| 摘要 |
An encapsulated element comprises a core of compacted powder of carbonaceous material and a particulate loading of metal or of nuclear fuel material distributed throughout the compacted powder of the core, the core having its outside surface covered by a compacted powder encapsulation of carbonaceous material free from said loading. The inside surface of the encapsulation is in intimate contact with and conforms precisely to the outside surface of the core, but there is no definite delineation between the encapsulation and core. The core may be made of natural or artificial graphite, purified or unpurified; petroleum coke, calcined or uncalcined; naturally occurring carbonaceous materials such as coal or lignite; mixed with ceramic materials or powdered metals with or without a binder. The binders may be coaltar pitches, petroleum pitches, resin binders, lignite, lignin or its derivatives. The nuclear fuel material may consist of particles of any uranium, plutonium or thorium compound which does not react with carbon at a temperature of not less than 900 DEG C. The nuclear fuel particles may be present with or without a carbonized coating, e.g. of pyrolytic carbon or a coating of aluminium oxide. After sizing, the ingredients of the core and encapsulation mixes are blended at or above room temperature. The blends are then crushed to the appropriate particle size for forming the core and encapsulation. The method of making the encapsulated element comprises forming a shell of the encapsulating mix which is open at the top; charging the core mix into the shell; shaping the core mix in the shell; closing the top of the shell by bringing a quantity of the encapsulating mix over the entire top of the shell; compressing the materials of the shell and core into a compact unitary element in which the material of the shell intimately contacts the core and performing a heating operation on the element at a temperature not less than 900 DEG C. The element may be spherical in shape. |
