A picture from the patent filing for what General fusion is trying to build with backing from Chrysalix Energy Venture Capital. GF will build a ~3 meter diameter spherical tank filled with liquid metal (lead-lithium mixture). Rams use compressed steam to accelerate pistons to ~50 m/s. Make compression wave in the liquid metal. Microsecond of fusion once per second. Note: This could be considered like a variant of “steam punk nuclear fusion” made real if it works.
“Within five years, large companies will start to think about building fusion reactors,” Wal van Lierop, CEO of Chrysalix Energy Venture Capital, said in an interview at the Clean Tech Investor Summit taking place here this week. In three to four years, scientists will demonstrate results that show that fusion has a 60 percent chance of success, he said.
Lierop has backed General Fusion’s Magnetized Target Fusion (MTF) model. An electric current is generated in a conductive cavity containing lithium and a plasma. The electric current produces a magnetic field and the cavity is collapsed, which results in a massive temperature spike. MTF has an advantage over other fusion techniques in that the plasma only has to stay at thermonuclear temperatures (150 million degrees Celsius) for a microsecond for a reaction to occur.
Canada’s General Fusion has received $1.2 million in venture funding to conduct further research on its fusion reactors, according to VentureWire. The company’s ultimate plan is to build small fusion reactors that can produce around 100 megawatts of power. The plants would cost around $50 million. That could allow the company to generate electricity at about 4 cents per kilowatt hour, relatively low.
GF will build a ~3 meter diameter spherical tank filled with liquid metal (lead-lithium mixture). The liquid is spun to open up a vertical cylindrical cavity in the center of the sphere (vortex). Two spheromaks (magnetized plasma “smoke ring”) are injected from each end of the cavity. They merge in the center to form a single magnetized plasma target. The outside of the sphere is covered with pneumatic rams. The rams use compressed steam to accelerate pistons to ~50 m/s. These pistons simultaneously impact the outside of the sphere and launch a spherical compression wave in the liquid metal. As the wave travels and focuses towards the center, it becomes stronger and evolves into a strong shock wave. When the shock arrives in the center, it rapidly collapses the cavity with the plasma in it. At maximum compression the conditions for fusion are briefly met and a fusion burst occurs releasing its energy in fast neutrons. The neutrons are slowed down by the liquid metal causing it to heat up. A heat exchanger transfers that heat to a standard steam cycle turbo-alternator to produce electricity for the grid. Some of the steam is used to run the rams. The lithium in the liquid metal finally absorbs the neutrons and produces tritium that is extracted and used as fuel for subsequent shots. This cycle is repeated about one time per second.
The use of low-tech pneumatic rams in place of sophisticated high power electrical systems reduces the cost of the energy delivered to the plasma by a factor of 10 making such a power plant commercially competitive. Because the fusion plasma is totally enclosed in the liquid metal, the neutron flux at the reactor wall is very low. Other fusion schemes struggle with a high neutron flux at the wall that rapidly damages the machine and also produces some radio-active material. Frequent robotic replacement of the then radio-active plasma facing components is a costly problem for many fusion machines.
General Fusion has patented this technology and believes that a reactor working on this principle could be built at a much lower cost than using the old magnetic and laser fusion approaches. Such a power plant would make fusion a commercially viable clean power source.
General Fusions patents are here
An interesting paper is Applications of predictions for FRC translation to MTF FRC is field reversible configuration.
We describe a physics scaling model used to design the high density Field Reversed Configuration (FRC) at LANL that will translate into a mirror bounded compression region, and undergo Magnetized Target Fusion compression to a High Energy Density plasma. The theta pinch formed FRC will be expelled from inside a conical theta coil. At Kirtland AFRL the FRC will be compressed inside aux conserving cylindrical shell. Semi empirical scaling laws, which were primarily developed and benchmarked for collisionless Field Reversed Configurations (FRC) are expected to remain valid even for the collisional regime of FRXL experiment. The scaling laws are used to predict the the time available for the translation compared to the lifetime of the FRC. This approach is used to outline the design and fabrication of the integrated MTF plasma compression experiment.