APPENDIX 20
Second supplementary memorandum by UKAEA
THE MAST FUSION EXPERIMENT AT UKAEA'S CULHAM
SCIENCE CENTRE, OXFORDSHIRE
1. Development of clean energy sources is
a national and international priority. Fusion, which powers the
sun and other stars, is increasingly seen (eg by the Chief Scientific
Adviser Sir David King) as a promising potential large-scale emission-free
source of electricity. To harness fusion energy on earth requires
a mixture of types of hydrogen to be heated to 150 million oC,
ten times hotter than the centre of the sun. The gas is kept away
from material surfaces by using a very strong magnetic bottle,
known as a tokamak. The Joint European Torus (JET) at Culham is
the world's leading tokamak, and has produced 16MW of fusion power.
It will be followed in France by the ITER machine[29].
If ITER works as expected, producing 500MW, it would be followed
by a demonstration power station.
2. In a conventional tokamak like JET and
ITER, the "plasma" of hot gas is shaped like an American
doughnut. UKAEA has pioneered a very promising alternative design,
known as the Spherical Tokamak, which is shaped more like a cored
apple and can produce the plasma, and hence fusion power, with
much weaker magnets than conventional tokamaks. As well as providing
a potential option for more compact, cheaper power stations, a
spherical tokamak could be a suitable design for a facility to
test components in power station conditions. Such a facility is
needed to strengthen the fusion development programme and speed
up the advent of fusion power. The first spherical tokamak experiment,
START, at Culham (1991-98) was made mainly using old and borrowed
equipment. START was an outstanding success, tripling the world
record for the key ratio of plasma pressure to magnetic pressure,
thereby revealing that spherical tokamaks have outstanding potential.
3. The success of START led to spherical
tokamaks being built all around the world. The UK is now neck-and-neck
with the US in having the leading experiment. The UK's Mega Amp
Spherical Tokamak (MAST) device (2000-present) was built on a
very tight budget, with the minimal power and equipment needed
to achieve the initial goal of seeing whether the promise of START
would be maintained in much bigger, hotter plasmas. It was, and
MAST has made many important contributions to tokamak science
generally.
4. With ten times the pulse length and temperature
of START, MAST has produced results that now justify further investment
to fully realise its huge potential. Major improvements to MAST
are needed in the capability to produce, heat and sustain high
pressure plasmas, increasing the pulse length by another factor
of ten, and the temperature by a further factor of three. Without
this investment, the development of spherical tokamaks - and more
generally fusion - will be slowed down and the UK may surrender
to the US the lead in an area that has been a UK success story.
As well as allowing further important experiments in support of
ITER, the upgrade would allow scientists to address the key question:
is continuous operation of high performance plasmas possible in
spherical tokamaks? The cost is approximately £30M funded
mainly by the Office of Science and Technology through EPSRC,
but partly by EURATOM. The upgrade has been endorsed by the Fusion
Advisory Board and UKAEA and EPSRC are in discussion on funding
options. Once approved, the upgrade will take about four years
to procure and install.
5. An upgrade of MAST would allow the UK
to remain at the forefront of fusion research at a time when JET
may have closed. Without it, the UK programme would endeavour
to play a key role in ITER, but this would be difficult without
a major experiment of its own both contributing to fusion development
and training young fusion scientists and engineers.
29 The ITER partners are the European Union, Japan,
China, USA, Russia, South Korea and India. Back
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