Thermal reradiation in the NET/ITER plasma chamber

Abstract

The reradiated heat flux in the NET/ITER plasma chamber and its effects on the thermal behaviour of the plasma facing components are analyzed under transient conditions for normal loadings and for the abnormal case of loss of cooling in the divertor. The axisymmetry and the actual geometry and thermal loading distribution in the presently envisaged plasma chamber configuration are taken into account and the heat removal in the divertor and first wall adequately modelled. The protection material considered is CFC composite brazed on the divertor TZM heat sink and mechanically attached to the 316L first wall structure with either conduction - or radiation - cooling at inboard and outboard. The results show among other things that significant heat flux can be reradiated. In the most favourable case (conductive protection at inboard and radiative at outboard) 0.28 MW/m 2 is reradiated at the equatorial zone of the outboard first wall for a nominal peak heat flux of 0.6 MW/m 2. However even in this case, the maximum steady state CFC temperature (∼ 1800°C for a 15 mm tile thickness) is probably too high for the requirements of plasma material interaction. Thus the viability of this radiativity cooled protection is questionable for pulses longer than − 200 s.