GB897449A - Improvements in or relating to refuelling machines for nuclear reactors - Google Patents

Abstract

897,449. Handling nuclear fuel elements. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Jan. 22, 1960 [Jan. 29, 1959; June 3, 1959], Nos. 3291/59 and 18956/59. Class 39(4). A reactor refuelling machine has incorporated in it adjacent to its normal refuelling equipment, separate equipment for use in conditions in which the normal equipment cannot be used, the separate equipment being similar to the normal equipment but modified to adapt it for use in the said conditions, whereby the separate equipment can be brought rapidly into operative position by moving the machine by a small amount. A typical condition in which the separate equipment would be used is the removal of a damaged fuel element from a reactor channel. As shown in Figs. 1a-1c (which are superimposed to form a single Fig. 1) the machine 1 has facilities for normal refuelling including a pressure vessel 2, a retractable nose piece 3 for sealing engagement with a selected reactor standpipe 4 and a rotatable fuel element magazine 5 having three tubes 6 alignable in turn with the nose piece, each tube having its own hoisting chain 7 driven by a common hoisting means 8. A seal plug 33 and telescopic connecting means 34 are attached to each chain 7. The separate equipment for use in abnormal conditions comprises a pressure vessel 9 housing a fuel element magazine 10 containing three tubes 11, the tubes being alignable in turn with a retractable nose piece 12. The tubes 11 may also be aligned with an outlet tube 13 having an isolating valve 14, a movable shield 15 and an access door 16. A grab 17 and shield plug 18 are suspended in the tube 13 from a cable 19 driven by a winch 20. One of the tubes 11 contains a dump can for receiving fuel element fragments. The reactor charge face comprises standpipe caps 21 and after removal of the selected cap the machine 1 is positioned thereover. The machine has fixed shielding 22 and removable shielding 23 to give access to a space 25 accommodating the nose pieces 3, 12. A tube 26 between the magazine 5 and nose piece 3 has a window 27 observed by a television camera 28, and a tube 29 between the magazine 10 and nose piece 12 has a window 30 for a television camera 31. To refuel a reactor an assembly consisting of a string of fuel elements suspended from a shielding plug 36 for a standpipe 4 is loaded into one of the magazine tubes 6 and another tube 6 is loaded with a spare plug 36. The shielding 23 is removed and the chain 7 of the empty tube 6 is lowered through the tube 26 until the plug 33 reaches its sealing position (Fig. 1a), the connecting means 34 being extended to connect with the standpipe plug 36. The shielding 23 is replaced and the nose piece 3 lowered to seal with the standpipe, coolant as used in the reactor and at the same pressure then being circulated through the vessel 2. The hoist 8 lifts the plug 36 together with its connected string of fuel elements into the empty tube 6. The magazine 5 is rotated so that its tube 6 loaded with the replacement fuel assembly is aligned with the standpipe and this assembly is lowered into the reactor. Should a fuel element be accidentally dropped into the reactor the spare plug 36 in the tube 6 is lowered into the standpipe and the reactor is depressurized, the nose piece 3 retracted and the connecting means 34 telescoped. The machine is moved a small amount so that the nose piece 12 may be lowered and sealed with the standpipe and the valves 14, 32 are opened. The grab 17 is lowered through an empty tube 11 and lifts the spare plug 36 into the magazine 10, the latter then being rotated to permit lowering of the grab through tubes 11, 29 to retrieve the damaged fuel element. The element is lifted into the tube 13, the magazine rotated, and the element deposited in the dump can. The vessel 9 may also be circulated with coolant. Specifications 873,073, 875,787, 889,536, 897,448, 897,450, 897,451, 897,454 and 897,458 are referred to.