Posts Tagged‘fusion’

Not Your Typical Fusion Reactor: The Stellarator.

When you read news about fusion it’s likely to be about a tokamak type reactor. These large doughnut shaped devices have dominated fusion research for the past 3 decades mostly because of their relative ease of construction when compared to other designs. That’s not to say they’re not without their drawbacks, as the much delayed ITER project can attest to, however we owe much of the recent progress in this field to the tokamak design. However there are other contenders that, if they manage to perform at similar levels to tokamaks, could take over as the default design for future fusion reactors. One such design is called the stellarator and its latest incarnation could be the first reactor to achieve the dream: steady state fusion.

Wendelstein 7-X

Compared to a tokamak, which has an uniform shape, the stellarator’s containment vessel appears buckled and twisted. This is because of the fundamental design difference between the two reactor types. You see in order to contain the hot plasma, which reaches temperatures of 100 million degrees celsius, fusion reactors need to contain it with a magnetic field. Typically there are two types of fields, one that provides the pinch or compressing effect (poloidal field) and another field to keep the plasma from wobbling about and hitting the containment vessel (toroidal field). In a tokamak the poloidal field comes from within the plasma itself by running a large current through the plasma and the poloidal field from the large magnets that run the length of the vessel. A stellarator however provides both the toroidal and poloidal fields externally requiring no plasma current but necessitating a wild magnet and vessel design (pictured above). Those requirements are what have hindered stellarator design for some time however with the advent of computer aided design and construction they’re starting to become feasible.

The Wendelstein 7-X, the successor to the 7-AS, is a stellarator that’s been a long time in the making, originally scheduled to have been fully constructed by 2006. However due to the complexity and precision required of the stellarator design, which was only completed with the aid of supercomputer simulations, construction only completed last year. The device itself is a marvel of modern engineering with the vast majority of the construction being completed by robots, totalling some 1.1 million hours. The last year has seen it pass several critical validation tests, including containment vessel pressure tests and magnetic field verification. Where it really gets interesting though is where their future plans lead; to steady state power generation.

The initial experiment will be focused on short duration plasmas with the current microwave generators able to produce 10MW in 10 second bursts or 1MW for 50 seconds. This is dubbed Operational Phase 1 and will serve to validate the stellarator’s design and operating parameters. Then, after the completion of some additional construction work to include a water cooling transfer system, Operational Phase 2 will begin which will allow the microwave system to operate in a true steady state configuration, up to 30 minutes. Should Wendelstein 7-X be able to accomplish this it will be a tremendous leap forward for fusion research and could very well pave the way for the first generation of commercial reactors based on this design.

Of course we’re still a long way away from reaching that goal but this, coupled with the work being done at ITER, means that we’re far closer than we ever were to achieving the fusion dream. It might still be another 20 years away, as it always is, but never before have we had so many reactor designs in play at the scales we have today. We’ll soon have two (hopefully) validated designs done at scale that can achieve steady state plasma operations. Then it simply becomes a matter of economics and engineering, problems that are far easier to overcome. No matter how you look at it the clean, near limitless energy future we’ve long dream of is fast approaching us and that should give us all great hope for the future.

Lockheed Martin Promises Fusion in 5 Years.

There’s little question in my mind that the future of energy production on earth lies within fusion. There’s simply no other kind of energy source that can produce energy on the same scale, nor over the extended periods of time that it can. Of course the problem is that fusion, especially the net energy positive kind, is an incredibly hard thing to achieve. So much so that in the numerous decades so far no one has yet made a device capable of producing sustained power output and the one project that might, ITER, is decades behind schedule. Thus you can imagine my scepticism when I hear that Lockheed Martin expects to have a device operable in 10 years with it being widely available in 20 (snicker).

Lockheed Martin Compact Fusion Reactor

The Compact Fusion project comes out of Lockheed Martin’s Skunk Works labs which have delivered such things as the venerable SR-71 in the past. They’re a highly secretive bunch of people which is why this announcement, along with a rather well designed website, has attracted quite a bit of interest as typically any project of theirs that might not deliver won’t see the light of day. Thus you’d assume that Lockheed Martin has some level of confidence in the project, especially when they’re committing to delivering the first round of these devices to the military in the not too distant future. Indeed if their timelines are to be believed they could even beat ITER to the punch which would be a massive coup if they pulled it off.

Their design has the entire reactor fitting on the back of a truck (although the size of said truck is debatable it looks to be the size of a tanker) which is an order of magnitude smaller than all other commercial fusion reactor designs. This is somewhat perplexing as the style of containment they’re going for, the tokamak style which ITER uses, scales up quickly (in terms of power) with increased plasma volume. There are limits to this of course but it also means that the 100MW figure they’re quoting, which is 20% of what ITER will produce, comes with its own set of problems which I don’t believe have good solutions yet.

