Patent GB-974248-A (GB)
Title: Improvements in and relating to method and means for refuelling nuclear reactors
IPC: G21C19/16
Filed: 1961-03-16
Abstract: 974,248. Fuelling reactors; rectors. BABCOCK & WILCOX Ltd. March 16, 1961 [March 16, 1960], No. 9645/61. Heading G6C. A method of discharging a fuel element from a fuel channel in a reactor core in which the element is transferred from the fuel channel to a control rod channel in the core without withdrawal from the biological shield and is discharged to storage means through a path including the central rod channel. As shown in Fig. 1 the core 1 in a pressure vessel 11 has control rod channels 3 each associated with a surrounding group of fuel element channels 2, coolant gas entering through ducts 12,13 and passing upwardly through the core channels and leaving through ducts 7, 8 extending from a canopy 6. A compartment 22 in the biological shield 21 contains a magazine 34 for the disposal of spent fuel elements; alternatively, a storage pond 23 may be provided. Charge tubes 25 extend from the floor 24 in alignment with the channels 3 each tube 25 terminating within the flared upper end of a conduit 27 extending upwardly from a channel. Branch tubes 28 from the sides of each conduit 27 extend to the upper ends of the group of channels 2 associated with that particular channel 3. There may be eight channels 2 and hence eight branches 28 per group (Fig. 2, not shown). The tubes 28 have coolant ports 31 and gas may also pass through the space between the flared ends of conduits 27 and the tubes 25. Downward extensions 32, 33 of the channels 3 lead to a pipe 33A extending to the magazine 34 or to the pond 23 through a pipe 36. The control rods 5 are controlled by winches 38 mounted above plugs 41 in the tubes 25, the components 5, 38, 41 being withdrawable to permit the insertion of a charging tool 42 secured to a charging machine 43 as shown for the tube 25 to the left of Fig. 1. The tool 42 comprises a tubular member 47 having at its lower end a side opening 44, the tube 47 being movable axially and rotatable by the machine 43 align the opening 44 with the entrance to a selected branch tube 28. A deflector plate 45 within the tube 47 opposite the opening 44 is biased to the inclined position shown but is moved to the vertical position by a pusher rod 46 when the tube 47 is lowered to its maximum extent towards the core due to the lower end of the rod engaging a houlder 61. In operation, to charge a channel 2 the fuel elements 4 are lowered individually by a winch controlled grab 82 from the machine 43 through the tube 47 and at the opening 44 are deflected by the plate 45 in to the tube 28 leading to the selected channel 2. To withdraw fuel elements 4 from a channel 2 the tube 47 is positioned as for he charging operation, the grab 82 being lowered and deflected by the plate 45 through the opening 44 so that the grab may engage the upper fuel element. The fuel element is withdrawn by the winch into the tube 47 and the latter is then lowered to its lowermost position so that the plate 45 is moved into its vertical position by the rod 46. The fuel element may then be lowered through the empty channel 3 into the magazine 34. In a modification (not shown) the control rods are tubular and not removed from the core when the components 38, 41 are removed, the fuel elements being lowered through the bores in the control rods. In another modification, Fig. 3, a hollow control rod 50 has a tubular extension 51 at its upper end supported by a cable 55 controlled by a winch 38. Keys 49 on the tube 51 are slidable in vertical keyways 48 in a sleeve 39 rotatable by a drive unit 54. The deflector plate 45 is mounted in the lower end of the tube 51 and the opening 44 is provided in the tube, the plate 45 and opening 44 functioning similarly the corresponding parts of Fig. 1. Any one of a lower set of apertures 57 in the tube 51 may be aligned with a branch pipe 58 when the tube 51 in the fuel element charging position, shown. When the tube 51 is lowered to its bottom position for a discharging operation the apertures 57 are aligned with the entrances to tubes 28 and a certain one of an upper set of apertures 69 in the tube 51 is aligned with the pipe 58. In operation, for charging fuel elements, the tube 51 is positioned by winch 38 and unit 54 so that opening 44 is opposite the selected tube 28 and a charge machine (not shown) above pipe 58 lowers the fuel elements singly through the pipe 58 and tube 51 into tube 28. For dishcharging fuel elements the tube 51 is positioned as for the charging operation, the grab being lowered through the pipe 58 and the spent fuel element is raised into the pipe. The tube 51 is then lowered to its bottom position in which the rod 46 moves the plate 45 into the vertical whereupon the fuel element is lowered through an aperture 69 and the hollow control 50 into the storage location. In a modification of Fig. 3, the pipe 58 and apertures 57, 69 are omitted and instead a passage 60 for the fuel elements is provided through the winch 38 and drive unit 54. According to a further modification, Fig. 4, hollow control rods 50 have downward tubular extensions 71 provided with ports, the tubes 71 being movable axially and rotatable by drive units 73, 74. A deflector plate 45 is situated in the bell mouth 70 of each rod 50. Ducts 90 through the units 73, 74 lead to fuel element disposed means. The upper end of each tube 25 has a plug 80 with a curved passage 83 permitting a cable 81 and grab 82 to be lowered from the charging machine 43. In operation, to charge a channel 2, the associated control rod 50 is moved by units 73, 74 to position the plate 45 opposite the selected tube 28, as shown for the left hand rod of the figure, the fuel elements being lowered by the grab 82. During discharge a spent fuel element is withdrawn into the tube 25 and the rod 50 moved to its lowest position so that plate 45 is moved into the vertical, the fuel element then being lowered through the rod 50, tube 71 and duct 90. The invention may be applied to reactors having horizontal channels, the grab being operated by a flexible pusher member such as a chain. Charging and discharging fuel elements may take place whilst the reactor is operating. A scheme for transferring the fuel elements within the core to equalize their irradiation is described with reference to Fig. 5, not shown.