SPUTTERING EROSION OF BERYLLIUM COATED PLASMA-FACING COMPONENTS - GENERAL-CONSIDERATIONS AND ANALYSIS FOR ITER DETACHED PLASMA REGIME

Sputtering erosion is a key performance issue for beryllium coatings i n future fusion reactors. Past analysis of this subject for various ed ge plasma regimes-as briefly reviewed here-shows acceptable erosion on ly for low duty factor devices. Erosion analysis is now focusing on a very low boundary temperature (less than or equal to 2 eV) 'detached p lasma' regime for the International Thermonuclear Experimental Reactor (ITER) Vertical Director design. Erosion and tritium codeposition cal culations are made for this regime using a coupled WBC/REDEP/DEGAS(+) code analysis. The analysis includes calculations of low energy, obliq ue incidence, sputtering yields using the VFTRIM-3D code calibrated to fit recent data on D-Be sputtering. We find that beryllium performs b etter than carbon for detached conditions due to the absence of chemic al sputtering. Beryllium performs worse than vanadium or tungsten. Net erosion rates of beryllium coated first wall components, due mainly t o physical sputtering by charge exchange D-T neutrals, vary from simil ar to 0 to 2 cm per burn-year along the wall. Tritium co-deposition in redeposited beryllium surface layers may be high. (C) 1997 Elsevier S cience S.A.