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Posted by Mark Halper

Helion Fusion Engine Artist Rend

Fancy bow tie. Helion’s Fusion Engine fires plasmoids of deuterium and tritium at each other from either   end. They collide and fuse in the middle, giving off direct electricity as well as heat captured by a coolant that could be FLiBe.

The paradox of fusion energy is that it is always 40 years away, and has been for some 60 years.

So scoff the fusion skeptics. And if you look at the projected timelines of the large intergovernmental fusion projects like ITER in France and NIF in California, you could easily join the ranks of those not holding their breath.

But as I’ve written here before, there are a number of smaller and privately-backed fusion initiatives that could solve the fusion riddle long before the ITERs or NIFs do.

One of those companies is Helion Energy, a Redmond, Washington-based company that claims it will build a 50-MWe pilot of its “Fusion Engine” by 2019 after which licensees will begin building commercial models by 2022. That’s hardly the 40-year odyssey we’ve long heard about.

Helion will obviously have to overcome many challenges in order to take the express lane to fusion land. I won’t write about all of them in this post.

But what strikes me as particularly relevant to Weinberg readers is how Helion (and the fusion community in general) is facing materials challenges and decisions that are similar to those confronting developers of alternative fission technologies like fast reactors and molten salt reactors (MSRs).

For example, Helion is contemplating the use of FLiBe – the molten salt that’s part of MSR designs – as a coolant and an electrical insulator. It’s also examining the abilities of different metals to withstand ferocious neutron bombardment – just the sort of thing that many fission researchers are also investigating as they try to move away from conventional fission reactors and to higher temperature and other alternatives.


Before I dive in to Helion, and in case anyone needs a refresher:  Fusion joins atoms together rather than splits them apart as fission does. Many experts regard its as the Holy Grail of energy sources, noting among reasons that fusion does not leave long-lived high-level waste; that it requires comparatively little fuel and its fuel is to a large extent easy to obtain and plentiful; and that it cannot meltdown (even if it does require temperatures of over 100 million degrees C) and leak harmful radioactivity. (It also creates helium, a substance with many uses but one that is in increasingly short supply).

“Fusion has the potential to provide nearly limitless, clean energy for both baseload and on-demand power,” notes David Kirtley, Helion’s interim CEO, who I spoke with via Skype recently. “Fusion fuels are inexpensive, sustainable and can be supplied with minimal environmental footprint.

Helion FusionExperiment

Don’t try this at home. Helion has built and tested an experimental version of the engine, without the    coolant and heat exchanger.

Helion’s small “Fusion Engine” uses principles of magnetism to generate heat that induces istopes of hydrogen to fuse. But it bears little visual resemblance to the giant 20-story “tokamak” that ITER is building in Cadarahce, France using different techniques of magnetism.

The Fusion Engine is a 28-meter long, 3-meter high bow tie-shaped device that at both ends converts gases of deuterium and tritium  (isotopes of hydrogen) into plasmoids  – plasma contained by a magnetic field through a process called FRC (field-reversed configuration). It magnetically accelerates the plasmoids down long tapered tubes until they collide and compress in a central chamber wrapped by a magnetic coil that induces them to combine into helium atoms. The process also releases neutrons.

The Fusion Engine provides energy in two ways. Like in a fission reactor, the energy of the scattered neutrons gives off heat that ultimately drives a turbine. Helion is also developing a technique that directly converts energy to electricity. The direct conversion will provide about 70 percent of the outgoing electricity according to Kirtley.


The overarching problem that Helion, ITER, NIF, and others are working to solve is that the amount of energy it takes to coax sustainable fusion reactions is greater than what can be harnessed from the reactions.

When you consider that temperatures inside many fusion designs hit 150 million degrees C, albeit briefly, then you can start to appreciate the amount of energy required to get things cooking. In Helion’s case, it is powering capacitors that convert the deuterium and tritium gas into plasmoids. It is also powering electromagnets that surround the narrowing cylinders through which the plasmoids shoot. The pulsing magnets induce the plasmoid to accelerate.

A fusion chamber also requires durable materials – doubly so since neutrons bombard the inside walls, severely testing their durability (except for in a process called “aneutronic fusion,” but more on that another time). Therein lies one of the main crossover points between fission and fusion development. Both are looking for materials that can handle high energy neutron bombardment and high temperatures. Although fusion has a kinder brand image than does fission, the fact is that it sets neutrons racing about just as fission does (again, aneutronic fusion does not do this).

