High heat-flux response of high-conductivity graphitic foam monoblocks

Abstract

Plasma-facing components based on the so-called monoblock design are planned for use in the divertor region of long-pulse plasma devices such as ITER and JT-60SA due to their capacity to handle high heat fluxes with active water cooling. The plasma-facing materials that are preferred for these monoblocks are tungsten for ITER or carbon-carbon fiber reinforced carbon (CFC) for JT-60SA. The requirements for the plasma-facing components include the ability to handle high plasma fluxes resulting in high temperatures. Therefore, reasonably high thermal conductivity is required. In this study, high thermal conductivity graphite foam is explored as a monoblock material. Four different test articles are created, two with the foam brazed to CuCrZr tubes, and two with the foam press fit to the tubes. These monoblocks are then thermally cycled at 8 MW/m2 in the high heat-flux test facility GLADIS to examine their robustness for long-pulse divertor applications. Experimental results are compared with computational fluid dynamics simulation. Graphite foam shows promise for use in a plasma-facing component, but further development is necessary to address the significant drop in thermal conductivity at high temperatures.