Development of Divertor High Heat Flux Components for ITER in JAERI

Abstract

Development of divertor high heat flux components is one of the critical issues to realize next generation fusion experimental reactors, such as ITER. In ITER, the surface heat flux to the divertor is designed to be 5 MW/m2 in normal operation and 20 MW/m2 in transient operation. To withstand such high heat fluxes, the plasma-facing surface of the divertor components is covered with refractory armor materials. A carbon-fiber-reinforced carbon composite (CFC) is one of the candidate armor materials for the ITER divertor plate. JAERI has vigorously been developing the divertor high heat flux components with CFC armor materials. High heat flux experiments of various divertor mock-ups were carried out in a high heat flux test facility in JAERI. As a result of a thermal cycling experiment, a small-scale divertor mock-up with 3D-CFC armor tiles could withstand a cyclic heat flux of 20 MW/m2 for 1000 cycles with no degradation of thermal performance. A silver-free braze technique using Cu-Mn braze material was found to be a promising solution for the ITER divertor application. As a result of thermal cycling experiments of full-scale ITER divertor mock-ups, the mock-ups with 1D-CFC armor tiles could endure a cyclic heat flux of 5 MW/m2 up to 1000 cycles with no degradation of the braze interface of the 1D-CFC armor tiles. On the other hand, the mock-up with 3D-CFC armor tiles showed detachment of some armor tiles in an early stage of the experiment.