For Helion, this means finding the right material to line the inside of the compression chamber where the plasmoids collide and release neutrons.

“This wall is exposed to high levels of radiation and high thermal load,” notes Kirtley. Helion is considering alloys including tungsten, beryllia and molybdenum. These materials will be familiar to engineers and scientists working on high temperature fission reactors. As Kirtley notes, “the tungsten alloy claddings in high-temperature reactors absolutely share material crossover.” Helion’s collaborators on so-called “first wall” development include the U.S. Department of Defense and the University of Washington, he says.

JohnSlough RedmondReporter

A man of two fusions. Helion co-founder John Slough and his company MSNW are designing a separate fusion reactor, called the Fusion Driven Rocket, meant for spacecraft propulsion.

As important as durability is, Helion has another ace up its sleeve. It has devised a technique that allows for “rapid replacement” of the wall, a breakthrough that Kirtley describes as “one of the key advantages” of the Fusion Engine. “We believe it is key to the engineering design of an economically feasible fusion energy system,” he says.

In Helion’s Fusion Engine, a coolant material will form a blanket that absorbs the neutrons and their heat after the neutrons escape through the wall. As is the case with some fission research companies, Helion is not yet sure what coolant it will use, although its preference is FLiBe – a molten salt of lithium fluoride and beryllium fluoride. The MSR reactor community will recognize FLiBe as one of the fluids that can serve as both a coolant blanket and a fuel carrier in an MSR. It is the substance that lends its name to Flibe Energy, the Hunstville, Ala. company that is developing a two-fluid FLiBe-based MSR.

Helion is also considering using lithium as the blanket coolant. Lithium is a common choice in fusion designs because it reacts with the neutrons to make tritium. Of the two hydrogen istopes commonly used in fusion – deuterium and tritium – tritium is the more difficult to obtain (deuterium is found commonly in seawater), so a process that replenishes tritium via interaction with lithium is a popular design among fusion engineers. Kirtley claims that Helion’s fusion process requires less tritium than do other fusion technologies and that the Fusion Engine makes some of its required tritium by fusing deuterium atoms in the collision.

“Our reactor design removes the majority of the complex tritium producing blanket,” says Kirtley.

Thus Helion has less need to breed tritium from lithium and it is therefore looking seriously at FLiBe, which is a more effective, less expensive and less problematic coolant than lithium, he notes.


The idea of using FLiBe as a fusion coolant is not new. The U.S. Department of Energy’s Idaho National Laboratory has investigated it in partnership with Lockheed Martin, the aerospace stalwart that is also developing a fusion reactor.  Likewise, Ralph Moir, the physicist known for his interest in hybrid fission/fusion reactors , published a paper on a fusion FLiBe coolant over 20 years ago at Lawrence Livermore National Laboratory in which he notes that FLiBe avoids the fire hazards of lithium as a fusion coolant. MIT and Argonne National Laboratory published separate papers on FLiBe and lithium’s usefulness in fusion reactors in the 1970s.

FLiBe might serve a second purpose on Helion’s Fusion Engine as well. Kirtley says the company wants to use it to provide electrical insulation to the electromagnets. By using FLiBe for that function as well as for the coolant blanket, Helion would simplify its materials needs and lower its costs, he notes.

Helion’s design comes from company co-founder John Slough, who is also a research associate professor at the University of Washington and who runs Redmond-based space propulsion firm MSNW LLC.

Slough is a fusion enthusiast, to say the least. He is designing a separate fusion reactor intended as a propulsion device that in principle could send manned spacecraft to Mars in 30 days. That project known as the Fusion Driven Rocket, has funding from the U.S. National Aeronautics and Space Administration.

The more earthly Fusion Engine has received about $7 million in funds from DOE, the Department of Defense and NASA. The company hopes to raise another $2 million by next year, $35 million in 2015-17, and $200 million for its pilot plant stage.

It will compete for development funds with other fusion initiatives, such as those at General Fusion, Lockheed Martin and the “aneutronic fusion” projects at Lawrenceville Plasma Physics and Tri-Alpha Energy. It will also compete against fission development. But given some of the material similarities with fission, it might also find itself in collaboration with some of those efforts.

