General Fusion's Approach

General Fusion is using the MTF approach but with a new, patent pending and cost-effective compression system to collapse the plasma.

General Fusion 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). This vortex flow is established and maintained by an external pumping system; the liquid flows into the sphere through tangentially directed ports at the equator and is pumped out radially through ports near the poles of the sphere. Two spheromaks (self confined magnetized plasma rings) composed of the deuterium-tritium fuel are then 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 gas to accelerate pistons to ~50 m/s. These pistons simultaneously impact a set of stationary anvil pistons at the surface of the sphere, which collectively launch a high pressure spherical compression wave into 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 overall energy balance with this design is as follows. During each cycle ~100 MJ of kinetic energy from the pistons is converted into ~15 MJ of compressional work done on the target plasma, which based on conservative estimates of energy loss rates (Bohm) within the plasma, would raise the temperature of the plasma from 100 eV to a peak of 10 keV, and increase plasma density from 10¹⁷ cm^-3 to a peak of 10²⁰ cm^-3 with a dwell time at peak compression of 7 microseconds (FWHM). The magnetic field of the plasma would also increase during compression from 10 Tesla to a peak value of 1000 Tesla. Under these conditions the plasma would yield ~600 MJ of fusion energy per pulse, which would be directly converted into thermal energy of the liquid metal distributed across the neutron penetration depth (e-folding distance ~30 cm). This 600 MJ of thermal energy can be converted via a heat exchange system into ~200 MJ of useful mechanical or electrical energy (1/3 efficiency). Thus ~100 MJ would go back into the piston kinetic energy of the next pulse, and ~100 MJ of electric energy would be put onto the grid as electricity. Outputting 100 MJ per pulse, and repeating once every second would yield an overall power output of 100 megawatts.

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 radioactive material. General Fusion's innovative use of the liquid metal wall provides a simultaneous solution of the multiple technical constraints needed to make fusion energy production a practical reality.

General Fusion is in the process of patenting this technology and believes that a reactor working on this principle could be built at a much lower cost than using the conventional magnetic and laser fusion approaches. Such a power plant would make fusion a commercially viable clean power source.

At General Fusion we are creating a world-class research facility to develop the technological and physics base to enable a breakeven magnetized target fusion experiment at the end of four years time. The new approach being pursued by General Fusion has the potential to yield the first economically viable fusion reactor, leading to commercialization and widespread use of fusion energy on a much more rapid timeline than any other route currently being considered. General Fusion is working in alliance with academic, industrial and governmental partners to implement a well-supported research and development pathway for this alternative approach to practical fusion energy.