GB1186321A - Process for Positioning a Wire along a Helical Path on a Cylindrical Fuel Element. - Google Patents

Abstract

1,186,321. Coiling helices. COMMISSARIAT A L'ENERGIE ATOMIQUE. 29 July, 1968 [28 July, 1967], No. 36048/68. Heading B3E. [Also in Division G6] A fuel element consisting of a cylindrical can filled with fuel material and closed by two plugs is provided with a helically wound wire for the purpose of providing precise spacing of the element from adjacent elements in a bundle, by forming at least one of the plugs 12 as a can obturator 20 with an end member 22 rotatable by means of a cylindrical stud 24 engaging with an easy fit in a blind hole 26 formed in the obturator 20 coaxially with the can 10. The ends of a suitable length of wire 16 are secured as by brazing to the end member 22 and to the other plug 14, and the end member 22 and can 10 are rotated relative to each other while guiding the wire 16 round the can. When the wire 16 has been positioned in a helix and tensioned, the end member 22 is secured to the obturator 20 by welds. In the fuel element illustrated, the upper plug 14 is in one piece and the upper end of the wire 16 is brazed on to a ring 18 welded into a recess in the plug 14. The lower end of the wire 16 is engaged in an orifice in the end member 22 of the lower plug 12 and is fixed to this plug by brazing. The wire 16 may be guided round the can 10 by means of a tubular chaser (Fig. 2, not shown), with an internal guide groove having a pitch corresponding to that desired for the wire 16. The chaser is threaded on to the end of the can 10 near the upper plug 14 and the end member 22 then rotated while the can 10 is held stationary. The chaser which is moved axially by a mechanism synchronized with the rotation of the end member 22 is allowed to rotate freely and thus follow a helical path. Another form of guide (Fig. 4, not shown), comprises a spigot having a guide groove which is urged by a spring against the wire 16, the guide being moved axially in synchronism with the rotation of the can 10 the end member 22 being held stationary in this case. The guide is prevented from rotating around the can axis. If the element is very long with a large number of turns of wire, a constant tension of the wire over the entire length of the element may be obtained by forming both plugs in two parts as is the plug 12 described above, the two end members 22 being rotated in opposite directions while the can 10 is held stationary, and by using two half-chasers moved synchronously in opposite direction, starting from the centre of the can.