Speaker
Youji Someya
(Sector of fusion research and development)
Description
Periodical replacement of in-vessel components is required for DEMO. The surface dose rate of in-vessel components for DEMO with fusion power of 1.5 GW is higher than that of shielding blanket in ITER by double digits. In addition, DEMO requires five-year cooling time for decreasing its dose rate to the level of ITER. Therefore, it is difficult to adopt the in-vessel maintenance scheme as ITER in terms of plant availability. To consider a maintenance process for DEMO, 3D shutdown dose rate map was analysed with MCNP-5 and DCHAIN-SP2001. The operation time of blanket (F82H) and divertor (W mono-block) is assumed to be 4 years and 1 year, respectively. The proposed maintenance scheme has an assumption that blanket integrated with shielding block (SB) is replaced through a vertical upper port whereas divertor also integrated with SB is replaced through a bottom port. To reduce dose rate, robot arm should approach from behind a SB and be fixed with an attachment of the SB. Based on the scheme, the dose rate in each maintenance port was evaluated.
Before replacement, the spatial dose rate in a maintenance port for blanket and for divertor at the beginning of maintenance was 0.01 Gy/h and 0.1 Gy/h, respectively. When the divertor with the SB was removed, the spatial dose rate in each maintenance port was 100 Gy/h. After the replacement with new equipment, the dose rate in each maintenance port would be 10 Gy/h. The spatial dose rate in vacuum vessel of ITER during maintenance is determined as 250 Gy/h according to the requirement for remote handling of shielding blanket. The proposed maintenance scheme can limit the use of remote equipment only in a maintenance port leading to the reduction of the dose rate in the maintenance area for DEMO in comparison with ITER.
Co-authors
Hiroyasu Utoh
(Sector of fusion research and development, Japan Atomic Energy Agency, Kamikita-gun, Aomori, Japan)
Hisashi Tanigawa
(Sector of fusion research and development, Japan Atomic Energy Agency, Kamikita-gun, Aomori, Japan)
Kenji Tobita
(Sector of fusion research and development, Japan Atomic Energy Agency, Kamikita-gun, Aomori, Japan)
Ryoji Hiwatari
(Sector of fusion research and development, Japan Atomic Energy Agency, Kamikita-gun, Aomori, Japan)
Youji Someya
(Sector of fusion research and development, Japan Atomic Energy Agency, Kamikita-gun, Aomori, Japan)
