It is well recognized that the structural integrity of plasma facing material after a plasma disruption is one of the most important issues that threaten the engineering feasibility of a fusion reactor. In order to evaluate, quantitatively, the damage as consequence of the plasma disruption, each basic process of the phenomenon must be clarified as well as the coupled ones. The present paper, therefore, focuses on the following issues: (1) electromagnetics, (2) heat conduction with melting, (3) structural mechanics when material melts and resolidifies, (4) magnetohydrodynamics of liquid metal with free surface, (5) simple evaluation of coupled problem, (6) lifetime evaluation of first wall and (7) a new concept of the first wall, so called thermal-stress-free.