Japan and the United States jointly achieve a new breakthrough in hydrogen-boron nuclear fusion

Japan’s National Institute of Fusion Science and the United States’ TAE Technologies have teamed up to realize the first hydrogen-boron fusion experiment in a magnetically confinement fusion plasma. The findings were published in Nature Communications.

The Norman reactor of TAE. Image source: TAE company

In the twisted “gut” of Japan’s large spiral device, trillions of hydrogen-boron fusion reactions occur every second. IMAGE CREDIT: NATIONAL INSTITUTE OF FUSION SCIENCE/SCIENCE SOURCE

Although these fusion reactions are far from net energy and require higher temperatures than standard fusion fuels, hydrogen-boron fuels are abundant and do not produce damaging particles. TAE CEO Michl Binderbauer noted in a statement that the findings suggest that this alternative fuel, a blend of protons and boron, has a place in utility-scale fusion power generation.

However, Dennis Whyte, director of MIT’s Center for Plasma Science and Fusion, believes it’s an interesting experiment that does little to convince skeptics to switch the fuel.

Nuclear fusion is often advertised as a carbon-free energy source that has an abundant and cheap fuel, a mixture of the hydrogen isotopes deuterium and tritium (D-T). In fact, tritium is so rare that it must be “grown” from lithium in reactors, and some scientists fear future shortages. In addition, when D-T fuel fuses at high temperatures, it produces a large number of high-energy neutrons, which is harmful to both humans and reactor structures.

TAE takes a different approach: fusing protons with boron, which is easily mined. This reaction produces no neutrons, only harmless helium, but it requires a temperature of about 3 billion degrees Celsius, or 200 times the heat in the sun’s core, and 30 times higher than what would be needed to fuse D-T. Researchers have shown that they can fuse protons and boron by using beams of particles aimed at solid targets or by exploding plasma with lasers.

Japan’s National Fusion Science Research uses a conventional fusion reactor called a Large Helical Device (LHD). The LHD, which began operating in 1998, is shaped like a twisted doughnut with electromagnets containing superthermal ionized fuel, known as plasma. In the experiment, the boron plasma was heated to about 20 million degrees Celsius, and a neutral hydrogen atomic beam was emitted into the plasma. Hydrogen-boron fusion produces high-velocity helium atoms, and the helium sensor developed by TAE recorded 150 times more collisions when using boron plasma in machines than when containing non-reactive gases, indicating that nuclear fusion is occurring.

The team’s computer simulations show that this equates to about 5 trillion fusion reactions per second. Whyte says most of these reactions are caused by beams of particles. In many fusion reactors, particle beams are used to make the entire plasma hot enough to fuse more widely. But the LHD results show that fusion only occurs at a few hot spots where the beam hits the plasma, and not elsewhere, because the fusion rate drops rapidly once the beam is turned off.

A fusion reactor that can generate electricity requires a wider range of fusion combustion to provide enough heat to sustain the reaction, plus some additional heat to collect to generate electricity. LHD is still a long way from that goal, but TAE believes it can achieve it with a very different plasma device. TAE’s various test benches have created a rapidly rotating plasma “smoke ring” that is stabilized and heated by a particle beam. To date, TEA’s largest machine, Norman, achieved a high temperature of 60 million degrees Celsius in 30 milliseconds.

Within a few years, TAE said, it will build a successor called Copernicus, with the goal of reaching 100 million degrees Celsius, which is the temperature required for conventional D-T fusion. Over the next decade, TAE hopes to build a more powerful machine, da Vinci, that approaches hydrogen-boron temperatures.

Whyte believes that neutrons are a huge challenge for classical nuclear fusion, but he thinks getting plasma to reach billions of temperatures could be just as difficult. Even if TAE did, each hydrogen-boron reaction would produce only half the energy of deuterium and tritium. “For it to be valuable, hydrogen-boron fusion will require strong engineering advantages.” (Source: China Science News Xin Yu)

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