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Spheromak Magnetic Fusion Energy Power Plant with Thick Liquid-Walls

R. W. Moir, R. H. Bulmer, T. K. Fowler, T. D. Rognlien, M. Z. Youssef

Fusion Science and Technology

Volume 44 / Number 2 / September 2003 / Pages 317-326


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A power plant based on a spheromak device using liquid walls is analyzed. We assume a spheromak configuration can be made and sustained by a steady plasma gun current, which injects particles, current and magnetic field, i.e., helicity injection, which are transported into the core region. The magnetic configuration is evaluated with an axisymmetric freeboundary equilibrium code, where the current profile is tailored to support an average beta of 10%. An injection current of 100 kA (125 MW of gun power) sustains the toroidal current of 40 MA. The magnetic flux linking the gun is 1/1000th of the flux in the spheromak. The geometry allows a flow of liquid, either molten salt, (flibe-Li2BeF4 or flinabe-LiNaBeF4), or liquid metal such as SnLi, which protects most of the walls and structures from damage arising from neutrons and plasma particles. The free surface between the liquid and the burning plasma is heated primarily by bremsstrahlung, line radiation, and some by neutrons. The temperature of the free surface of the liquid is calculated and then the evaporation rate is estimated from vapor-pressure data. The impurity concentration in the burning plasma, about 0.8% fluorine, is limited to that giving a 20% reduction in the fusion power. The divertor power density of 620 MW/m2 is handled by high-speed (100 m/s) liquid jets. Calculations show the tritium breeding is adequate with enriched 6Li, and a design is given for the walls not covered by flowing liquid (~15% of the total). We identified a number of problem areas needing further study to make the design more self-consistent and workable, including lowering the divertor power density by expanding the flux tube size.

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