Boron instead of deuterium and tritium: For the first time, researchers have triggered the nuclear fusion of hydrogen and boron in a plasma and demonstrated it using helium nuclei that were formed. The success, achieved at a test reactor in Japan, may be a first step toward cleaner fusion power plants that don’t produce radioactive neutrons, the team reports in Nature Communications. In addition, unlike tritium used in common fusion reactors, boron is an abundant raw material.
Nuclear fusion is the energy source of the future. However, it is still not clear which technology breakthrough and practical implementation of fusion power plants can be achieved. Physicists are currently experimenting with very different types of reactors – from systems based on the tokamak principle, such as the large reactor ITER, to starbursts such as Wendelstein 7-X, to laser fusion, which has recently achieved plasma ignition. What these fusion reactors have in common is that they use mostly heavy hydrogen in the form of deuterium and tritium as fuel.
The problem with this: The fusion of deuterium and tritium releases large amounts of high-energy, radioactive neutrons, which require complex shielding. In addition, the isotope tritium only exists in trace amounts in nature and must therefore be obtained from radioactive material or from fusion reactors. The total global supply of tritium is currently less than 20 kg.
Boron as an alternative fusion fuel
However, a possible alternative could be the fusion of hydrogen with boron. This metalloid occurs abundantly in nature and, unlike tritium, is neither toxic nor radioactive. “Moreover, the fusion reaction with boron produces no neutrons, only helium in the form of three alpha particles,” explain RM Magee of TAE Technologies and colleagues. Thus, a fusion reactor that uses protons and boron as fuel will be safer, more environmentally friendly, and easier to handle.
However, there is a catch: To ignite nuclear fusion in a hydrogen-boron plasma, temperatures 30 times higher than in a deuterium-tritium plasma are required. “This makes it difficult to operate the reactors with this fuel in such a way that the fusion energy generated is greater than that used for heating,” the physicists explain. In order to implement the cleanest and easiest to use fusion technology, major physical hurdles must first be overcome. The researchers stress that “these obstacles can be overcome.”
Fusion test at the Japanese star
Magee’s team has now taken an important step: they have released and demonstrated the fusion of water with boron in an magnetic confinement reactor plasma for the first time. To do this, they used the Large Spiral Device (LHD) in Japan, the second largest stellar device in the world after Wendelstein 7-X. In the experiment, physicists first put tiny boron grains into the hydrogen plasma of a fusion reactor. “The measurements show that a large amount of boron accumulates in the plasma medium,” they explained.
In the next step, high-energy protons were released into the plasma using several ion beam injectors. “The calculations predict that the boron density and ion beam parameters achieved in the experiment should result in a fusion rate of about 100 billion per second if all three high-energy emitters are fired simultaneously,” Magee and colleagues say. They checked whether this was indeed the case with the help of detectors that can detect helium nuclei produced when protons fuse with boron.
The fusion of boron and hydrogen has been detected
Result: The alpha detector did indeed detect a sudden increase in helium nuclei in the test reactor plasma. “The particle numbers indicate a fusion rate that is in good agreement with theoretical calculations,” Magee and his team wrote. “This is the first evidence of nuclear fusion of hydrogen and boron in a magnetic confinement plasma.” According to the physicists, the experiment represents an important step towards future fusion reactors using this fuel.
“This experiment provides us with a large amount of data that we can work with right now,” says co-author Michel Benderbauer, CEO of TAE Technologies. “It shows that hydrogen and boron fuels have a place on the fusion energy pathway.” While there is still a long way to go before such a fusion plasma can be ignited, physicists are confident that boron fusion reactors will one day produce clean matter. , can become a non-radioactive energy source.
New type of fusion reactor by 2030
TAE is already working on fusion reactors that, unlike tokamak and stars, have a linear structure. In this so-called field inverted configuration (FRC), the plasma is surrounded by linear magnetic field lines and a toroidal electric field, so that a kind of “smoke ring” of free floating plasma is created in the cylindrical reactor. Initial laboratory-scale trials have already been successful, and the first larger systems are now being developed.
The Californian company plans to complete prototypes of these reactors by 2030, which will then produce more fusion energy by 2040 than they need to operate. (Nature Communications, 2023; doi: 10.1038/s41467-023-36655-1)
Source: Nature Communications, TAE
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