Patent GB-1234190-A (GB)
IPC: G21C7/12
Filed: 1967-12-13
Abstract: 1,234,190. Controlling reactors. FAIREY ENG. Ltd. 6 Dec., 1968 [13 Dec., 1967], No. 56627/67. Heading G6C. A control element drive mechanism incorporates a rapid-drive unit adapted to be assembled in one condition for effecting scram withdrawal of a neutron-absorber control element and in another condition for effecting scram insertion of a fuel control element, the drive mechanism providing normal low-speed drive for the associated control element in both directions with the rapid-drive unit assembled in either condition. The drive mechanism comprises a reversible frame 11 made of end plates 12, 13 and parallel tie rods 15 which constitute a slideway. Each end plate 12 or 13 has mounting means (not shown) which enable the frame 11 to be fixed with one end adjacent the reactor core and aligned with a fuel or control channel. A leadscrew 23 is journalled at its ends in bearings in the two end plates 12, 13 and is driven by a motor 45 through a reduction gear 46. A nut 27 in threaded engagement with the leadscrew 23 is mounted non-rotatably in a housing 28 secured to a driven saddle 20. The driven saddle 20 and a follower saddle 21, which are urged away from one another by compression springs 22 acting between them, are slidably mounted on the tie rods 15. The housing 28 also carries a solenoid 29 and latching members 30 pivotally mounted at 32 and connected by pivoted links 35 to an armature sleeve 36 slidably mounted on the housing 28. When the solenoid 29 is energized, the sleeve 36 is moved to rotate the latching members 30 into engagement with abutments 38 on the follower saddle 21 so as to latch the two saddles 20, 21 together. A damping cylinder 40 of dashpot type is mounted at one end of the frame 11 to receive a piston attached to the outer face of the follower saddle 21 when this reaches the limit of its travel away from the driven saddle 20, upon de-energization of the solenoid 29. A pair of rods 51 (only one shown) connect the follower saddle 21 to a coupling yoke 52, to which the associated control element is attached by means of an extension bar 53. The drive mechanism can be employed for either scram insertion or withdrawal by means of a simple conversion involving reversing the mounting of the frame 11. Fig. 1 shows the frame 11 mounted for a scram-withdrawal action, for use with a fuel control element. In the event of an emergency, an external safety device will de-energize the solenoid 29, thereby releasing the latching members 30, whereupon the compression springs 22 force the follower saddle 21 rapidly away from the driven saddle 20 and thereby effect the scram withdrawal of the fuel control element. To convert the drive mechanism for use with an absorber control element, the frame 11 is dismounted, reversed end - to - end, and remounted opposite the required control channel by means of the end plate 13. The motor unit 44 is mounted on the end plate 12 and the follower saddle 21 is coupled to the yoke 52 of the absorber control element by another pair of rods 51 which are shorter in length. The drive mechanism will now operate as before through the leadscrew mechanism 23, 27 to provide the normal drive for the control element. However, on release of the latch members 30 under " fault " conditions, the springs 22 will drive the follower saddle 21 inwardly giving a scram insertion of the absorber control element.