Among the top puzzles in the development of fusion energy is the best shape for the magnetic facility — or “bottle” — that will provide the next steps in the development of fusion reactors. Leading candidates include spherical tokamaks, compact machines that are shaped like cored apples, compared with the doughnut-like shape of conventional tokamaks. The spherical design produces high-pressure plasmas — essential ingredients for fusion reactions — with relatively low and cost-effective magnetic fields.
A possible next step is a device called a Fusion Nuclear Science Facility (FNSF) that could develop the materials and components for a fusion reactor. Such a device could precede a pilot plant that would demonstrate the ability to produce net energy.
The two most advanced spherical tokamaks in the world today are the recently completed National Spherical Torus Experiment-Upgrade (NSTX-U) at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL), which is managed by Princeton University, and the Mega Ampere Spherical Tokamak (MAST), which is being upgraded at the Culham Center for Fusion Energy in the United Kingdom.
ITER (International Thermonuclear Experimental Reactor) is an international nuclear fusion research and engineering megaproject, which will be the world's largest magnetic confinement plasma physics experiment. It is an experimental tokamak nuclear fusion reactor that is being built next to the Cadarache facility in Saint-Paul-lès-Durance, south of France.
The ITER project aims to make the long-awaited transition from experimental studies of plasma physics to full-scale electricity-producing fusion power stations. The ITER fusion reactor has been designed to produce 500 megawatts of output power for several seconds while needing 50 megawatts to operate. Thereby the machine aims to demonstrate the principle of producing more energy from the fusion process than is used to initiate it, something that has not yet been achieved in any fusion reactor.
Construction of the ITER Tokamak complex started in 2013 and the building costs are now over US$14 billion as of June 2015. The facility is expected to finish its construction phase in 2019 and will start commissioning the reactor that same year and initiate plasma experiments in 2020 with full deuterium–tritium fusion experiments starting in 2027. If ITER becomes operational, it will become the largest magnetic confinement plasma physics experiment in use, surpassing the Joint European Torus. The first commercial demonstration fusion power station, named DEMO, is proposed to follow on from the ITER project
High performance superconducting magnets play an important role in the design of the next step large-scale, highfield fusion reactors such as the Fusion Nuclear Science Facility (FNSF) and the Spherical Tokamak (ST) pilot plant beyond ITER, which is under construction in the South of France. Princeton Plasma Physics Laboratory (PPPL) is currently leading the design study of FNSF and the ST pilot plant study. ITER utilizes present-day state-of-the-art low temperature superconducting (LTS) magnet technology based on the cable-inconduit conductor design where over a thousand multi-filament Nb3Sn superconducting strands are twisted together to form a high current-carrying cable inserted into a steel jacket for coil windings. Researchers present design options of the high performance superconductors in the winding pack for the FNSF toroidal field magnet system based on the toroidal field radial built from the system code. For the low temperature superconductor options, the advanced Jc Nb3Sn RRP strands (Critical current 1000 A / mm2 at 16 Tesla, 4 K) from Oxford Superconducting Technology (OST) are under consideration. For the high temperature superconductor options, the rectangular shaped high current HTS cable made of stacked YBCO tapes will be considered to validate feasibility of TF coil winding pack design for the ST-FNSF magnets.
Highlights and the long timeline
It is good to know there are some 16 Tesla superconducting wire being made in significant volume.
So a plan that will be several projects with tens of billions in funding leading to a possible commercial device generating power in 2060 or much later
The following timetable was presented at the IAEA Fusion Energy Conference in 2004 by Christopher Llewellyn Smith:
Conceptual design is to be complete by 2017
Engineering design is to be complete by 2024 (after input from ITER D-T tests, and data from IFMIF - both delayed as of 2016)
The first construction phase is to last from 2024 to 2033
The first phase of operation is to last from 2033 to 2038
The station is then to be expanded and updated (e.g. with phase 2 blanket design)
The second phase of operation is to start in 2040
In 2012 European Fusion Development Agreement (EFDA) presented a roadmap to fusion power with a plan showing the dependencies of DEMO activities on ITER and IFMIF.
Conceptual design to be complete in 2020
Engineering design complete, and decision to build, in 2030
Construction from 2031 to 2043
Operation from 2044, Electricity generation demonstration 2048
This 2012 roadmap was intended to be updated in 2015 and 2019, but EFDA was superseded by FusionForEnergy (F4E).
This is easily a $200 billion 50 year plan. That would not generate commercial power for 50 or more years if the schedules stopped slipping.
It seems all other lower cost fusion alternatives could be easily funded. Yes, they also might end up being costly paths in which case they should be abandoned as well.
The far lower technical risk option are advanced nuclear fission (molten salt, supercritical water, advanced breeder) reactors. Tokamaks even if they work as envisioned are not projected to be superior in terms of lower cost energy or cleaner. There are multiple options for closing the fission fuel cycle, which would mean no long lived waste.
Therefore, tokamak fusion looks like a long winding path to energy that is not lower cost or vastly cleaner.