Patent GB-985305-A (GB)
Title: Improvements in or relating to grabs for nuclear reactors
Inventor: LEE RALPH
IPC: G21C19/11
Filed: 1961-01-09
Abstract: 985, 305. Fuelling reactors. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Jan 1, 1962 [Jan. 9, 1961], No. 793/61. Heading G6C. A grub 9 displaces a fuel element container 5 in a tube 2 extending from the charge face (not shown) of the reactor shielding 1 to a chamber 3 accommodating a magazine 4 having tubes 6 for receiving the container, there being, as shown, three tubes 2 each having a grub 9 and associated respectively with containers 5 arranged on three concentric circles on the magazine. Each grab 9 comprises a tubular body 12 through which a string of interconnected fuel elements may pass into the container, the body having on its inner surface three cams 13 spaced at 120 degrees and a single cam 14, these cams co-operating with three lifting pins 15 spaced at 120 degrees on the outer surface of the copper end of each container 5. A series of locking balls 28 in recesses in the grab body 12 are controlled by a sleeve 30 slidable on the body such that when a container 5 is supported in a tube 6 by pins 7, Fig. 2, and the grab is lowered over the container the sleeve 30 engages the top of the magazine 4 and moves upwards relatively to the body 12 whereby on enlarged section 31 of the sleeve comes opposite the balls which may thus move outwards away from the interior of the body and cease to impart this locking action on the pins 15. However, when the grab lifts the container the sleeve 30 moves down and its smaller section 32 ceases the balls 29 to project into gaps 54, 55 between the cams 13,14 in the path of movement of the pins 15 and thus prevent accidental release of the container. The cams 13,14 are shown developed in Fig. 4 and the sequence of movements of a pin 15 is indicated by the shaded path in that Fig. the other two pins taking similar paths. On lowering of the grab 9 on to a container 5 supported in the magazine 4 the pin passes through the space 27 between two cams 13 and engages the inclined face 16 if cam 14 whereby on further lowering the grab rotates 30 degrees anticlockwise relatively to the container 5 until the pin reaches the notch formed between cam faces 16, 17. The grab is now raised so that the pin moves down the vertical face 17 and engages inclined face 25 if a cam 13, continued raising of the grab causing the pin to enter the notch 24 and the container to be rotated clockwise 30 degrees relatively to the grab. The grab now lifts the container into the position shown in the left hand tube 2 in Fig. 1, the sleeve 30 moving down to the ball locking position. A fuel element discharge machine (not shown) now lowers a string of fuel elements 35 suspended from shield plugs 36, 37 through the grab body 12 into the container and a coupling 38 between the plugs and fuel element string is disconnected. The grab lowers the container and sleeve 30 is moved to unlock the balls by engaging the magazine, the container now being supported again by its pins 7 Continued lowering of the grab causes pin 15 to leave notch 24 and move up vertical face 26 to engage another inclined face 16 and on further lowering the grab rotates through 30 degrees anticlockwise relatively to the container 5 until the pin reaches the notch formed between the faces 16, 17 The grab is now raised causing the pin to move along face 17 and engage inclined face 21 of cam 13, further raising causing a further relative movement through 30 degrees and the pin to move through the space 27 whereby the grab is disengaged from the container.