Is there a faster, cheaper route to fusion energy?
Excerpted from The Future Postponed, Massachusetts Institute of Technology, 2015
Anne White: Cecil and Ida Green Associate Professor in Nuclear Engineering
For more than 50 years, scientists have pursued fusion energy as a means of generating electric power, because it is a potentially ideal energy source for human civilization—inherently safe, with an inexhaustible fuel supply of hydrogen isotopes mined from the sea, and no greenhouse gas emissions.
The goal is still far off. The international community is investing $10s of billions of dollars to build the ITER facility in France in order to study fusion reactions which are self-sustaining. But those experiments won’t be ready for more than a decade, and will leave many critical issues in extracting useful electric power from a fusion reactor unsolved. What if there were
a faster, cheaper route to fusion energy, based on recent superconducting magnet technology and advances in materials science?
Fusion—the process by which hydrogen atoms combine to create helium and in the process release huge amounts of energy—is what powers the sun. Containing the ionized gases that fuel the process at temperatures even hotter than the core of the sun in an earth-bound reactor requires powerful magnetic fields. ITER will use an early generation of superconducting magnets, capable of producing only a moderate strength magnetic field. Those magnets must be kept cooled to -452 degrees F while close to the hot gases, adding to the engineering complexity.
Recent progress on superconducting wires or tapes has been quite rapid, such that new high temperature superconductors are now commercially available. This progress has been largely achieved by U.S. industries. Magnets made from these materials can already operate at temperatures far above early generation designs, and can generate and tolerate much stronger magnetic fields. Future superconducting materials may eventually permit room temperature superconducting magnets. And for fusion, magnets are critical: doubling the strength of the magnetic field—about what the new magnets would permit over those in the ITER design—increases the fusion power per volume sixteen-fold. That in turn would permit a smaller, less expensive fusion reactor which operates at higher power density, with more stable plasma characteristics, while also reducing the scale of challenging engineering and materials problems. Preliminary calculations suggest that such designs, once perfected, might be capable of producing 100’s of megawatts of electric power.
New superconducting magnets that exploit recent technology could enable powerful fusion devices with greatly decreased size, accelerating fusion energy’s development. There is thus an opportunity for the U.S., if it chose, to leapfrog over existing efforts and reclaim a lead in fusion research.
The recent superconductor developments represent an exciting new opportunity to pursue a faster development track to practical fusion power. But the U.S. fusion program does not have a superconducting experimental device, and there are currently no plans to build one or, indeed, any new fusion reactors. Instead, the most advanced superconducting fusion experiments in the world are currently operating in China and South Korea, with new superconducting experiments under construction in Japan, Germany and France. European and Asian countries also have aggressive plans to accelerate their own development of fusion energy. Significantly, all of the fusion devices currently opera- ting and planned have had to employ the older generation of superconducting technology. This creates an opportunity for the U.S., if it chose to invest in a high-field, high-temperature super- conductor device in parallel with its support for ITER, to leapfrog current device capabilities and help to reclaim a lead in fusion research.
The advanced superconducting magnet technology could lead to revolutionary advances in fusion reactor designs, both for “tokamaks” (like ITER and the major existing U.S. facilities) and for “stellarators”, (an alternative configuration which might more easily achieve continuous operation). In fact, support for basic research in large-scale, high temperature, superconducting magnet technologies would have a large payoff for whatever new course the U.S. magnetic fusion science program might follow in the next decade, irrespective of device configuration or mission.
Such a new course would require significant resources, not just for fusion research, but
also for additional research into high temperature superconducting materials and magnet designs. But it would also have significant spinoffs beyond fusion, such as high current DC power distribution cables, superconducting magnetic energy storage, and improved super- conducting radiotherapy devices. Providing the materials and expertise to build and operate an advanced superconducting fusion device would also generate significant economic activity; the current U.S. fusion program employs more than 3600 businesses and contractors spread across 47 states.
The U.S. has world-leading depth in measurement, theory and computation for fusion research, but it cannot be sustained for long in the absence of new experimental facilities. No research program can guarantee a successful outcome, but the potential to accelerate the development of fusion as a source of clean, always-available electricity should not be ignored. Practical fusion power would transform energy markets forever and confer huge advantages to the country or countries with the expertise to provide this energy source to the world.