Patent GB-897448-A (GB)
Title: Improvements in or relating to refuelling machines for gas-cooled nuclear reactors
Inventor: LONG EVERETT
IPC: G21C19/16
Filed: 1959-01-29
Abstract: 897,448. Handling nuclear fuel elements. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Jan. 22, 1960 [Jan. 29, 1959; June 3, 1959], Nos. 3290/59 and 18955/59. Class 39(4). A refuelling machine for coupling to a selected standpipe 4 of a gas-cooled reactor to permit refuelling to be carried out whilst the reactor is in operation comprises a gasfilled pressure vessel 2, only the lower part of which is shown, having a retractable nose piece 3 carrying a sealing member 10 which may engage a standpipe 4 after removal of a cap 64. The nose piece 3 comprises a pair of concentric tubes 11, 12 held together at their upper ends by a shoulder 23 on the tube 12 loosely retained within a recess 22 on the tube 11 by a member 20 secured to the latter, the loose connection allowing for slight mis-alignment between the nose piece and standpipe. The upper end of the tube 11 carries a seal 8 slidably engaging a tube 7 depending from the vessel 2, the tube 12 having a screw thread 13 co-operating with a nut 14 mounted for rotation within a recess 15 of a support sleeve 16, the nut being driven by an electric motor through a shaft 30 and gear-wheel 28. The pressure vessel 2 rotatably supports a magazine 58 having three tubes 59 each of which may accommodate a string of fuel elements suspended from a shield plug 63 which normally seals the end of a standpipe 4. The vessel 2 has three hoisting chains, only one of which is shown and designated 60, associated respectively with the tubes 59, each chain carrying a seal plug 61 to which is attached a telescopic connector 62 for engagement with a plug 63. The plug 61 has a conical surface 67 making sealing engagement with a seat 68 on a tube 39 secured to the vessel 2. A sleeve 33 secured by a flange 34 to the tube 11 carries a sealing member 38 in sliding engagement with the tube 39, the lower end 36 of the sleeve being received with clearance within a standpipe 4 when the latter is sealed to the nose piece 3. To refuel a reactor channel the machine 1 is positioned over the appropriate standpipe with the nose piece retracted and the magazine 58 is rotated to bring an unoccupied tube 59 in line with the nose piece and the respective connector 62 is lowered until the plug 61 is in its sealing position shown in Fig. 1. The connector 62 is extended to permit manual engagement with the plug 63 and the shaft 30 is rotated to lower the nose piece 3 so that the sealing member 10 embraces the standpipe. Coolant gas at the same pressure as that in the reactor is admitted to the inlets 43, 44, the coolant from inlet 43 passing through passage 42 into space 41 and through apertures 40 upwardly into the pressure vessel 2. This coolant leaves the vessel 2 through an outlet (not shown) whence it is recirculated, the coolant also filling the tube 39 sealed by the plug 61. The coolant from inlet 44- flows through passage 45 into the space 46 and down through apertures 35 in the flange 34 into the annular space between the lower end 36 of the sleeve 33 and the end of the standpipe to cool the seal 10, the coolant then entering the sleeve as far as the plug 61. The assembly comprising the shield plug 63 and its attached fuel elements is hoisted into the vacant tube 59 and the magazine 58 rotated to bring a tube 59 filled with a replacement assembly into line with the nose piece 3, this replacement assembly being lowered into the fuel channel by the hoist associated with that tube. The nose piece 3 is retracted to permit the machine to be moved away but the plug 61 is left in the position shown to seal the tube 39 so that the coolant may continue to be applied at the inlet 43 to cool the irradiated fuel in the vessel, the coolant applied to inlet 44 being stopped. Specifications 897,449, 897,450, 897,451, 897,454 and 897,458 are referred to.