GB1122981A - Improvements relating to grabs for use in nuclear reactors - Google Patents

Abstract

1,122,981. Grabs for lifting nuclear fuel elements. FAIREY ENG. Ltd. 17 Sept., 1965 [18 June, 1964], No. 25297/64. Heading B8H. A grab for nuclear fuel elements has balls 16 caged in an inner sleeve 12 which are urged inwards to grip a fuel element by the descent of an outer sleeve 13, and balls 19 which lock the sleeves together in their two extreme positions. When the grab is lowered on to an element a plunger 24 is raised and cam surfaces 31, 32 allow the balls 19 to move inwards as the sleeve 13 descends. The grab may be used to remove a seal plug 70, Fig. 5 (not shown), and its suspended fuel element from a standpipe mouth 71. The grab is lowered over and latched on to a collar 85 of the plug by balls 16 as described above and then jaws 75, which lock the plug 70 to the standpipe 71, are released. To do this, actuator jaws 60, 61 on the fuelling machine are moved into engagement with bobbins 50, 57, and the bobbin 50 is depressed to compress a sealing-ring below the plug 70. The jaws 61 and bobbin 57 are next raised to lift the inner grab sleeve 12, which is latched to the collar 85 of the plug 70, thereby releasing the latch between a sleeve 78 and a spigot 79 and raising the sleeve 78 sufficiently to withdraw the jaws 75 by means of cam-fingers 82. During this movement the cam head 31 falls and pushes lock-up balls 19 outwards to lock together the sleeves 12,13 with the balls 16 in latching engagement with the collar 85. After small movements of the fuelling machine to release the gas pressure from the pipe the jaws 60, 61 are retracted and the fuel element withdrawn by the hoist mechanism and deposited in a magazine.