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The Influence of Physics Parameters on Tokamak Reactor Design

David A. Ehst, Kenneth Evans, Jr., Weston M. Stacey, Jr.

Nuclear Technology

Volume 43 / Number 1 / April 1979 / Pages 28-41


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Twelve important tokamak reactor parameters were surveyed, and the results of sensitivity studies serve as a guide for reactor design. Numerous magnetohydrodynamic equilibria are studied to determine influences of geometry, pressure profile, safety factor, and beta on the plasma current. A steady-state transport model, which averages particle and power balances in flux space, reveals the effects of temperature and density profiles, impurities, and temperature on power density and i τ. The blanket/ shield thickness, major radius, and magnetic field are likewise shown to influence reactor performance. For a fixed beta and reactor power, the design is quite insensitive to the relative contributions of density and temperature profiles to the total pressure over a wide range of profile widths, whereas the current generally increases for more D-shaped plasmas. If beta increases significantly at low aspect ratio or high elongation, reactor size can decrease; for the scaling laws βt = 0.21 A−1 and βt = 0.05 k, the plasma current may increase prohibitively for A ≲ 3.0 and k ≳ 2.0. Significant improvements occur at large power levels; typically, power output doubles with 15 to 20% increases in major radius and current.

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