Global Courant 2023-05-13 09:45:50
This is the third and final part of a three-part series. Read part 1 here and part 2 here.
The historic successes of the EAST tokamak propelled China to the global leadership position in magnetic fusion.
The advanced design of the reactor, the excellence and creativity of the EAST team and the hands-on focus on solving concrete scientific and technical fusion problems give us reason to expect more breakthroughs in the near future.
For the time being, the EAST research program seems to be mainly determined by the needs of the ITER project, in which China is actively participating. However, ITER is a very, very slow elephant, which will almost certainly be overtaken by faster, cheaper and more advanced devices.
By the time it is finally deployed, ITER will almost certainly be technologically obsolete. A masterpiece of high-tech engineering, but with a total cost estimated to be between $22 and $65 billion, ITER will still be just an experimental device.
If all goes well, the follow-up project of a tokamak-based prototype fusion power plant – the “DEMO” – is expected to go online in 2050. Assuming the DEMO proves viable, commercial plants will follow.
From my point of view, this perspective is excruciatingly long and costly, and would make magnetic confinement fusion virtually irrelevant to solving the world’s energy problems for the foreseeable future.
The ITER nuclear fusion project is costly and may be behind nuclear times. Image: Facebook
As mentioned above, China is currently working on its own large fusion power generating tokamak, the China Fusion Engineering Test Reactor (CFETR). At first glance, the philosophy of CFETR resembles that of ITER. But that may not be entirely true, nor have significant changes been ruled out.
Interesting, from my point of view, would be the possibility of using the CFETR as the core of a hybrid fusion-fission reactor, in which neutrons from the fusion reactions would be used to drive fission reactions in a subcritical blanket. Research is already underway into this possibility.
As a matter of fact, hybrid fusion-fission reactors have been the subject of extensive research in China for many years. A major advantage of such a system is that the fusion reactor part no longer needs to provide a net energy surplus; the energy required to sustain the fusion reactions would be many times outweighed by the energy released in the fission reactions.
This drastically reduces the requirements for the fusion system compared to a “pure” fusion plant. Hybrid reactors would therefore offer a much shorter term option than the ITER-DEMO scenario.
(It should be noted that in addition to tokamaks, many other types of fusion devices can serve as neutron sources for hybrid reactors.)
On the other hand, it is conceivable that the results of China’s EAST and other experimental devices in different countries could improve the viability of the ITER and reduce the time to reach ignition and net thermal output.
Despite being a very slow elephant and consuming a large amount of resources, ITER at the very least provides a platform for large-scale international cooperation in fusion science and technology, and building a corresponding industrial base. It would not make sense to stop participating in this project.
At the same time, however, it is wise to look at other possibilities to realize fusion via the tokamak route.
I have previously written for Global Courant about compact, high-field tokamaks that use many times stronger magnetic fields and will benefit greatly from the emergence of high-temperature superconductors, which were not available when the ITERs magnet system was designed. Another example is the spherical tokamak with a high field.
EAST works with very different plasma parameters, but many of its results, as well as the technological achievements embodied in its design, are undoubtedly relevant to high-field devices.
In my opinion, the history of attempts to realize fusion using tokamaks has been shaped by an important methodological problem: the attitude towards nonlinear self-organizing processes in magnetically confined plasmas. That includes their ability to concentrate energy and structure themselves in a very inhomogeneous way.
I think it’s fair to say that, given the first calculations conducted by AD Sakharov in 1950-51, the development of tokamaks has tended to overlook or ignore self-organizing phenomena, orienting instead towards the vision of achieving an essentially uniform, featureless, quiescent plasma.
The history of high-density pulsed systems, especially plasma focus and related devices, has taken a different course. (See my article on the plasma focus here).
Dense plasma focus. Photo: LPP Merger
Of course, when the tokamak was born, nonlinear self-organizing processes were much less known and understood than they are today. Only gradually is their essential role in both the successes and failures of tokamak devices realized.
It would make sense, instead of battling the plasma’s natural self-organizing tendencies, to befriend them and learn how to exploit them to realize viable fusion power in times to come.
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