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Nuclear fusion: What of the future? 215

the forefront of fusion research, most recently having a fully beryllium plasma-facing
wall installed to mimic conditions in ITER. Other currently operational tokamaks
include ASDEX-U, EAST, WEST, DIII-D, and SST-1 [28–32]. NSTX-U [33]
and MAST-U [34] are spherical tokamaks, with MAST-U focusing on divertor and
exhaust physics.
ITER is the next-generation power-plant-scale (target: 500MW fusion power)
tokamak currently under construction at Caderache, France [35]. It is intended to
be capable of long (100s of seconds) pulses and generate significant fusion power
in a range of experimental scenarios to prove the controlled plasma physics required
for commercial fusion power. ITER is an international collaboration between the EU,
China, India, Japan, Korea, Russia, and the United States, covering nearly half the
world’s population. Much of the contribution is in-kind, with the partners supplying
components rather than the ITER Organization carrying out conventional procure-
ment. This is intended to allow each partner to build up industry interest and support
for fusion as well as acquiring the engineering and development skills required for
future work in the area. ITER is supported by a satellite tokamak, JT-60SA, being built
in Naka, Japan. JT-60SA is a superconducting tokamak intended to investigate how to
optimize the operation of fusion power plants following ITER through the study of
advanced modes of plasma operation. ITER should be operational by 2025, with burn-
ing (thermonuclear D-T) plasmas by 2035 [36]. If successful, ITER will prove the
plasma physics basis for fusion power plants. There is some scope, for example,
the Test Blanket Module (TBM) program for testing of some fusion technology within
ITER, which will provide essential information but is somewhat limited in scope due
to lack of available space within the machine and the low lifetime neutron dose, which
the materials will experience. A parallel materials program based around an Interna-
tional Fusion Materials Irradiation Facility (IFMIF) is also under development [20].
Following ITER, there will need to be a prototype power plant to demonstrate the
integrated operation and development of technology suitable for commercialization.
There are many concepts (generically called DEMO) in circulation, designed to fit
into different local energy markets. One of the most ambitious—in terms of a fully
integrated research program—is the European EUROfusion program [37] aimed at
delivering a complete set of fusion power plant technology around the middle of
the century. The progression of these systems is shown in Table 5.3.
Among the alternative magnetic fusion concepts, W-7X is a JET-scale stellarator,
located at Greifswald, Germany [38]. Starting operation in 2015 and possessing sup-
erconducting coils, it is intended to demonstrate steady-state plasma operation and
extend knowledge of stellarator performance toward the power plant domain. Addi-
tionally, the China Fusion Engineering Test Reactor (CFETR) program to develop a
tokamak neutron source for materials and component testing is expanding [39].
There are also a number of alternative approaches being conducted by private com-
panies, using concepts, which may permit smaller, higher power-density machines,
although typically with a less comprehensive experimental bases and thus higher-risk
(for example, [40–42]). In general, these companies are currently focused on the
physics issues or a narrow technology option, such as high-field magnets using, for
example, high-temperature superconductors, and do not have comprehensive