible endwise to allow the ferrules to engage tongues 10 extending longitudinally from the facing inner edges of the strip members 5 in the grid tiers 2, 3. The ferrules 9 are formed with dimple-shaped back stops 11 which limit the movement of the fuel pins away from the stops 7 against the resilient action of the bow springs 8. In an alternative form of spacer grid (Fig. 4, not shown), the bow springs extend diagonally inwards from one corner of each cell and the bow springs of a group of four adjacent cells are connected to common boxshaped end ferrules. The locating members for the end ferrules are in the form of tongues positioned in pairs extending across the ferrules diagonally to form a cross at the points of intersection of the strip members of the two tiers.