GB1384564A - Control apparatus for nuclear reactors - Google Patents

Abstract

1384564 Controlling reactors CLARKE CHAPMAN Ltd 4 April 1973 [8 May 1972] 21329/72 Heading G6C Control apparatus for nuclear reactors comprises a U-shaped guide, a first limb of which guides a weight and the second limb of which guides a neutron-absorber element, the weight and the element being connected by a flexible member extending around the curved base of the U-shaped guide, means being associated with the first limb for holding the weight in an upper position prior to releasing it and for lifting the weight to restore it to its upper position. A reactor core 12 contained in a pressure vessel 10 has guide tubes 14 passing through it (only one shown) and each affords a passageway for entry of an absorber rod 18 into the core 12. One such rod is shown in retracted position at the entrance to the tube 14. The lower end of each tube 14 communicates with the limb of a U-tube 20, the other, longer limb of which extends upwardly past the core 12 towards the top of the vessel 10. Each absorber rod 18 is connected via two dummy elements in the form of rods 22, 24 to one end of a flexible steel strip 26 which extends around the curved base of the U-tube 20 and is connected at its other end to a rodshaped weight 28. The flexible strip 26 is provided with spaced pairs of rollers 30. The vessel roof 40 has a stepped opening 44, closed by a tubular plug 46 and seals at 48 and connected to a tubular duct 42 which in turn is connected to the upper end of the longer limb of the U-tube 20. The upper end of weight 28 is connected to the lower end of a tubular armature assembly 50. The annular armature proper (52) is releasably held by an annular electromagnet (54) (Fig. 2, not shown) which depends from the lower end of the plug 46. Also depending from the lower end of plug 46 is a tube 56 carrying at its lower end a tubular hydraulic shock absorber 58, a movable member of which is engageable by the annular under-surface of the armature (52). A re-cocking rod 70 extends through the plug 46 and has a disc (72) at its lower end engageable with the annular under-surface of the armature (52). In order to shut down the reactor quickly, the electromagnets (54) of all the control devices are de-energized so that the weights 28 are released and the absorber rods 18 are pushed up into the core 12. Where the apparatus is applicable as a primary control, additional mechanism is necessary for providing the normal control movements while the weight is effective, as already described, to move the control rod into the core in an emergency.