Erosion and Redeposition of Divertor and Wall Materials during Abnormal Events De91 006439

.. this time. lt is then expected that the next generation of large tokamaks have to be deHigh energy deposition to in-vessel comsigned to withstand several hundreds of these ponents of fusion reactors is expected to disruptions. Another abnormal condition reoccur during abnormal operating conditions, sults when a neutral beam used in heating the This high energy dump in short times may replasma shines through the vacuum chamber to sult in very high surface temperatures which parts of the wall with no plasma present. A may cause severe erosion as a result of third abnormal event results from the genera,melting and vaporization of these comtion of runaway electrons with very high ponents. One abnormal operating condition energy and their deposition on wall areas folresults from plasma disruptions where the lowing a plasma disruption. plasma loses confinement and dumps its energy on reactor components. Another abnormal The high energy deposition in short times condition occurs when a neutral beam used in during various abnormal events will result in heating th_ plasma shines through the vacuum very high surface temperatures and may cause vessel to parts of the wall with no plasma melting and vaporization of these compopresent in the chamber. A third abnormal nents. The net erosion rates resultlng from event that results in high energy deposition both melting and vaporization are very imporis caused by the runaway electrons to chamber tant in estimating the lifetime of such components following a disruption. The components.I Materlals for plasma facing failure of these components under the expected components must have the ability to withstand high heat loads can severely limlt the repeated high heat loads associated with these operation bf the fusion device. The abnormalities without suffering disabling redeposition of the eroded materials from damage. The effect of plasma disruption on these abnormal events over the first wall and divertor candidate materials for current other components may cause addltlonal probdisruption parameters expected in a machine 1ems. Such problems are associated with tri, like ITER is analyzed. The damage expected tium accumulation in the freshly deposited mafrom a neutral beam shine through to parts of terials, charge exchange sputtering and addithe first wall is also analyzed. The intertional impurity sources, and material action of runaway electrons with reactor compatibility issues, components and the resulting damage is