Patent GB-961388-A (GB)
Title: Improvements in or relating to nuclear reactor fuelling devices
Inventor: MESANGES PIERRE DEQUENES ET LE
IPC: G21C19/04
Filed: 1962-10-23
Abstract: 961, 388. Fuelling reactors. ELECTRICITE DE FRANCE (SERVICE NATIONAL). Oct. 23, 1962 [Nov. 13, 1961], No. 40112/62. Heading G6C. A train of fuel elements is removed from the channel of a reactor core by increasing the flow of coolant through that channel to produce a blowing out of the elements, the rate of movement of the elements being controlled by a movable stop which abuts the leading end of the fuel element train and is withdrawn at a controlled speed. As shown, each channel 14 in the core 10 contains a train comprising 15 fuel elements 24, an upper reflector block 26 and lower blocks 18, 20, the coolant passing upwardly through the channel through a circuit comprising a heat-exchanger 32 and blower 34. A group of channels are served by a charge chute 36 extending through a standpipe 38, a charging machine 42 being sealed to the standpipe through an intermediate part 40 including a valve. The lower end of the chute 36 is sealed to the channel 14 and its upper end engages a telescopic tube 52 which is lowered from the machine 42 after opening a valve 48. The machine includes a pressure vessel 46 in which a tube 64 is universally mounted at 61 so that a sealing sleeve 70 at its lower end may be engaged with the upper end of the tube 52 or with a selected one of four storage tubes 56, 58, 60 and 62, the tubes 58, 60, 62 being supplied with coolant through pipes 66, 68 to cool the elements stored therein. Each tube 58, 60, 62 can receive five fuel elements 24, i.e. one third of a train. A hoist 72 on the machine controls a counterweight 74, this counterweight including a grab, an arm 76 enabling the counterweight to be laterally retracted out of alignment with the tube 64. A shielded flask 78 carried by the machine 42 and connected thereto by valves 79, 80 includes a grab whereby it may store spent fuel elements received from the machine or new fuel elements to be delivered to the machine, the retraction of the arm 76 permitting operation of this grab. The force exerted by the coolant for blowing out the fuel elements is controlled by a suction circuit extending from the pivoted tube 64 through a pipe 81, valve 87, blower 84 and returning to the blower 34 through pipe 86. A brand from the pipe 81 connects with the pressure vessel 46 through a valve 82, and a by-pass pipe 88 connects the output of blower 84 with the pressure vessel through a valve 90. Operation. The grab on the counterweight 74 removes shield plugs temporarily blocking the shoot 36 and places them in the tube 56, the counterweight then being lowered on to the top of the train. The blower 84 is started and the valve 90 gradually closed until the pressure drop in the channel 14 is sufficient to raise the train, the hoist 72 being operated to lift the counterweight so that the train rises at a desired rate. The actual pressure drop occurs across the lowermost block 18 whereby this block pushes the train upwards. When the upper block 26 has entered the tube 64 the remainder of the train is arrested by a locking device 54 at the top of tube 52 and the tube 64 is pivoted so that the grab on the counterweight 74 may place the block 26 in the tube 56, the remainder of the train being held against the device 54 by the coolant pressure. The counterweight is again lowered on to the train and the first five spent fuel elements 24 (i.e. the top third of the train) are allowed to enter the tube 64 by the counterweight after withdrawal of the locking device 54, this device then being operated to arrest the sixth element of the train. The sleeve 70 is disengaged and the valve 90 is opened to increase the flow in tube 64 so that the fifth element is separated from the sixth element. The tube 64 is connected to the storage tube 60 and the counterweight is lowered to force the spent elements into the tube 60 where they are retained by a lock (not shown). The arm 76 is retracted to permit the fuel elements in the tube 60 to be lifted by the grab of the flask 78 into the latter and to enable five new fuel elements in the tower to be lowered into the tube. The next five spent elements 24 are removed in the same manner by using the storage tube 62. The last five elements are only half-spent and these are placed in the tube 58 and are returned to the top end of the channel 14 after the ten new fuel elements have been inserted. In a modification (Fig. 3, not shown) the spent fuel elements are not removed to the flask but are discharged from the machine 42 through a conduit into a pool adjacent the reactor.