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Vol.
XXVII No. 52
December
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An
Artificial Sun On Earth?
Raghu
LAST
week major world and nuclear powers meeting in Washington took further steps,
but encountered a major hurdle, along the road towards a dream project for a
nuclear reactor or power-generation system based on fusion rather than the
conventional fission-based power plants. The US, Canada, European Union, Russia,
Japan, China and South Korea committed themselves firmly to the International
Thermonuclear Experimental Reactor or ITER Project, the acronym being Latin for
the way, which, at an estimated US 10 billion dollar (Rs 47000 crore) is
the largest international collaborative research and development Project since
the Space Station. But they also failed to decide upon where to locate the
Project, the two main contenders being France and Japan, with geo-political
considerations playing the main role in the postponement of this decision.
Before
we discuss the various issues involved and their implications, let us first
clarify some of the basics. Put simply, fission reactions are based on splitting
atoms releasing huge quantities of energy as during the first nuclear bombs
dropped on Hiroshima and Nagasaki. Fusion reactions, on the other hand, are
based on forcing the nuclei of atoms together releasing even greater amounts of
energy, as in the Hydrogen Bomb but also, more commonly, as in the sun and the
stars.
In
nuclear power plants as against nuclear bombs, the problem lies in controlling
the enormous amounts of energies released and harnessing it for generating
electricity rather than for unleashing a gigantic explosion. In conventional
fission-based plants, energy is generated by triggering a chain reaction of
splitting uranium atoms if left to itself, this chain reaction will build up to
an explosive release of energy as in a bomb but, in a power plant, the reaction
is moderated and controlled so that the heat generated can be used to produce
steam which drives turbines to generate electricity. Scientists and engineers
have achieved this over the previous six decades and more, and have also tried,
with mixed success, to tackle the accompanying environmental problems and the
even more serious problem of handling the hazardous wastes.
But
harnessing fusion to generate power on a commercial scale is still a distant
goal. Since this is tantamount to replicating the energy-generating mechanism in
the sun and the stars, fusion-based nuclear power generation has been likened to
having an artificial sun on Earth.
POWER
FROM FUSION
In
a fission reaction, a heavy atom such
as that of Uranium is bombarded with neutrons (electrically neutral particles
from the nucleus of an atom) which split the atom into roughly equal parts,
release two or three more neutrons and large amounts of energy. If there is a
critical mass of Uranium, such that there are always sufficient numbers of atoms
left to be split, a chain reaction results.
Atoms
of lighter elements too can be used to produce energy. In such a reaction,
negatively charged electrons are separated from the nucleus of an atom, which
now has residual positive charge, and which is then forced to join with another
similarly charged nucleus. When the two charged nuclei join, they combine to
form a new element with slightly less mass than the original, this lost
mass being converted into energy as per Einsteins famous equation. In the sun
and in stars, for instance, hydrogen atoms join together to form a new element,
helium, and release enormous amounts of energy.
The
problem is that, to make charged nuclei come together, they must be provided
sufficient energy to overcome the force with which the similarly charges are
repelled from each other. In the sun, this is achieved due to the prevalent high
temperatures of over 15 million degrees Celsius and the high pressures over
100,000 times that on the earths surface. In a nuclear reactor, it has not
been possible anywhere near the levels of pressure generated in the sun but, to
compensate, higher temperatures are possible. In order to achieve the energy
levels required to generate and sustain fusion reactions in a reactor,
temperatures of around 100 million degrees Celsius, or 10 times the temperature
in the sun, is required. In experimental reactors, temperatures of around 300
million degrees have been achieved!
At
such high temperatures, the electrically charged gases form a state of matter
called a plasma, a form of gas that has a great deal of energy looking for a way
out. This brings in a new problem, that of how to contain the plasma.
Controlling the whirls and eddies of the plasma and keep it burning like a
miniature sun has been a formidable task for nuclear scientists and engineers.
