GB1402788A - Nuclear reactor and control mechanism therefor - Google Patents

Abstract

1402788 Controlling nuclear reactors COMMISSARIAT A L'ENERGIE ATOMIQUE 19 June 1973 [20 June 1972] 29028/73 Heading G6C Nuclear reactor control apparatus comprises a sleeve 24 (Fig. 3) disposed in the core, a control rod (23) (Fig. 2, not shown) movable in the sleeve and having a top extension 25 terminating in a head 33 releasably held by a gripper 26 provided at the lower end of a tube 27 which can be raised and lowered to position the control rod, an axially movable gripper actuating rod 49 enclosed in the tube 27, an outer guide tube 28 which is raisable and lowerable independently of the tube 27, and, in its lower position (as shown) overlies and closes the top of the sleeve 24, and a mechanism for raising and lowering the guide tube 28, the mechanism including a splined joint to allow the tube 28 to move axially, without rotation of its drive, in response to differential thermal expansion between the sleeve 24 and a main containment vessel (2) (Fig. 1, not shown) relative to which the drive is fixed. Guide tube drive.-The upper end of the guide tube 28 (Fig. 4) passes through a supporting frame 57 secured in a larger one 13 of two rotatable plugs in the reactor top shield and terminates in a threaded part 64 surrounded by and meshing with a rotatable nut 65 whose enter surface has axial splines 66 meshing with splines on an axially fixed drive ring 67 supported on roller bearings 77. An outer surface part of the ring 67 is toothed and meshes with a pinion 69 at the lower end of a shaft 70 the latter being rotatable either by a manually operable crank 104 (Fig. 5) via gearing 101, 102 or by a non-manual means (not shown). Control rod drive.-The control rod drive tube 27 is guided in the guide tube 28 through the agency of bearing pads 54 (Zig. 3) and, at its upper end, projects from the guide tube 28. The projecting part (Fig. 5) is formed externally with teeth 86, so as to constitute a rack, meshing with a pinion 87 on a horizontal rotatable shaft 88 connected by an electromagnetic coupler 89 to a gear train 90, 91 and a motor reduction gear unit 92. For normal operation the coupler 89 is engaged, but for emergency operation it is disengaged to allow tube 27 to fall freely, this fall being braked by a fluid dash-pot (Fig. 6, or Fig. 7, not shown)' Gripper actuation.-The gripper 26 embodies pivoted jaws 34 (Fig. 3) shaped to co-act with a rounded protuberance 50 at the lower end of the actuating rod 49. At its upper end (Fig. 5) the rod 49 projects beyond the control rod drive tube 27 and has a threaded part surrounded by and meshing with a rotatable nut fixed to a gear 93. The latter meshes with a gear 94 splined to an elongate shaft 96 which is rotatable from a reduction gear unit 99 via gearing 97, 98. The gears 93, 94 are housed in a casing 95 secured to the upper end of the control rod drive tube 27 to move axially with the latter relative to the shaft 96.