Quest for sustainability: Can nuclear fusion help fuel the world?
By SUSHMITHA RAMAKRISHNAN
WASHINGTON: If you work in atomic energy, you’ve probably heard the joke: Generating electricity from nuclear fusion is always just 30 years away. But despite its complexity, scientists working on the technology say it’s worth the trouble. That’s because the nuclear fusion reaction has a higher energy potential than all other energy sources we know. It can release nearly 4 million times more energy than chemical reactions like burning coal, oil or gas, and four times more than nuclear fission, the process currently used in all nuclear power plants around the world.
Discovered in the early 20th century, fusion is seen as the future of energy by many policymakers, especially in Europe. But is nuclear fusion really a ‘greener’ alternative to what we’re doing now, and how far have we come in generating electricity from this process?
To look into this, DW visited the International Thermonuclear Experimental Reactor (ITER), a large collaborative project between nuclear fusion experts from 35 nations.
Located a couple of hours from the scenic coast of southern France, ITER stands out along the idyllic landscape surrounding it. The project’s compound is laden with metal sheds, workshops and equipment. Busy scientists and technicians roam the reactor’s campus in hard hats, rubber boots and neon vests.
Sitting at the center of this industrial landscape, Pietro Barabaschi, the Director General of ITER, promises that the future of fusion energy is bright. He explains that generating fusion energy is like burning firewood.
“First, you start a flame, heat the wood and at some point a chemical reaction starts, and then this reaction is enough to burn the rest of the wood.” Atoms are composed of a nucleus (containing protons and neutrons) and electrons. In fusion, two atoms are merged into one by smashing their nuclei. In a bid to achieve a stable nucleus, the newly formed atom sometimes chucks out a high-energy neutron previously used to bind the neutron to the nucleus.
Nuclear fusion scientists want to convert this excess energy into electricity that lights up our homes. Technically we already harness commercially viable energy from fast-flung neutrons in nuclear fission power plants. So why don’t we just stick to it? In fission, instead of fusing two light atoms, a heavy atom is split into two or more. All nuclear power plants in the world use fission reactors to generate electricity. France, where ITER is located, gets 70% of its energy from nuclear fission. However, it is not a popular source of fuel in most countries due to public fears of harmful radiation, stoked by accidents such as the Chernobyl disaster, the meltdown at Fukushima and the US Three Mile Island partial meltdown.
The main difference between nuclear fission and fusion is the radioactivity of the fuel each method creates, says ITER knowledge officer Akko Maas. He has been with the project since its early days. “In fission, the uranium that you use and the plutonium that you create are both radioactive. And once you have gotten the energy out of them, you are still left with radioactive material.” Of the two base materials considered most efficient for fusion energy, deuterium is not radioactive, but tritium is. However, its radiation is comparatively weak and short-lived.
“If you choose the materials correctly, even on an industrial scale, you can limit the radioactivity from fusion to 100 to 200 years, which is far more manageable than if you talk about the 40,000 years we see in fission,” Maas says.
In addition to being highly efficient, proponents say nuclear energy could dramatically reduce our dependence on fossil fuels. Nuclear energy itself is considered a carbon-free alternative to fossil fuels because its creation does not emit greenhouse gasses — its major byproduct is helium, an inert, non-toxic gas.
Further, deuterium is abundant in seawater, and scientists are trying to produce tritium using lithium in situ. Renewable energy sources like wind and solar alone cannot meet global baseline energy needs. Nuclear fusion, if successful, could provide well above that.
While all of this sounds rosy, it is still a distant dream. For fusion to become a reality, we need a technological breakthrough in plasma physics. “Technically, it’s difficult to achieve a fusion reaction that is self-sustained and stable,” Barabaschi says.
The sunshine and the warmth we feel on Earth is the result of fusion — the process occurs naturally in the core of the sun under extreme temperature and pressure.
The challenge is to replicate what happens in the sun’s core without the pressure arising from the gravity of the sun’s heavy mass. In order to achieve fusion on Earth, gasses need to be heated to extremely high temperatures of about 150 million degrees Celsius (270 million degrees Fahrenheit), around 10 times the temperature of the sun’s core. At this point, the gasses become plasma, which is nearly a million times lighter than the air we breathe. All the protons, neutrons and electrons that compose it are separated.
Fusion researchers have established that creating a plasma by heating a mixture of deuterium and tritium is the easiest way to achieve an environment to fuse and yield energy. At ITER, a device called the tokamak uses a strong magnetic field to confine the plasma used for fusion experiments.
In these extreme conditions, particles in this plasma collide rapidly, creating heat. But paradoxically, as the temperature rises even further, the collision rate — and therefore the heating effect — drops.
“It is like the plasma is switched off beyond a certain point,” says Barabaschi, perplexed. To go back to the wood analogy, it is like not knowing how to ignite a fire that will sustain the “burning plasma.” This is the biggest challenge faced by fusion experiments around the world. What is one’s woe is another’s boon. The “switching off” of the plasma in unfavourable conditions also means that the reaction stops if there is any instability. This makes fusion safer than fission, experts say.
A meltdown like the one at Fukushima is unlikely to happen in a fusion reactor, says Gilles Perrier, head of safety and quality at ITER. In a fission reactor, there would be a radioactive core that would still need to cool if the reactor were to shut down.
“In fission, the risk of an accident is much higher. In fusion, it is really low,” Perrier says. He says safety in a fusion plant has three parts to it: Confinement of plasma, reduction of radiation exposure and prevention of tritium contamination. The plasma is confined in a vacuum vessel. “Even in the worst-case scenario of a plasma leak, the impact will be confined to the site,” he says. At this point, the most electricity scientists have been able to generate from fusion is 59 megajoules of energy over five seconds. That is about enough electricity to run a small light bulb for two months.
This article was provided by Deutsche Welle