GB1278799A - Nuclear fuel elements - Google Patents

Abstract

1278799 Fuel elements COMITATO NAZIONALE PER L'ENERGIA NUCLEARE 5 Aug 1969 [20 Aug 1968] 39204/69 Heading G6C A vented fuel element bundle comprises a space provided at the top of the bundle, a plurality of small tubes whereby the released fission gases are conveyed towards the upper section of the space, and means for conveying these gases from the lower section of the space to the exterior of the fuel element. Each fuel rod 1 in the bundle consists of a metal tube 9 housing nuclear fuel 8, fertile material 11, 14 and a porous medium 12, with a space 10 between the fuel 8 and fertile material 11 for allowing for fuel expansion and for receiving condensed fission products. The upper end of tube 9 is connected to a capillary tube 3 by means of an adapter plug 13. In one embodiment, shown in Fig. 8, fuel rods 1 are housed in a duct 2 of hexagonal cross-section beneath a chamber 32 of toroidal form for collecting the gaseous fission products. Two passages are provided for a liquid metal coolant flow: one is between the duct 2 and the outer wall of the chamber 32; the other passage 33, which has the profile of a Venturi tube, is defined by the inner wall of the chamber 32. A plurality of apertures 28 are provided at the narrowest section of passage 33. The capillary tubes 3 pass through the bottom of the chamber 32 and extend to the top of the chamber. Gaseous fission products flow from chamber 32 through the apertures 28 and are removed by the small portion of the coolant which flows through the passage 33. The latter by means of a tube 30 communicates with a part of the cooling system where the gases are separated from the liquid metal coolant. The dimensions of the chamber 32 are such that, in any predictable transient conditions, the coolant level within the chamber will never reach the upper ends of the tubes 3.