Fusion energy has recently been a hot topic. Much of the coverage is a combination of hope, technical illiteracy, and fantasy. Given the over 70-year history of fusion hype over fusion reality, some have called it “the fornever fuel.”
In January 1958, for example, the British press proclaimed that the domestic “Zeta” fusion experiment meant that commercial fusion power was only 20 years away. A giant headline on the Daily Mail proclaimed, “A SUN OF OUR OWN!” The experiment at the Harwell nuclear site turned out to be a failure.
Recently, some needed reality has intruded on the fusion fantasy. Chief among the realists, the Congressional watchdog agency, the Government Accountability Office, issued a report last month titled “Fusion Energy: Potentially Transformative Technology Still Faces Fundamental Challenges.”
The GAO report notes the broad hype generated by last year’s successful Lawrence Livermore National Laboratory experiment generating more energy than used by lasers to heat and fuse the tritium fuel. Despite the breathless reportage of a “breakthrough” and implications and claims of rapid development of a new way to make electricity, GAO carefully warned that “several challenges must be overcome to achieve commercial fusion, and stakeholders’ projections of this timeline range from 10 years to several decades.”
Fusion enthusiasts have been predicting that the advent of commercial application of smashing hydrogen atoms together in a controlled environment (unlike the easier task of uncontrolled fusion, aka hydrogen bombs) was only 25 years away for over 70 years. Always only 25 years away? Skepticism is warranted. The GAO report outlines why.
GAO observes that a 2020 Department of Energy advisory committee projected commercial fusion energy “in the mid-2040s.” The world’s largest fusion experiment, the International Thermonuclear Experimental Reactor, keeps slipping its estimate of when it will demonstrate a practical possibility of fusion, and announced it previous 2035 estimate will have to be scrapped. Building a commercial fusion plant after that is likely to take decades. GAO points out that “fusion has not achieved net energy gain,” despite the Livermore success.
A key problem, according to GAO, is plasma physics. Says the report, “Some aspects of plasma behavior are poorly understood, making it difficult to optimize plasma confinement and reliably drive fusion energy production. For example, turbulence is a highly complex behavior in which regions of a burning plasma move in ways that current methods cannot fully predict.”
GAO adds, “In addition, self-heating or ‘burning’ plasmas could exhibit as-yet-unknown behaviors. So far, nearly all plasma research has been done on plasmas heated by an external source. As of March 2023 only one facility, NIF, has created a burning plasma.” That event lasted only infinitesimally.
Then there are unknowns about materials that can withstand the enormous forces and assaults fusion reactions will impose. GAO: “In a commercial fusion energy power plant, materials will need to last for months or longer to avoid frequent repair or replacement of components. However, when subjected to the stresses that fusion plasmas generate, materials currently available degrade or fail too quickly for commercial use.”
The hype about fusion claims it is “clean,” apparently meaning that it won’t produce spent nuclear fuel, which is true. Nor will it produce greenhouse gases. Also true.
It will produce radioactive waste, caused by neutron bombardment. The failure to detect neutrons was the key evidence that the 1980s Fleishman and Pons “cold fusion” frenzy was fantasy. Notes GAO, “Neutrons can degrade the mechanical and thermal properties of materials, and change their physical properties. They can also transmute elements in components into new elements, which would reduce their structural soundness and even make them radioactive.” The report adds, “Some materials can withstand high heat, high neutron flux, or ion damage, but no existing material can simultaneously tolerate all three of these stresses at the levels and durations that would be needed for a commercially viable fusion energy system.” Doesn’t sound “clean” to me.
Another fusion trope is “abundance”, meaning hydrogen, the most common element on our planet, will be the fuel. But a key fusion fuel is tritium, a largely man-made isotope of hydrogen, barely found in nature, which is also radioactive. Again, GAO debunks the abundancy claim, observing that “the global supply of tritium is far too limited to meet the needs of commercial fusion energy plants. The only appreciable source is from fission in certain nuclear power plants, many of which are expected to retire in the coming decades. Meanwhile, tritium cannot be effectively stored because it decays quickly, with a half-life of around 12 years. The global available inventory is predicted to peak in 2027 at about 27 kilograms (about 60 pounds), of which ITER experiments could consume the majority. Further, a fusion energy system that produces 1GW of power could consume about 56 kg of tritium per year.”
Some fusion fanatics claim their machines will be able to “breed” tritium by using the plentiful neutrons to bombard a lithium blanket and create all the tritium necessary. So far, this is purely theoretical handwaving. An article in Science last year cast serious doubts about this answer to the tritium problem.
Finally, fusion enthusiasts claim the technology offers “safety,” presumably meaning fusion plants won’t face some of the safety issues of fission reactors. Commercial fusion plants won’t be capable of melting down. They do, however, present large, unprecedented safety challenges. The culprit is heat. As GAO notes, “In order for fusion to occur, the plasma must reach a temperature of about 150 million Kelvin, about 10 times as hot as the sun. The plasma then transfers heat to the parts of the fusion device that face the plasma.”
Magnetic confinement fusion technologies, such as the donut-shaped Tokomak or the twisty donut (and once discarded) Stellarator are designed to use a “diverter” to control the enormous heat energy. GAO notes that “the divertor can experience extremely high bursts of heat that create significant thermal stress, causing even heat-tolerant materials to fail. Using simulations and experimental data, researchers have developed methods to avoid such bursts, but these methods remain to be fully tested.”
The bottom line: don’t count on fusion to make a serious contribution to world electricity production on any predictable time schedule. Demonstrating the technology as practical is still decades away at best. Developing an economic, commercial scale reactor is, at best, additional decades after that.
–Kennedy Maize
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