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September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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Fusion Science and Technology
August 2025
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U.S. nuclear fuel recycling takes two steps forward
Late last week saw two announcements from companies working to recycle used nuclear fuel on a commercial scale, providing welcome news to anyone hoping to see the United States move to unlock the hidden potential of the more than 94,000 metric tons of spent fuel stored at power plant sites around the country.
D. R. Mikkelsen, H. Maassberg, M. C. Zarnstorff, C. D. Beidler, W. A. Houlberg, W. Kernbichler, H. Mynick, D. A. Spong, P. Strand, V. Tribaldos
Fusion Science and Technology | Volume 51 | Number 2 | February 2007 | Pages 166-180
Technical Paper | doi.org/10.13182/FST07-A1297
Articles are hosted by Taylor and Francis Online.
We explore whether the energy confinement and planned heating in the National Compact Stellarator Experiment (NCSX) are sufficient to test magnetohydrodynamic (MHD) stability limits, and whether the configuration is sufficiently quasi-axisymmetric to reduce the neoclassical ripple transport to low levels, thereby allowing tokamak-like transport. A zero-dimensional model with fixed profile shapes is related to global energy confinement scalings for stellarators and tokamaks, neoclassical transport properties are assessed with the DKES, NEO, and NCLASS codes, and a power balance code is used to predict temperature profiles. Reaching the NCSX goal of <> = 4% at low collisionality will require HISS-95 = 3, which is higher than the best achieved in present stellarators. However, this level of confinement is actually ~10% lower than that predicted by the ITER-97P tokamak L-mode scaling. By operating near the stellarator density limit, the required HISS-95 is reduced by 35%. The high degree of quasi-axisymmetry of the configuration and the self-consistent "ambipolar" electric field reduce the neoclassical ripple transport to a small fraction of the neoclassical axisymmetric transport. A combination of neoclassical and anomalous transport models produces pressure profile shapes that are within the range of those used to study the MHD stability of NCSX. We find that <> = 4% plasmas are "neoclassically accessible" and are compatible with large levels of anomalous transport in the plasma periphery.