The development and thermal testing of graphite/metal bonds for fusion reactor applications

As the energy content of tokamaks increases, the erosion rate of the first wall will become severe and a thick coating or cladding of low-Z materials may be needed. For this purpose, graphite/Mo or graphite/W clad materials with an intermediate layer of Mo, V, Mo-V or V-Ti were prepared by a solid state reaction bonding technique. The claddings obtained were evaluated as to their possible use as first wall materials for fusion reactors. Pulsed electron beam heating experiments showed that the graphite/Mo cladding survived one second pulses of heating at a power density up to 15 MW/m2. On the other hand, the flux limit was 25 MW/m2 for the graphite/W cladding for the pulses of 1.5 s. However, when melting of the substrate occurred, a poor adhesion zone was formed close to the melt area and this requires further investigation. (orig.)