China’s EAST Fusion Reactor

There is a lot of confusion regarding China’s new EAST fusion reactor. I can clarify things a bit.

All Tokamak fusion reactors build to date, including EAST, have been test reactors. They are not reactors intended for commercial power production. They are intended to study things like plasma characteristics, scaling laws, and to solve various problems inherent in creating and sustaining a controlled fusion reaction here on earth.

With the exception of EAST, all tokamak fusion test reactors built thus far have had copper coils for the magnets that confine the plasma. Because very high currents are required to produce the necessary magnetic fields, huge currents must flow through these coils which causes them to overheat in sixty seconds or less. Thus existing reactors have not been able to do research on things that involve long term operation. In addition, existing reactors dissipate a huge amount of heat from those coils and require a huge amount of refrigeration to remove it.

A commercial reactor will need to operate for months not seconds. To be practical, a commercial reactor will need to rely on superconductive coils for magnetic confinement. This will eliminate the energy lost to copper resistance and the heat associated with it, allowing long operations. Building coils from superconductors is a non-trivial engineering problem because most superconductors are brittle ceramic materials.

EAST is the worlds very first fusion reactor to use superconductive magnets for plasma confinement. This will allow it to do longer experiments maintaining a plasma for more than 15 minutes. ITER was to serve this purpose but the Chinese energy crises is too severe to wait twelve years to start answering questions pertaining to continuous operation. China assembled their own superconductive Tokamak reactor in seven months. Between engineering and fabrication of components the project has been in the works for about eight years. They are also participating in ITER but I believe they will be feeding fusion generated power to their power grid before ITER sees first plasma.

The western media has gotten the idea that China has already succeeded in creating 100 million degree plasmas of deuterium and tritium and controlled fusion. This is a misunderstanding which I suspect relates to the fact that the Chinese language does not have verb tense. The verb is the same for past, present, and future. China releases a news press release that states that the reactor had seen first plasma and that it will fuse deuterium and tritium in a 100 million degree plasma to produce energy and given the lack of tense in the Chinese verb took that to mean already had rather than will.

EAST saw first plasma in September, only seven months after construction began. This is a major milestone because it proved that the superconductive coils worked as designed, and since this had never been done before, that’s a major advancement towards commercial fusion power generation. First plasma and subsequent tests used ordinary hydrogen and not deuterium or tritium.

EAST has not produced any fusion power yet because it has not been fueled with the deuterium – tritium mixture that will fuse at the temperatures obtainable in a Tokamak reactor design. However, the accomplishments thus far is nothing to be sneezed at. The Chinese, in constructing EAST, tackled one of the largest engineering problems surrounding the construction of a commercial power generating fusion reactor by solving the superconducting magnetic confinement problem.

EAST is not a commercial power generation reactor. Commercial reactors will have a lithium blanket which will both capture neutrons preventing their escape and breed tritium from lithium. EAST will not have a lithium blanket. Commercial reactors will be have a capacity of around 600 MW but EAST will only operate at 15-20 MW power levels. Commercial reactors will be constructed to remove the heat (and use it to make electricity) continuously. EAST will only have sufficient cooling for about 15-20minutes of operation.

I do not know if EAST will be capable of scientific break even or not. Plasma confinement efficiency improves with the size of the device. My understanding is that it improves with the cube of the size, so a machine twice as large can confine plasma 8x better. EAST may not be large enough to achieve break even, but improvements in confinement technology have been reducing the minimum size of a machine capable of producing break-even.

Whether or not it achieves break-even it will answer many of the questions necessary towards engineering a commercial power reactor and it deserves to be recognized for the tremendous accomplishment that it represents.

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