Abstract: Removal of the graphite structure from the nuclear fuel material of fuel elements of gas-cooled high-temperature reactors is performed by heat-treatment of the fuel elements in oxygen-containing gas at temperatures below 700.degree. C. until the carbon or graphite structure is loosened up and converted into a mechanically removable material. During heat-treatment, mechanical forces are preferably applied for continually removing the outer layers that are most heavily attacked and transport of the dust into cooler temperature zones. For this purpose, the fuel elements are agitated during heat-treatment, as by an oscillating sieve or by brushes. Pre-impregnation with a material catalyzing the combustion is useful if it is important to have the heat-treatment temperature as low as possible.

Abstract: A top reflector for a nuclear-reactor vessel, i.e. the containment for a nuclear-reactor core, especially of a high-temperature or pebble bed reactor, is composed of laterally contiguous bodies (e.g. of graphite) which can be suspended from a support and in which means is provided for the form-fitting interengagement of the adjacent bodies to prevent collapse of the top reflector upon failure of the suspension.

Abstract: A nuclear energy plant with a reactor protecting container in which below the reactor core there is provided a cooled collecting container for molten core masses while cooling pipes are inserted in the wall of the collecting container. The cooling pipes are designed as heat pipes. One end of the pipes is arranged within the region of the inner wall of the collecting container. The other end of the pipes extends into the inner chamber of the cooling tank which is arranged outside the reactor protecting container or containment and is open toward the atmosphere.