Designing a Fusion Power Plant with Superconducting Training Magnets

Fusion power has the potential to revolutionise global energy production with a reliable, low CO2 (not zero due to the use of steel, concrete etc. that typically produce CO2 during manufacture), low radioactivity power supply, that is readily available at the point of need. The ITER and SPARC reactors are already under construction, with plans to begin full-power (Qfus ≥ 10) operation in the early 2030s; proving that fusion is a viable energy source. To see wide adoption however, reactors must be made as commercially attractive as possible. Here we present superconducting pilot reactor designs that have been optimised for minimum capital cost using the PROCESS systems code. Key design choices were made using technologies that are either available now or already in development; with concentrated effort these reactors could be built on 2030-2040 timescales. We focus primarily on the reactor from this set with the lowest overall capital cost, our “preferred” reactor: a 100 MW net electricity producing tokamak with REBCO superconducting toroidal field coils and central solenoid and Nb-Ti superconducting poloidal field coils. In addition, we have investigated using ductile, remountable Nb-Ti training coils (named after the training wheels of children’s bicycles) during the commissioning phase of a reactor to remove the risk of brittle failure of the full-power magnets during this stage. Such magnets would operate at lower field, but would enable thorough machine testing. Finally, we investigate and predict how advances in magnet technologies could effect our preferred reactor design and cost, and conclude that the effects of such advances do not justify waiting yet longer before beginning detailed reactor design and construction

Analysis of Tokamak fusion device parameters affecting the efficiency of Tokamak operation

Nuclear Power has been available as a relatively clean and reliable energy source for several decades. While tokamak engines have been in existence almost as long as successful fission-powered nuclear generators, they have not yet reached operational success for energy generation. This meta study collates key fusion device parameters and determines ideas on the applicability of fusion devices for energy. This paper supports the argument that toroidal tokamaks are not limited by volume whereas spherical designs have a potential volume limit, spherical tokamaks use a lower magnetic field current than toroidal tokamaks. Further scientific and engineering progress is required before tokamak devices can be a viable technology to be used for energy generation

Calculation of Asymmetry factor using the Solution of Equilibrium Problem

In this work we presented a theoretical calculation of the asymmetry factor (Shafranov parameter) by solving the simplest Grad–Shafranov Equation (GSE) with the  Solove’v assumption for a low-beta and large-aspect-ratio tokamak with a circular cross section.  In this paper we calculated the current-independent relation for the asymmetry factor (Shafranov  parameter)

Spatiotemporal evolution of runaway electrons from synchrotron images in Alcator C-Mod

In the Alcator C-Mod tokamak, relativistic runaway electron (RE) generation can occur during the flattop current phase of low density, diverted plasma discharges. Due to the high toroidal magnetic field (B = 5.4 T), RE synchrotron radiation is measured by a wide-view camera in the visible wavelength range (~400-900 nm). In this paper, a statistical analysis of over one thousand camera images is performed to investigate the plasma conditions under which synchrotron emission is observed in C-Mod. In addition, the spatiotemporal evolution of REs during one particular discharge is explored in detail via a thorough analysis of the distortion-corrected synchrotron images. To accurately predict RE energies, the kinetic solver CODE [Landreman et al 2014 Comput. Phys. Commun. 185 847-855] is used to evolve the electron momentum-space distribution at six locations throughout the plasma: the magnetic axis and flux surfaces q = 1, 4/3, 3/2, 2, and 3. These results, along with the experimentally-measured magnetic topology and camera geometry, are input into the synthetic diagnostic SOFT [Hoppe et al 2018 Nucl. Fusion 58 026032] to simulate synchrotron emission and detection. Interesting spatial structure near the surface q = 2 is found to coincide with the onset of a locked mode and increased MHD activity. Furthermore, the RE density profile evolution is fit by comparing experimental to synthetic images, providing important insight into RE spatiotemporal dynamics