SE7700135L - DEVICE AT GALLER, SPEC FOR REACTOR - Google Patents

Abstract

1517670 Fuel elements COMMISSARIAT A L'ENERGIE ATOMIQUE 29 Dec 1976 [9 Jan 1976 14 Jan 1976] 54249/76 Heading G6C A spacer grid for a nuclear fuel assembly comprises an array of interfitting flat sheet metal members defining compartments, narrow corrugated strips projecting into the compartments and forming separations between openings of substantial width formed in the sheet metal members, and an outer frame, the sheet metal members where they are joined to the corrugated strips are alotted or otherwise cut away to increase resilience at that point and increase the permitted deflection of each strip under the action of the same applied force. As shown in Fig. 3, the flexibility of each corrugated strip 5 is improved by providing slits 10 near the junctions between the sheet metal members 2 and the strip 5. The slits 10 extend parallel to the opposite edges of the sheet metal members 2 and the twisting of that portion of the member 2 between the slit 10 and the strip 5 itself is thus made to take part in the bending of the strip 5. The projecting portion 6 of the strips 5 are intended to apply the fuel pins against bosses 7, 8 formed in the sheet metal members 2. In alternative embodiments, Figs. 4 and 6 (the former, not shown), slits 12 are formed in the sheet metal members 2 on each side of each corrugated strip 5 so that the strips 5 directly incorporate the bosses 7, 8. This results in interdependence of the compartments since a force applied to any one corrugated strip is transmitted to the bosses of the adjacent compartment and so on in sequence, thus achieving equalization of the forces applied to the fuel pins throughout the entire grid. In the Fig. 6 embodiment, each corrugated strip 5 is provided with open portions 13 so as to form two bearing arms 14 extending on each side of the central position 6. A fuel pin applies a force first to the arms 14 and as the force increases so the extremities 14a of the arms 14 are applied against the solid portion of the strip 5. If the force continues to increase, the fuel pin bears on the central portion 6 and then produces deflection of the strip 5 itself. This embodiment thus utilizes two successive spring actions. The outer frame may be provided with external ribs (20) (Fig. 8, not shown) extending at right angles to the longitudinal direction of the sheet metal members, or with rounded teeth (9) (Fig. 9, not shown) provided on the end edges of the frame and which are shaped to bulge outwardly of the frame before inclining inwardly.