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(Editor's Note: This article originally appeared in Plenty in October 2006. MNN is republishing it for the resource information it provides.)

There's an old joke within the scientific community that fusion power is the energy source of the future—and always will be. That’s because the challenges of making it work on a commercial scale are so daunting that, to date, no one has invested enough resources to even assess whether fusion power could be cost-effective and feasible. But a major research effort into fusion’s promise is now underway in France, where a long-stalled project—an international facility known as the International Thermonuclear Experimental Reactor (ITER)—will be constructed. In late May, the U.S., the European Union, Japan, China, Russia, South Korea, and India signed an agreement to underwrite the ambitious project. Officials estimate that ITER will take eight to ten years to build, at a cost of $5.9 billion (of which the U.S. is funding 10 percent). Another $5 billion will be needed to operate it over the next 20 years.

The hope is that ITER will help scientists and engineers get their arms around a process that is well understood theoretically, but is not commercially viable. Thermonuclear fusion is the merging of two atomic nuclei to form a heavier nucleus—a process that releases huge quantities of energy. Fusion reactions, in which hydrogen atoms fuse together to form helium, are what keeps our sun burning bright; on a hot July day at the beach, you can feel the heat and energy it creates. The process differs from nuclear fission, or the splitting of atomic nuclei (typically uranium), which also releases vast quantities of energy and forms the basis for modern-day nuclear power. For many reasons, fusion presents an attractive answer to global energy problems: It requires tiny amounts of raw material, and very cheap raw material at that—chiefly, deuterium (or “heavy hydrogen”), an isotope of hydrogen that is naturally abundant in ocean water, and tritium, another hydrogen isotope. Unlike fossil-fuel burning power plants, fusion would not pollute the air; unlike nuclear  ower, it poses no risk of a meltdown or other catastrophic accident. And, an added bonus in a security-conscious world: Its materials cannot be used for the renegade manufacture of weapons of mass destruction.

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There’s one catch, though, and it’s a big one—it’s tough to maintain a fusion reaction over a long period of time. For fusion to take place, you’ve got to squeeze enough hydrogen atoms close enough together to force the positive-charged protons (which naturally repel each other) in their nuclei to merge. And that takes a lot of energy. The sun’s fusion reactions have been sustained for eons because of the intense heat and pressure at its core, but on earth, creating and sustaining a fusion reaction requires extremely high temperatures—up to 100 million degrees Fahrenheit, or about six times hotter than the inside of the sun (though it should be noted that some holdouts believe that fusion reactions can occur at much lower temperatures; see article below).

Over the past five decades, millions have been spent by industry and governments on basic research into fusion. So far, scientists have been able to create a fusion reaction by heating gaseous forms of deuterium and tritium until they merge to form helium. The resulting plasma, or superheated gas, is contained in a vacuum that’s held in place by a colossal magnetic field—all of which is insulated by a meters-thick metal “jacket.” Several facilities around the world, including the state-of-theart Tokamak reactor housed at MIT, have succeeded in generating these reactions for brief periods. But scientists and engineers are still grappling with how to sustain the reaction without a net loss of energy—and how to harness the immense energy it releases to generate power. They’re also not sure how to control the radiation that results from fusion, nor have they identified materials that are durable enough to withstand the thermal and magnetic stresses necessary to sustain fusion reactions.

ITER will have capabilities that allow many of these questions to be addressed, say researchers. It will be about ten times the size of MIT’s Tokamak reactor, and will take a crucial technological step toward creating a sustained fusion reaction by heating the plasma using excess radiation and heat from the fusion reaction itself, instead of an external heat source. “ITER won’t solve all the problems,” says Earl Marmar, the senior research scientist in the department of physics at MIT, who runs the university’s Alcator C-Mod fusion reactor. “We’ll need a next-generation reactor after ITER, one close to commercial scale” that will be capable of producing more energy than it takes to run it.

Still, the technological challenges are immense. One controversial assessment, which appeared in the March 2006 issue of Science, was penned by the late William E. Parkins, an alumnus of the Manhattan Project and former chief scientist at onetime aerospace giant Rockwell International. Parkins declared that the engineering and cost obstacles to fusion are practically insurmountable. And certainly, many scientists and engineers acknowledge this point; Marmar, for one, estimates that it could take 30 to 35 years and $75 to $100 billion to bring fusion power to commercial scale. But he’s also not willing to give up on its promise. “Right now, we’re spending about $1.5 billion per year worldwide,” he says. “We need to pick up the pace. I think we see a fairly clear path to fusion power, but the obstacles are not inexpensive.”

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So, fusion power may indeed be the energy source of the future. But, given the immense investments that will be required, it’s a safe bet that other sustainable energy sources will reach the marketplace long before fusion comes to fruition.

Left out in the cold

For a brief time in the spring of 1989, it seemed that the world’s energy problems were solved. A pair of chemists at the University of Utah, Martin Fleischmann and Stanley Pons, held a press conference where they announced that after several years of experimentation, they had succeeded in achieving nuclear fusion at room temperature by electrolyzing some “heavy water” (deuterium oxide, or D2O) using electrodes made of platinum and palladium. The process gave off bursts of excess energy that could not be explained by normal chemical reactions, they said.

This was electrifying news to the scientific community, and in the weeks that followed, labs around the world set out to reproduce Fleischmann and Pons’s lowenergy nuclear reaction, which came to be called cold fusion. Researchers reported widely mixed results: Some found excess heat, but only erratically and rarely; others noted anticipated fusion byproducts like bursts of neutron radiation, but again only irregularly; still others noted the appearance of an expected fusion byproduct, tritium, but in vanishingly small quantities. Many researchers found no signs of fusion whatsoever.

In a matter of weeks, it became clear that the two men had made some serious procedural mistakes in their experiments—and had not been entirely forthcoming in explaining how they conducted their tests. Most of the excitement about their new “discovery” quickly died down, but some scientists continued to test room-temperature fusion, and have sometimes reported promising results.

Today most scientists maintain that cold fusion is simply impossible according to the laws of nuclear physics. Nevertheless, in 2004, the Department of Energy convened a panel of 18 international scientists to review the state of knowledge on cold fusion and to assess whether it was sound science, pseudo-science, or jus wishful thinking in a world that’s seeking ways to create clean energy. Ultimately, twelve of the panelists concluded that there was no real evidence that cold fusion could ever occur. But five thought that it had some promise, and one was convinced it was a real phenomenon. Though some experiments continue, the promise of cold fusion seems far more remote than it did during those fleeting weeks some 17 years ago.

Story by Michael W. Robbins. This article originally appeared in Plenty in September 2006.

Copyright Environ Press 2006

Cold fusion: Boom or bust?
A research facility will probe whether fusion power is feasible