Patent GB-1136118-A (GB)
Title: Reactor control rod drive system
Inventor: BONNAURE PIERRE
IPC: G21C17/12
Filed: 1966-04-19
Abstract: 1,136,118. Winches. EUROPEAN ATOMIC ENERGY COMMUNITY. 19 April, 1966 [20 April, 1965], No. 17126/66. Heading B8B. [Also in Division G6] A drive system for a nuclear reactor control rod which can also be used as a safety rod for fast shut-down comprises a reel 1 on which is wound a cable 3 by which the rod is suspended, the reel 1 being rotatable in screw-threaded engagement on a fixed shaft 2, a gear 5 driven by a motor 18 and a coupling between the gear 5 and the reel 1 which is releasable so that the reel 1 may be released for free rotation, the gear 5 also being in screw-threaded engagement with the shaft 2, a braking element 16 having a resilient impact surface 17 engageable by the reel 1 at the unwinding end of its movement along the shaft 2, the gear 5 being independently movable along the shaft 2 for recoupling with the reel 1 at the unwinding end, and indicating means for the location of the rod which is connected to the gear 5 and disconnected from the reel 1 when the coupling is released. The cable 3 is wound in a single layer on the reel 1 and the pitch of the screw-thread is equal to that of the cable turns whereby a constant point of departure is obtained where the cable leaves the reel. The coupling between the gear 5 and the reel 1 is provided by a movable lever 8, one end of which passes through an aperture 22 in the gear 5 and which is formed as a driver lug 8a co-operating with a lug 4 on the reel 1. The lever 8 is supported on a bearing 23 for rocking movement between the coupling and decoupling positions, the ends of the lever 8 remote from the driver lug 8a being guided by a pin 24 in the groove of a sleeve 25 freely slidable on the shaft 2. Another lever 6 pivotally secured at one end on the gear 5 has the other end passing through the aperture 22 and normally pressed against the driver lug 8a by a spring (not shown). In the coupling position the lug 4 is situated between the driving lug 8a and the end of the lever 6, while in the decoupling position the lever 8 is so locked by the lever 6 that it cannot return to the coupling position. An electromagnet 9 has a movable armature 26 connected to the sleeve 25 by a third lever 27, a pin on the end of which runs in a helical groove 12 of the sleeve 25. In the operative state, i.e. when current is flowing through its winding, the electromagnet 9 holds its armature 26 in the left-hand end position (Fig. 1) in which a spring 13 is compressed and the sleeve 25 in the rght-hand end position. The motor 18 drives the gear 5 forwardly or backwardly according to reactor control requirements. Decoupling is initiated either by current failure or by deliberate disconnection of the current in the electromagnet 9 whereupon the armature 26 moves to the right by means of the spring 13, the sleeve 25 moves to the left, and the lever 8 draws the driver lug 8a back into the aperture 22. The reel 1 then rewinds until it reaches the impact surface 17 of the brake system. Recoupling is effected by bringing the gear 5 axially up against the reel 1, whereupon the lug 4 presses the lever 6 back against the spring 7 until the lever 8 is unlocked and rocks into the coupling position under the force of the energized electromagnet 9, as transmitted by the lever 27 and the sleeve 25. The motor 18 is then reversed and moves the gear 5 and the reel 1 to the right. The indicating means may consist of a forward/reverse counter connected to a reduction gear between the gear 5 and the motor 18. The counter can be directly calibrated to show the height of the control rod in the reactor duct.