555 N. Kensington Avenue, La Grange Park, Illinois 60525, U.S.A.
[1] International Nuclear Societies Council, "A Vision for the 2nd 50 Years
of Nuclear Energy," American Nuclear Society, LaGrange Park, Illinois,
March 1996
CONCLUSIONS
- The long-term benefits of fusion energy are sufficiently great to
warrant a sustained effort aimed at advancing fusion science and
technology. International cooperation is a cost-effective complement to
strong national programs.
- Recent scientific progress in fusion research has been encouraging
and warrants an enhanced and expanded fusion engineering and technology
development program.
- Based on the continuing success of physics and technology
development programs, it appears technically feasible to develop fusion
energy to the commercial stage within the first half of the 21st century.
Increased funding, however, will be needed.
- To be commercially successful, fusion must demonstrate social,
environmental, and economic attractiveness relative to its future
competitors. Fusion must anticipate and meet future regulatory and
licensing requirements. Fusion power plant design studies indicate that
fusion has the potential to meet these challenges.
- Power-producer interest and participation will be the true measure
of the commercial attractiveness of fusion.
- Although applications studies for fusion have concentrated on
electric-power production, there are other possible applications (e.g.,
hydrogen and synfuel production or waste destruction).
SUMMARY
Given the long-term payoff from fusion, appropriate priority and
funding levels should be set to maintain the momentum of both the Magnetic
Fusion Energy (MFE) and Inertial-Fusion-Energy (IFE) (MFE) programs.
Coordinated national laboratory, university, industrial, and power producer
involvement is essential.
At the present stage of fusion development, the Tokamak is the most
advanced MFE concept and the most cost effective and technically viable
approach to demonstrate a sustained, controlled fusion reaction producing
net energy. Development of alternative MFE concepts with potential
advantages is also an important part of the fusion program. The glass
laser is currently the most developed driver for single-pulse
Inertial-Confinement-Fusion (ICF) target physics studies. However, glass
lasers may not be the most attractive driver for IFE and the heavy-ion,
induction accelerator is also being developed as a promising candidate
driver for IFE. The fusion program also should include sufficiently broad
components of basic research, supporting technology, and engineering to
permit the development of the mainline concepts and, at a lower level,
several other promising confinement and heating approaches.
Over time, the costs of the international research and
development for fusion will be a tiny fraction of the total expenditures
for world-wide energy use. The American Nuclear Society (ANS) believes
that a balanced approach to fusion research emphasizing tokamaks and glass
lasers while supporting the development of promising alternate concepts
will facilitate and accelerate the timely introduction of an important,
practical, reliable, safe, and environmentally attractive sustainable
energy source.
THE FUSION PROCESS
At very high temperatures, electrons are stripped from atomic
nuclei to form a plasma (ionized gas). Under such conditions, the
repulsive electrostatic forces that keep positively charged nuclei apart
can be overcome and the nuclei of select light elements can be brought
together to fuse and form other elements. Nuclear fusion of light elements
releases vast amounts of energy and is the fundamental energy-producing
process in stars. For a given mass of fuel, the energy released from
fusion substantially exceeds the energy released from fission (the
neutron-induced splitting of heavy elements such as uranium) and far
exceeds (by millions of times) the energy released in chemical reactions
(e.g., the burning of coal, gas or oil).
Some fusion reactions are easier to produce than others. Some
products of the various fusion reactions are more desirable than others.
The first generation of fusion plants is expected to employ a plasma fuel
mixture of the less common isotopes of hydrogen: deuterium and tritium. A
helium nucleus and a neutron are the products of this fusion reaction.
Deuterium constitutes 0.015% of the hydrogen content of the Earth's water,
and represents an essentially inexhaustible terrestrial fuel supply.
Extraction of the deuterium fuel is inexpensive. Tritium is radioactive
and is not naturally available in useful amounts, but it can be produced in
quantity by capturing fusion product neutrons in lithium-bearing components
of the fusion machine itself. Lithium is a plentiful element available in
the Earth's crust.
Tritium poses a modest biological hazard, so fusion plants must
incorporate safety features. Although fusion byproducts tend to be benign,
neutron activation of certain structural materials is another safety and
environmental concern. By the appropriate choice of materials, most
long-term radioactive waste generated from fusion should qualify for
shallow land burial, rather than deep geologic disposal. By the standard
measures of environmental impact (land use, mining, emissions, waste
disposal, etc.), fusion should rank as an attractive energy source. With
only a small inventory of fusion fuel in the machine at any time, the risk
of accidental power excursions is negligible. Advanced fusion fuel cycles
can be expected to reduce both the tritium and neutron-activation concerns,
but will require further development.