Indeed whilst the project will be standing on the shoulders of numerous giants that have come before them there’s still a lot of fundamental challenges standing between them and a working reactor 5 years down the line. However should they be able to achieve that goal it will be the start of a new age of humanity, one where even our wildest energy demands could be met with the use of these clean running fusion reactors. The possibilities that something like this would open up would be immense however the the long running joke that fusion is always 20 years away still rings true with Lockheed Martin’s compact reactor project. I would love for my scepticism to be proven wrong on this as a fusion powered future is something humanity desperately needs but it’s always been just out of our reach and I’m afraid it will continue to be for a least a while longer.

Finally, Confirmation of How the Sun Works.

The sun is an amazing celestial object. Even though it looks about the same size as our moon when viewed from Earth’s surface it’s almost 400 times further away which should give you an idea of just how unfathomably large the sun is. It also heavily influences nearly every aspect of our Earth, providing nearly all of the energy that we, and all other lifeforms on this planet, consume on a daily basis. You’d be forgiven for thinking that we understood it completely however as whilst nearly anyone would be able to tell you that the sun is powered by fusion we, funnily enough, didn’t actually have proof of this.

That is, until now.

Giant_prominence_on_the_sun_eruptedIt sounds silly right? The theory of the sun being a giant ball of fusion has been around for 75 years and is pretty much established as a scientific fact. Indeed many of the observations that we’ve made of the sun support that theory and the small scale replicas we’ve made also seem to exhibit similar properties. However the surface of the sun, as we see it, doesn’t really tell us the whole story. Indeed the light emitted from the surface of the sun is hundreds of thousands of years old, spending most of its life worming its way out of the deeper layers of the sun. Should we want to verify that for sure we need to observe the products of fusion reactions happening now and, bar venturing into the sun itself, there’s only one way to do that: by observing one of our universe;’s most elusive particles, the neutrinos.

Specifically the neutrinos are called PP neutrinos, those which arise from the fusion of two protons to form helium. A fusion reactor on the scale of the sun generates countless numbers of these particles every second and, thanks to their near massless nature, they rush out unimpeded directly from the sun’s core. However the same properties which allow them to move at such great velocity away from the sun also prevents them being easily detected. Combine this with the fact that PP neutrinos carry less energy than regular neutrinos do you can see why definitive proof of fusion happening within the sun as eluded us for so long. Researchers in Italy though crafted an experiment to capture these ever elusive particles and their research has finally bore fruit.

The Borexino experiment uses a large device called a scintillator, essentially a large array of light detecting devices immersed in ultrapure water. It’s then buried deep underground (about 1.4KM) in order to shield it from cosmic rays and other stray radiation. This experiment was specifically designed to verify the solar output of neutrinos against the standard solar model in order to verify that fusion was indeed occurring within our sun. It began collecting data about 7 years ago and at the beginning of this year they had enough data to submit their final report. The results line up perfectly with what the standard solar model predicts which, for the first time, verifies that fusion is indeed occurring within our sun and has been for a very long time.

It may seem like a silly thing to do but verifying things like this is the key to ensuring that our understanding of the universe is in line with reality. We might have known that fusion was going on the sun for decades but without definitive proof we just had a good model that matched some of the observed behaviours. Now we know for sure and that means that our standard solar model is far more robust than it was previously. Thus, with this new information at hand, we can dive even deeper into the model, probing the various curiosities and figuring out just what makes our sun tick. We might not ever know everything about it but part of the fun of science is finding out what you don’t know and then trying to figure it out.


There’s More to the World of Fusion Than Just Tokamaks.

The world of fusion is currently dominated by a single project: The International Thermonuclear Experimental Reactor. It is by far the biggest project ever undertaken in the field of fusion, aiming to create a plant capable of producing sustained bursts of 500MW. Unfortunately due to the nature of fusion and the numerous nations involved in the project it’s already a decade behind where it was supposed to be with conservative estimates having it come online sometime in 2027. Now this isn’t an area I’d usually considered ripe for private industry investment (it’s extremely risky and capital intensive) but it appears that a few start-ups are actually working in this area and the designs they’re coming up with are quite incredible.

General Fusion Magnetized Target Reactor

There’s 2 main schools of thinking in the world of fusion today: inertial confinement and magnetic confinement. The former attempts to achieve fusion by using incredible amounts of pressure, enough so that the resulting reaction plasma is 100 times more dense than lead. It was this type of fusion that reached a criticla milestone late last year with the NIF producing more energy in the reaction than they put into it. The latter is what will eventually power ITER which, whilst it has yet to provide a real (non-extrapolated) Q value of greater than 1 it still has had much of the basic science validated on it, thus providing the best basis from which to proceed with. What these startups are working on though is something in between these two schools of thinking which, potentially, could see fusion become commercially viable sooner rather than later.

