GB1170740A - Method and apparatus for the production of Fuel and/or Breeder Elements for Nuclear Reactors - Google Patents

Abstract

1,170,740. Fuel elements. KERNFORSCHUNGSANLAGE JULICH G.m.b.H. 13 Dec., 1966 [16 Dec., 1965], No. 55725/66. Heading G6C. A fuel element in which the fuel material is disposed in a chamber between an outer spherical casing formed of carbon, more particularly hard carbon, graphite, ceramic material, or sintered metal and a core body, is formed by applying a filler body shellwise to the core body by spraying-on or casting of a material which is readily removable thermally, chemically or mechanically, applying the casing to the filler body, removing the filler body, introducing fuel material into the resulting chamber between the casing and the core body, and sealing the casing. A synthetic plastics material such as polyethylene, or a metal may be used for the filler body. It is expedient in some cases to make the core body and the casing from the same material. At least two diametrally oppositely situated and radially directed pins, the lengths of which extend through the casing, may be arranged on the core body. During the step which follows the spraying-on or casting of the filler body on to the core body, and wherein the casing is expediently applied by pressing, these pins serve to centre the core body in the press apparatus. If graphite powder, mixed with phenol resin, pitch and/or other binding agent, is used for the casing and the core body, a spherical core body is first pressed at a pressure of 1500 to 2000 kg/cm.<SP>2</SP> The press tools are kept at about 250‹ C. so as to obviate arranging the hexagonally built-up graphite crystals in such a manner that in the finished mouldings zones are formed in the equatorial region which have an irregular orientation, so-called pressure wedges. If the filler body is of polyethylene or metal, the member formed of the core body and the filler body is held at about 1250‹ C. after the pressing-on of the casing for a period of some weeks. The filler body melts and frees the desired chamber, also the phenol resin used as a binder is coked. In a further stage, the body intended for accommodating the fuel material is heated for graphitization in an electric furnace at 2500‹ to 3000‹ C.