General Fusion, the Canadian firm founded in 2002, plans to accomplish a net energy gain from their experimental reactor apparatus this year.

With a ‘proof of concept’ now accomplished for the first reactor device the firm hopes to drive a deuterium-deuterium reaction to fusion that will produce as much and a bit more energy than used for the reaction itself.  That would provide a fueled ‘proof of concept’ energy production.

Its looks like the firm will get its fueled proof of concept to enable a build of a larger more powerful machine.

General Fusion Progress Chart. Click image for a larger view.

General Fusion Progress Chart. Click image for a larger view.

General Fusion’s approach is a hybrid between magnetic fusion and inertial confinement fusion known as “magnetized target fusion”.  Magnetic fusion uses magnetic fields to hold relatively low-density fuels like plasma of deuterium and tritium for a sufficient time that a lot of nuclei collide and fuse. Inertial confinement fusion involves imploding a small sphere of fuel with such energy that the nuclei momentarily reach very high-density fusion conditions.

General Fusion’s hybrid uses a magnetized target fusion trapping a relatively low-temperature and low-density plasma of deuterium and tritium in a magnetic field (similar to magnetic fusion) and then compresses the plasma to high-temperature and high-density fusion conditions (much like inertial confinement fusion). The hybrid approach compresses the target more slowly than inertial confinement fusion, allowing the energy for compression to be delivered by much less expensive technology than for example lasers. Magnetized target fusion also creates higher density conditions than magnetic fusion, reducing the required containment time. Together, this combination of a slower compression rate and shorter containment time results in a simpler, cheaper and less power-intensive fusion generator design.

The concept is for a repeating reactor running in a cycle.  The cycle would fuel and form the fuel plasma, trap it in the magnetic field, compress it to the reaction and then harvest the heat.  Then repeat.

The reactor will consist of a spherical tank filled with a liquid mixture of lead and lithium. The liquid metals will be spun by tangential injection to create a vertical cylindrical vortex cavity in the center of the sphere.

A pair of plasma injectors will be mounted on each end of the vortex cavity that will heat puffs of deuterium-tritium gas to 1 million degrees using a high-voltage electrical discharge from a bank of capacitors. Each puff of gas will form in the midst of magnetic fields that will cause it to form a closed, toroidal (doughnut) shape and to peel off the end of the injector somewhat like a smoke ring.

The two plasma toroids, one from each injector, will meet in the center of the vortex and combine to form a single magnetized plasma target, somewhat analogous to the combination of two soap bubbles. This combined plasma at the center of the reaction chamber will have a maximum life of a few hundred microseconds before it dissipates.

Next comes the compression.  About 200 pneumatic pistons will surround the tank with the lead and lithium inside. These pistons will impact the tank, inducing a spherical acoustic compression wave in the liquid metal that will travel to the center of the sphere. As the acoustic wave travels through the lead and focuses towards the center, it will intensify and concentrate into a powerful focused shock wave. When the shock wave arrives at the plasma fuel, it will rapidly collapse the swirling metal vortex cavity and the plasma confined within it, creating thermonuclear conditions in the process.

The pneumatic pistons will be controlled by a system that times their impacts precisely to create a symmetrical compression shockwave in the tank. The control system will adjust the timing of individual piston impacts to control the shape of the cavity as it collapses; compensate for physical and thermal effects and variations within the generator; and, adjust for changes over time as equipment wears and parameters vary.

When the fuel fuses it will release energy in charged helium atoms and freed neutrons. The neutrons will exit the plasma to be slowed by the surrounding liquid metal, transferring heat to the lead in the process. The neutrons will eventually be absorbed into the nuclei of the lithium dissolved in the lead, transforming it into tritium and more helium.

The now heated metal solution will be pumped out of the chamber and passed through a separator that removes both the tritium and helium from the solution. The tritium will then be separated from the helium and directed back to the plasma injectors as fuel.

Then the metal solution will pass through a heat exchanger that transfers the heat to water to create steam. Approximately half of this steam energy will be used to re-power the pistons and the remaining half can be used in a standard turbine to generate electricity.

Then repeat.

General Fusion Reactor At Scale Graphic. Click image for the largest view.

General Fusion Reactor At Scale Graphic. Click image for the largest view.

Calculations have it that each fusion pulse will result in approximately 100 MJ of net electrical output. Varying the cycle repetition rate will control the overall power plant output; if repeated once per second, the net output will be 100 MW. At this power output, a power plant would consume only 18 kg of deuterium and 60 kg of lithium per year.

General Fusion web site has a more extensive explanation and more graphic images.  Its one of the best web sites your humble writer has seen a quite a while.  It’s both pretty well written and easy to navigate.

The catch is the concept is a slow version of a thermonuclear event.  The Canadians are comfortable with that, but the American hyper excitable media would twist the reality into a threat.  The most often seen thermonuclear use is with hydrogen bombs and the U.S. media could be counted on to “blow” the facts completely out of reality making a bomb where there isn’t one.

General Fusion has a long way to go.  The concept and design is quite complex, requires exact timings and will require very robust construction.  While not a bomb, the acoustic shockwaves are going to produce quite a liquid hammer effect and there will be significant heat and pressures to control to exploit the energy release.

There is little question that the physics can be made to work.  The questions will be facility longevity, costs and electricity rates to earn a profit.  It looks like with enough money and engineering skill applied the reactor and energy harvest can be accomplished.  But will it be too much money?

The Canadians seem to think they can get it done on commercial economics.  Lets hope they are right.


9 Comments so far

  1. Bård Havre on May 24, 2013 4:41 AM

    30 years too late.The energy train has now left the station.

  2. Bård Havre on May 24, 2013 4:43 AM

    30 years too late.The LENRgy train has now left the station.

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