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.
It 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.
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.
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.
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.
The 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.
I’ve mentioned before that I’m a big supporter of nuclear (and renewable) sources of energy and how frustrated I am that the social stigma attached to it has seen what would otherwise be a clean and safe source of power slip by the wayside. Many people seem to think that there’s more danger inherit in this technology than there is in other power generation when this is simply not the case, but it seems that incidents of reactors past are still fresh in everyone’s mind. Still with countries like France pioneering the way for nuclear energy I’ve always held out that hope that one day we can transition away from our current energy dependency on oil and coal.
It would seem that Obama isn’t as short sighted as many of his constituents are:
In his speech, Mr. Obama portrayed the decision as part of a broad strategy to increase employment and the generation of clean power. But he also made clear that the move was a bid to gain Republican support for a broader energy bill.
“Those who have long advocated for nuclear power — including many Republicans — have to recognize that we will not achieve a big boost in nuclear capacity unless we also create a system of incentives to make clean energy profitable,” Mr. Obama said.
He also strikes on one of the biggest problems (other than the social stigma) that nuclear power faces: the cost. Current estimates for new reactors peg the total construction cost between $6~10 billion dollars with costs of construction going up faster than other means of power generation. Obama hits the nail on the head when he says that incentives are needed as the majority of western countries are quite hostile to new nuclear plants. The amount of regulation and beaucracy involved in setting up these plants typically makes them unprofitable for those who would want to set them up. Guaranteeing funding for the majority of the work means that a lot of the risk is absolved by the government, making the endeavour much more attractive.
Obama also gets kudos for using the proper spelling of nuclear (although that could be the reporter, I haven’t heard the speech myself. If you’ve got a link to it let me know!).
There is however hope for future reactors like the Westinghouse AP1000 (Yes, that Westinghouse) which has been commissioned by China for the princely sum of just $2 billion, a drastic reduction in cost. Additionally with China’s economy still growing strong they’ve planned a grand total of 100 of these reactors to be built over the course of the next decade which will have the added side effect of driving massive economies of scale when it comes to building AP1000 plants. With time I can see this reactor tech becoming a lot cheaper than their coal and oil counterparts, a critical step in driving mass adoption of nuclear technology.
However, whilst I believe that nuclear is the solution to many of our current problems I do not believe that it is the final solution to our insatiable craving for energy. Research shows that as GDP increases so does energy consumption, so you can imagine that a country like China who is just beginning to create a giant middle class will create a demand for energy on a scale that we haven’t seen before. Whilst nuclear will be capable of sustaining them (and others) in the short term the fact remains that nuclear is really just a far more efficient fossil fuel, and alternatives must be sought.
Currently my hopes remain in fusion technology. Whilst they still fall under the umbrella of fossil fuels they produce far and away more energy from orders of magnitude less fuel. However the technology is still in its infancy and requires significant amounts of research before commercial reactors become available. The good news is that many see the potential in this future technology with projects like ITER attracting funding and involvement on an international scale. People might say that fusion is always 20 years away, but I have my hopes for this technology.