Patent GB-964679-A (GB)
Title: Imporoved nuclear reactor fuel handling system
IPC: G21C19/18
Filed: 1962-07-19
Abstract: 964,679. Fuelling reactors. GENERAL DYNAMICS CORPORATION. July 19, 1962 [Aug. 2, 1961], No. 27908/62. Heading G6C. [Also in Division B8] An apparatus for handling elements in a nuclear reactor includes a housing, sealable in relation to an opening in the reactor vessel top, said housing including a vertically movable grapple controlled by flexible metal tapes. Referring to Fig. 1, the apparatus comprises a high temperature gas cooled nuclear reactor 21, a canning machine 31, used for encapsulating spent fuel elements &c., a storage pit 29-for housing unused fuel elements, and a charging machine 25 for transporting new and used fuel elements &c., as required. The apparatus may also be used for handling and canning radio-active samples and control rods. The charging machine moves on rails and comprises a carriage on which is mounted a tubular housing 39 above which is situated the grapple actuating mechanism 199, and an operating console 96. Referring now to Fig. 2 the base of the housing is filled with lead shielding 107 in the form of blocks or shot. At the lower end of the housing is situated a ball type valve 111 and a sleeve mounted sealing flange 161 for engaging the ports in the reactor, canning machine or storage pit. Cooling means may be located about the housing for dissipating heat from used fuel elements. The grapple retracts within a tube 105 extending axially through the tubular housing 39 (Fig. 2) and comprises (see Fig. 8) three radially spaced grippers 47 which, on relative axial movement between them and their associated cam pins 181, grip or release the fuel element 41 through cam grooves 185. The gripper, which is biassed inwardly, may be expanded to grip the interiors of objects. The grapple is suspended from the grapple actuating mechanism 199 (Figs. 1 and 4) by two flexible steel suspension tapes 51, 53 secured via a tension equalizer bar 191 to the grapple body 175. A third flexible steel gripper actuating tape 55 is attached to a gripper actuating rod 183 attached to a movable plunger 184 within the grapple body 175; this plunger carries the cam pins 181, which will move relative to the grippers 47 since the latter are pivotally fixed at their upper ends to the grapple body 175. The grapple actuating mechanism (Fig. 4) comprises an electric motor which drives a first drum 204 having therein a pair of grooves to accomodate the two suspension tapes, and a second drum 213 accomodating the gripper actuating tape. The three tapes leave their respective drums in an upward direction and pass over two idler pulleys 217, 233, before leaving the mechanism in a downward direction through a sealing unit 283, which may include a shower 291 for removing contaminant from the tapes. Both tape drums have a common drive and unwind tape at the same rate; in order to extend or retract the centre or gripper actuating tape 55 to actuate the gripper, its idler pulley 233 is raised or lowered on a guide rail 237 by a motor driven cam. Provision is made in the mounting of the two load bearing idler pulleys for the tensions in the two supporting tapes to be monitored. Canning machine. This comprises (Fig. 13) an access port 305 for loading the cans and caps, a ball valve 85 with purging means for loading spent fuel elements into the cans from the charging machine, a capping mechanism 77 for positioning caps on the cans and an induction coil 357 for brazing caps to cans, and a conduit 325 extending downward to a storage area in which used canned fuel elements are stored until their radiation level has dropped sufficiently for them to be removed. Loading of cans 75 takes place through the ball valve 85. Machine operation. To transfer a used fuel element to the canning machine, the charge machine is located over the reactor access port and the pressure plate 161 (Fig. 2) engaged sealingly to the reactor. The chamber 43 is purged and filled with helium and the reactor access port 23 and charging machine value 115 opened. After the grapple has raised the used fuel element into the tubular housing 39, the reactor port and charging machine valve are closed, and the space therebetween purged and filled with air, and the pressure plate raised. The charging machine is positioned over the canning machine access port 35, and the pressure plate lowered into sealed contact therewith. A cap and can have already been positioned within the machine and the seal 343 inflated. After the machine has been purged and filled with helium, the charging machines and canning machine valves are opened and the used fuel element is lowered directly into the can 75. The grapple is then withdrawn and the canning machine valve 85 closed. The space between the valves is purged and filled with air, and the pressure plate withdrawn. The capping arm 347 is actuated by a cylinder 351 to position the cap on the top of the can and the brazed joint therebetween formed by means of the induction heating coil 357. The capping arm is retracted and the canning machine chamber 71 evacuated by purging means 87. At this stage it is preferable to leak test the brazed joint, after which the chamber 71 is filled with air, the seal 357 deflated and the canned fuel element released by the arm 327 and dropped down the conduit to the used element store.