In the 1985 hit movie Back to the Future, the not-so-mad scientist Doc finally powers his stainless-steel, time-traveling DeLorean car with "Mr. Fusion" — actually a Krups grinder — that turns kitchen scraps into unlimited energy.
If only it were that simple. Nuclear fusion, the process in which hydrogen nuclei are jammed together to form helium, releases the energy that drives the sun and stars. It is also the process that Edward Teller and colleagues harnessed to make hydrogen bombs. The first H-bomb exploded in 1952. But that energy was — literally — gone in a flash. Dreams of using sustained fusion power to generate electricity have been around ever since. The reality has been eluding scientists and engineers for more than half a century.
Fission, which releases energy through the splitting of heavy nuclei, has proven more manageable. Its energy can also be released in a flash — as it was over Hiroshima and Nagaski — but it has been contained in reactors for generations. The first Hanford reactors started cranking out plutonium back in 1944. Other reactors have lit light bulbs and powered submarines since the 1950s. Like it or not, fission reactors generate nearly 20 percent of this nation's electricity.
Fusion reactors generate nothing. In fact, there are no fusion reactors. Only four years after Back to the Future came out, two scientists working at the University of Utah claimed to have created "cold fusion" in a glass of heavy water. The claim made headlines around the world, but scientists at other laboratories found no evidence that it was true. The accepted wisdom is still that to produce fusion power on earth, you need temperatures of 100 million degrees.
For now, while some scientists at the University of Washington and elsewhere pursue their own ideas, world fusion research centers on the international ITER project. The $20-to-50-billion complex rising in Cadarache, France, designed to heat plasma — ionized hydrogen gas — to temperatures as high as 150 million degrees The ITER reactor follows the conventional "tokamak" design, basically a huge metal donut that contains the plasma in a powerful magnetic field. Containment that lasts long enough to produce significant amounts of power has been the holy grail of fusion research. ITER has been described as "the most expensive scientific instrument on Earth."
The project is envisioned as the step that leads to a full-scale demonstration power plant. However, it has gone way over budget and behind schedule, and it may or may not ever be finished. The U.S., the European Union, Russia, China, India, Japan and Korea are all contributing dollars and expertise. They are, in fact, contributing so many dollars that Nature recently complained ITER was basically sucking up all the fusion research money in the world.
The magazine explained that "in 2009, as ITER’s costs increased, fusion-program managers in the U.S. Department of Energy were told by the administration of President Barack Obama that they would have to fulfil their share of ITER from a flat budget. In the ensuing crunch, nearly all the department’s alternative fusion-research programmes have been cancelled.
"Congress is furious," Nature reported, imputing more unity to our national legislature than anyone else has recently observed. "This year, the Senate voted to cancel the US contribution to ITER in fiscal year 2015, although the House of Representatives voted to maintain that contribution by boosting the fusion budget." Nature suggested that the political chaos "provide[s] openings for Congress and the energy department to restore some of the funding for alternative fusion research.
"Academic projects worthy of consideration include a radically simplified design for a fusion power reactor developed by Thomas Jarboe and his group at the University of Washington in Seattle: they believe that it could be built for about one-tenth of the cost of a tokamak."
Has Jarboe, a UW professor, of aeronautics and astronautics, really built a better mousetrap? He thinks he's on the way to building one.
Jarboe says that the one-tenth figure is accurate. How could his group possibly build something for so much less? Easy, he says. In fact, there's nothing very exciting about his approach; all else being equal, even in the rarefied world of fusion reactor design, smaller will be cheaper. In his approach, he said, "we have a hole in the donut instead of the donut." Jarboe explains that "in order to have closed containment, you need to have a toroidal [i.e., donut-shaped] field." However, he explains, it turns out that "you don't need a toroidal vessel." Instead, if you deliver electric current just right from the outside, "the plasma has a lot of its own current that will make it toroidal."
In the classic design, current goes through the hole in the donut, requiring that the vessel be thick enough to shield the central power source from the neutrons that the plasma is shooting out. "It takes about a meter and a half of shielding to shield a coil," he says, so that the whole vessel winds up 4 or 5 meters in diameter. Because his machine "doesn't have a hole, you only have to shield the outside." And the cost is dramatically reduced.
His own experimental device, which is a long way from developing the 100-million-degree temperatures required for actual fusion, looks rather like a big stainless steel bass drum resting on its side with a deeply recessed copper head. If you look closely, you see a kind of dimple in the copper. Copper conduits, which carry bundles of electrical wiring, arc into the drumhead. Jarboe describes them as "mug handles." He explains that the plasma is created and contained within the copper vessel. The stainless steel structure — "part of my dowry from Los Alamos," where he worked before he came to the UW in 1989 — is a vacuum tank that maintains extremely low pressure inside the copper. The mug-handle injectors zap the outside of the plasma with an asymmetrical electromagnetic current.
