General Fusion MTF Power Generation

This material describes another serious attempt to produce sustainable fusion energy and it is interesting. I am somewhat skeptical that this will actually succeed, if only because I find it difficult to believe that this contraption can be made to work physically. I would not want the build out job.

The images need to be looked at individually as they are much better enlarged.

At least we are now getting a number of serious attempts at producing fusion energy, even when the protocol is not obviously promising. We need that because the breakthrough may come from a special insight on one of these rigs.

One attraction to this system is the fact that neutrons will be absorbed by the working fluid and carried off. It can not be that simple but it is still a major improvement.

Otherwise, this protocol is meant to run hot and to directly support a thermal power generation system which makes it very attractive to the power industry in general. It really is a stand alone power generator that one can envisage in a power plant.

I am also pleased to see that they are exploiting physical shock waves. I have occasionally pondered that problem over the years after I came across some work that was suggestive in that direction. A shock wave has enough energy to approach the levels we will need. Fortunately not easily enough for accidental events.

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.

The use of low-tech pneumatic rams in place of intrinsically expensive high power pulsed electrical systems reduces the cost of the energy delivered to the plasma by a factor of 10 making such a power plant commercially competitive even against the cheapest fossil fuel.

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.

The liquid metal is used to rapidly push energy into the plasma via compressional heating, hold it at maximum pressure for long enough for the fusion output to be significant, efficiently absorb the fusion output energy, and protect the mechanical structure of the device during fusion.

The pumping system that creates the vortex flow also provides a natural means to extract the fusion-heated liquid metal and run it through a heat exchanger to drive a turbine and produce electricity. Unlike other pulsed fusion concepts, with the General Fusion design no structural elements are destroyed during the fusion pulse. This enables rapid pulse repetition rates and low cost of operation since the direct cost of each pulse is only the cost of the fuel that is burned.

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.

"The closest to a potential reactor scheme is what General Fusion is proposing." - R. Kirkpatrick, Los Alamos National Laboratory [Popular Science, Janury 2009]

General Fusion Research Update

General Fusion is using the MTF (Magnetized Target Fusion) approach but with a new, patent pending and cost-effective compression system to collapse the plasma. They describe the injectors at the top and bottom of the above image in the new research paper. The goal is to build small fusion reactors that can produce around 100 megawatts of power. The company claims plants would cost around US$50 million, allowing them to generate electricity at about four cents per kilowatt hour.
If there are no funding delays, then in 2010-2011 for completion of the tests and work for an almost full scale version (2 meters instead of 3 meter diameter).

The third phase for General Fusion is to raisee $50 million for a net energy gain device with a target date of 2013 if the second/third phase are roughly on schedule.

If they get $300-500 million for commercialization, the first commercial scale unit could be 2016-2018.

Note: Any fusion power system would have applications for space. Lowering energy costs helps with space. Better and lighter power systems are good for space colonies and industrialization.

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.

http://4.bp.blogspot.com/_VyTCyizqrHs/ScF6gwA1bcI/AAAAAAAADL0/c5vYhV1l5zg/s1600-h/gf1.JPG

General Fusion report on the development of compact toroid (CT) accelerators to create the target plasma for magnetized target fusion (MTF) devices. Due to the requirements of high initial density of *10^17 cm-3, strong internal fields of 5–10 T, and base temperatures of [100 eV, a design based on conical compression electrodes is an effective avenue to pursue. Progress is being made at General Fusion Inc, (Vancouver, Canada) to develop a pair of large CT accelerators for generating an MTF target plasma. In this design, tungsten coated conical electrodes (with a formation diameter of 1.9 m, a radial compression factor of 4, and overall accelerator length of 5 m) will be used to achieve ohmic heating and acceleration of the CT, yet with low wall sputtering rates. A pair of these accelerators can be synchronized and shot at one another, producing a collision and reconnection of the two CTs within the center of an MTF chamber. Depending on the choice of relative helicities, the two CTs will merge to form either a spheromak-like or an FRC-like plasma. [FRC is field reversed configuration.

An FRC (field reversed configuration) is an elongated plasma ellipsoid conducting an azimuthal current which reverses the direction of an externally applied magnetic field. The resultant field provides for toroidal plasma confinement without requiring a toroidal vacuum vessel or coil set.
Experimental Results from the First Proof of Concept System

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