On today’s episode, a different approach to fusion power.
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Nuclear fusion technology is improving rapidly, with this week’s announcement from the Eurofusion
Consortium that the Joint European Torus in Oxfordshire, UK generated a stable plasma for
five seconds on December 21. The energy of the plasma, 59 MJ, is not large, about the
amount needed to boil 60 kettles of water, but it surpasses the previous record from 1997 when
22 MJ of heat were produced. The reaction burned a deuterium and tritium fuel mix, the same fuel
currently used in the much larger ITER tokamak in southern France, and the JET team expects
that their progress in stable plasma containment will have applications in the much larger project.
Both JET and ITER are toroids and use magnetic confinement to contain the super-hot plasma.
For decades, this was considered the only practical way to handle plasma, which is so
hot that no known material can contain it. There are other, alternate techniques, one of which is
under construction now, by Vancouver, Canada based General Fusion. The firm uses a unique technique:
mechanical compression of a large spherical mass of liquid metal to symmetrically collapse
a liquid vortex cavity in a few milliseconds. The fusion reactions create heat which is absorbed by
the liquid metal and can be extracted to power turbines. A test reactor is under construction
at a UK Atomic Energy Authority site in Britain. Another novel approach is under
development by Foothill Ranch, California-based TAE Technologies, who have developed a linear
device using technology that the firm calls an advanced beam driven field reversed configuration.
This approach is radically different from tokomaks or compression technologies,
combining conventional plasma containment with a particle accelerator, in a hybrid arrangement
that can accommodate hydrogen – boron, deuterium – tritium or deuterium – helium-3 fuels. The firm
has been experimenting since 1998, and the current fifth generation reactor prototype is compact,
by large torus standards, at 80 feet long, 22 feet high and weighing approximately 60,000 pounds.
The reactor cost $150 million to build, and currently operates on hydrogen and deuterium fuel.
The accelerator component of the reactor injects neutral beams to heat and stabilize fusion plasmas
and the firm believes that the technology can be adapted to create a treatment system for
selectively targeting cancer cells. Power production is of course the primary goal,
and the current system operates at around 70 million° C. Temperatures needed for the
preferred aneutronic hydrogen-boron fuel are several billion degrees, and the temperature
rise by factor of almost 30 will be a technical challenge requiring a new generation of test
reactors. The problem is immense. The plasma is described by hundreds to thousands of variables,
and to infer plasma behaviour from multiple indirect measurements, the firm uses a Google
AI system to simulate instrument readings from specified initial plasma conditions. TAE believes
that the combination of a heavily instrumented device and the modelling power of a Google
supercomputer will lead to a rapid understanding of plasma density and temperature, which are
essential for breakeven fusion power production. And what does the firm regard as rapid? They
currently estimate that a workable prototype of the commercial reactor could be ready in a decade.
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