ROLE OF RADIATION IN VAPOR SHIELDING OF FIRST WALL DURING DISRUPTION

An initially ablated vapor may provide an important radiation shield t o reduce the heat load and the further ablation of the Be divertor str ike plate during an ITER disruption. Thus, we investigate the role of line emission in Be at relevant temperatures and densities. For an ion density of 10(18) cm(-3) (10(24) m(-3)), We calculate that there is s ignificant line emission and re-absorption in the temperature range fr om 3 to 10 eV. The re-absorption limits the line emission that strikes the plate. Line transfer calculations coupled with detailed atomic mo deling predict that lines contribute 10-50% of the impinging plate rad iation. We note that because of this effect, previous calculations usi ng multi-group radiation transfer may under-estimate the vapor shieldi ng for these ITER-relevant parameters.