Next Big Future October 26, 2015
The Tri-alpha Energy nuclear fusion reactor prototype has been feature in recent Time magazine and New York Times artices.
Tri Alpha’s reactor is very different from the towering tokamaks that dominate the fusion skyline, or the supervillain lasers of the NIF. You could think of it as a massive cannon for firing smoke rings, except that the smoke rings are actually hot plasma rings, and the gunpowder is a sequence of 400 electric circuits, timed down to 10 billionths of a second, that accelerate that plasma ring to just under a million kilometers an hour.
And there are actually two cannons, arranged nose to nose, firing two plasmas straight at each other. The plasmas smash into each other and merge in a central chamber, and the violence of the collision further heats the combined plasma up to 10 million degrees Celsius and combines them into a single plasma 70 to 80 centimeters across, shaped more or less like a football with a hole through it the long way, quietly spinning in place.
But a fusion reactor’s work is never done. Positioned around that central chamber are six massive neutral beam injectors firing hydrogen atoms into the edges of the spinning cloud to stabilize it and keep it hot. Two more things about this cloud: one, the particles in it are moving in a much wider orbit than is typical in, say, a tokamak, and hence are much more stable in the face of turbulence. Two, the cloud is generating a magnetic field. Instead of applying a field from outside, Tri Alpha uses a phenomenon called a field-reversed configuration, or FRC, whereby the plasma itself generates the magnetic field that confines it. It’s an elegant piece of plasma-physics bootstrappery. “What you get within forty millionths of a second from the time you unleash your first little bit of gas,” Binderbauer says proudly, “is this FRC sitting in here, fully stagnant, no more moving axially, and rotating.”
The machine that orchestrates this plasma-on-plasma violence is something of a monster, 23 meters long and 11 meters wide, studded with dials and gauges and overgrown with steel piping and thick loose hanks of black spaghetti cable. Officially known as C-2U, it’s almost farcically complicated–it looks less like a fusion reactor than it does like a Hollywood fantasy of a fusion reactor. It sits inside a gigantic warehouse section of Tri Alpha’s Orange County office building surrounded by racks of computers that control it and more racks of computers that process the vast amounts of information that pour out of it–it has over 10,000 engineer control points that monitor the health of the machine, plus over 1,000 physics diagnostic channels pumping out experimental data. For every five millionths of a second it operates it generates about a gigabyte of data.
In June the reactor proved able to hold its plasma stable for 5 milliseconds.
That’s not a very long time, but it’s an eternity in fusion time, long enough that if things were going to go pear-shaped, they would have. The reactor shut down only because it ran out of power–at lower power, and hence with slightly less stability, they’ve gone as long as 12 milliseconds. “We have totally mastered this topology,” Binderbauer says. “I can now hold this at will, 100% stable. This thing does not veer at all.”
Tri-alpha energy has raised over $200 million. Paul Allen and others have invested.
General fusion in Canada has raised $94 million. Jeff Bezos (CEO of Amazon) and the Canadian and Malaysian government have invested.
Generla Fusion has built prototypes of the reactor’s major subsystems, including a spherical chamber for the liquid metal vortex with 14 huge spikes projecting out at all angles–the spikes are massive hammers that do the squeezing.
Helion Energy has raised about $30 million. Helion Energy is already on its fourth-generation prototype. Its approach also has two plasmas colliding in a central chamber, but it will work in rapid pulses rather than sustaining a single static plasma. Helion is focused on developing a smaller-scale, truck-size reactor, and doing it as fast as possible. The company’s website states in no uncertain terms that it will have a commercial reactor operational within six years.
General Fusion’s reactor will be a mixture of lead and lithium, which will catch the neutrons. As a bonus, when you hit lithium with neutrons, you get tritium. So two birds, one stone.
Helion’s reactor will fuse deuterium and helium-3, which produces fewer neutrons, though it requires more heat and raises the problem of finding enough helium-3, which is also rare. Tri Alpha plans to fuse protons (otherwise known as hydrogen nuclei) with boron-11. This reaction produces no neutrons at all, and both elements are plentiful and naturally occurring. “We’re always saying, if you want to buy our plant,” Binderbauer says, “we’ll give you a lifetime supply of fuel for free.” The reason hardly anybody else is pursuing it is that proton-boron-11 fusion requires much higher temperatures, insanely much higher: 3 billion degrees Celsius.
Helion Energy will investigate staged magnetic compression of field-reversed configuration (FRC) plasmas, building on past successes to develop a prototype that can attain higher temperatures and fuel density than previously possible. The team will use these results to assess the viability of scaling to a power reactor, which if successful would offer the benefits of simple linear geometry, attractive scaling, and compatibility with modern pulsed power electronics.
Key Benefits of Helion’s Approach
* Magneto-Inertial Fusion: By combining the stability of steady magnetic fusion and the heating of pulsed inertial fusion, a commercially practical system has been realized that is smaller and lower cost than existing programs.
