Researchers at the Joint European Torus (JET), a fusion experiment in Oxfordshire, generated 59 megajoules of heat during a 5-second burst of fusion. This was more than double the previous record of 22 megajoules set by the same facility in 1997. These results were discussed and presented online on (https://www.youtube.com/watch?v=H99hvPlC4is).
Fusion is the process of combining two atomic elements to form another element releasing energy in the process. Capturing the energy released is the aim of fusion reactors currently in development around the world. Such reactors have been in development for over 50 years and include projects such as the Stellerator, Tokamak, and the International Thermonuclear Experimental Reactor (ITER) currently under construction with a target completion date of 2025.
JET is experimenting with the combination of deuterium (an isotope of hydrogen which is readily available in seawater) and tritium (a by-product of nuclear fission which is extremely rare) to form helium gas. To describe the fusion process in JET simply, the deuterium and tritium are heated to millions of degrees where the atomic nuclei fuse together to form helium and release energy.
While the results of JET are described as a "major milestone", the effects of the experiment may be more impactful on the design of ITER. JET may provide risk mitigation for the longer burn experiments which are set to be carried out at ITER. Improvements in equipment allow for these higher temperatures, but the proof of concept provided by JET and resulting data may be useful in further enhancing the equipment.
For example, the burn time achievable at JET was limited at least in part by the use of copper coils which would overheat if the time was increased. ITER is a tokamak-based design that uses strong magnetic fields to confine the very hot plasma needed to induce the fusion reaction. The coils used are toroidal field coils of a superconducting winding pack with a surrounding stainless steel coil case. Such coils may have the same material limitation on temperature.
The development of these coils represents just one of the engineering challenges for ITER. In order to keep the fusion reaction stable for minutes, hours, or days. Operating the reactor for such prolonged periods requires a design that can withstand abnormal events such as plasma disruptions. The material engineering challenges, instrumentation and control challenges, and obstacles present in many other technical fields are still being developed. Just at JET's milestone will benefit the development of ITER, the innovative approaches to addressing these complications will benefit not only ITER, but also other industries much like the space program did years ago.
It's a major milestone on the way to proving that fusion's a viable and sustainable energy source for the future.
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