Energy

Fusion Research: What About the U.S.?

Fusion’s grand challenge requires global cooperation–and U.S. research funding.

The site for the International Thermonuclear Experimental Reactor (ITER) has finally been chosen: southern France. Both the European Union and Japan were bidding to host ITER, and the selection of one of them opens the way to the scientific demonstration of controlled fusion energy production and removes perhaps the last major impediment to a project under consideration for nearly 20 years.

This result is good news for the two bidders, for the rest of the ITER consortium (the United States, Russia, China, and South Korea), and for the citizens of the world, since it enables us to take the next step toward developing a sustainable energy source – nuclear fusion, the process that powers the sun – that produces zero climate-changing emissions.

Nuclear reactions that release energy by combining light nuclei like hydrogen’s to form heavier nuclei such as helium’s are called fusion. They are, in a sense, the opposite of the fission reactions that generate power in present-day nuclear plants. Fission breaks up the nuclei of heavy elements such as uranium. Fusion has the potential to provide practically inexhaustible energy with greatly reduced radioactive waste.

The fuel in a fusion reaction must be subjected to tremendous heat, which turns it into an electrically conducting gas called a plasma. The plasma state must be maintained long enough for the reactions to occur. In stars like our sun, gravity confines the plasma in a wonderfully stable and long-lived configuration. A human-scale fusion reactor must use a much stronger confining force: a magnetic field. ITER will use a donut-shaped magnetic containment device called a tokamak.

But confining a plasma tightly enough to enable useful energy release is far more difficult than early researchers had hoped. Many important optimizations have been developed, but one unavoidable measure is to make the plasma large. Existing large tokamaks typically have a plasma radius of three meters and have demonstrated substantial energy releases. But keeping their fuel in a plasma state has required additional heating.

The next big step is to create a plasma that keeps itself hot with its own fusion reactions. The ITER collaboration has designed a reactor that should sustain such a “burning plasma.” It will require a plasma about twice as large as those produced by current tokamaks and superconducting magnets that consume negligible electric power. ITER will cost about $5 billion to construct.

Fusion is the kind of grand technological challenge that calls for international cooperation. But the length of time its development will require can breed skepticism and discourage policymakers. In the mid-1990s, cuts in the United States’ fusion research budget led it to pull out from the ITER consortium. Thankfully, it rejoined in 2003, but in a more junior role, reflecting its relatively modest funding of fusion projects: $290 million in 2006, less than half Europe’s commitment.

The United States still has two world-renowned tokamaks – one at MIT, the other at General Atomics in San Diego – whose research will be crucial in helping to resolve and prepare for challenges that ITER faces. But U.S. leadership in fusion plasma science cannot be sustained without a renewed commitment of resources. The United States’ present 10 percent share of ITER will call for peak expenditures of perhaps $150 million per year – mostly for industrial procurements, not for research.

If that money were taken from the existing federal fusion research budget, it would decimate U.S. fusion research. That is why the U.S. fusion community’s overwhelming enthusiasm for ITER is predicated on strong domestic support for fusion and plasma physics research, plus additional funds for ITER construction. Even if the U.S. increased its funding for fusion research to $500 million per year, that would still be substantially less than it spends separately on high-energy physics, fossil energy research, and basic energy sciences, not to mention the recent budgets of the Missile Defense Agency ($9 billion) and NASA ($16 billion).

Ultimately, fusion could prove to be one of the most environmentally attractive energy options. The United States should seize the opportunity to play a strong role in ITER’s success and demonstrate its commitment and long-term vision as a scientific collaborator by revitalizing its overall fusion program.

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