Patent GB-936454-A (GB)
Title: Improvements in nuclear reactor refuelling machines
Inventor: LANGDON KENNETH PEERS THOMAS
IPC: G21C19/06
Filed: 1960-04-14
Abstract: 936,454. Servicing reactors. BABCOCK & WILCOX Ltd. April 14, 1961 [April 14, 1960], No. 13536/60. Class 39 (4). A refuelling machine for servicing a gascooled reactor whilst on load comprises a pressure vessel containing two rotary magazines one of which forms part of hole preparation means and the other of which serves as a fuel element container. The machine performs all the necessary operations for refuelling and eliminates the need for a separate hole preparation machine. As shown, the machine 12 having shielding 13 is supported between its ends by a gimbal ring 14 carried by a traversing structure 11 movable on a gantry 7, the gantry being movable on rails 6 on the pile cap 4. The gimbal ring mounting may be as disclosed in Specification 936,451. Thus a telescopic nose unit 18 extending from the bottom 17 of the machine pressure vessel 15 may be connected to a selected reactor standpipe 5. Each standpipe serves a group of nine channels in the core 1, the centre channel of the group receiving a control rod. The pear-shaped lower end 16 of the vessel 15 receives an annular magazine 22 having inclined compartments 24 for receiving fuel elements or a debris basket, this magazine being driven by a motor through a Geneva mechanism (Figs. 10, 11, not shown) whereby it may be moved in steps by a distance equal to that between two adjacent compartments. The magazine is supported at its upper end by an encircling ball-race 32 fixed to the vessel 15. A further magazine 21 extends from the upper end of the vessel 15 and penetrates into the central opening of the annular magazine 22, the magazine 21 being supported at its upper end by an encircling ball race 131 and being rotatable by a motor 141 in an auxiliary pressure vessel 138 through a bevel gear ring 134. The magazines 21, 22 are radially spaced from one another by rollers 34 mounted on vertical axes on the magazine 22. The magazine 21 has five compartments 23 for respectively receiving an emergency biological shield plug, a controlrod and drive 59, a charge shoot 102, a charge shoot shield plug and a drive tube 101, which may be splined to the shoot to form a driving connection therefor. The construction of tube 101 is disclosed in Specification 936,455, and it includes two concentric tubes (Fig. 9, not shown) which are driven synchronously to effect bodily rotation of the shoot about a vertical axis, one of the tubes being driven alone to cause lateral movement of an articulated shoot leg 103 whereby the leg may be aligned with the core channel to be serviced. The magazine 21 also has a fuel element transfer tube 61, rotation of the magazine permitting a selected compartment 23 or a lower continuation portion 72 of the tube 61 to be aligned with the nose unit 18. The upper end 70 of the tube 61 has lead shielding 71 and may be aligned with a pipe 181 leading to an auxiliary pressure vessel 183 containing a hoist 184 controlling a grab 186 on a cable 185. Between the end 70 and portion 72 the tube 61 includes a section 73 pivoted at 74 whereby the section 73 may be aligned either with a selected compartment 24 of the magazine 22 or with the tube portion 72. Mounted on the top plate 142 of the magazine 21 and associated, respectively, with four of the compartments 23 are four identical sprocket driving units 144 (Fig. 4, not shown), each unit controlling a chain 160 carrying a grab 163. Also mounted on the plate 142 and associated, respectively, with the tube 61 and compartment 23A containing the charge shoot shield plug, are two identical rack driving units 143 (Fig. 4, not shown), the unit associated with the tube 61 serving to control the pivoted tube section 73 and the other unit serving to control a flap (Fig. 8, not shown) for retaining the plug in the compartment. A single driving motor 171 in an auxiliary pressure vessel 170 serves to drive any selected one of the six driving units 143, 144, the motor 171 being automatically coupled by a mechanical clutch 173 to that unit which is associated with the particular compartment 23 or the tube 61 which is in alignment with the nose unit 18. The machine is cooled during refuelling by a circulator 200 connected to a heat-exchanger 201, the gas entering the end 16 of vessel 15 through a duct 209 and passing through the compartments 24 whence it is deflected back to leave through duct 210. A second gas stream from vessel 183 circulates downwardly through compartments 23 and a tube extension 213, this gas then moving upwardly through tube 72 to mix with the gas which has passed through the compartments 24. Cooled gas from circulator 200 is also supplied to auxiliary pressure vessels 138, 170 and 183. In performing a servicing operation the magazine 21 receives into one of its compartments 23 the control rod and drive unit 59 by means of a grab 163 and is then rotated to permit lowering of the charge shoot 102 from another compartment 23. The compartment 23A is aligned with the nose unit 18 and the grab 186 lowered therethrough to retrieve the charge shoot shield plug which is retained in that compartment by operation of the flap. The magazine 21 is further rotated to permit lowering of the drive tube 101 from another compartment 23 and the shoot leg 103 is aligned with the core channel to be serviced. Finally, the magazine 21 is rotated to align the tube 61 with the nose unit 18. The grab 186 is lowered through portions 70, 73 and 72 of the tube 61 into the core channel to retrieve the uppermost fuel element and lift it into the portion 73, the portion 73 then being pivoted into alignment with an empty compartment 24 of the magazine 22 and the fuel element is lowered into this compartment. The tube portion 73 is returned to its vertical position, the magazine 22 is indexed through one step and the next fuel element is similarly removed. Some of the compartments 24 contain new fuel elements and these are then loaded into the channel by a similar procedure of pivoting the tube portion 73.