GB1473009A - Nuclear reactor - Google Patents

Abstract

1473009 Controlling nuclear reactors COMMISSARIAT A L'ENERGIE ATOMIQUE 4 Dec 1974 [14 Dec 1973] 52470/74 Heading G6C The invention concerns an arrangement for guiding control rods of e.g. a pressurized water reactor, in which each rod (Fig. 1, not shown) comprises a multiplicity of absorber pins (2) whose upper extremities are connected by radial spiders (6) to a common, central stem (4). The guiding arrangement comprises (Fig. 3) a rigid top plate 16 supported, at its periphery, against the reactor vessel, a plurality of relatively long vertical tubes 22, an intermediate plate 20, relatively short tubes 28 and a bottom plate 27 (which forms the top plate of the reactor core). Each long tube 22 is of sufficiently large diameter to contain an entire control rod; its upper end is secured to the top plate 16 opposite a respective aperture 24 therein and its lower end is secured to the intermediate plate 20 opposite a plurality of apertures 32 therein equal in number to the number of pins provided on the control rod. The intermediate plate 20 lies below the level of coolant outputs from the reactor vessel. The short tubes 28 each lie in alignment with aligned apertures 32, 40 in the intermediate and bottom plates 20, 27 so that each tube 28 encompasses a single pin of the associated control rod. Both intermediate and bottom plates 20, 27 are provided with further apertures 34, 42 for coolant flow. The short tubes 28 may be sufficiently rigid to afford the sole mechanical connection between the intermediate and bottom plates 20, 27 but, alternatively, are relatively thin-walled and the mechanical connection is afforded otherwise (Fig. 5, not shown). Further guidance of a control rod within each long tube 22 is afforded by an arrangement of vertically-spaced guide plates 44 (Fig. 4) within the long tube; each plate 44 comprises smalldiameter apertures 46 for passage of the absorber pins 2, a larger central aperture 48 for passage of the central stem 4 and radial slots 50 connecting the larger and smaller apertures and for passage of the spider 6.