General Fusion is a Canadian company based in Vancouver, British Columbia, which is developing a fusion power device based on magnetized target fusion (MTF). The company was founded in 2002 by Dr. Michel Laberge. The company has more than 150 employees in three countries, with additional centers co-located with fusion research laboratories near London, and Oak Ridge, Tennessee, US.
The device under development injects the magnetized target, a plasma mass in the form of a compact toroid, into a cylinder of spinning liquid metal. The target is mechanically compressed to fusion-relevant densities and pressures, by anywhere from a dozen to hundreds (in various designs) of steam-driven pistons.
In 2018, the firm published papers on a spherical tokamak, instead of a toroid. It is unclear if this represents a major design change. In June 2021, the company announced it would build 70% of a full scale fusion demonstration plant in the UK as part of a public-private partnership with the UK Government.
Organization
General Fusion's CEO is Greg Twinney.
Michel Laberge, Chief Science Officer, holds multiple responsibilities at General Fusion, including building partnerships with international research institutions, and overseeing partnerships with governments and other companies, and technology development strategy.
The board of directors is chaired by Klaas De Boer, who currently chairs AIM-listed Xeros Technology Group and serves on the Boards of SmartKem and vasopharm.
Technology
General Fusion's approach is based on the Linus concept developed by the United States Naval Research Laboratory (NRL) beginning in 1972. Researchers at NRL suggested an approach that retains many of the advantages of liner compression to achieve small-scale, high-energy-density fusion. According to Laberge, Linus could not properly time the compression using the technology of the era. Faster computers provide the required timing. However, this claim is not borne out by the literature as various Linus devices with no timing constraints, including systems using single pistons, were built during the experimental runs during the 1970s and demonstrated fully reversible compression strokes.
General Fusion's magnetized target fusion system uses a ~3 meter sphere filled with a mix of molten liquid lead and lithium. The liquid is spun, creating a vertical cavity in the centre of the sphere. This vortex flow is established and maintained by an external pumping system; liquid flows into the sphere through tangentially directed ports at the equator and exits radially through ports near the poles of the sphere.
A plasma injector is attached to the top of the sphere, from which a pulse of magnetically confined deuterium-tritium plasma fuel is injected into the center of the vortex. A few milligrams of gas are used per pulse. The gas is ionized by a bank of capacitors to form a spheromak plasma (self-confined magnetized plasma rings) composed of the deuterium–tritium fuel.
The outside of the sphere is covered with steam pistons, which push the liquid metal and collapse the vortex, thereby compressing the plasma. The compression increases the density and temperature of the plasma to the range where the fuel atoms fuse, releasing energy in the form of fast neutrons and alpha particles.This energy heats the liquid metal, which is then pumped through a heat exchanger to generate electricity via a steam turbine. The plasma forming and compressing process repeats and the liquid metal is continuously pumped through the system. Some of the steam is recycled to power the pistons.
In addition to its role in compressing the plasma, the liquid metal liner shields the power plant structure from neutrons released by the deuterium-tritium fusion reaction, overcoming the problem of structural damage to plasma-facing materials. The lithium in the mixture breeds tritium.
Fusion Demonstration Program
The Fusion Demonstration Program is a 70% scale prototype which was being built in Oxfordshire, UK with a reported cost of US$400 million. It had been announed that the core technology had been proven out and was ready to be put together and that the plant was to commence operations in 2027. However the plant was put on hold in 2023 when the company announced that it would instead build a different machine in Canada aimed at demonstrating breakeven by 2026.
The plant had several key differences from the commercial power plant concept: