High-temp. gas-cooled reactor core of graphite blocks - contg. fuel elements of varying form causing gas channel outlet throttling

摘要

Core is composed of a number of fuel element units, each consisting of a prismatic graphite block of polygonal, esp. hexagonal cross-section, contg. vertical chambers in which numerous fuel elements are stacked and traversed by the coolant gas. The coolant gas passages are substantially parallel to the axis of the graphite block. The fuel elements in the fuel element units basically are of differing geometrical form and/or differing main dimensions, the fuel elements which cause a larger pressure drop in the coolant gas being located towards the outlet end of the hot coolant gas passages. Used in particular for a helium-cooled reactor. For a given permissible maximum temp. at the centre of the fuel elements, the gas outlet temp. can be increased without the total pressure drop across the core rising. The elements towards the outlet end of each chamber are smaller in size than the remainder, thus increasing the pressure gradient in this region and increasing the heat transfer at the surfaces of these smaller elements. This enables a higher gas outlet temp. to be used.