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 t wo-dimensional discrete ordinate method and their peak nuclear respons es were evaluated. From the results, it was found that the duct wall o f about 410 mm thickness was required in case of no shield structure b ehind the divertor in order to satisfy the radiation limits of TFCs. T aking overestimation due to the analysis model simulating the exhaust duct with a toroidally continuos opening into account, nuclear respons es may possibly be lower than the radiation limits by 300 mm thick duc t wall. By providing a 480 mm thick shield with 140 mm wide slits behi nd the divertor, nuclear responses were reduced to about 1/20, and the y were equal to or lower than the radiation limits for 200 mm thick du ct wall. Also, taking overestimation, nuclear responses may possibly b e more than six times lower than the radiation limits for 200 mm thick duct wall.