GB921348A - Improvements in or relating to servicing mechanisms for fluid-cooled nuclear reactors - Google Patents

Abstract

921,348. Servicing reactors. GENERAL ELECTRIC CO. Ltd. Jan. 2, 1962 [Jan. 4, 1961], No. 371/61. Class 39 (4). A servicing arrangement in which it is required to serve a group of eighteen fuel element channels 2 in a reactor core arranged on three circles of different radii centred on a control rod channel 4, Fig. 1, the arrangement utilizing a rotatable charge shoot having an articulated radially adjustable selector tube for engaging the ends of the channels, comprises an indexing member carried by the shoot and co-operating with sensing means within the reactor pressure vessel, the indexing member being coupled to a cam mechanism for radially adjusting the selector tube as disclosed in Specification 916,980, whereby as the shoot is rotated through intervals of 30 degrees the selector tube is automatically radiused to serve sequentially three channels situated, respectively, on the outer, middle and inner circles. The indexing member, Figs. 3, 4, 5, comprises a body 5 having a pair of spring-loaded plungers 6, 7, the plunger 6 carrying three stops 9 projecting through slots 10, four spring-loaded stops 11 being mounted in body slots 12. When the plunger 6 is raised, the stops 11 rotate under their spring-loading through 90 degrees from their projected position, Fig. 5, to their retracted position, Fig. 7. The sensing means comprises six vertical slots 15 around the control rod channel 4. In operation, the shoot is rotated to any one of six positions in which a channel 2 on the outer circle may be serviced and is then lowered, this movement being arrested by the stops 11 engaging the upper end of channel 4 at positions mid-way between the slots 15, Fig. 5, the cam mechanism positioning the selector tube to its outer radius. To service an adjacent channel 2 on the middle circle the shoot is rotated through 30 degrees and lowered whereby the stops 11 enter slots 15 and the shoot weight is taken by stops 9, the spring 19 loading plunger 6 being compressed so that stops 11 retract, Fig. 7. In this axial position of the body 5, the selector tube is moved to its middle radius by the cam mechanism. To service an adjacent channel 2 on the inner circle the chute is rotated through a further 30 degrees whereby the stops 9 enter slots 15, the stops 11 being ineffective since they remain retracted, this axial movement being arrested by a flange 16, Fig. 8. The selector tube is moved by the cam mechanism to its inner radius. To reset the indexing member to permit servicing of another channel 2 in the outer circle, the projecting pin 8 of plunger 7 is depressed, thereby pivoting the stops 11 and permitting them to be re-latched by the plunger 6 (Fig. 9, not shown). Specification 878,506 also is referred to.