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Release -- Superconductor Week does not edit or endorse the following
news release:
University of Twente puts
cables for fusion reactor ITER to the test
Enschede, Netherlands, 8 March 2007:
The Low Temperature Division
of the University of Twente has signed a prestigious research contract:
scientists of the group will start tests on the superconducting wires and cables
for the thermonuclear ITER-project
to be built in France. Cables with minimal losses and degradation are an
important successfactor of nuclear fusion. A unique test site, in which the
cables are subject to strong mechanical forces and extremely low temperatures,
will prove their quality.
Superconducting magnets will be about one third of
the building costs of the International Thermonuclear Reactor, to be built in
Cadarache in France; this experimental reactor aims at delivering 500 Megawatt
by nuclear fusion. November 2006, the participating countries have signed the
contracts for building this reactor. Parallel to this, the G8 countries have
placed nuclear fusion high on their agendas as a sustainable way of generating
energy.
The magnets are crucial in keeping in control the plasma, in which fusion takes
place. They exist of giant coils of superconducting cables. Losses in the cables
during control of the magnets results in loss of magnetic fields as well.
Well-functioning of the reactor is therefore highly dependent of cables with
minimal losses and degradation in time. From all participating countries,
reference cables are sent to the University of Twente for testing. One single
test takes about two weeks, and the scientists estimate to receive 20 samples
for testing.
Cold pressure
The currents through these cables and the magnetic fields are extremely high:
over ten thousand Amperes and 13 Tesla, respectively. This results in very
strong mechanical forces on the cables. The separate wires of which the cable
consists, are already protected by a heavy steel mantle, but still they are
pressed together by the strong forces. In the lab, these forces are simulated.
The cable therefore is cooled down to 4.2 Kelvin (minus 269 degrees Celsius),
which is the normal operating temperature. A strong mechanical press simulates
the forces present under normal operation. Would temperatures rise too much
caused by this pressure, the wires loose their superconductivity and the
magnetic field disappears, resulting in a vanishing plasma.
The European Domestic Agency, responsible for the
European contribution to ITER, chose the
Low Temperature Division because of the extensive knowledge of and experience
with the behaviour of superconducting cables. The group is highly reputed in the
worldwide research area. Thanks to this experience, the scientists already
proposed essential design improvements for the cables, resulting in less
degradation and a reliable and economical way of operating the cables during the
entire life of the reactor. The first cables using the ‘Twente model’ have
already been made.
Sustainable energy
Nuclear fusion is seen as one of the answers to the worldwide energy
issues: it is clean, safe and sustainable and does only produce short-living
radioactive waste. The energy is generated from melting together light and heavy
atomic nuclei, within a plasma at extremely high temperature. Nuclear fusion is
the energy source of the sun and the stars. Compared to fossil fuels, this
source of energy is inexhaustible.
The test site is developed by scientists of the Low Temperature Division led by
prof. Horst Rogalla. The High Current Superconductivity section of this group
takes care of the ITER-tests and is part of the Institute for Mechanics,
Processes and Control Twente (IMPACT). The tests are coordinated by Mr. Arend
Nijhuis.
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