GB1311240A - Nuclear fuel element with multiple fuel tubes - Google Patents

Abstract

1311240 Fuel elements UNITED NUCLEAR CORP 6 Oct 1971 [21 Jan 1971] 46373/71 Heading G6C In a nuclear fuel element having an array of parallel fuel tubes restrained from bowing and vibration by spacer devices in predetermined spaced relation along the length of the fuel tubes, the spacer devices are prevented from shifting lengthwise of the fuel tubes by employing at least one of the fuel tubes as a capture tube, the walls of which are continuous from end to end and have at least one pair of external lugs for each spacer device formed integrally with the walls of the tube, the lugs of each pair being spaced apart lengthwise of the tube and engaging the opposite edges of projecting sections of a spacer device. The spacer devices each comprise a rigid, thin metallic band which surrounds the fuel tubes 7 and is divided internally into a number of cells by two sets of spaced, parallel, rigi i metallic strips 10, 11 intersecting each other at right angles, and by two sets of parallel pairs of resilient members 12, 12a and 13, 13a intersecting each other and the rigid strips 10 at right angles. Each fuel tube 7 is contacted by the spacer devices at four points 90 degrees apart, two of these contacts being with beads formed on the rigid strips 10, 11 and the other two with the resilient members 12, 12a and 13, 13a. The (or each) capture tube 15 is similar to a fuel tube 7 but has at each of a number of positions spaced along its length four pairs of lugs 16, 17, 18 and 19 projecting from the surface of the tube at right angles to one another. The cells 20 through which the capture tube 15 passes differ from the remaining cells of the spacer devices in that the central portions of the rigid strips 10, 11 are pressed inwardly to form ledges 21, 22 of the same width as the resilient members 12, 13, the latter having inwardly bowed portions 23, 24. The upper and lower lugs of each pair of lugs 16, 17, 18 and 19 engage respestively the upper and lower edges of ledges 21, 22 and bowed portions 23, 24, During assembly, the capture tube 15 is inserted with the flat surfaces between adjacent lugs parallel with the sides of the cell 20 and is then rotated through 45 degrees. The capture tube 15 is closed by end plugs and filled with fuel pellets except for a void space adjacent the upper end plug, there being an insulation disc having a central aperture for the passage of fission gases above the uppermost pellet, and a coil spring between this disc and the top end plug. A suitable material for the sheathing of the capture tube is stainless steel or a zirconium alloy.