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Design of Self-Cooled, Liquid-Metal Blankets for Tokamak and Tandem Mirror Reactors

Yung Sheng Cha, Yousry Gohar, Ahmed M. Hassanein, Saurin Majumdar, Basil F. Picologlou, Dai Kai Sze, Dale L. Smith

Fusion Science and Technology

Volume 8 / Number 1P1 / July 1985 / Pages 90-113


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Results of the self-cooled, liquid-metal blanket design from the Blanket Comparison and Selection Study (BCSS) are summarized. The objectives of the BCSS project are to (a) define a small number (about three) of blanket concepts that should be the focus of the blanket research and development (R&D) program, (b) identify and prioritize the critical issues for the leading blanket concepts, and (c) provide technical input necessary to develop a blanket R&D program plan. Two liquid metals [lithium and lithium-lead (17Li-83Pb)] and three structural materials [primary candidate alloy (PCA), ferritic steel (FS) (HT-9), and vanadium alloy (V-15 Cr-5 Ti)] are included in the evaluations for both tokamaks and tandem mirror reactors (TMRs). There are major differences in relevant design parameters between a tokamak and a TMR, such as surface heat flux, first-wall erosion rate, and magnetic flux density. As a result, the magneto-hydrodynamic (MHD), heat transfer, and structural requirements for a tokamak reactor are much more stringent than that of a TMR. This has a significant impact on the design philosophy for the blankets. The reference design for the tokamak reactor is the poloidal/toroidal flow module, whereas that for a TMR is of the tube configuration similar to the Mirror Advanced Reactor Study design. Analyses were performed in the following generic areas for each blanket concept: MHD, thermal hydraulics, stress, neutronics, and tritium recovery. Integral analyses were performed to determine the design window for each blanket design. The Li/Li/V blanket for tokamak and the Li/Li/V, LiPb/LiPb/V, and Li7Li/HT-9 blankets for the TMR are judged to be top-rated concepts. In general, the blanket concept of a TMR is ranked higher than that of a tokamak reactor for the same coolant/structural material combination. This is the result of less stringent design requirements for a TMR compared to that of a tokamak reactor. Because of its better thermophysical properties and more uniform nuclear heating profile, liquid lithium is a better coolant than liquid 17Li-83Pb. From an engineering point of view, vanadium alloy is a better structural material than either FS or PCA since the former has both a higher allowable structural temperature and a higher allowable coolant/structure interface temperature than the latter. Critical feasibility issues and design constraints for the self-cooled, liquid-metal blanket concepts are identified and discussed.

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