EROSION REDEPOSITION ANALYSIS OF THE INTERNATIONAL THERMONUCLEAR EXPERIMENTAL REACTOR DIVERTOR

Sputtering erosion of the proposed International Thermonuclear Experimental Reactor (ITER) divertor has been analyzed using the REDEP computer code. A carbon-coated plate, as well as beryllium and tungsten plates, have been examined at medium and low plasma edge temperatures. Peak net erosion rates for carbon and beryllium are very high (approximately 20 to 80 cm/burn·yr) though an order of magnitude less than the gross rates. Tritium buildup rates in co-deposited carbon surface layers may also be high (approximately 50 to 250 kg/burn·yr). Plasma contamination from divertor sputtering, however, is low (≲0.5%). Operation with low-Z divertor plates at high duty factors, therefore, appears unacceptable due to erosion, but may work for low duty factor (approximately 2%) 'physics phase' operation. Sweeping of the poloidal field lines at the divertor can reduce erosion, typically by factors of approximately 2 to 8. A tungsten-coated plate works well, from the erosion standpoint, for plasma plate temperatures of approximately 40 eV or less.