Our sun generates sufficient energy to sustain all human, animal and plant life
on our planet and who knows where else in our solar system. The energy of sun
and of other stars in the universe are generated by nuclear fusion and the goal
of trying to reproduce this system on earth is indeed tempting. But taming the
power that lights up the cosmos is a daunting challenge.
ADVANTAGES
OF FUSION
Fuels
commonly used in fusion reactors are deuterium and tritium, both isotopes of
hydrogen, and both non-radioactive. Deuterium occurs naturally in sea water from
which it is extracted, which is why all fusion reactors are located on coasts.
Tritium does not occur naturally but can be made within the reactor itself from
lithium, the lightest metallic element (but heavier than hydrogen or helium)
which is used as a blanket to control the speed of the fusion reaction by
slowing down the neutrons released from the fusion of deuterium and tritium to
form helium. Lithium also is abundantly available on the earth’s crust all over
the world, thus promising an almost limitless availability of material for
fusion reactors.
Fusion
has several other advantages over fission. Quantities of raw material used are
very low, with grammes of material being used compared to kilogrammes in fission
reactions. 1 gramme of fusion fuel could produce as much energy as 10,000 kg of
fossil fuel. The fusion process has in-built safety features: fusion reactions
require leak-tight confinement and if any leakage takes place, this results in
extinguishing the plasma, like a candle getting blown out if the door is opened,
and stopping the energy generation. There is no chain reaction in fusion unlike
in fission where the danger is of the chain reaction going out of control. In
fusion, if excess plasma gets generated, temperatures will rise beyond the limit
(close to which they are operating in reactors) after which the fusion reactions
start winding down by themselves. Fusion processes are also limited by the
quantum and rate of refueling without which the plasma gets rapidly
extinguished: also, many conditions together must be satisfied and failure of
any one leads to energy loss and plasma extinguishment. Further, reaction
products from fusion are either absorbed by the surrounding lithium or are non
radio-active like helium. There are no hazardous wastes produced, minimal
exhaust releases into the environment and de-commissioning poses no long-term or
other hazards, all making fusion power a highly attractive proposition.
ITER
PROJECT
For
over five decades, efforts have been underway in various countries to harness
fusion energy for power generation. Putting these diverse efforts together, USA,
Europe (including mainly Britain, Germany, France, Italy, Switzerland and
Spain), Japan and Russia got together over a decade ago to form the ITER Project
under which various engineering design activities (EDA) have been carried out
between 1992 and 2001. Canada, South Korea and China joined in later, China
being the latest entrant, with the US re-entering under the George W Bush
administration after an earlier withdrawal by the Clinton administration.
ITER
has been described as the boldest nuclear initiative since the infamous
Manhattan Project which developed the nuclear bomb during the second World War.
Its goal is to design and develop the first-ever production-scale fusion system
to produce energy at the level of a conventional power plant. However, given the
limited state of current knowledge and experience with the technology, the ITER
Project will not deliver a full-fledged running power plant but will produce 500
MW (mega-watts) of power for 500 seconds or longer during each fusion
experiment.
In
doing so, ITERs mission is to demonstrate the scientific and technological
feasibility of fusion energy for peaceful purposes. It will demonstrate moderate
levels of power multiplication i.e. generating more energy than is put in,
demonstrate essential technologies in a system integrating the necessary physics
and engineering, and test important elements essential for the harnessing of
fusion as a practical energy source. ITER will thereby provide, in a single but
multi-dimensional and integrated experiment,
the next major step towards a commercial-scale pilot plant which would be
the next task. The experimental technology demonstrator under the ITER is
expected to begin construction in 2006 and become operational in 2014. However,
fusion research is expected to take another 20 years before it comes up with an
operational and economically viable commercial-scale power plant.