* Modular, Distributed Power: A container sized, 50 MW module for base load power generation.
* Self-Supplied Helium 3 Fusion: Pulsed, D-He3 fusion simplifies the engineering of a fusion power plant, lowers costs, and is even cleaner than traditional fusion.
* Magnetic Compression: Fuel is compressed and heated purely by magnetic fields operated with modern solid state electronics. This eliminates inefficient, expensive laser, piston, or beam techniques used by other fusion approaches.
* Direct Energy Conversion: Enabled by pulsed operation, efficient direct conversion decreases plant costs and fusion’s engineering challenges.
* Safe: With no possibility of melt-down, or hazardous nuclear waste, fusion does not suffer the drawbacks that make fission an unattractive alternative.
In April, General Fusion issued a crowdsourcing challenge to come up with a written proposal for a “robust seal technology” capable of withstanding extreme temperatures and repetitive hammering for the purpose of isolating “the molten lead from the vacuum” inside their fusion reactor.
And after examining the 60 credible proposals submitted from 17 different countries, the General Fusion team has selected the winning entry proposed by Kirby Meacham, a Cleveland mechanical engineer who trained at MIT.
The challenge for the “Method for Sealing Anvil Under Repetitive Impacts Against Molten Metal” was issued via the Massachussets based Innocentive crowdsource platform, with over 335,000 registered “solvers” in almost 200 countries, all poring over similarly complicated technical problems submitted by innovators seeking the wisdom of the crowd to overcome a particular technical hurdle.
The winner of General Fusion’s anvil seal challenge claims his $20,000 prize in exchange for transferring exclusive Intellectual Property rights to the solution.
General Fusion is already hinting at using the Innocentive platform again to gain insight into its experimental plasma physics data.
General Fusion is set to close another round of funding in late summer 2015, with the participation of additional investors.
General Fusion is nearing significant milestones. General Fusion’s Approach is Magnetized target fusion (MTF). Magnetized target fusion is a hybrid between magnetic fusion and inertial confinement fusion. In MTF, a compact toroid, or donut-shaped magnetized plasma, is compressed mechanically by an imploding conductive shell, heating the plasma to fusion conditions.
General Fusion has a full-scale prototype [of the injectors and other subsystems], twin plasma injectors resembling five-metre-long cones, each attached to opposite ends of a three-metre-diameter sphere, would pulse a few milligrams of hydrogen gas, heat it until it becomes a plasma, and inject it into a vortex of swirling liquid metal. Electricity circulating in the plasma would create magnetic fields that bind the plasma together and confine the heat.
From there, an array of as many as 300 huge pistons attached to the sphere’s shell would act like synchronized jackhammers, ramming it at 200 km/hr. This would send shockwaves into the very centre of the chamber, compressing the hydrogen isotopes to 100 million degrees celsius — hot enough for fusion to occur, and good enough to generate clean electricity from steam turbines.
General Fusion reached its milestones on the piston timing about two years ago. Technicians are now perfecting functionality of the plasma injectors.
The nearly 200 capacitors that send 10-gigawatt bursts into General Fusion’s machine were “recycled” from an old laser fusion experiment in Los Alamos, California.
Here is 2013 paper on the progress on the driver timing and the injector work.
General Fusion, which shares investors with D-Wave, is about two to three years out from creating its own power plant. Today, the pistons work well, and the plasma is hot enough and dense enough. Within the last month, the gas donut has started lasting long enough for the system to work, so now the company is turning its focus to compression and timing, according to Michael Delage, VP of strategy and corporate development.
General Fusion thinks it can provide power at a cost of seven cents per kilowatt hour, comparable to the cost of coal.
General fusion also wants to heat the spheromak to 500 eV before injection. They have reached 200 eV, while they would want to reach 500 eV and expect actually to exceed 600 eV.
31 page presentation on General Fusion from mid-2013
In the TEDX talk of 2014 – there is the offhand mention that the plasma lifttime issue of getting to 100 microseconds had good progress
The Plan from 2012
In a 2014 Nature paper, there is the statement that the General Fusion “beefier” prototype will be built perhaps by the end of 2016.
General Fusion has demonstrated the idea with a small-scale device, using pistons driven by explosives, and has raised about $50 million from venture capitalists and the Canadian government. If the company can win another $25 million or so, Laberge says, it will build a beefier implosion system that can compress the plasma to the levels needed for fusion — perhaps within the next two years.
Not sure if the beefier prototype would be the net gain prototype since previously that was $80-100 million.
General Fusion is developing full scale subsystems to demonstrate that they can meet their performance targets. This includes full scale plasma injectors and acoustic drivers, and liquid metal vortex compression tests. Every step is matched with simulation to guide ongoing development work.
Author: brian wang on 10/26/2015