Divertor plate erosion and radiating vapour shield formation during hard disruptions: Theory and numerical modelling

The time evolution of radiating vapour shields over eroding solid surfaces and the resulting erosion rates are modelled by one dimensional (I-D) and 1 1/2-D resistive MHD codes. Graphite or carbonized divertor plates subjected to high energy deuterium plasma particles during disruptions or giant ELMs are considered. The energy flux range assumed corresponds to ITER, conditions. Various physical phenomena having a primary effect on the erosion rate, such as collisional interaction of the energy carriers with the target (solid surface or vapour particles), electrostatic shielding, magnetohydrodynamic interaction and radiant energy transport, are investigated in detail. In the 1-D and 1 1/2-D approximations used and for the energy input parameter range considered (Q(0) = 10(11) W/m(2)) ablation rates of the order of 10(28)m(-2).s(-1) were obtained. It is shown that processes, such as lateral expansion, lateral drift, radiation losses through the lateral surfaces of the scrape-off layer (SOL) and the Hall effect, may notably change the predicted erosion rates and warrant a more elaborate, at least 2-D, treatment of the problem.