VAPOR SHIELDING AND EROSION OF WALLS DURING TOKAMAK DISRUPTIONS

In evaluating the lifetime of ITER plasma facing components (PFC) agai nst heat loads that are not normal, credit is taken from the existence of a plasma shield which effectively protects the wall from excessive evaporation. The plasma shield formed from vaporized PFC material tho ugh beneficial for the PFC could become a potential threat for the tok amak because of the possible penetration of the impurity ions into the central plasma. This paper discusses various aspects of plasma shield s for a rather wide-range of heat load conditions. Evaporation and mel ting of PFCs, physical properties of the plasma shields, plasma shield :efficiencies for tilted targets and estimations on impurity transport from the plasma shield into the SOL of the main plasma are addressed The numerical results for power densities 0.1-10 MW/cm(2) are obtained with the newly developed 2D radiation-magnetohydrodynamics (R-MHD) co de FOREV-2. (C) 1998 Elsevier Science B.V. All rights reserved.