Nearby in a cluttered lab on the top floor of the UW's Aerospace Engineering Research Building stands a bank of capacitors to store the electrical energy that flows through the injectors. Enthusing about a recent lightning display, he points out that each burst of electricity in his machine carries the energy of nine lightning bolts.
Jarboe explains that the oscillating magnetic field, which he thinks of as rubber bands that flex and exert pressure, basically shakes the plasma, and this shaking gives it a certain stability, which is necessary to achieve sustained fusion. Maybe the process is a bit like shaking an omelet pan to give the eggs a certain shape. What does it mean to make plasma "stable?" "The definition of stability in plasma physics," he explains, "is if you push on the plasma it pushes back. A stable plasma has real structure. I think of it like a block of rubber: You push on it, it wants to come back in its original shape."
Jarboe says that a different shape isn't all that sets his concept apart from the one being followed at ITER. The conventional design has an efficiency of about one-tenth of 1 percent, he says. In contrast, "our concept has a 41-percent efficiency." The difference between Jarboe's approach and the competition lies in the method of forcing current into the plasma. His method "drives all the electrons at low speed," he explains. "The other methods drive a small part of the electrons at high speed."
Jarboe doesn't contest Nature's complaint that ITER is basically sucking up all the fusion research money in the world. He explains that roughly half of the U.S. fusion budget goes directly to ITER. With the half that's left over, American fusion researchers are "working frantically to solve [ITER's} problems so it will work." As a result, there is very little money left for other concepts and government-funded researchers are by-and-large "not working on any new ideas."
Elements of his own research may be able to help the ITER project: "That's why we're funded," he says.
But — although the U.S. Department of Energy has been funding his research since before he got his Ph.D. — he's not sure he can get federal money to take his project to the next stage. He says that next step would involve building a larger vessel and testing it at higher energies. Instead of containing the plasma for six microseconds at a burst, he'd up the time to two whole seconds. His new reactor would be about 12 feet across. He could still build it in the AERB, but he'd probably want to do so in the basement, where he'd have access to cranes. He figures that building the next stage would cost about $8 million in capital costs plus $5 million a year for five years. He figures on four years to build it, another year to get experimental results. He sent an unsolicited proposal to the government; it was turned down.
But he hasn't given up. The federal government isn't the only source of research and development funds. In recent years, venture capitalists — including Microsoft co-founder Paul Allen — have started bankrolling fusion research at startup companies. (They are, in other words, investing in an enterprise that may not pay off before the capitalists themselves are long gone.) Jarboe says that venture capital is his hope for future funding, too.
Jarboe realizes that a lot of people are way more excited about getting power directly from the sun — via solar panels dispersed over millions of rooftops — than about getting it through replication of the sun's fusion process. Still, he believes, the world will continue to want "base load" power — the kind of continuous, non-weather-dependent power produced by dams and coal plants and nuclear reactors — and that "if this works like we think it will, we could actually be competitive with coal."
The fuel is readily available. In Jarboe's experiment, as in ITER, the fuel is a mixture of two hydrogen isotopes, deuterium and tritium. The deuterium can be extracted from seawater and is available commercially. The tritium is produced in fission reactors and can also be bought. If his design is scaled up to produce high-energy neturons, the device will make its own tritium in a fluid mix of fluorine, lithium and beryllium that circulates around the outside of the reactor to cool the metal wall and absorb the neutrons.
Unlike fission reactors, which rely on the splitting of atomic nuclei, a fusion reactor would not produce large volumes of highly radoactive spent fuel to be guarded for millennia. The structure itself would be bombarded by neutrons and would therefore become radioactive. In time, as structural components wore out and were discarded, they'd have to be shielded. But the volume would be modest and, Jarboe explains, even using common materials, the scrap would only stay dangerously radioactive for a century or so. (If you used more exotic materials, that period could be cut back to a matter of months.) He himself has already lived more than half a century, he reasons, so there should be no problem transmitting knowledge of the hazard from one generation to the next. In his experience, "even liberals" seem OK with the idea of a century.
Decades ago, Eugene Wigner, the great Hungarian-born physicist who designed the original Hanford reactors and won a Nobel Prize for physics in 1963, was asked when he thought fusion might become feasible. "In 1957, I bet money that we would have fusion in five years," Wigner replied. "I lost the bet. Now, I won't guess."
If all goes well, how much longer should the development of commercial fusion take? Jarboe doesn't guess, either. Conventional wisdom has long been "30 years once you know how to do it," he explains. No one has figured out how, so that 30-year figure just keeps rolling into the future. He thinks "we may know how to do it" now, but he hasn't quite proved that. If he scales up his experiment and it works as expected, however, "we'll know that we know."
