Induced nuclear reactions: processes – systems – and elements – Nuclear fusion – Chamber structure or material
Patent
1994-06-29
1996-12-10
Wasil, Daniel D.
Induced nuclear reactions: processes, systems, and elements
Nuclear fusion
Chamber structure or material
165168, G21C 1108
Patent
active
055838952
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to forming a sealed passage in a part of refractory composite material.
A particular, but non-exclusive, field of application of the invention is making structures of refractory composite material that are cooled by a flow of fluid.
Refractory composite materials are materials that comprise fiber reinforcement constituted by fibers of refractory material, densified by a matrix that is also of refractory material. The refractory material constituting the fibers may be carbon or a ceramic (e.g. silicon carbide). The same applies to the material constituting the matrix.
Densification of the fiber reinforcement by the matrix consists in filling the voids initially present around the reinforcement with the material that constitutes the matrix. Such densification may be implemented by impregnating the fiber reinforcement with a precursor of the matrix and by subsequently transforming the precursor. Thus, a carbon matrix may be obtained by impregnating the fiber reinforcement with a resin having a high coke content, by causing the resin to cross-link, and by pyrolysis. Another common densification technique consists in performing chemical vapor deposition or infiltration. To this end, the fiber reinforcement is placed in an enclosure into which a gas is admitted, the gas being such that under determined conditions of temperature and pressure it causes matrix-constituting material to be deposited on the fibers of the reinforcement, said deposition being produced by the gas decomposing or by a chemical reaction between the components of the gas on contact with the fibers and throughout the volume of the reinforcement. Thus, a carbon matrix may be obtained by decomposing one or more gaseous hydrocarbons.
Whatever the technique used for densifying the fiber reinforcement, the voids initially contained therein are never completely filled. The composite material retains residual porosity.
Refractory composite materials are remarkable for their thermostructural properties, i.e. their excellent resistance to mechanical forces, thus enabling them to constitute structural elements, in combination with their ability to retain this mechanical strength up to temperatures that are relatively high.
Nevertheless, in applications at very high temperatures (e.g. above 1700.degree. C.) and over periods of time that are relatively long, it is necessary to consider active cooling of parts made of refractory composite material.
Thus, to achieve thermal protection of a deflector of a toroidal enclosure used for electromagnetic confinement of a plasma, proposals have been made to fix bricks of carbon/carbon (C/C) composite material (having carbon fiber reinforcement and a carbon matrix) on metal tubes conveying a flow of cooling fluid. The bricks of C/C composite material provide thermal protection while the metal tubes serve both to provide the cooling fluid circuit and to provide the structure that imparts mechanical strength to the assembly. The use of different materials, namely a refractory composite material together with a metal, raises difficulties associated with the differences in thermal expansion of said materials.
In the same application, U.S. Pat. No. 5 023 043 (corresponding to EP 0 181 385) describes a thermal protection structure made up of graphite elements having housings in which metal tubes are brazed to enable a cooling fluid to flow. The metal tubes provide the mechanical strength of the structure, since graphite cannot perform that function. The tubes are made of a material, such as molybdenum, that has a coefficient of thermal expansion that is close to that of graphite, and they are dimensioned so as to avoid being subjected to deformation in use.
In the prior art thermal protection systems mentioned above, the thermal protection function is provided by the C/C composite material or by the graphite, while the structural function is provided by the metal tubes of the cooling circuit.
The properties of refractory composite materials make it possible to consider implementing a thermal
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Filipuzzi Ludovic
Huet Philippe
Societe Europeenne de Propulsion
Wasil Daniel D.
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