GB991258A - Nuclear reactor fuel elements - Google Patents

Abstract

991,258. Nuclear fuel elements. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. May 23, 1963 [June 4, 1962], No. 21432/62. Heading G6C. A cluster of fuel members having sheaths of moderating material, e.g. graphite, in contact with one another except at voids which permit coolant flow over the members, is supported between end plates, each of the sheaths consisting of separate lengths the ends of which are sealed into perforated support grids. The junction between upper and lower sections 3, 4 of a fuel member is shown in Fig. 7, each section comprising a series of subsection 3a arranged end-to-end and enclosed by graphite sheaths 10, 11. Each sub-section 3a comprises tubular fissile members 5 mounted on a graphite spine 6 and enclosed in a graphite sleeve 8. The sub-sections 3a comprises tubular fissile members 5 mounted on a graphite spine 6 and enclosed in a graphite sleeve 8. The sub-sections 3a interconnect by means of a spigot 14 on the upper end of each spine 6 engaging with a socket 15 of the lower end of each sleeve 8. The ends of the sheaths 10, 11 are of reduced section to form spigots 19 which engage with sockets 20 in a graphite support grid 2. The junctions between the spines 6 and sleeves 8, between adjacent sleeves 8, and between sheaths 10, 11 and the grid 2 are high temperature bonded to provide a firm and rigid joint between the sections 3, 4. Referring now to Fig. 6, the upper end plate 12 has on its underside three screw-threaded sockets 22 for the location of the upper ends of fuel members 1a and seventeen sockets 23 for the location of the upper ends of the remaining fuel members 1. Each fuel member 1a has a metal end cap 24 with an extension 25 carrying a flexible diaphragm 26. A screw-threaded collar 29 engages each socket 22 to clamp the diaphragm 26 to the plate 12,the collar 29 being countersunk to allow flexing of the diaphragm whereby differential expansion of the fuel members 1a can be accommodated. To accommodate thermal expansion of the fuel members 1, the upper sections 3 have graphite extensions 31 which slidably engage the sockets 23. The lower ends of the fuel members 1, 1a are located in the lower end plate 13 by countersunk apertures 34 and secured by screw bolts 35 as shown in Fig. 8. The lower sleeves 8 are secured in the lower ends of the sheaths 11 by screw threaded collars 36 and have tubular extensions 37 to which are bonded stainless steel tubular end caps 38 screw threaded to engage the bolts 35. Each of the fuel members 1 has a resiliently flexible bellows 39 interposed between the extension 37 and the end cap 38 so that they are merely laterally located by the apertures 34 and end caps 38 whilst the members 1a are rigidly secured to the lower end plate 13. Fission products can be purged from the fuel members by a stream of coolant gas drawn through apertures 58 in the sheaths 11, upwardly between the sleeves 8 and the sheathes 11, 10, thence downwardly via the interfaces sleeves 8 tubular members 5 and tubular members 5/spines 6, and out through a nozzle 46b. Side apertures 53 in a conical member 46 secured to the underside of plate 13 provide access for cooling fluid which flows upwardly through passageways 52 to the passageways between the fuel members 1, 1a and the apertures 33 in the plate 12. For charging and discharging the cluster into and from a reactor core, a central bore 32 provides access for a lifting grap to a lifting attachment 55 secured to the plate 13, the bore 32 normally being closed by a plug 56 to which is attached an elongate graphite rod 57. Specification 967,203 is referred to.