Japan is committed to zero greenhouse gas emissions by 2050. And like Japan, all mankind must find ways to reduce CO emissions2 and develop new sources of energy with less impact on global warming. One of these solutions is fusion. It is the opposite of nuclear fission, which involves splitting a heavy atomic nucleus. This is what conventional nuclear power plants do. Fusion, on the other hand, consists of assembling light atomic nuclei. It does not produce high-level radioactive waste or CO2 and it can be interrupted at any time so that there is no danger of an uncontrollable nuclear event. It generates massive amounts of thermal energy through the same process that occurs in the sun, while being completely safe. It is truly the dream energy source of the future.
Fusion research is happening all over the world. The largest company is ITER, the international thermonuclear experimental reactor, possibly the largest research project in human history. Japan plays a major role as the leader of the superconducting fusion test facility known as JT-60SA. This will be used to perform a number of revolutionary performance tests. The next step is the validation test of a prototype reactor, followed by implementation on a commercial reactor.
Fusion reactor development roadmap
In part 1 of A Fusion of the future – meeting the challenge of ever-increasing energy demand while reducing CO emissions2 emissions, we discussed the key role of the JT-60SA in plasma ignition testing and validation *, and looked at the assembly process for this advanced machine. In Part 2, we’ll take a more in-depth look at the assembly process, with a special focus on the people who made it possible.
* The fourth physical state of matter (after solid, liquid and gas). Fusion generates plasma at over 100 million degrees Celsius.
The ultra-precise JT-60SA – helps create a mini sun on earth
In a corner of the Naka Fusion Institute in the unattractive town of Naka, Ibaraki Prefecture, there is a huge device soaring about 16 meters into the air and holding a vacuum vessel in the shape of a donut. This is the JT-60SA, an extremely complex engineering project overseen by Toshiba in collaboration with the National Institutes for Quantum and Radiological Science and Technology (QST).
The JT-60SA is designed and built with tolerances of a few millimeters by ten meters, an incredibly high level of precision. Many of the major components were manufactured overseas and assembled at the Institute. It has been a complex and difficult process. Welding the vacuum chamber that generates the plasma was particularly difficult, as was the positioning of the support struts under the chamber. We asked Keiichi Sagawa, Project Manager at Toshiba, to tell us which aspects really tested the capabilities of the Toshiba team.
Keiichi Sagawa, Deputy Director, Electrical Systems Division
Toshiba Energy Systems & Solutions Corporation
âWe have developed a special welding technique designed to minimize distortion,â says Sagawa. âThen we had to match it to each different weld point. And we had to offset each component of the vacuum chamber very slightly during the welding. If our calculations had been wrong, the vacuum chamber would not have been plus was a perfect circle – it could have ended more like a spiral. We had to measure each part in three dimensions and simulate the degree of warping caused by the welding. And then, of course, we had to be extremely careful during the process of welding proper. It was a constant back and forth, trying to compensate for the few millimeters of shrinkage caused by welding. ”
The splice joint components themselves are welded together
Non-lubricated sliding mat (low friction, wear resistant)
âThe next step after welding was to attach the support struts by gravity to the vacuum chamber. It was one of the most difficult aspects of the whole operation. The spacers needed to be screwed in, but the screw set alone weighed about a ton so we were dealing with the forces of gravity while trying to loosen the screws little by little and avoid driving them into the vacuum chamber. .With the help of very experienced Toshiba engineers, we figured out how to keep the center axis of the gravity strut screw in position, and consist of a special mechanism to minimize the load on the screws. In this way we succeeded in assembling all the support spacers with an accuracy of Â± 1 Â°. The work has been successfully carried out, thanks to expert engineers, who have over 30 years of experience working with screw connections. ”
Cooking before the plasma operation, the vacuum chamber is rinsed to expel the air then heated to 150 – 400 Â° C for several hours or even several days to gasify or vaporize the residual surface impurities
More than half a century of technology development on fusion-Toshiba leads the way
Every major project process has its challenges – but for the JT-60SA, every step of the way was a new challenge – so say Yusuke Shibama of QST, who was involved from the initial design phase, and Masaya Hanada, deputy director of QST. Naka Fusion Institute, which oversees the construction of the JT-60SA. They believe it was the combination of a large number of innovative solutions in areas such as high precision welding that finally got them there, and raved about the partnership with Toshiba.
âWe knew that Toshiba had very experienced manufacturing engineers with the expertise to meet any technical challenges that presented themselves.“Shibama said.” Without them we could not have gone this far. They have people with over 30 years of experience in specific fields, the absolute experts in the field. It’s that level of expertise that really sets them apart. ”
âToshiba is like a breeding ground for excellence,â he adds. âThe engineers there are constantly polishing and refining the technology, like a samurai polishes his sword. They made the vacuum chamber in-house, but they are also determined to work with us to assemble components from other manufacturers. In a meeting, they “would produce a report as big as a thesis, and we would like to go through it.” Toshiba and QST worked very well together on the JT-60SA, and I think it’s important to share this particular journey with others for the sake of posterity. ”
Yusuke Shibama, Principal Investigator, JT-60SA Tokamak Device Group,
Tokamak Systems Technology Department, Naka Fusion Institute,
National Institutes for Quantum Science and Technology
Hanada describes the merger as the “great engineering store.” To develop fusion, you don’t just need fusion engineers, you also need need people who understand the technical complexities and can manage the project as a whole. Working with Mr. Sagawa on the JT-60SA has been very productive not only for us but for Japan in general. Because it lays the foundation for the future of the fusion industry in this country and the people who will lead it. I think we have a real advantage in this area. ”
Masaya Hanada, Deputy Director General, Naka Fusion Institute,
National Institutes for Quantum Science and Technology
Toshiba has been working on fusion since the 1970s, and this long-standing expertise has proven invaluable in addressing the veritable plethora of technical challenges with the JT-60SA, including core design, superconducting coils, power source and the heating elements. Toshiba also has years of experience in industrial plant construction and field engineering. According to Sagawa, this enormous “Toshiba knowledge base” was essential to the success of the JT-60SA.
âThe assembly process of the JT-60SA posed a series of unexpected and unforeseen challenges: electrical, mechanical, hardware, physics and welding, to name a few. Toshiba has expertise in literally all of these areas. We have incredible depth and breadth in our knowledge base. We have been working on fusion for almost half a century, and on top of that we have installed nuclear power plants and other industrial facilities all over the world. It is this level of experience and expertise that led to our being selected for the JT-60SA project. ”
QST is equally excited about Toshiba’s knowledge base and the future of its fusion research partnership with Toshiba. The project is really starting to prepare for the plasma ignition. Hanada puts it this way: âThere wouldn’t be a plasma researcher who wouldn’t be excited about the prospect of doing cutting-edge research on the world’s largest fusion device. Plasma ignition is just the last part of this exciting journey. It is up to the engineers and technology leaders of the future to continue to work hard on the front lines, for the good of humanity.