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Can hydrogen be the transportation fuel in an otherwise nuclear economy?
Let’s face it: The global economy should be powered primarily by nuclear power. And it probably will by the end of this century, with a still-significant assist from renewables and hydro. Once nuclear systems are dominant, the costs come down to where gas is now; and when carbon emissions are reduced to a small portion of their present state, it will become obvious that most other sources are only good in niche settings. I mean, why use small modular reactors to load-follow when they can just produce that power instead of buffering it?
E. Barbato, V. Pericoli-Ridolfini, C. Castaldo, B. Esposito, E. Giovannozzi, C. Gormezano, G. Granucci, M. Leigheb, M. Marinucci, F. Mirizzi, L. Panaccione, S. Podda, M. Romanelli, P. Smeulders, C. Sozzi
Fusion Science and Technology | Volume 45 | Number 3 | May 2004 | Pages 323-338
Technical Paper | Frascati Tokamak Upgrade (FTU) | doi.org/10.13182/FST04-A517
Articles are hosted by Taylor and Francis Online.
Strong electron internal transport barriers (ITBs) are obtained in the Frascati Tokamak Upgrade (FTU) with the combined injection of lower hybrid (LH) (up to 1.9 MW) and electron cyclotron (EC) (up to 0.8 MW) radio-frequency waves. ITBs occur during either the current plateau or the ramp-up phase, both in full and partial current drive (CD) regimes, up to ne0 > 1.4 × 1020 m-3, relevant to ITER operation. Central electron temperatures Te0 > 8 keV, at ne0 [approximately equal to] 0.8 × 1020 m-3, are sustained for up to 36 confinement times. The ITB extends over a region where a slightly reversed magnetic shear is established by off-axis LHCD and can be even larger than r/a = 0.5. EC power is used either to benefit from this improved confinement by heating inside the ITB or to enhance the peripheral LH power deposition and CD with off-axis resonance. Collisional ion heating is also observed, but thermal equilibrium with the electrons is not attained since the electron-ion equipartition time is always 4 to 5 times longer than the energy confinement time. An extensive transport modeling of these discharges, performed by means of the ASTRA code, is also presented. During the ITB phase, the ion diffusivity is close to the neoclassical value while the electron shear-dependent Bohm-gyro-Bohm model accounts quite well for Te(r,t), The Ray Tracing Fokker-Planck model, used to describe the LHCD physics, appears satisfactory to analyze and interpret the experimental results. It turns out that the barrier radius is mainly influenced by the LHCD deposition. In particular, a wider barrier is obtained the lower qa is and the larger the plasma density is.