Transient thermal and stress analyses of the ITER shielding blanket/first wall under off-normal conditions

Transient thermal and stress analyses have been conducted with the following three off-normal conditions for the shielding blanket and first wall (FW) structure of International Thermonuclear Experimental Reactor (ITER). (1) Loss of Flow Accident (LOFA) (2) Loss of Coolant Accident (LOCA) (3) Power Excursion Condition (PEC) The main results obtained are as follows : 1) In case of FW LOFA/LOCA, time to reach 400degC is 18 s at Beryllium surface, in case of shield LOFA/LOCA, time to reach 400degC is 90 s at 316SS internal rib, and in case of FW and shield LOFA/LOCA, time to reach 400degC is 17 s at Beryllium surface. 2) In case of FW LOFA/LOCA, maximum temperatures to satisfy 3Sm limits are 280degC for FW Cu alloy and 285degC for 316SS internal rib and in case of shield LOFA/LOCA, maximum temperatures to satisfy 3Sm limits are 248degC for FW Cu alloy and 170degC for 316SS internal rib. However, detail design guideline for off-normal conditions should be established and the stress should be reevaluated in future. 3) In case of FW LOFA/LOCA, plasma must be shut-down in a few seconds after the initiation of these events so as to prevent excursion of FW temperature and stress, while plasma shut-down requirement could be relatively relaxed in case of shield LOFA/LOCA. 4) Stresses and displacements during FW LOFA and FW LOCA are nearly equal. So are those during shield LOFA and LOCA. 5) Power excursion up to 1.8 GW shows no problem. (author)