Patent GB-1368498-A (GB)
Title: Nuclear reactor installation incorporating apparatus for controlling movement of a control member thereof
IPC: G21C9/027
Filed: 1971-11-26
Abstract: 1368498 Controlling reactors INTERATOM INTERNATIONALE ATOMREAKTORBAU GmbH 26 Nov 1971 [28 Nov 1970] 55109/71 Heading G6C  A nuclear reactor control apparatus, for moving a control member between a first position and a second position in which its degree of insertion in the reactor core is less than that in the first position, comprises an insertion device for bringing about movement of the control member from its second position to its first position so as to reduce reactivity of the core. This device (Fig. 4) comprises a helical spring 38 bearing at its lower end on a fixed abutment plate 37 and at its upper end on a flange armature 45 fixed to the upper end of a tube 43 extending downwardly coaxial with the spring 38 to a retaining device 47 by means of which it is coupled to a shaft 34. The control rod 1 (Fig. 1) formed of three hinged sections is connected via a coupling device 7, a traction rod 8 and a bayonet connection 9 to a rod 10, which in turn is connected via a releasable gripper clutch (29) (Fig. 3, not shown) to the lower end of the shaft 34. Coaxially within the tube 43 is a threaded spindle 29 carrying a nut 40 to which is secured a disc 41. An annular electromagnet 44 is mounted on the disc 41. On rotation of the spindle 39 by means of an electric motor 52 through reduction gearing 50, an overload clutch 51 and a gas-seal packing 49, the disc 41 slides downwardly together with the electromagnet 44 and armature 45 (when the eletromagnet is energized), thus compressing the spring 38 while at the same time lowering the shaft 34. In the lowermost position of the shaft 34, the control rod 1 is positioned with its lower end fitted in sealing fashion in a reduced diameter portion of a guide tube 2, thereby preventing entry of coolant into the tube 2. In the event of a shut-down, the control rod 1 is raised into the reactor core to the position shown in Fig. 1 where it is adequately cooled by flow of coolant. To bring about rapid shut-down, the current to the electromagnet 44 is cut off releasing the armature 45 which is pressed up by the biased helical spring 38, drawing the tube 43 along with it. By this means the control rod 1 is pulled into the core zone. As the control rod 1 approaches its shut-down position, it is decelerated by a damping piston (13) on the rod 10 entering a damping cylinder (12), (Fig. 2, not shown). The guide tube 2 is retained at its upper end in a centering tube 6 which is connected at its upper end to a guide tube (17), (Figs. 2 and 3, not shown), which in turn is connected at its upper end to a plug (18). The plug (18) comprises a sealing cone (19) and an upward extension sleeve (20) having an external screwthread threaded into a nut (21) by means of which the sealing cone (19) can be raised to bear against a correspondingly shaped internal core (22) to prevent the escape of gas from the reactor. Simultaneously, the tubes (17) and 6 are also raised, to such an extent that a gap is formed between the tubes 1 and 2, thus enabling the reactor cover to be rotated (providing the bayonet connection 9 is released) for the purpose of changing fuel elements.