NIFS-998

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Author(s):

N. Yanagi, A. Sagara, T. Goto, S. Masuzaki, T. Mito, G. Bansal, Y. Suzuki, Y. Nagayama, K. Nishimura, S. Imagawa and O. Mitarai,

Title:

Heat Flux Reduction by Helical Divertor Coils in the Heliotron Fusion Energy Reactor

Date of publication:

Nov. 2010

Key words:

22 IAEA Fusion Energy Conference, FTP/P6-21

Abstract:

In order to best utilize the built-in helical divertors in the heliotron-type fusion energy reactor, we propose a new divertor sweeping scheme which could effectively reduce the divertor heat flux and mitigate the erosion of divertor plates. The concept employs a small set of helical coils, which we call the °»helical divertor coils°…. It is found that the divertor legs can be moved effectively by modulating the amplitude of the current in the helical divertor coils by pm2 % of the amplitude in the main helical coils. Despite the movement of divertor legs, the magnetic surfaces show almost no change with this scheme. The width of strike points is enlarged to ~800 mm and a fast sweeping reduces the heat flux < 1 MW/m^2 on time average having the total power flow of ~600 MW to the divertor regions with a 3 GW fusion power. Erosion of divertor plates would also be mitigated and the replacement cycle could be significantly prolonged. Regarding the engineering design of the helical divertor coils, we propose that these coils be fabricated using YBCO high-temperature superconductors. The coils could be constructed with prefabricated segments and jointed on site.

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