Shutdown dose rate assessment during replacement of in-vessel components for a multi-module-segments maintenance scheme-based fusion DEMO reactor

Someya, Yoji; Uto, Hiroyasu; Hiwatari, Ryoji; Tanigawa, Hisashi; Tobita, Kenji

3D radiation map analyses were conducted using a code of DCHAIN-SP2001 on the basis of provisional water cooled fusion DEMO reactor as fusion power of 1.5 GW and major radius of 8.2 m. This analysis was performed assuming a divertor exposed for 1.0 FPY (full power year) and a blanket exposed for 4 FPY, respectively. As a result, after 1 month after shutdown the dose rate at the plasma center was 10 Sv/h. It dropped to 100 Sv/h at replacement port (upper and bottom). It was found that replacement of in-vessel components for DEMO could be possible. This is reason that the replacement method for fusion DEMO reactor can lower environment dose rate than the replacement method for shielding blankets in vacuum vessel for ITER by limiting a movable range of the remote handling equipment in maintenance port for DEMO.