Radioactivity Sputtered from Cooling-Pipe Materials into Coolant in the ITER Cooling System

The radioactivity induced by D-T neutron sputtering from piping materials to the coolant is described. The sputtering yields were calculated based on the systematics for (n,p), (n,), (n,2n), and (n,np) reactions. Four candidate piping materials of AISI Types 316L and 304 stainless steel, Incoloy 800, and V-4 Cr-4 Ti alloy were investigated to estimate their radioactivity sputtered to the coolant. The investigation shows that radioactivity of ~1500 to 2000 Ci sputtered into the coolant at 1000-s plasma burn time of ITER, and after 1-day cooling, a few curies of gamma activity remain in the coolant, which will accumulate in the heat exchanger.