GB1361698A - Nuclear reactor having control-rod retaining means - Google Patents

Abstract

1361698 Controlling reactors WESTING- HOUSE ELECTRIC CORP 1 Aug 1972 [13 Sept 1971] 35872/72 Heading G6C A nuclear reactor control rod mechanism includes pivoted magnetic levers 4 movable between a holding position in which they are capable of engaging a control rod drive shaft 10 and a release position in which the levers are displaced from the drive shaft, and permanent magnets 22 movable between a first position (right-hand side of the Fig.) in which they lie in a magnetic circuit including parts of the levers so as to provide a magnetic face to retain the levers in their holding position and a second position (left-hand side of the Fig.) in which they permit the levers to assume their release position. The levers 4 are pivoted about pins 5 to a bushing 6 slidable in a tube 1. A spring 14 biases the lower ends of the levers into engagement with a groove 9 at the head of drive shaft 10. The force exerted by the spring is insufficient to hold the shaft 10 against the action of gravity thereon, the shaft 10 being held up normally by means of an electromagnetic gripper mechanism (not shown). With the magnets 22 in their lower (second) position, they are shunted by enclosing tubes 21, so that the levers are able to release the shaft 10 should the gripper mechanism become de-energized. However, with the magnets 22 in their upper (first position) they co-operate with magnetic members 20 in the wall of tube 1 to provide a magnetic path (allowed) which acts on the levers to retain them in their holding position. The magnets 22 are normally urged to their lower position by means of thrust exerted downwardly by members 37 which are secured to a missile shield. When, for refuelling, the shield and members 37 are raised, the magnets 22 move to thier upper position under the action of springs 31. The slidable mounting of bushing 6, and an arrangement of Bellville washers 43, enables the bushing 6 and levers 4 to accept any shock which might occur should the gripper mechanism be de-energized while the levers 4 are retained in their holding position. In a modification (Figs. 7-9, not shown), the magnetic members 20 are replaced by annular members (52) to eliminate necessary alignment procedures. Coils 13 are provided to determine the positions of the control rod. To permit replacement of coils 13, their support tube 48 can be detached from a tube 18 supporting the magnet arrangement by virtue of the provision of a bayonet connection comprising co-operable pins and slots.