Patent Number: 039490262
Section: description

One embodiment of the method according to the invention will now be given hereinafter by way of example without thereby implying any limitation of the invention. a. Fabrication of the jacket: a graphite powder (particle size within the range of 80 to 125 .mu.) is mixed in the dry state with 20 % by weight of a phenolic resin, PA1 an aluminium mould which has previously been coated with a lubricant is filled with this mixture while being subjected to vibrations in the cold state, PA1 the mixture is heated in a hot-air oven at 300.degree.C, PA1 the jacket is removed from the mould and then has a density of approximately 0.72, PA1 coking is carried out in a nitrogen atmosphere at 900.degree.C, PA1 consolidation is carried out by means of a treatment at 900.degree.C with methane over a period of 5 hours (velocity of the methane stream: 6 cm/sec.). PA1 the jacket is filled while being subjected to vibrations with a mixture of 60 % of fuel particles (particle diameter of 1100 .mu.) and of 40 % graphite (in which a proportion of 20 % has a particle size within the range of 0 to 80 .mu. and in which a proportion of 80 % has a particle size within the range of 80 to 125 .mu.), PA1 the complete assembly is closed by a plug fabricated from a graphite paste (having a particle size within the range of 80 to 125 .mu.) to which are added 2 % polysaccharides, PA1 the fuel element is impregnated with propane at 940.degree.C over a period of 10 hours (velocity of the propane stream: 1 cm/sec.), PA1 there is thus obtained a fuel element in which the carbonaceous matrix has a density of 1.6. The jacket finally obtained then has a density of approximately 0.70 and a total open pore volume of 70 %. b. Fabrication of the fuel element: The fuel elements obtained by means of the method according to the invention can also be employed in water-cooled reactors of the pressurized-water or boiling water type. The powdered resins are preferably thermosetting resins such as urea formaldehyde, epoxydes, melamine formaldehyde, polyurethanes, phenol-formaldehyde and polyesters. The resin used in the example is a phenol-formaldehyde resin of the type sold under the trademarks "Resophene PB 105", "Resophene PL 353", "Resophene PL 149", by the Promedo Co and "Resin TPR" by Borden Chemical Co. The mixture of resin and graphite is heated to thermoset the resin which holds the mass together until the subsequent coking operation. The deposition of carbon by cracking of the gaseous hydrocarbon is disclosed in report CEA-R 2535 "Fabrication et proprietes de corps carbones prepares par craquage de gaz naturel" 1964 available at Documentation Francaise, Secretariat General, Direction de la Documentation, which is incorporated herein in its entirety. Said treatment is effected in a furnace, for example in an electrical furnace, preferably a high frequence induction furnace. Gaseous hydrocarbon or mixture of gaseous hydrocarbons such as methane, butane, propane, propene, etc.. are injected into said furnace. The element situated in the furnace is consequently in contact with the gaseous hydrocarbon stream. The velocity of said stream is a few cm/sec and the temperature is between 700.degree. and 1000.degree.C.