High thermal conductivity carbon-carbon composites arecandidates for the first wall of the International ThermonuclearExperimental Reactor (ITER). However, carbon-carbon compositeshave relatively high erosion rates caused by hydrogen bombardmentwhen the plasma disrupts. Such erosion may require frequentreplacement of the first wall panels and tiles, seriously reducingthe duty factor of the reactor. This program attempts to developa system to effect in situ repair of the damaged carbon-carbonsurfaces (without removing the original panels or tiles). Thissystem delivers a mixture of hydrocarbon gas and fine high thermalconductivity vapor-grown fibers or graphite powder to a nozzle formixing, heating, and deposit of a fiber-reinforced isotropic carbondirectly onto the damaged surfaces. The structure of the repaircarbon composite is tailored by controlling the depositionconditions to match the original carbon-carbon. In Phase I, amodel for the carbon deposition process is being developed. Themodelling work guides the conceptual design of the system. Preliminary design is being completed in Phase I. The equipmentwill be constructed in Phase II and operated to establishworkability. An experimental program based on the model developedin Phase I will be implemented to optimize deposition conditions. The structure of the repair carbon will be analyzed, anddepositions will be established to match the original carboncarbon. Specimens of the repair carbon will be fabricated for irradiationat Oak Ridge National Laboratory.Anticipated Results/Potential Commercial Applications as described by the awardee:It is anticipated that a model will be developed todefine conditions for deposition of a fiber-reinforced isotropiccarbon on the surface of the damaged carbon-carbon first walltiles. A conceptual design of a repair system will be completed,and preliminary drawings will be issued. The development of thisapparatus will have a positive effect on ITER economics bysignificantly reducing the downtime needed to replace first wallcarbon-carbon. The system may be used to develop strong joints incarbon-carbons.
