Patent GB-844764-A (GB)
Title: Improvements in or relating to nuclear reactors
Inventor: DEW ROBERT NORMAN
IPC: G21C19/22
Filed: 1956-09-27
Abstract: 844,764. Nuclear reactors; handling material in radioactive environment. GENERAL ELECTRIC CO. Ltd. Sept. 26, 1957 [Sept. 26, 1956], No. 29607/56. Class 39(4). [Also in Group XXIV] In a reactor having stacks of fuel elements constructed, e.g. as disclosed in Fig. 10 of Specification 791,011 and arranged in vertical channels 5 in a graphite core 1 constructed as disclosed in Specification 837,608, the loading and unloading of the fuel elements is performed by remotely-operable means positioned beneath the reactor and capable of extension through openings in the biological shield 13 and pressure vessel wall 12, the means including an auxiliary vessel 86 which is pressurized with CO 2  to match the coolant gas pressure in the pressure vessel 12 as disclosed in Specification 789,022 thereby permitting fuel handling during operation of the reactor. The channels 5 have pipe extensions 6 arranged in groups, each group comprising thirty-six pipes arranged in rows of six, the lower extremities of the pipes of a group lying on the surface of a sphere, Fig. 1a. A fuel element shoot 15 jointed along its length by a bellows 16 at the centre of curvature of the spherical surface may be located opposite any tube 6 of a group by extending its upper part laterally through an opening in a cylindrical housing 19 and by rotating the housing, the shoot then being sealed to the pipe by a sleeve 35 moved by a CO 2  operated piston 37. The extension of the shoot through the housing 19 is controlled by a wire rope 21 connected to a rod 23 actuated by a CO 2  operated piston 25, and the amount of this extension is determined by a stop 26 connected with the piston and coacting with a selected one of a number of arcuately-extending stops 27 of different angular extent on the surface of a drum 28, the drum being rotatable on the lower part of the shoot 15 through gearing 31 and a rack and pinion 33 driven by a CO 2  operated piston and cylinder 34. The shoot 15 and housing 19 form a unit which, when the shoot is wholly within the housing, may be passed through a desired one of a number of stack pipes 9, associated with the pipe groups 6, extending through the shield 13 and terminating in a mouth 14. The lower end of the unit 15, 19 has concrete shielding 43 and terminates in an end piece 44 having openings receiving lugs 45 integral with a tube 48 whereby rotation of the latter within a cylindrical lead shield 41 causes rotation of the unit. The parts 41, 48 constitute a second unit, the units 15, 19 and 41, 48 normally occupying positions side-byside within the vessel 86, Fig. 6, but being mountable one upon the other as later described to provide a continuous passage for the fuel elements through the tube 48 and shoot 15. The fuel elements in a channel 5 rest on a graphite sleeve 54 supported by a seating 55 retained by catches 56, Fig. 2, and these catches are released by a head 58 attached to the upper end of a chain 59 which is inserted through the passage 48, 15, 6 to convey the fuel elements to or from a channel 5. To permit the chain to support a compressive load it is provided at its joints with rollers which engage the inner surface of the passage, Figs. 4, 5 (not shown), (see Group XXIV); also the chain, has rollers whereby it may be driven by a sprocket 136 through a stowage tube 140. The head 58 comprises three concentric parts 60, 61, 62, the parts 60, 62 being joined at the base 63 and the part 61 being axially movable. Initially, the whole load of the fuel element column is taken by the part 60, this load being transmitted to the base 63 through a strain gauge load cell 68 or, alternatively, a transducer, whereby the load may be weighed, the part 61 then being moved upwards to release the catches 56 by varying the pressure of CO 2  supplied to a chamber 64. The movement of the part 61 is indicated by a microswitch 73 operated by a roller 74. The vessel 86 is mounted on a wheeled carriage running on tracks on a turntable (not shown) positioned beneath the reactor whereby a nozzle 87 on the vessel may be positioned beneath any one of the standpipes 9. Two television cameras (not shown) on the top of the vessel 86 aid the alignment of the nozzle which is then clamped to the mouth 14 by eight hydraulically-operated piston clamps 89. A jacket 91 around the vessel may be filled with water in an emergency. A magazine 92 having a lead shield 93 and wheels 97 running on guide rails 98 has twenty open-ended compartments 96 each holding five fuel elements, two compartments holding the fuel charge for one channel 5. Each end of the shield 93 has a pair of openings 95 and the magazine may be rotated to bring any one of the compartments 96 into alignment with the openings so that when the units 15, 19 and 41, 48 have been placed one upon the other and lifted into a stack pipe 9, the magazine may be moved there-beneath by a hydraulic ram 99 to provide a continuous passage from the mouth 141 of the chain tube 140 through a compartment 96 to a channel 5, Fig. 14. The units 15, 19 and 41, 48 are lifted, respectively, by hoists 107, 108 running on vertical girders 109, 110, Figs. 7, 8, attached to a gantry unit 101 driven along horizontal backs 102 by a hydraulic ram (not shown). The gantry unit 101 also has transverse guide rails 131 for trolleys 126, 127 serving to remove an old door 129 and concrete plug 132 from the mouth 14 of a stack pipe 9 prior to the removal of the fuel elements and serving also to re-insert the plug with a new door 128 after refuelling. The doors have bellows seals as disclosed in Specification 844,766. A trolley 133 running on fixed horizontal tracks 103 and carrying a lead shield 134 serves to remove the plug 132 from an old door 129 and replace it on a new door 129. The trolleys 126, 127, 133 are driven by COz operated piston and cylinder arrangements (not shown). To perform an unloading operation, the unit 41, 48 is raised to unlatch an old door 129, Figs.15, 16 (not shown), and is then lowered to permit removal of the door and plug 132 by trolleys 127, 133. The gantry unit 101 is moved and the unit 15, 19 raised through a stack pipe 9 and temporarily clamped in position, the gantry then being returned and the unit 41, 48 raised and connected to the unit 15, 19. Finally, the magazine 92 is moved beneath the units 15, 19 and 41, 48. Loading is performed in a similar manner, the operation being concluded by raising the plug 132 on a new door 129 and latching the latter in the pipe mouth 14. The Provisional Specification describes a modified arrangement with reference to Figures. Specifications 791,011 and 837,608 also are referred to. Reference has been directed by the Comptroller to Specifications 789,022 and 800,388.