Images provided by Helion. Photo of John Slough from Redmond Reporter via Helion. 


  1. Martin Kral says:

    Looks like Flibe is the key to both fission and fusion technology. Maybe Kirk Sorenson was smart to name his comany Flibe Energy.

  2. Jaro says:

    .This is another case of “inventors” failing to credit their predecessors.
    Specifically, the featured illustration, “Fancy bow tie. Helion’s Fusion Engine” is a spiffified 3D color version of a “rendition of two Tri-Alpha fusion reactors” ( ), which itself is a very old illustration that originally came out decades ago, from one of Bogdan Maglich’s Migma Fusion ventures (I have personally had a copy of that same illustration, on my various PCs, for something like 15 years…)
    Maglich’s Migma concept has been around for over 40 years — with about as much results to show for all the efforts, as any other fusion energy scheme.
    But it still attracts lots of sponsorship funding: It appears that an important part of that success is hiding the history of this fusion scheme, and constantly presenting it as a new concept.
    Its deception, pure and simple.

  3. Robert Steinhaus says:

    I am grateful that your blog covers the topic of molten salt fusion and you kindly mentioned Dr. Ralph Moir, who was for four decades perhaps the most versatile nuclear designer at the Lawrence Livermore National Lab. It is hard to mention everything in a short article, but it may be worth mentioning one other Ralph Moir designed Molten Salt Fusion System that is very economical and practical and is at a high state of technical readiness such that it could be used, with minimal delay, to actually produce power from fusion to heat homes and light factories today.

    Molten Salt PACER Fusion –
    There is only one form of fusion that today produces any net energy (more energy out than the energy required to power the fusion experiment). That form of fusion was designed at Los Alamos and Lawrence Livermore Labs and is called PACER fusion. PACER fusion is a inertial confinement fusion concepts and has been demonstrated and field proven to work (as components – the PACER fusion development program was shut down in the mid-1970s by the Nixon Administration at about the same time as Molten Salt Reactor research was shut down at ORNL – no completed PACER fusion power plant has yet operated).All current Inertial Confinement Fusion concepts currently are repetitive pulse energy generators producing energy through a succession of controlled small fusion bursts.

    A comparison of ICF Fusion approaches –
    National Ignition Facility produces a 1.8 Megajoules burst per shot which is the energy produced from burning 0.014 gallons of gasoline (while producing no net energy)

    Sandia z-pinch experiment produces a 30 Megajoules burst per shot which is the energy produced by burning 0.23 gallons of gasoline (while producing no net energy)

    PACER Fusion experiment produces 1.2552 x 10^7 Megajoules per shot which is the energy produced burning 92,290 gallons of gasoline (with commercially significant large amounts of net energy)

    PACER fusion is proven fusion technology that today is capable of producing net energy (at the Gigawatt level – with a fusion gain factor q>=100,000) which other fusion programs only promise to deliver in 20 – 50 years. PACER fusion requires no physics or technology breakthroughs to build and could reliably produce Gigawatts of electrical power from fusion in less than 3 years. PACER fusion uses a tiny amount of fissile material to produce the conditions necessary to reliably ignite a D-D or D-T fusion plasma while producing >99% of its energy from fusion and < 1% of its energy from fission. In contrast to other fusion approaches, Molten Salt PACER fusion devices are small (9" dia. x 48" long) and cheap, LLNL's target cost for mass produced PACER devices was under $2000 dollars per device without nuclear fuels. To produce power at an average level of 1GWe required igniting one 1.2 x 10^7 Megajoules LLL PACER device every half hour (LANL PACER devices were larger, around 1.92 x10^8 Megajoules requiring a burst only once every eight hours to produce power at a level of 1GWe). D-D fusion, which requires no rare and costly radioactive Tritium, is practical for producing power in PACER fusion reactors. Most other fusion reactors now attempt easier to initiate D-T fusion.

    For more information I suggest you visit Dr. Ralph Moir's PACER fusion website –

    Practical D-D fusion to fully power the planet longer than the earth has existed or the sun will burn

  4. Robert Steinhaus says:

    Molten Salt based liquid first walls for fusion reactors can help fusion reactors stand up to intense neutron bombardment and achieve commercial lifetimes of 30 years.

