GB868021A - Improvements relating to fuel element charging apparatus for gas cooled nuclear reactors - Google Patents

Abstract

868,021. Shoot construction. A. E. I.-JOHN THOMPSON NUCLEAR ENERGY CO. Ltd. June 10, 1959 [June 18, 1958], No. 19541/58. Class 78 (1). [Also in Group XL (a)] Each group of fuel element channels in the core 22 of a gas-cooled reactor is serviced through a stand pipe 13 extending through the pressure vessel 14 and disposed along the central axis of the group, the upper end of the stand pipe being sealed with a coupling 15 as described in Specification 851,459, and having a valve which may be opened when the coupling is sealed to a charging machine 16. A shoot 17 extends through the stand pipe from the charging machine to a locating socket 23 and a grab (not shown) on the machine 16 lowers the fuel elements singly through the shoot and into a selected fuel element channel. The shoot 17 comprises an outer tubular metal sheath 18 and an inner tubular duct which is flexible over the lower portion 19 but rigid above the point 20. The inner duct is connected to the charging machine and the sheath 18 is rotatable about the duct by bearings. The lower part of the sheath 18 has a longitudinal aperture 21 whereby the duct portion 19 may be laterally displaced therethrough and brought into alignment with the selected fuel channel. A parallelogram linkage 34 connects the sheath 18 with collars 32, 33 rotatable about the duct 19, the collars being connected to a pair of bars 31 attached at their top ends to a channel member 35 of semi-circular cross-section. The upper end of the member 35 is pivoted to the sheath 18 by a pin 36 and an arm 37 pivoted to the member is pivoted at 46 to a slider 38 vertically positioned by a rod 39 extending into the charging machine. Rod 39 is pivoted to a member 42 which in turn pivots at 43 about the slider 38. The end 47 of the member 42 abuts the end 48 of the arm 37 and initiates its rotational movement from the vertical position. Hence, upward movement of the rod 39 causes the channel member 35 to swing outwards. The fuel channel is selected by turning the sheath 18 so that the aperture 21 faces in the required radial direction and then laterally displacing the duct 19 by the rod 39. A gastight seal is made between the duct and the selected fuel channel by expanding a bellows 44 by wires which extend into the charging machine. To permit the coolant gas to flow at a controlled rate through the fuel element channel which is being serviced an orifice 45 is provided in the duct 19, the orifice having a sliding valve plate controlled by wires extending up into the charging machine. Thus, in a discharge operation, the gas flow, which would otherwise tend to increase as the number of fuel elements in the channel is reduced, is reduced by decreasing the size of the orifice. In a discharge operation, coolant gas may be additionally passed down the shoot from the discharge machine. The duct 19 comprises a series of short rigid tubes 51 spaced apart and connected by bellows sections 52. Adjacent tubes are located relative to one another by slotted clips 56 fitting over pins 57. A pair of longitudinal slots 55 receive projections on the fuel elements to maintain them correctly orientated for insertion in the fuel channels. In a modified shoot construction, Fig. 7, the shoot is rotatably supported by the charging machine and the inner tubular duct comprises an upper rigid portion 67, a flexible portion 62 and a lower rigid portion 61. The duct is laterally displaced through a longitudinal aperture 21 in the outer sheath 18 by arms 74, 75 of U-shaped cross-section pivoted together at 76, the arm 74 being pivoted at 77 to the rigid portion 61 and the arm 75 pivoted at 78 to a vertically movable control rod 79. The upper end of the portion 61 has an arm 72 of U-shaped cross-section pivoted at 73 to the sheath 18. The locating spigot 64 is mounted on a telescopic sleeve 63 having slots 65 receiving pins 66 extending from the sheath 18 whereby a gas-tight connection may be established between the spherical end surface 71 of the duct and a conial surface (Fig. 10, not shown), formed at the upper end of the fuel channels by lowering the shoot after the duct has been brought into alignment with the selected fuel channel. An aperture 84 in the duct portion 67 is provided with a sliding valve to control the gas flow through the shoot as in the first embodiment. Specification 859,351 also is referred to.