GB1275223A - Nuclear reactor fuel-rod casings - Google Patents

Abstract

1275223 Fuel elements SIEMENS AG 21 May 1970 [22 May 1969] 24754/70 Heading G6C A nuclear fuel rod comprises a metallic casing 2 closed at its ends by plugs 6, 7 welded as at 8, each plug 6, 7 having a peripheral surface part 63, 73 which extends axially from the weld 8 into the casing 2 and which tapers in the axial direction away from the opposing plug. The casing 2 contains nuclear fuel tablets 3, 4 formed with recesses in their end faces in order to take up thermal expansion of the tablets during operation. A ceramic tablet 5 provides thermal insulation of the lower end plug 6 from the fuel, whereas the upper end plug 7 is separated by a space from the hot central zone of the fuel. The plugs 6, 7 have respectively a recess 62 and an annular groove 72 which serve to render uniform heat dissipation conditions in the casing 2 and in the end plugs, thus facilitating the welding operation. The plug 7 may be fixed in position by one of several methods starting with an empty tube of uniform cross-section. For example, the plug 7 may be inserted into one end of the tube 2 and the tube pressed against the taper of the plug in order to taper the tube. On removing the pressing force, the tapered portion of the tube springs away from the taper of the plug, which is then moved forwards into contact with the tapered portion and urged further forwards so as to resiliently deform the tapered portion and bring a forward edge of the plug adjacent with the end of the tube. The plug 7 is then welded to the end of the tube 2. Alternatively, the end of the tube 2 is tapered before the plug 7 is introduced. After the plug 7 is fixed in position, the tube is charged with fuel and the plug 6 is inserted into the opposite end of the tube which is then shaped to conform to the taper of the plug 6. The shaping force is removed and the tapered portion of the tube springs away from the tapered portion of the plug 6, which is then moved forwards, in a similar manner to that in which the plug 7 was moved, and welded in position. Both the plugs are locked in position during the welding operation by virtue of the resilience of the tube, and there is thus no need to use a special tool to hold the plugs in position.