United States should prepare to build a prototype fusion power plant, panel says | Science

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United States should prepare to build a prototype fusion power plant, panel says | Science

A new National Academies of Sciences, Engineering, and Medicine report calls for a complete rejuvenation of the U.S. fusion program, which hasn’t built a tokamak like the National Spherical Torus Experiment at the Princeton Plasma Physics Laboratory since the 1990s.

Elle Starkman/PPPL Communications (CC BY-NC)

Just in time for the holidays, a panel of leading scientists has presented a plan for nuclear fusion research in the United States that reads like a wish list. The United States should stick with the controversial ITER project, a hugely expensive fusion reactor now under construction near Cadarache in France, says a report released today by the National Academies of Sciences, Engineering, and Medicine. But even if the United States quits ITER, it should prepare to build its own fusion power plant as a follow-up, the report says. To do all that, the United States should boost spending on fusion research by $200 million per year, or 35%, it concludes.

The report reflects the will of the broader fusion community, say the co-chairs of the 19-member report committee, Michael Mauel, a fusion physicist at Columbia University, and Melvyn Shochet, a particle physicist at the University of Chicago in Illinois. “We listened very carefully to the community, especially some of the younger scientists who are very active in the field, and what we heard from the scientists is a desire to get on with fusion energy,” Mauel says. “We’re not just studying this thing, we’re trying to see if it really does work.”

In nuclear fusion, light nuclei fuse to form heavier nuclei and release energy. The process powers the sun, and for decades physicists have worked to turn fusion into a practical source of power on Earth. Their main approach has been to use magnetic fields to confine and squeeze ionized gases, or plasmas, of deuterium and tritium in doughnut-shaped devices called tokamaks, so that the deuterium and tritium fuse to make helium. ITER aims to be the first tokamak to obtain a “burning plasma” that produces more energy through fusion than is pumped into the device to maintain the plasma, a key milestone toward developing fusion power.

ITER has a troubled history, however. The project was first proposed in 1986 as a joint endeavor between the Soviet Union and the United States, which opted out in 1998, only to rejoin in 2003. At the time, the project was supposed to cost $10 billion, with the United States covering 9% of the total. Since then, ITER’s cost has ballooned so that the U.S. share alone will cost between $4.7 billion and $6.5 billion, and the schedule has slipped; the first plasma isn’t expected until 2028. ITER has become a political football, with appropriators in the U.S. Senate repeatedly trying to pull the United States out of the project, and their counterparts in the House of Representatives striving to keep the United States in. For fiscal year 2019, the United States will contribute $132 million to ITER, well short of the $250 million contribution that would be optimal for the project.

Give the uncertainties, in May 2016 the Department of Energy (DOE) asked the National Academies to study how best to advance fusion energy sciences in the United States in the case that the country remains in ITER and in the case that it withdraws. And the 252-page report, released today in Washington, D.C., makes only two recommendations: that the United States remains in the ITER project, and that it do the research and development for a so-called compact pilot plant (CPP). The CPP is essentially a prototype power plant that, unlike ITER, would be able to run continuously and generate electricity. In fact, the report argues, the case for building a CPP is so compelling that the United States should go forward with those plans even if it decides to pull out of ITER.

Researchers in other countries also have plans to build prototype power plants after ITER. For example, scientists in Europe have plans for a Demonstration Power Station or DEMO. But the CPP would differ from those plans by leveraging the latest advances in high-temperature superconducting materials, computing, and plasma physics to make a fusion reactor that was significantly smaller and cheaper than current designs. For example, the DEMO is expected to be significantly bigger than ITER. In contrast, the CPP would be about one-eighth the size of ITER. To do that, it would have to employ magnets made of high-temperature superconductor that achieve fields twice as high as ITER’s field.

The report presents an inspiring vision for the U.S. fusion community, says Steven Cowley, director of DOE’s Princeton Plasma Physics Laboratory in New Jersey. “The fundamental message is that the U.S. fusion program has to have an ambition to drive through and generate some kilowatts of power,” he says. “What’s the point of having a fusion program if you don’t have a goal to develop the first fusion power plant?”

However, Cowley quickly adds, researchers don’t yet know how to build the CPP and have years of R&D ahead of them. They will also need the knowledge they’ll gain from ITER, he says. Mauel notes that if the United States pulls out of ITER, it would have to build a similar experiment of its own before building the CPP. That would only make the process longer and more expensive, he says. “There is no shortcut” around ITER, he says.

An obvious question is whether Congress is willing to increase the funding for DOE’s fusion energy sciences program, which stands at $564 million per year. “I think adding $200 million [per year] for 2 decades is an extremely unlikely scenario, given [DOE’s] priorities,” says William Madia, a vice president at Stanford University in Palo Alto, California, and a longtime observer of DOE. However, one Democratic staffer in the House says the call shouldn’t be dismissed out of hand. “I wouldn’t say that these numbers are wildly out of step with what’s possible,” says the staffer, who is not authorized to speak on the record.

The report falls short of a specific plan by which DOE would go about realizing the goal of a CPP. “I don’t see any viable budget scenario for this until the community comes together too and says what they’re going to do and what they’re not going to do,” Madia says. In fact, DOE has charged its fusion energy sciences advisory committee to come up with just such a long-range plan, which is due in December 2020. In the past, however, the fusion community has struggled to unite behind such long-range plans.

Observers generally agree that the ITER project now has more credibility than it had a few years ago, decreasing the likelihood that the United States will pull out. The credit for that goes Bernard Bigot, the nuclear physicist who took over as director-general of the troubled organization in 2015. “I like what I’ve been seeing the last couple of years, and it’s because of what Bernard has done,” Madia says. In fact, ITER has stabilized enough that the biggest problem it faces may now be the United States’s lagging contributions to the project, the House staffer notes. “It’s in much, much better shape,” says the House staffer, “but it’s gone from the international organization being the biggest problem to the U.S. being the biggest problem.”

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