Patent GB-940919-A (GB)
Title: Improvements in or relating to nuclear reactor fuelling arrangements
Inventor: HILLIARD PETER THOMAS
IPC: G21C19/18
Filed: 1961-07-11
Abstract: 940,919. Fuelling reactors; reactors. BABCOCK & WILCOX Ltd. July 11,1962 [July 11, 1961], No. 25150/61. Heading G6C. In a gas-cooled reactor having a core with upright fuel channels enclosed within a pressure vessel, a fuelling machine, including a fuel element magazine, is disposed within the pressure vessel above the core and is positionable in relation to the channels by rotational movements about an upright axis and by horizontal translatory movements. Fuelling arrangements. As shown, Fig. 1, a gas-cooled reactor core 1 having upright fuel channels (not shown) is supported by a biological shield 5 in a pressure vessel 3. A fuelling machine 23 is movable along a trackway on a gantry 20 having rollers 21 engaging a circular runway 22 within the pressure vessel. The machine 23 includes a hoist and a replaceable fuel element magazine rotatable about a vertical axis whereby fuel elements may be transferred between the fuel channels and the magazine compartments. A duct 30 forming a lateral extension of the pressure vessel supports a track member 32 and the gantry 20 may be aligned with this track member so that the machine 23 may be moved to a zone 31 within a vertical shaft 33. The shaft 33 has a lining shown diagramatically at 33a and extends at its lower end to a decay pond 34 and includes valves 35, 35a to provide a gas lock. In a fuelling operation, which may be performed whilst the reactor is under load, the machine 23 is brought to the zone 31 and the magazine containing spent fuel elements is lowered by a hoist 37 through the opened valve 35. The magazine is released from the hoist and the latter is withdrawn, the valve 35 then being re-closed. Valve 35a is opened and a conveyer 38 is lifted therethrough to receive the magazine and lower it into the pond 34. A magazine containing new fuel elements is introduced into the lining 33a through a valved port 36, the valves 35, 35a being closed. The port 36 is closed, valve 35 is opened and the new fuel element magazine is raised by the hoist 37 on to the machine 23, the machine then returning to the gantry 20. In a modification (Fig. 2, not shown) a biological shield extends across the top of the core beneath the fuelling machine and supports the latter, the shield having openings closed by removable plugs; also, the duct forming the lateral extension leads to two vertical shafts, one shaft serving for discharging a spent fuel element magazine and the other for introducing a new fuel element magazine. In a further modification, Fig. 3, the fuelling machine 23a movable on a gantry 20 as in Fig. 1 operates in conjunction with a fuel handling machine 23b similarly movable on a gantry 59 rotatable on a circular runway 61 beneath the core 1 within the pressure vessel 3. The fuelling machine 23a includes a non-demountable fuel element magazine 25 and a fan for drawing coolant thereover but does not include a hoist. The machine 23b includes a rod 65 formed of links and wound on a drum 64 so that the rod may be thrust through a nozzle 66 into the fuel channels. In operation, spent fuel elements in a channel are raised by the rod 65 so that they are loaded into the magazine 25, the machine 23a then being moved on a track 32 to a zone 57 so that the fuel elements may be discharged singly through a shaft 50a. The empty magazine is now moved to a zone 58 where it is loaded with new fuel elements through a shaft 52a. In a further modification, Fig. 4, the fuelling machine 23 is carried by a gantry 70 pivotally supported on a vertical axis on a carriage 71 movable along a runway 72 to fuel element discharging and charging zones 48, 49. According to another modification, Fig. 5, it is not necessary to remove the machine 23 from a position above the core 1, the spent fuel elements being discharged from the magazine 25 through a conduit 75 to a magazine 76 situated outside the pressure vessel 3, the space around the magazine 76 being pressurised to equal that in the reactor. Another conduit and magazine (not shown) similar to 75, 76 are provided for loading the magazine 25 with new fuel elements. According to a further modification (Fig. 6, not shown) the pressure vessel is of concrete and the shaft 33 of Fig. 1 extends through the vertical wall of a biological shield interposed between the pressure vessel and the core. Reactors. In Fig. 1 the space beneath the shield 5 is divided into two coaxial parts 6a, 6b by a sleeve 6, a conduit 7 leading to the part 6a and a coaxial conduit 8 leading to the part 6b. The part 6b contains superheater tubes 9, evaporator tubes 10 and economiser tubes 11, channels 17 leading from the part 6b to an annular space formed between coaxial sleeves 15,16. A blower 13 causes the coolant gas to flow through the space between conduits 7, 8, through space 6a and channels 12, through the core 1 into the space 14, the gas returning through the space between sleeves 15,16, through channels 17 and space 6b to the conduit 8. Thus the machine 23 is cooled by the coolant flow. The reactivity is controlled by rods (not shown) operated by cables 40 extending over pulleys 41 to a control unit 42. Alternatively, reactivity is controlled by varying the height of neutron absorbing liquid contained in tubes extending through the core.