Fusion provides the energy of the sun and all stars, but harnessing fusion for civilian electric power has proven exceptionally difficult. For over 50 years the U.S. government has pursued fusion to produce electric power, primarily by confining an extremely hot, ionized gas (a plasma) of fusion fuels using magnetic fields. In spite of great progress in some aspects of the problem, the mainline federal fusion program veered badly off course. The primary approach to magnetic fusion power is called “tokamak,” a donut-shaped magnetic bottle invented by the Russians. Initial engineering studies suggested that the tokamak might be a commercially viable source of electric power. Even though that hope collapsed over the past two decades, the federal program stayed with the concept.
Several illusions lie at the heart of the tokamak program.
Showpiece Cost Escalation. Larger and larger tokamak experiments have been built and operated worldwide, largely without fusion fuels. In the early 1990s a number of countries, including the U.S., banded together to build a very large tokamak experiment using deuterium and tritium fusion fuels to produce roughly 500 MW of thermal energy. That showcase project, called ITER, had an initial cost estimate of $5 billion and now appears to have escalated to an inferred $50 billion while being significantly delayed.
Why “inferred”? As ITER.org states, “Because multiple Members are collaborating to build ITER, each with responsibility for the procurement of in-kind hardware in its own territory with its own currency, a direct conversion of the value estimate for ITER construction into a single currency is not relevant.” So an enormous cost overrun for the fusion showpiece has been obscured.
Market Denial. Energy professionals recognize that to be viable, a new technology must have advantages over what’s already in the market. Consider how an ITER-like commercial fusion reactor might compare to a commercial pressurized water reactor (PWR). A long-standing rule of thumb tells us that a rough cost comparison can come from comparing the relative masses of systems of similar capabilities. A decades-old comparison of an early ITER core design with a PWR indicated that the tokamak would be roughly 60 times more expensive—clearly well out of the range of commercial interest.
Radioactive Waste. Both ITER-tokamaks and PWRs will produce large amounts of radioactivity. However, an ITER-tokamak reactor would produce many times more radioactivity than a PWR. While the tokamak’s radioactive waste would decay in about 100 years compared with the PWR waste decay of roughly 10,000 years, huge amounts of radwaste of any kind are undesirable.
Safety. Fusion advocates have claimed the technology is inherently safe, because if a hot fusion plasma were to escape its confinement, it would be immediately cooled when it collides with an adjacent wall. Thus, fusion concepts cannot cause a nuclear runaway, as can happen in conventional fission reactors, as at Fukushima. But the huge tokamak superconducting confinement magnets can accidentally quench, releasing their stored energy. That energy is roughly equivalent to a World War II “blockbuster” bomb. Containing such an event, however unlikely, would require a huge, fortress-like building, further adding costs to a fusion power plant. Thus, an ITER-tokamak power plant will not be inherently safe, and because an ITER-tokamak is very large, a building to contain a superconducting magnet quench will be huge, resulting in an additional increase in costs.
Technology Shortcoming. Recently, an ITER-tokamak technology showstopper emerged. Tokamaks inherently leak hot plasma, which is channeled into a side region, called a divertor. Divertors in tokamak experiments have worked well for decades, because the energy deposited has been relatively small. In ITER the energy deposited will be much, much larger. As a result, a panel of engineers recently considered how an ITER divertor might be built and found, “The present knowledge base of tokamak divertor physics is not complete enough to specify a divertor ‘solution,’…. In fact, we do not know that a solution exists even in principle.”
Delusions: Program Contradiction and Tribalism
Over two decades ago, the U.S. fusion research program narrowed its focus to research and development on tokamaks and its near cousins. Later, government policy changed to limiting the fusion program to “basic science.” In response, program activities changed very little. So why is the program still so narrow, especially when it’s obvious that ITER-tokamak fusion is a commercial loser? Why doesn’t the program encompass some of the fusion concepts that may offer more attractive paths to fusion power? Calling the program a science program is contradicted by its content.
Tribalism is a strong loyalty to one’s own tribe, party, or group. The Department of Energy (DOE) office that runs the fusion program has made it clear that it is interested in funding only tokamaks or similar research. Anyone who hopes to attract DOE fusion program funding had better support what the office wants or they will not qualify for support. Those who are currently involved in the program dare not challenge the program bias. That situation can be viewed as forced tribalism; it’s certainly not balanced basic science.
Hope for Commercial Fusion Power
While the current tokamak focus is not commercially viable, decades of related experience provides important lessons for researchers to identify other, potentially attractive approaches to fusion power. A number of such concepts exist, some involving high neutron fluxes and others devoid of direct neutron production, such as the proton-boron 11 fuel cycle.
Examples of p-11B concepts include: the Polywell, which is inherently small, uses magnetic cusps and an electrostatic potential well; the Tri Alpha field-reversed configurations, heated by ion beams, inside a cylindrical, truck-sized vacuum chamber containing solenoids; and the Lawrenceville Plasma Physics dense plasma focus with some fresh ideas that could solve some old problems. In addition, the independent DOE ARPA-E program is supporting some interesting concepts outside of the tokamak-plagued DOE fusion program. One or more of these and other concepts might yield a fusion power concept that the market could embrace. With a realignment of the mainline fusion program, benefiting from the ITER-tokamak experience, hope for fusion power could be rekindled and hopefully realized.
— Dr. Robert L. Hirsch headed the U.S. government fusion program from 1972 to 1976 and has since worked in industry and nonprofits.