Kernbrennstoffelement

1,010,268. Fuel elements. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. April 7, 1964 [April 8, 1963], No. 13995/63. Heading G6C. A nuclear fuel element comprises an outer container enclosing an annular fuel body and resilient means for urging into intimate contact the surfaces of the fuel and container, to improve heat transfer therebetween. The outer container 18 is of graphite; seven such tubes are mounted between an upper graphite grid 16 and a lower grid 17 to form a fuel assembly. Coolant gas enters the container 18 through a vent 22 in its upper metal cap 19, and passes through reactive graphite 24 and an orifice 25 to the fuel, and thence through porous material 34, 35 to a small bore pipe. The fuel is in the form of annular rings, each ring formed by a number of segments and urged radially outward by a helical graphite member 26c or by a tubular spine 26a having a longitudinal split 26b. The fuel assembly is provided with a ring of electrical contacts 39, e.g. for thermocouple leads. A gas cooled reactor in which the fuel elements described can be used is helium cooled and utilizes a reflector of graphite blocks which are cooled by incoming coolant; moderation is by the graphite fuel element casings. Capillary tubes for each fuel element of each fuel assembly pass through coupling, pressure measuring and filtering devices and thence to the reactor coolant inlet; by this means the integrity of the fuel tubes may be monitored since a failure in a fuel tube will give rise to a marked purge line pressure increase.