Part 4 of 6 Parts (Please read Part 1, 2 and 3 first)
A Field Reverse Configuration (FRC) reactor does not look like a smoke ring that forms in the plasma of a tokamak. FRC reactors look more like an elongated U.S. football or maybe a short fat cigar. The reason for the “Field Reverse Configuration” name is that in an FRC, the magnetic fields curve around the outside of the ‘football” and then loop back through the long axis. This configuration of the plasma only lasts for a millisecond before it dissipates.
This is one of the main reasons that very few researchers continued with the FRC reactor approach after the introduction of the tokamaks. Those that continued with FRC research pinned their hopes on finding a way to stabilize the FRC. If this problem could be solved, an FRC reactor wouldn’t need to be much more than a cylindrical vacuum chamber with a relatively weak magnetic field traveling down the midline to hold the plasma football in place.
Self-organization should make it comparatively simple for the dense, hot plasma inside the FRC to achieve the conditions required for nuclear fusion. Another benefit of the FRC approach is that it would not be limited to deuterium-tritium fuel. FRCs should be able to reach the much higher temperatures needed to burn aneutronic fuels such as deuterium-helium-3 or proton-boron-11.
These fusion reactions generate most of their fusion energy in the form of protons or helium-4 nuclei which can be captured and controlled by magnetic fields unlike neutrons. This would make it much simpler to draw energy from the fusion products before they cause serious damage to the walls of the reactor vessels. And an FRC reactor should need much less shielding against radioactivity than the neutron producing deuterium-tritium fusion reaction in tokamaks.
Cohen says that, in theory, FRC reactors could solve the size, cost and complexity problems associated with tokamaks. However, to work in practice, FRC researchers have to make a series of critical design choices. These include how to form, stabilize and control the FRC, how to heat it, what type of fusion fuel to use, etc. He said, “You multiply all those options, you get roughly 80 different potential FRC designs.”
TAE has been working on one of these designs since 1998 when it was founded. Proton-boron-11 was chosen as their fuel. The proton-boron-11 fusion reactions can be thought of as the ultimate in fusion energy generation that does not emit neutrons. The only output of this reaction is just three positively charged helium-4 nuclei which are commonly knows as alpha particles. The original name for the company was TriAlpha taken from the products of the reaction.
There are some significant problems with utilizing proton-boron-11 for a fusion fuel. One problem is that the multibillion-degree threshold for igniting fusion in such fuel is twenty to thirty times higher than the temperatures required to ignite the deuterium-tritium fuel mix used in tokamaks. In addition, proton-boron-11 fuel only produces about half as much energy per fusion reaction as the deuterium-tritium fusion reaction.
Please read Part 5 next