The Nation March 12, 2016
The path to creating sustainable fusion energy as a clean, abundant and affordable source of electricity has led to a point where the international fusion experiment, ITER, is poised to produce more energy than it uses when it is completed in 15 to 20 years, said Ed Synakowski, associate director of Science for Fusion Energy Sciences at the US Department of Energy (DoE).
Speaking last Saturday at the DoE’s Princeton Plasma Physics Laboratory, Synakowski traced the discoveries that have led to this moment. Synakowski was a researcher on the Princeton Lab’s Tokamak Fusion Test Reactor from 1988 to 1997. He was also head of research of the National Spherical Torus Experiment from 1988 to 2005.
“Getting there, if you think about nuclear fusion, is going to take some moments of discovery, some ‘aha’ moments,” Synakowski said. “We’re taking the process that powers the sun and the stars and bringing it to earth for the benefit of mankind.”
Under a fusion power road map developed by European scientists, the next step after ITER would be to build fusion power plants that could begin generating electricity as early as the middle of this century, Synakowski said. Fusion energy would supplement other green sources of electricity, such as wind and power, which have great potential but face the challenge not only of relying on the weather but of storing energy, he added. “Any robust clean energy infrastructure will benefit greatly from a mix that includes renewables as well as something like fusion,” he said. “You need something that’s clean and has the potential of stable, reliable electric power.”
Another sign of progress on the road to fusion energy was the February 3 celebration of the first hydrogen plasma at the Wendelstein 7-X stellarator in Greifswald, Germany, which is collaborating with Princeton researchers.
EMC2 and polywell reactors
A promising alternative path to fusion is the cube-shaped “polywell” reactor being championed by EMC2 Inc, funded by the US Navy for over 20 years. Jaeyoung Park, who leads the EMC2 effort, estimates that a $30-million push over three years could remove the remaining scientific obstacles to successfully developing commercial fusion power technology.
Fusion energy is based on the same process that takes place in the sun, where gravity holds together hot ionised gas, called plasma, and hydrogen nuclei collide together and fuse, creating a burst of energy.
Fusion energy uses two isotopes of hydrogen: deuterium, which can be extracted from seawater, and tritium, a radioactive isotope that is not naturally available but can be produced in a fusion reactor. Unlike many other forms of energy, it takes a small amount of fuel to produce a large amount of energy.
A power plant that produces 1,000 megawatts of energy consumes 9,000 tonnes of coal a day and emits 30,000 tonnes of carbon dioxide, the greenhouse gas linked to climate change. A fusion power plant producing the same amount of energy would produce less than 2 kilos of helium as a byproduct. And compared to the byproducts of nuclear plants, which remain radioactive for thousands of years, the small amount of radioactive material produced in fusion reactions would remain radioactive for tens of years.
Synakowski noted that humankind’s energy consumption has increased over the centuries as people’s life span has increased. In the past 160 years, US life expectancy has doubled from 40 to 80, Synakowski said. That has been partly due to the availability of energy, he said, and has caused political instability as developing countries strive to obtain a plentiful energy source that will improve their people’s quality of life. The increased life span has also required additional energy. Meanwhile, the source of energy has also evolved from wood to coal, to petroleum, natural gas and nuclear sources of electric power. “Energy drives a quality of life that isn’t going away,” he said.
Synakowski traced the roots of fusion energy to Princeton astrophysicist Lyman Spitzer, whose “Project Matterhorn” in the 1950s produced fusion energy in a device dubbed a “stellarator”. Spitzer’s stellarator had the same basic elements of modern fusion devices, using magnets on the outside to create a magnetic field to contain the super-heated plasma away from the walls.
Other fusion experiments include the British “pinch” and the Russian-invented “tokamak”, a doughnut-shaped device. The Russians achieved an electron temperature of up to 20 million C, which convinced the Princeton Lab to switch to the tokamak.
The switch paid off on December 9, 1993, when the facility achieved a world-record 6.3 million watts of fusion power with a 50-50 mix of deuterium and tritium. In June of 1994, TFTR would generate headlines worldwide when it produced 10.7 million watts of fusion power.
Synakowski has no doubts about fusion energy’s potential to change the world. “I feel most fortunate to have been a part of this journey, to be able to witness it, to be able to work in this field and to allow it to stimulate additional moments of discovery for me,” he said. “I can’t think of another field of science that is more compelling, both for the beauty of it and the practical import of it.”