Writing in the Nov. 21 issue of Science, UCI physics professor Norman Rostoker, UCI research physicist Michl Binderbauer, and University of Florida physics professor Hendrik Monkhorst, say the fusion-powered ITER is beset by daunting design and engineering obstacles. These include its mammoth size, maintenance challenges and the need to protect itself and the surroundings from the high-energy neutrons it would produce.
For three decades, the world's scientific community has looked to the Tokamak, an experimental fusion reactor that would be fueled by a mix of deuterium and tritium, as a possible solution to long-term global energy needs. ITER would produce energy using the Tokamak design. In the research and design stages since the late 1960s, ITER represents an unprecedented collaboration among fusion scientists from the United States, Europe, Japan and Russia forged to develop the next generation of nuclear energy. Plans call for the design phase to end in 1998 and for construction to begin at an undetermined time and location.
"The research that led to plans for ITER has yielded a lot of important information, and most of our work is based on that research," Rostoker said. "But we don't think it has any hope of creating a reactor that anyone will want."
Rostoker, Monkhorst and Binderbauer instead propose a colliding beam fusion reactor that would be fueled by protons and boron, rather than the deuterium-tritium mix that would power ITER. The reactor they have designed, on paper, would produce a very small fraction of the radioactivity of ITER, in turn allowing the facility to be much smaller, easier to maintain and environmentally safe, Rostoker said.
"These reactors could replace all gas, coal and oil-fired power stations in the world," Monkhorst said. "They would be very safe and environmentally benign."
The team plans to develop a commercial reactor over the next 10 years with money from private investors. The product of five years of investigation, their work differs from other fusion research through the years because it is devoted mainly to reactor design questions, instead of focusing on fusion experiments and theory that eventually might lead to reactors, Rostoker explained.
Rostoker, Monkhorst and Binderbauer belong to a growing international chorus of scientists voicing doubts about ITER, the first experimental reactor that would attempt to harness fusion, the same power that fuels the sun and other stars. But the project has become so mired in controversy -- from its anticipated engineering problems to political division over its monumental costs -- that its chances of ever being built are in serious doubt, Rostoker said.
One of ITER's main shortcomings, the researchers write, is its fuel source: deuterium and tritium, which produce high energy neutrons.
"Since most of the energy produced is in the neutrons, protecting the device from itself presents a difficult engineering problem," said Rostoker, who has studied fusion science since 1958.
ITER's neutrons would require elaborate shielding, which in turn would require the plant itself to be huge -- roughly five times the size of today's nuclear fission power plants, according to Rostoker. ITER's radioactivity, combined with its size, would mandate a remote construction site, in turn making it necessary to transmit power over long distances, inevitably leading to power loss.
Also, ITER's proposed reactor design, the Tokamak, poses significant challenges to accessing and maintaining its coils, vacuum system and other internal components because they would be radioactive.
Rostoker, Monkhorst and Binderbauer propose a reactor design known as a field-reversed configuration, which would enable reactor components to be mounted on rails, providing much easier, and less expensive, maintenance than ITER. It could be placed in cities to avoid significant transmission losses.
Monkhorst said their reactor would work like this: Beams of boron and hydrogen would be sent into a reactor where magnets would cause the beams to bend, causing the nuclei to collide and fuse. The fusion would create energetic-charged particles that could then be converted directly into electrical power.
The conversion process of the proposed reactor would be twice as efficient as heat conversion, in which coal is burned to heat water and produce steam, which runs turbines that produce electricity. Rostoker and his colleagues said their reactor would convert nearly 90 percent of the particle energy it generates into electricity, compared with, at most, 40 percent for a traditional coal-burning power plant or a deuterium-tritium Tokamak.
What's more, the reactor would cost half as much to run annually as coal- burning fossil plants, the researchers said, mainly because the fuel is accessible and inexpensive, and because safety measures are minimal due to the greatly reduced radioactivity the reactor would produce. Monkhorst said it would require about 200 grams of boron to run a 100-megawatt reactor per day at a cost of only a few dollars.
The reactor would not produce so-called greenhouse gases that contribute to global warming, the researchers said. Energy in the form of electricity and helium gas would be the reactor's only products. If complications arose during operation, the reactor would quickly shut itself down, they said.
Developing safe and cost-efficient new sources of energy is imperative, the researchers said, because existing nuclear fission power plants built in the 1950s and '60s must be closed down within the next decade as their operation licenses expire. A license typically is valid from 40 to 50 years; the plants must be closed due to radiation damage, and many components must be buried due to high levels of radioactivity. But Rostoker, Monkhorst and Binderbaeur said these problems would be absent in their colliding-beam fusion reactor with proton-boron-11 fuel.
Contact:Tracy Childs, UC Irvine
(714) 824-5484
Steve Orlando, University of Florida
(352) 392-0186
sfo@ufl.edu
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