Annex: 2002-03 Fusion Income to Culham
|JET: Operations, Miscellaneous||6
Deuterium and tritium are isotopes of hydrogen in which,
in addition to the proton in normal hydrogen, the nucleus has
one or two neutrons respectively. Deuterium combining with tritium
(to produce helium, neutrons and energy) is the most likely fusion
reaction to be used in future fusion power plants as it occurs
at the lowest temperaturesaround 100 million degrees Centigrade.
D-T fuel has been used in JET and in a US tokamak TFTR which has
now been dismantled.
Very large quantities of deuterium are available from seawater.
Tritium does not occur naturally, because it is unstable to radioactive
decay. In a power plant, tritium would be produced by the escaping
neutrons reacting with a blanket containing a lithium compound.
European Atomic Energy Community. Most of the funding for
JET is from EURATOM. Approximately one quarter of the funding
for the UK national programme is from EURATOM (the remainder is
from OST/EPSRC), though this fraction will decline as the EURATOM
programme focuses on ITER construction.
Until recently it has been envisaged that fusion will be
developed in a sequential manner from JET, through ITER and then
a device that demonstrates electricity generation and tests power
plant components (DEMO) to a prototype power plant (PROTO). This
would have taken about 50 years. However, growing environmental
and security of supply concerns have led to pressure for development
of fusion as an energy source on a more rapid timescale. In November
2001 a group of European experts, chaired by the Chief Scientific
Adviser to the UK Government, examined for the Council of Ministers
a "fast track" to fusion power. In this DEMO and PROTO
would be combined, reducing the timescale by about 20 years. This
would require increased focus on electricity generation technologies
in the latter stages of ITER and, in parallel to ITER, testing
in IFMIF of how materials respond to the sustained doses of fusion-energy
neutrons typical of a power plant.
The International Fusion Materials Irradiation Facility (IFMIF)
is a proposed device that would test the structural integrity
of fusion power plant materials under appropriate neutron irradiation
damage conditions. The required fluence of high energy neutrons
would be produced by a beam of deuterium reacting with a lithium
target. A conceptual design has been produced. In the Fast Track,
IFMIF is built and operated in parallel to ITER, and not at a
International Thermonuclear Experimental Reactor. A project
funded under IAEA auspices, initially by four parties (EU, USA,
Japan, Russia), to design a sustained burning tokamak plasma for
physics and technological demonstration of fusion power. When
the Engineering Design Activities were extended by three years
in 1998, the US reduced its involvement and then withdrew, and
the focus shifted to a design with reduced technical objectives
and therefore reduced construction cost (- 4 Billion Euro). This
design was completed in 2001. At the time of writing, the US is
expected to rejoin, and China and Korea have both shown strong
interest in joining. Negotiations on how ITER would be built and
operated as an international project are nearing completion. There
are candidate sites in France, Spain, Japan and Canada. Decisions
on whether and if so where to build ITER are expected in 2003.
Joint European Torus, sited at Culham. The world's largest
tokamak, capable of mimicking the geometry of ITER, and associated
facilities such as the tritium handling plant. Exploitation of
the JET Facilities was by a separate legal entity, the JET Joint
Undertaking, until this terminated on 31 December 1999. Since
then JET has been operated by UKAEA, under contract to EURATOM,
as a user facility for Task Forces of visiting European (including
Mega Amp Spherical Tokamak at Culham. Experiments started
in December 1999 and as well as addressing the feasibility of
the spherical tokamak as a fusion device, help refine understanding
of the physics of ITER operating regimes.
Electrically neutral particles. High energy (14 MeV) neutrons
are products of deuterium-tritium fusion reactions; in a power
plant they would be used to produce tritium from lithium compounds
and they would be the energy source for electricity generation.
A very compact form of the tokamak in which the plasma appears
almost sphericalit resembles a cored apple. Pioneered at
Culham through first the START and now the MAST experiment. Several
other countries have now built spherical tokamaks following the
very successful experiments on START.
Small Tight Aspect Ratio Tokamak at Culham. Holder of the
world record plasma ß for a tokamak, where ß measures
the ratio of plasma to magnetic energy. Experiments ceased in
1998, for completion of its successor, MAST.
The most successful device yet found for magnetic confinement
of plasma. Its magnetic field is made up from helical lines of
force on toroidal surfaces, and is generated by currents in both
external coils and in the plasma itself. In this magnetic bottle
the very hot ionised gas required for fusion, the "plasma",
is contained without minimal contact with materials surfaces (contact
would cool the plasma and damage the materials). START, MAST,
JET and ITER are all tokamaks.
Why Has Fusion Taken So Long?
It is occasionally reported, most recently in the Economist,
that the goal of achieving fusion as an operating electricity
production system is never brought any nearer in spite of the
R&D work that is done. This is used to discredit fusion R&D
and imply that no progress is being made.
These sentiments are so at odds with the observed continuous
progress in fusion, especially in the last decade, and the positive
outcomes of serious analysis of fusion R&D, most recently
in the UK in reviews by A D Little and a panel of physics professors,
that some look at what lies behind these statements is necessary.
It is clear that when the time-scale to develop fusion is
estimated, people form a view of how much work remains to be done
and how long it would take to complete that work with foreseeable
levels of R&D budget. This immediately gives one reconciliation
between the actual major progress in fusion and the claims that
it is not brought any closer in time. Assuming the rate of progress
is given by the number of man years invested, then the time-scale
for fusion development has two components: not only does it depend
on the success of the research, it also depends on the rate at
which the research is carried out, that is the R&D budget.
Obviously, a declining budget will delay the development.
In fact, world fusion expenditure has declined over the last
20 years. The reduction in the UK fusion R&D budget is one
of the most extreme (a factor three in real terms; it is now,
as a fraction of GDP, one of the lowest in the developed world),
but other programmes such as the US have also reduced substantially.
This in itself is sufficient to delay fusion development by many
A related issue, particularly in the light of the strong
international dimension of the fusion research programme, is the
decision making progress. A natural outcome of declining budgets
is a lack of firm decisions to fund the move on to the next stage
in development because such decisions oppose declining budgets.
Although this effect is harder to quantify, it is clear that the
present decision process to build ITER, the next fusion device,
conceived as a world-wide venture, could have taken place 10 years
ago. Similarly with
JET, the existing European device, years were lost in the decision
making process even after the machine was designed. Without these
delays, we would probably already be running a large scale fusion
facility producing very high levels of fusion power, and we would
now be discussing the siting of a demonstration power plant.
Overall then it is possible to estimate the delays introduced
into the fusion development programme, in the last 20 years, by
the declining budgets and the associated lack of strong decisions
to move on to the next stage of R&D. The estimates are given
below, although it is perhaps difficult to separate out these
two sources of delay since they are coupled together.
|Cause of delay
|Declinging budgets||20 years
|Decision delays||10-15 years
It appears then, that there is no imcompatibility between
the progress in fusion on the one hand, and the length of the
development process. At the same time that progress has been made,
the rate of progress has been slowed by a reducing R&D budget.
This has a compounding effect of discouraging strong decisions
to move on to the next stage. Achieving fusion was brought closer
by increased investment prompted by the oil crisis in the 1970's,
but during the 1990's the time-scale has been allowed to increase
again by reducing funding levels. Although it is difficult to
be precise with this analysis, it appears that the way to delay
fusion development is to cut the R&D fundingthat is
not a very surprising result!
It should be remembered that environmental and security of supply
concerns were much less a decade ago, so there was understandably
much less pressure then to get on with fusion development and
build ITER. Back