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A conception of a compact fusion power plant, developed by researchers at the Massachusetts Institute of Technology

Alexander Creely

U.S. physicists rally around ambitious plan to build fusion power plant

U.S. fusion scientists, notorious for squabbling over which projects to fund with their field’s limited budget, have coalesced around an audacious goal. A 10-year plan presented last week to the federal Fusion Energy Sciences Advisory Committee is the first since the community tried to formulate such a road map in 2014 and failed spectacularly. It calls for the Department of Energy (DOE), the main sponsor of U.S. fusion research, to prepare to build a prototype power plant in the 2040s that would produce carbon-free electricity by harnessing the nuclear process that powers the Sun.

The plan formalizes a goal set out 2 years ago by the National Academies of Sciences, Engineering, and Medicine and embraced in a March report from a 15-month-long fusion community planning process. It also represents a subtle but crucial shift from the basic research that officials in DOE’s Office of Science have favored. “The community urgently wants to move forward with fusion on a time scale that can impact climate change,” says Troy Carter, a fusion physicist at the University of California, Los Angeles, who chaired the planning committee. “We have to get started.”

Fusion scientists and DOE officials strived to avoid the sort of meltdown they suffered during their last planning exercise. Six years ago, the fractious community was already reeling from budget cuts that forced DOE’s Fusion Energy Sciences (FES) program to shutter one of three major experiments. Then, the associate director for FES decided to write the plan himself, with limited input. Many researchers rejected the road map.

This time, DOE wants no infighting. “We’ve been told in no uncertain terms that either you guys get in line, or you’re going to get nothing,” says Nathan Howard, a fusion physicist at the Massachusetts Institute of Technology. For the first time, FES leaders let researchers hash out consensus in a series of workshops and meetings. Howard and other leaders of that process used anonymous polling and even hired a facilitator to ensure the “loudest voices in the room” couldn’t dominate deliberations.

The process was also comprehensive, says Carolyn Kuranz, a plasma physicist at the University of Michigan, Ann Arbor. FES mainly funds research on magnetically confined fusion, in which an ionized gas or plasma is squeezed and heated until atomic nuclei fuse and release energy. But it also supports smaller efforts in plasma physics, such as using high-power lasers to re-create plasmas like those in stars. The consensus building did not neglect them. “This was the first time we included the whole portfolio and the entire community,” Kuranz says.

The plan that emerged does not call for a crash effort to build the prototype power plant. During the next decade, fusion researchers around the world will likely have their hands full completing and running ITER, the international fusion reactor under construction in southern France. ITER, a huge doughnut-shaped device called a tokamak, aims to show in the late 2030s that fusion can produce more energy than goes into heating and squeezing the plasma.

ITER will teach valuable lessons about a “burning plasma,” researchers say. But they add that its cost of more than $20 billion is far too steep for an actual power plant. So, after ITER, U.S. fusion researchers want to build a much smaller, cheaper power plant, leveraging recent advances such as supercomputer simulations of entire tokamaks, 3D printing, and magnet coils made of high-temperature superconductors.

The new fusion road map identifies technological gaps and nearer-term facilities to fill them (see partial list, below). “By identifying [a power plant] as a goal, that can trigger more research in those areas that support that mission,” says Stephanie Diem, a fusion physicist at the University of Wisconsin, Madison. For example, in a fusion power plant a barrage of energetic neutrons would degrade materials, so the report calls for developing a particle-accelerator–based neutron source to test new ones.

Fusion wish list

U.S. researchers have agreed on the need for projects that would aid a future power plant (first three rows) and advance basic plasma science. However, funding limits could curtail plans.

ProjectFlat budgets2% increasesUnconstrained
Neutron source to test materials for fusion power plantYes, but highly delayedYes, but delayedYes
Tokamak to test integrated systems for fusion power plantNoYes, but highly delayedYes
Facility to test “blanket” that would surround reactor and absorb neutronsNoNo Yes
Matter in Extreme Conditions UpgradeNo, but develop furtherNo, but develop furtherYes
Solar wind facilityNoNo Yes
Multipetawatt laserNoNoYes
Powering the Future Fusion and Plasmas, Fusion Energy Sciences Advisory Committee (2020)

Such technology development pushes a sensitive boundary for the fusion program. Fusion investigators have long complained that DOE’s Office of Science has limited them to basic research. Now, DOE leaders are more receptive to a practical approach, says James Van Dam, DOE’s associate director for FES. “There’s been much more openness and interest in fusion moving ahead.”

To realize their ambitions, fusion scientists will need more funding from Congress. The planning committee considered three scenarios: flat budgets, increases of 2% per year, and unconstrained budgets. Only the most generous scenario would allow DOE to build new facilities, the report says. FES’s annual budget is now $671 million, including $247 million for ITER.

Tighter budgets might strain the newfound consensus. Plasma physicists want several new facilities, such as one to simulate the solar wind. But without a funding boost, they won’t even be able to build a project DOE has already said it wants: the Matter in Extreme Conditions Upgrade, which would improve a petawatt laser at the SLAC National Accelerator Laboratory to create energetic plasmas so they can be probed with the lab’s x-ray laser.

No matter how things play out, the fusion plan expresses the will of younger scientists who led the community exercise, says Scott Baalrud, a plasma theorist at the University of Iowa. “People don’t get into this career just to study the science that may one day, long after they’re dead, lead to a fusion reactor,” he says. “They want to get going and change the world.”