Patent GB-967150-A (GB)
Title: Method and devices for handling fuel elements in a nuclear reactor
Inventor: GEMUCHIAN ANDRE
IPC: G21C19/04
Filed: 1963-03-22
Abstract: 967,150. Fuelling reactors. SOC. INDATOM, and COMPAGNIE DES ATELIERS ET FORGES DE LA LOIRE. March 22, 1963 [March 23, 1962; Aug. 23,1962 (2); Feb. 5, 1963; Feb. 8, 1963], No. 11515/63. Heading G6C. A fuelling shoot adapted for lowering into a reactor by a grab and having a displaceable fuel element guide arm for connection with the selected fuel element channel is characterized in that whilst the shoot is being lowered the guide arm is held in its retracted position within the shoot by the tractive force of the cable due to the weight of the shoot whereas when the shoot comes to rest on a support within the reactor so as to reduce the tractive force the guide arm opens out a predetermined distance to be aligned with the selected channel. As shown, Fig. 1, the reactor channels 3 are served in groups through access holes 12 by a charge machine 14 having a casing 15 enclosing a winch 16 controlling a cable 17 supporting the shoot 13. A unit 19 enables the shoot to be given a definite orientation before it is lowered into the selected hole 12, the displacements being at intervals of 60 degrees to enable the shoot to serve a selected one of six groups of channels 3. As shown in Fig. 2 the six shaded areas 27 represent the six groups, each group having five channels a...e, the central channel 26 being in alignment with a hole 12. When the shoot comes to rest on its support in the reactor the guide arm opens out automatically the required distance to serve a selected one of the channels a...e and also rotates about the longitudinal axis of the shoot to be aligned with the selected channel, the extent of these two movements of the guide arm being determined by a cam (described later) which is preset by the unit 19 before the shoot is lowered. The shoot, Figs. 3, 5 comprises top and bottom parts. 30, 31 rigid with one another, the part 30 having a hexagonal crosssection co-operating with a similar cross-section of the access holes 12 whereby the shoot is maintained in its correct orientation to serve a selected group 27. The portion 31 terminates in a cone 32 having a tip 33 which bears in a seating formed in the central channel 26 at the top portion 34 of the reactor core. Supports 35, 36 on the portion 31 pivotally carry a stirrup member 37 by means of a hollow shaft 43 and a swivel pin 40, the shaft 43 also being rotatable in the portions 30, 31 and carrying a cam 90. Link rods 52, 53 forming a deformable quadrilateral are pivoted to the stirrup 37 at 50, 51, the rod 52 having at its other end a spacing member 54 comprising a guide finger 55 co-operating with the cam 90. This other end of the rod 52 is pivoted at 56 to a link rod 57 pivoted at 58 to the rod 53, an extension of the rod 57 being pivotally connected at 59 to a support 60 of a carriage 61. A link rod 79 is pivotally connected at 78, 80 to the top of the carriage 61 and the link rod 53, the arrangement being such that when the links 52, 53 move about their pivots 50, 51, the carriage 61 is maintained vertical. The winch cable 17 extends through the shaft 43, over pulleys 62, 63 and through a hole 74 in the carriage 61 to a grab 68 adapted for holding a fuel element 70. A conical recess 72 in the upper end of the carriage co-operates with the grab 68 whereby when the shoot is lowered its entire weight is taken by the cable 17 and the carriage 61 is maintained in its retracted position as shown in Fig. 5. The cam 90, Fig. 6, has six grooves 100...105 receiving the finger 55 and corresponding, respectively, to the fuel element channels, 26, d, e, c, a, b, these grooves determining the extent of downward movement under gravity of the link 52 about its pivot 50 and also the degree of pivotal movement of the stirrup 37 in the part 31 about the axis of the shaft 43 and pin 40. Groove 100 is very short, groove 103 is rectilinear, grooves 101, 102 are helical with right-hand pitch and grooves 104, 105 are helical with a left-hand pitch. In Fig. 5 the groove 100 is in alignment with the finger 55 so that fuel elements may be transferred to or from the central channel 26 through a hole 76 in the cone 32. A counter-cam 92 operating in conjunction with the cam 90 is secured to a plate 91 integral with the part 31, a tooth 94 on the spacing member 54 co-operating with an opening 93 in the cam. Recesses 107, 108, 106, 109 in the cam 92 operate, respectively, in conjunction with grooves 101, 102, 103, 105 in the cam 90. A simplified shoot capable of serving only fuel element channels at one particular radial distance from the shoot axis and in a fixed radial direction as determined by the hexagonal-section of the access hole 12 is described with reference to Fig. 7 (not shown), the cams 90, 92 and stirrup member 37 being omitted. In another embodiment of the simplified shoot (Fig. 8 not shown) the link rods are replaced by tubular members embracing the shoot when in the closed position. In a modification of Fig. 8 (Fig. 10, not shown) a metal ribbon is provided to enable the shoot to be closed and withdrawn from the reactor in the event of breakage of the cable 17. Moreover, a pivoted stop member may be provided at the bottom of the, carriage 61 (Fig. 11, not shown) to retain a fuel element 70 should it be accidentally released by the grab 68, this stop member being moved into an inoperative position by mechanical engagement of the carriage with the upper end of the fuel channel to be served. To prevent unwanted upward movement of the fuel elements in the channel being served due to the coolant flow a counter-flow of coolant is directed down the shoot and to this end the shoot is made gas-tight. Such a gas-tight shoot, Figs. 13, 14, comprises a sleeve 303 of hexagonal cross-section for engagement in similar-shaped access holes 301, a downward extension 303a of the sleeve having an open side and engaging at the foot 308 thereof in a central reactor channel 309. A tube 305 slidable in the sleeve 303 has an internal groove 321 for engagement by a lifting grab (not shown), the tube being connected by a pin 313 to a connector pipe 304 having an open upper side providing a passageway for a knuckle joint 306. The joint 306 is connected by a pin 317 to the pipe 304 and has a sliding surface making a gas-tight seal with a concave bearing surface 306a formed in the tube 305. Link rods 307 connect a pin 318 on the extension 303a with a pin 319 on the pipe 304. When the shoot is lowered the tube 305 is in its upper position in the sleeve 303 and the pipe 304 is in its closed position. When the foot 308 meets the channel 309 the tube 305 continues to move down and the pipe 304 moves out to engage the sleeve 316 at the end of the fuel channel 302.