Speaker
Hiroyasu Utoh
(Japan Atomic Energy Agency)
Description
Maintenance is one of the critical issues in the DEMO design. Several maintenance schemes has been comparatively evaluated from the viewpoint of plasma positional control, in-vessel transferring mechanism of blanket segment, and pipe connection in order to establish a feasible reactor maintenance scheme on the DEMO reactor. Two options has been selected as likely remote maintenance schemes on DEMO; the banana-shaped segment transport using all vertical maintenance ports (BSAV), and the saddle-shaped segment transport using limited number of horizontal maintenance ports (SSLH). First, those schemes are quantitatively examined from the viewpoints of space for welding/inspecting and access of maintenance devices, and we conclude that both schemes still have several technological issues, however, demonstration of both maintenance schemes in DEMO is considered as feasible. Maintenance scheme also affects the configuration of in-vessel components, the arrangement of poloidal field (PF) coils, which have an impact on the plasma performance/control. Especially, higher plasma elongation requires a passive stabilizing effect on the positional instability by the in-vessel components as well as the vacuum vessel. Hence, we evaluate the stabilizing effect depending on the maintenance schemes of BSAV and SSLH. We analyze the stabilizing effect by the eddy current on the in-vessel component and the vacuum vessel for both maintenance schemes of BSAV and SSLH. These results suggest that the conducting shell of SSLH has a higher stabilization effect on vertical stability than of BSAV. In contrast, comparing BSAV and SSLH on the control coil power, we find that the BSAV scheme reduces the control coil power. For SSLH, four control coils (PF coils) are located far from the equatorial plane, thus the control coil current in SSLH becomes greater than that in BSAV. Therefore, from an overall perspective, the BSAV scheme seems to have an advantage regarding plasma vertical stability.
Co-authors
Akira Aoki
(Japan Atomic Energy Agency, Rokkasho, Japan)
Haruhiko Takase
(Japan Atomic Energy Agency, Rokkasho, Japan)
Hiroyasu Utoh
(Japan Atomic Energy Agency, Rokkasho, Japan)
Kenji Tobita
(Japan Atomic Energy Agency, Rokkasho, Japan)
Nobuyuki Asakura
(Japan Atomic Energy Agency, Rokkasho, Japan)
Ryoji Hiwatari
(Japan Atomic Energy Agency, Rokkasho, Japan)
Yoshiteru Sakamoto
(Japan Atomic Energy Agency, Rokkasho, Japan)
Youji Someya
(Japan Atomic Energy Agency, Rokkasho, Japan)
