Patent GB-1225460-A (GB)
IPC: G21C7/14
Filed: 1969-12-19
Abstract: 1,225,460. Controlling reactors. SIEMENS A.G. 19 Dec., 1969 [21 Dec.,1968], No. 62108/69. Heading G6C. Means for connecting a control rod to a prime mover comprise aligned drive rods 15, 17 located for axial movement through a guide member 7, one end of drive rod 15 being connected to the prime mover, one end of drive rod 17 having a coupling device arranged to co-operate with the control rod to establish a releasable connection between drive rod 17 and the control rod, and coupling means 151, 153 which provide a releasable connection between the opposite ends of the drive rods 15, 17, the arrangement being such that when this connection is released axial movement of the drive rod 17 occurs to cause simultaneously the establishment of a fluid-tight seal of the guide member 7 and the release of the control rod by the coupling device. The reactor container has a rotatable cover 1 formed with an opening in which is located a hollow insert to which is secured an outer guide tube extending downwards into the container into the neighbourhood of a thermal shock plate. Extending coaxially within and downwardly beyond the outer guide tube is an inner guide tube. Between these guide tubes is a shielding plug 9 secured to the insert in the cover 1. The interior of the plug 9 serves to guide axial sliding movement of the member 7 to which the inner guide tube is rigidly secured. Inner drive rods 14, 16 are connected by a coupling means. The coaxial drive rods 14, 15 are connected to a magnetic holding device (Fig. 2, not shown) which is moved up and down by means of a spindle drivingly connected to a motor and gearing. Situated within the inner drive rod 16 is an ejecting rod (not shown) having at one end a cupped portion for receiving the end portion of the control rod when this is coupled to the drive rod 17, and being spring- loaded so as to urge the control rod into the reactor core upon its release from the coupling device. In normal operation, the drive rods 15, 17 and inner drive rods 14, 16 are moved up or down together with the control rod, the rod 15 being coupled to the rod 17 by means of a locking sleeve 151 and locking balls 153 engaging in a slot at the upper end of the rod 17, and the rod 14 being coupled to the rod 16 by means of a ball coupling 141, 142 engaging in a slot 161 at the upper end of the rod 16. At the lower end of the sleeve 151 is an increased internal diameter portion. If the sleeve 151 is raised relative to the rod 17, against the force of a spring 152, so that the balls 153 can enter this increased internal diameter portion, the coupling 151, 153 is broken and a tapered portion 171 of the rod 17 sealingly engages a tapered portion 72 of the guide member 7. In the event of a rapid shut-down being required, the magnetic holding device is deenergized and the rod 14 thrust downwards by the action of a compressed spring (not shown), this causing release of the coupling 141, 142 and the rod 16 to fall relative to the rod 17, and a plunger 162 carried by the rod 16 is pressed against the tapering internal surface of a cavity in the rod 17 to establish a fluid-tight seal. This displacement of the rod 16 is sufficient for a gripper head at its lower end to urge gripping pawls mounted on rod 17 outwards (Fig. 5, not shown) so as to release the control rod, the spring-loaded ejecting rod then shooting the control rod into its fully inserted position in the reactor core. For the release under non-alarm conditions of the couplings between rods 14, 15 and rods 16, 17, the control rod is initially lowered to its lowermost position, and the magnetic holding device is then de-energized and the coupling 141, 142 released in the same way as in the event of a rapid shut-down being required. The member 7 is then raised with the aid of a turning tool mounted on a shaft 19 carrying a travelling nut by which the movement of the member 7 can be accurately adjusted, the member 7 pushing before it the locking sleeve 151 which is raised relative to the rod 17 against the force of the spring 152, and the coupling 151, 153 is broken. The rod 17 then falls and the tapered portion 171 sealingly engages the tapered portion 72. The rod parts situated outside and inside the reactor container are thus disconnected and the chamber of the upper rod system can then be cleaned by gas flushing and later removed. In an alternative construction (Fig. 4, not shown), the locking balls 142, 153 are replaced by locking pawls. After the uncoupling of the rods 16, 17 situated inside the reactor container from the rods 14, 15 outside the container, the drive is removed from the shaft 19, and accordingly the member 7 remains in its uppermost position and the reactor parts situated outside the reactor container can be removed. Fuel element changing operations with the aid of the rotation of the cover 1 can then be performed.