The picture above is General Fusion’s Magnetized Target Fusion reactor a new prototype that combines magnetic confinement with aspects of its inertial brethren. In the middle is a giant core of molten lead that’s spinning fast enough to produce a hollowed out center (imagine it like an apple with the core removed). The initial plasma is generated outside this sphere and contained using a magnetic field after which it’s injected into the core of the molten lead sphere. Then pistons on the outside of the molten sphere compress it down rapidly, within a few millionths of a second, causing the internal plasma to rapidly undergo fusion reactions. The resulting heat from the reaction can then be used in traditional power generators, much like it would in other nuclear reactors.

The design has a lot of benefits like the fact that the molten lead ball that’s being used for containment doesn’t suffer from the same neutron degradation that other designs typically suffer from. From what I can tell though the design does have some rather hefty requirements when it comes to precision as the compression of the molten lead sphere needs to happen fast and symmetrically. The previous prototypes I read about used explosives to do this, something which isn’t exactly sustainable (well, at least from my point of view anyway). Still the experiments thus far haven’t disproved the theory so it’s definitely a good area for research to continue in.

Whether these plucky upstarts in fusion will be able to deliver the dream faster than ITER though is something I’m not entirely sure about. Fusion has been just decades away for the better part of a century now and whilst there’s always the possibility these designs solve all the issues that the other’s have it could just as easily go the other way. Still it’s really exciting to see innovation in this space as I honestly thought the 2 leading schools of thought were basically it. So this is one of those occasions when I’m extraordinarily happy to be proven wrong and I hope they can dash my current skepticism again in the not too distant future.

Fusion Milestone Reached, Many More To Go.

There’s a long running joke that fusion reactors are always 20 years away, something which people began saying about 60 years ago. It’s not that we get it wrong per se, more that we have a tendency to underestimate the complexity of achieving the next step, something which is usually written off as a simple piece of engineering. We’re now acutely aware of the fact that the practical aspects of running a fusion based power plant are likely going to require significant advancements in materials science and that’s if the theoretical models we have turn out to be correct. Whilst we’ve been able to fuse atoms for a long time now the end goal of fusion power generation, a self sustaining plasma, has yet to be achieved but one theoretical model recently got a jolt of hard science behind it lending a lot of credence to the whole field.

NIF hohlraumThe National Ignition Facility has been dedicated to studying Inertial Containment Fusion, ostensibly because it aligns with most of their overarching goals (one of which is weapons research). Of the two main branches of fusion research, the other being Magnetic Confinement Fusion, ICF is something of a poor sibling in terms of research dollars and large scale experiments. This is not to say its claim is any less valid just that, at least in this armchair physicists understanding, its brand of fusion doesn’t lend itself particularly well to be scaled up to the power generation levels at least not with its current modelling. However NIF has announced today that, for the first time ever for any fusion experiment, their reaction released more energy than what was pumped into it; a sure sign that nuclear fusion was occurring.

It’s a pretty amazing feat and is definitely something that NIF should be proud of, however that does not take into account the total energy of the system which was several orders of magnitude higher than the energy produced at the other end. Thus for such a system to go past full unity it would need an input to output multiplier somewhere in the thousands, much more than what they’re currently achieving. Still as far as I was aware we weren’t even entirely sure if this kind of fusion was feasible, given the strict requirements on many of the parameters. Of course such challenges aren’t entirely unique to this brand of fusion but you have to wonder why after the initial burst of research into ICF things started to slow down considerably with MCF being the reigning champion for many decades now.

From what I can tell though, with my admittedly limited knowledge on the subject matter, MCF has the greatest potential to translate into powerplant scale devices much sooner than those using ICF as a base. Indeed the challenges presented to using MCF do lend themselves well to scale (although large magnetic fields always present some trifles) whereas ICF the challenges increase dramatically with scale as it becomes significantly harder to ensure the right reactions happen to sustain fusion. Of course I’m willing to be told otherwise on this as I could just be suffering from some geek lust for ITER’s sultry designs.

In any case it’s extremely exciting to see the progress that’s being made as it bodes well for a future that could be free of fossil fuels. Whilst I’d love to believe that we’re 20 years away now (and indeed ITER’s schedule puts the first DT reaction within that time frame) I’m going to need to see a few more milestones like this one to start believing it. We’re tantalizingly close however with the evidence constantly building that we’re on the right track to producing all the energy we need without having to dump untold tons of carbon back into our atmosphere.

And that’s why it’s worth spending billions of dollars on researching every possiblity for developing a sustainable fusion reactor.

Obama Gone Nuclear With Power.