Two general approaches to fusion technology have received emphasis:
magnetic confinement and inertial confinement. In magnetic fusion, a hot
(over 100 million degrees Celsius) plasma is confined by strong magnetic
fields and heated by external sources until the fusion reaction becomes
self-sustaining. A "burning" plasma, with sufficient size and density to
sustain itself by self-heating, is said to be "ignited." The magnetic
field also insulates the machine structures from the hot plasma. In
inertial fusion, small fuel pellets are bombarded by intense laser or
particle beams to produce an ignited, dense plasma, held by inertia for
brief energy-producing pulses. Several distinct variations of these broad
approaches are being pursued in a number of laboratories worldwide.
FUSION PROGRESS
Begun over 40 years ago, fusion research, particularly in the last
two decades, has made outstanding progress, incorporating state-of-the-art
advancements in physics understanding and technological developments as
they have become available. Production of 2 megawatts of deuterium-tritium
fusion power in November of 1991 in the Joint European Torus (JET) and 10.7
megawatts (approaching energy breakeven) in the Tokamak Fusion Test Reactor
(TFTR) at Princeton Plasma Physics Laboratory in November 1994 were recent
milestones in MFE development. Experiments continue to be performed in
specific tokamaks operating around the world to build upon these
achievements and to provide increased scientific understanding. Recent
advances include the achievement of improved energy confinement and the
improved methods for handling high heat fluxes. With the object of sharing
the benefits and reducing the costs to each country for a "next step"
ignited tokamak experiment, the European Community ( including Canada),
Japan, Russia, and the U.S. are collaborating on the design of the
International Thermonuclear Experimental Reactor (ITER). The programmatic
objective of ITER is to demonstrate the scientific and technological
feasibility of fusion energy for peaceful purposes. If the four partners
decide to begin construction of ITER at the conclusion of the design phase
in 1998, ITER would begin operation in 2007. ITER will produce about 1.5 GW
of fusion energy. The present U.S. MFE program emphasizes research on
fusion science which can form the basis of construction and operation of a
demonstration plant followed by construction of commercial power plants.
Though most of the U.S. ICF research progress has been directed
toward defense programs, there is a strong synergism with the civilian IFE
program. Progress to date includes a greater understanding of both
direct-drive and indirect-drive target performance and improvements in
laser and particle-beam drivers. The 40-kilojoule glass laser at Lawrence
Livermore National Laboratory is currently working to resolve
indirect-drive target physics issues. The Omega laser at the University of
Rochester is being upgraded to a 30-kilojoule direct drive facility. The
U.S. inertial program is currently directed toward demonstration of target
ignition and modest energy gain in a proposed National Ignition Facility
(NIF), with anticipated operation around 2002.
Duplicating the conditions of stars on Earth in order to realize
controlled fusion energy will require complex and expensive machinery. The
fusion energy program is a customer for advanced structural and
high-heat-flux materials, superconducting magnets, powerful laser and
particle beams, power-conversion apparatus, advanced computers, robotics,
and other applications.
Although the fuel for fusion is inexpensive and abundant, present
design studies indicate that fusion power plants will be costly so that it
is important to develop designs with significantly lower capital costs. The
present studies of magnetic and inertial fusion power plants show that,
with continued success in improving the physics performance of fusion
experiments and developing the required technologies, fusion has the
potential to provide mankind with a very long term energy source that is
both economically competitive with other long term options, and has many
safety and environmental advantages.
The American Nuclear Society (ANS), founded in 1954, is a not-for-profit
scientific and educational society of more than 15,000 scientists,
engineers, and educators from universities, government and private
laboratories, and industry.
Public Position Statements are the considered opinions and judgements of
the Society in matters related to nuclear science and technology. They are
intended to provide an objective basis for weighing the facts in reaching
decisions on important national issues.
For additional information contact
the American Nuclear Society, 555 N. Kensington Avenue, LaGrange Park,
Illinois 60526. Telephone 708-352-6611
ADDITIONAL COPIES
of ANS Public Position Statments are available from ANS.
With requrests for single copies, send a self-addressed, stamped envelope
($0.32 stamp each statement). Quantities are available at prices that will
be quoted on request.