    The logic behind thick, liquid-walled, fusion concepts
    by R.W. Moir

    A quote from article above –
    “The concept of a thick liquid surrounding the fusion reaction region promises to give advantages to fusion that could lower its cost of electricity by an important 20%, lower its development cost by billions of dollars by easing the materials development problem, and make the environmental and safety advantages of fusion even greater. With these potential advantages, there is considerable incentive to invest research funds into the liquid-walled concept to see if the claims are as advantageous as they appear, because these advantages could have such an important consequence on fusion’s development.”

  5. Cavan Stone says:

    Jaro, I believe you are misinformed regarding Helion’s design. Magolich’s design is a particle accelerator with magnetic fields to create self colliding beams. Tria-alpha’s and Helions designs are creating the equivalent of smoke rings in plasma by initiating an EMP pulse in a chamber already containing the fusionable gasses

  6. Elmar Moelzer says:

    Good article.
    It is worth mentioning that Tri Alpha is persueing a simillar approach to Helion, which gives both of them more credibility. I am not sure to what degree, but there has been some cross exchange of knowhow between the two companies.
    I think that Helion has a great shot at making this work and wished they would get more funding.

  7. Andrew Palfreyman says:

    It seems from my reading that Lawrenceville’s Focus Fusion (Dense Plasma Focus) is leading the pack. They already have nailed the confinement time and the temperature quite comfortably, and have a roadmap to get the plasma density up to snuff. Their device is small and aneutronic.

  8. Anonymous for now says:

    Ho hum…

    There is an enormous amount of sci-fi, myth and ignorance regarding this subject and it is disheartening. In order to create a fusion reaction with a _viable_ power output several things must happen.

    1. The pressure of the fuel must be extreme, so high that only a material that does exist but is still not well understood is required. Every proposal I’ve seen omits this material. In all these cases, they are merely proposing multi-billion dollar conventional bombs.
    2. Magnetic fields and other assorted forms of black magic are irrelevant as a containing “force” as magnetic fields exert back pressure which must likewise be contained. Magnetic fields are for _control_ and current induction, but not much else.
    3. “Pulsing” is a charlatan’s game. What matters is the joules energy released per second. Thus you must average the output over each second in a per second sustained reaction to understand the actual power output.
    4. 11B and H are NOT aneutronic. Academics used that term because the _relative_ neutron flux is low. At _realistic_ power levels the neutron flux even for 11B and H is ungodly. It is totally unmanageable with the fuels usually proposed … as in, there is no material known that can manage it without a massive regeneration scheme (in the liquid case). In the solid case, nature has no answer, so technologists will not have one either.
    5. Thus, the _only_ viable fuel on the distant horizon is 11B and H. None of the others are feasible until dramatic and major materials science advances are made … like those of Star Trek. If we want to run a light bulb for a few billion dollars, that’s another story. But that is not the object here. The object is to produce power competitive with what we can get with fission reactors.
    6. The _key_ difference between fission and fusion, from an engineering point of view, is that fusion requires _enormous_ pressure to get useable power. This is the key technological challenge. Conversely, trying to side-step this reality by using temperature instead requires input energy far exceeding what the fusion reaction itself can provide … thus no real net energy without wicked materials.
    7. Indeed, the cooling issue is severe. It requires something like liquid lithium or FLIBE circulated at extremely high rates to remove the heat energy even in a viable design. This by itself is a challenge. In vacuum, it requires a considerable and robust heat rejection system.
    8. In order to initiate fusion under such enormous pressure guess what? No one has even suggested using what is actually required … by nature. It is an extremely energetic source, but I digress at my peril.

    I designed a viable fusion reactor both for electrical power generation and kinetic, steady-state power. I learned from that design that it can be done, but because of these issues it would be a massive capitalization project. But in this day and age no one seems to care about good science and fact. So, someone waves their hands and gets funding because those funding it are incapable of due diligence. This reactor could have been designed by any reasonably intelligent person who took an intro college course in physics (and a smattering of graduate math). This country is going to h&* in a hand basket because people are willing to trade “patents” and pay for intellectual property, even when the term is an oxymoron. They are just ripping off rich people and the government. Sorry if I sound negative, but someone needs to be blunt to get this message across to people. Thanks for the article.

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