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In this paper in the framework of the feasibility studies of the International Tokamak Experimental Reactor (ITER), the thermal behavior of the monoblock divertor plate has been investigated at the Joint Research Centre of the Commission of the European Communities. The design consists of cooling tubes embedded in a protective armor of graphite, a material that has given good results in plasma physics experiments. Previous parametric studies, based on a thermal flux peak of 15 MW/m[sup 2] and different materials, led to the choice of a Mo-Re alloy for the tubes and a high-conductivity carbon-fiber composite called SEP for the graphite armor. To comply with a design temperature of 1273 K, an allowable protective layer only 5 mm thick was indicated; however, because of the high erosion rate due to sputtering, the lifetime of such a plate would be unacceptable from an engineering standpoint. To overcome this difficulty, it has been proposed that the separatrix be swept to lower the flux peak during the transient. The nominal working condition then becomes a sweeping of the separatrix moving around the null point with a radius of 40 mm and frequency of 0.3 Hz: this generates a thermal load varying in timemore » on the divertor plates. The results lead to the conclusion that plasma sweeping can reduce the surface temperature peak of the divertor, allowing a 16-mm-thick protective layer of the armor.« less |
