Shielding Analysis for Toroidal Field Coils Around Exhaust Duct in Fusion Experimental Reactors

Shielding analyses for toroidal field coils (TFCs) around the exhaust duct in a nuclear fusion experimental reactor have been performed by two-dimensional discrete ordinate method, and their peak nuclear responses were evaluated. From the results, it was found that the duct wall of about 410 mm thickness was required incase of no shield structure behind the divertor in ordsr to satisfy the radiation limits of TFCs. Taking overestimation due to the analysis model simulating the exhaust duct with a toroidally continuos opening into account, nuclear responses may possibly be lower than the radiation limits by 300 mm thick duct wall. By providing a 480 mm thick shield with 140 mm wide slits behind the divertor, nuclear responses were reduced to about 1/20, and they were equal to or lower than the radiation limits for 200 mm thick duct wall. Also, taking overestimation, nuclear responses may possibly be more than six times lower than the radiation limits for 200 mm thick duct wall.