TECHNOLOGIES
IN ITER
The
technologies involved have developed over several decades since the end of World
War II. The basic problem confronting scientists was, although collision between
nuclei released substantial energy, a large amount of energy was required to
generate the plasma and therefore, could energy output be made greater than
energy input. Soon ideas from nuclear physics, astrophysics and plasma physics
came together to provide a realistic possibility. But there were huge
engineering problems involved in designing and building a reactor, chief among
which was how to contain and control the plasma in the absence of the massive
gravity available in the sun and the mostly larger stars and the obvious
difficulty of any containing material being able to withstanding the
million-degree temperatures generated.
Among
many approaches being pursued by American, British and Soviet experimental
physicists and engineers, Soviet researches provided the crucial breakthroughs.
Sakharov and Tamm first suggested that the plasma could be contained within a
magnetic field. Soviet experimental successes with this approach were first
revealed to an astonished world in 1956 by Kurchatov. By the time the
“Atoms for Peace” conference was held in Geneva in 1958, the genie was
out of the bottle, fusion was no longer a secret and information started getting
shared in the global scientific community.
In
the early ’70s, the Soviets had built a reactor in the shape of a doughnut or vada
i.e. a tube forming a circle with a hole in the middle. This design was
called a “tokamak” after a Russian snack of that shape. Tokamak
reactors soon came to be adopted worldwide and were further developed, the most
advanced perhaps being the Joint European Torus (i.e. the toroidal doughnut
shape) or JET reactor at Culham, UK, set up under the European Fusion
Development Agreement, then becoming the flagship programme of the ITER Project
and the world’s largest and most powerful fusion reactor, which started
operation in 1983. In 1981, JET demonstrated the generation of over 1 MW of
power in a short burst. Other important experimental fusion reactors are in
Japan, the second-largest after JET, France, Germany, Canada and Spain.
While
these various national projects were gradually incorporated into ITER, to take
the concept of fusion power to the next stage required an experiment so large
that it could only be conceived as an international co-operative venture. And
this is where the present phase of the ITER comes in along with the requirement
of commencing work on a single-site experimental reactor.
SITE
SELECTION
Even
the most naive person could have foreseen that, although the ITER agreement
calls for arriving at a consensus on the ITER site based on objective criteria
and a transparent decision-making process, the decision would inevitably be one
guided by geo-political considerations.
Four
sites were initially short-listed: Clarington in Canada, Cadarache in France,
Vandellos in Spain and Rokkasho-mura in Japan. Of these Clarington, where a
nuclear power station is situated 60 kilometres east of Toronto on Lake Ontario,
was dropped first, despite noisy threats by Canada to opt out of ITER if its
site was not selected, since Clarington did not offer as many advantages as the
other sites brought to the table. The Vandellos site in Spain lost out just
before the Washington conference because Spain was not seen as having the depth
of research expertise and experience that France and Japan had, leaving these
two countries to clash in the finals.
France
has strengths in nuclear fusion research and in related science and engineering,
and the reactor at Cadarache, located in southern France in the Provence region,
also holds the record for the highest power generation through fusion. Cadarache
was also endorsed as the EU’s candidate at a European meeting prior to the
Washington conference where it was supported by Russia, China and the UK. But
the US, whose definition of the “evil empire” seems to include France
these days, raised a resounding NO! Japan’s Rokkasho-Mura site, located in the
northern tip of the main Hokkaidu island, also has a strong and distinguished
fusion research record but is located in a seismically sensitive area. Japan has
of course offered to meet all the costs if its site is chosen whereas the Eu has
pledged 2.4 billion Euros if Cadarache is selected. Its bid was supported in
Washington by the US and South Korea. If money and geo-politics are to be the
decisive factors, Japan is likely to breast the tape first while the US pulls
France back!
In
any case, the ITER Project is expected to be underway fairly soon. And despite
the usual doomsayers, who see red anytime anything nuclear is mentioned. Nuclear
power, especially from fusion, still holds great promise and, for all the
scare-mongering, the last word on nuclear energy has not been spoken. Research
on nuclear energy must continue and, in this field, cannot be done at a small
laboratory scale. Nuclear energy, especially from fusion, is an option the world
needs to keep open.
