For the time being, no electric cars can drive, but American scientists have taken an important step in nuclear fusion research. They generated more energy with a nuclear fusion reaction than was needed to start that reaction. Researchers at the US Lawrence Livermore National Laboratory announced this on Tuesday afternoon.
The experiment at the US National Ignition Facility (NIF) boosts nuclear fusion by bombarding a fusion fuel capsule, which consists of heavy variants of hydrogen atoms, with powerful laser beams. On the morning of December 5, it managed to generate 3.15 megajoules of energy in a fraction of a second, compared to the 2.05 megajoules that went into it. For comparison: 2.05 megajoules is as much energy as half a kilo of TNT provides.
Researchers have been trying for decades to realize nuclear fusion, the phenomenon that also creates the energy of the sun, on Earth in a controlled manner. It would be an almost inexhaustible energy source that produces no greenhouse gases and less radioactive waste than the current nuclear power plants. But it is difficult to realize because of the extremely high temperature and pressure that are required for atomic nuclei to fuse (fuse), releasing energy.
Very low efficiency
“It is a good result from the perspective of fusion research,” says Marco de Baar, director of the Eindhoven research institute Differ. “It is the first time that nuclear fusion has been started in a controlled way, with more energy coming out than they put in. But I don’t see it happening that they will make a power station with this technology.”
This has to do with the fact that the 2.05 megajoule is not all the energy that was used. The lasers have an efficiency of less than one percent. The experiment draws about 300 megajoules from the electricity grid to ultimately deliver 2.05 megajoules to the fuel.
The NIF experiment consists of the world’s largest laser system that generates 192 laser beams that the researchers aim at a gold cylinder with a ball in the center of less than two millimeters in size – smaller than a peppercorn. It consists of a shell of a kind of diamond with the fusion fuel inside. The 192 laser beams heat the cylinder, causing the walls to emit X-rays. That X-ray radiation compresses the ball, causing the shell to fly off, the fuel to implode and fusion to start.
Heavy variants of hydrogen
The fuel consists of deuterium and tritium, heavy variants (isotopes) of hydrogen atoms. They fuse to form helium nuclei. Earlier this year, NIF researchers showed that the fusing fuel can heat itself. Now they show that they can do this so efficiently that 3.15 megajoules of energy are produced while taking in 2.05 megajoules of radiation.
That’s an impressive technological achievement, but it’s still a long way to fusion power generation. The American researchers estimate that it will take several decades before fusion current comes out of the socket.
To build a power plant with this technique, the entire process will have to be much more efficient. Besides hundreds of megajoules going into the experiment to deliver 3.15 megajoules, the lasers can only do this trick once a day at most, after which they have to cool down. For a significant power plant you would have to rush through ten of those capsules per second, nuclear fusion researcher Niek Lopes Cardozo of Eindhoven University of Technology stated after the results were published earlier this year.
Test ‘mini bombs’
Energy generation was also not the goal of NIF, which was founded in 1997. “NIF is part of a program to test the reliability and maintenance of existing nuclear weapons without the use of nuclear tests. So their goal is to test mini-bombs,” says De Baar.
According to De Baar, there is still no reactor concept ready for the NIF technique with which a power station could be built. Work is also being done on other nuclear fusion techniques, which, for example, try to get fusion plasma going and to keep it under control with magnetic fields. Although these experiments do not yet produce more energy than they consume, there are reactor concepts. But even that way, it will take decades for the first nuclear fusion power plant to be built.