The Forgotten Nuclear Technology Set To Cause A Revolution
Thorium reactors are set to become a game changer.
Most people don’t understand how extraordinary nuclear power is. Its carbon emissions per unit of energy are lower than solar power, it causes significantly fewer deaths per unit of energy than any other form of energy, and it produces on-tap 24/7 energy no matter the weather. It is the holy grail of green energy for all intents and purposes. But it is by no means flawless. Nuclear energy is cripplingly expensive, the fuel production causes geopolitical tensions and undermines national security, nuclear fuel extraction is far from being ecologically harmonious, it directly fuels nuclear weapon proliferation, reactors have the potential to be even safer than they currently are, and there is still a significant issue of how do we safely manage nuclear waste? However, a forgotten nuclear technology from the 60s promises to solve all of these issues: thorium reactors. But, is this just an atomic pipe dream or a genuinely revolutionary technology?
Let’s start with the basics. How does a thorium reactor work? Well, it’s a slight twist on how a typical uranium-powered reactor works.
A typical nuclear reactor uses a specific isotope of uranium; uranium 235 (U235), which makes up around 5% of the nuclear fuel in the reactor. U235 by itself isn’t particularly radioactive, but in a process known as fission, it can absorb a slow-moving neutron and transmute into U236, which is highly unstable and radioactively decays almost instantly, splitting into two smaller atoms, releasing three slow-moving neutrons and a tonne of energy. These neutrons can then go on to cause three other U235 atoms to undergo fission, creating a self-sustaining nuclear chain reaction. All a nuclear reactor does is control how many of these neutrons go on to cause fission and convert the released energy into electricity.
A thorium-based nuclear reactor goes about this process entirely differently. These reactors use a specific isotope of thorium, thorium 232 (Th232). Th232 itself isn’t radioactive or fissile, meaning it can’t undergo fission after absorbing a slow neutron. However, after absorbing a much more energetic fast neutron, it transmutes into uranium 233 (U233), which is fissionable through the same slow neutron absorption process as U235. So, a thorium reactor first requires its fuel to be irradiated to “breed” its fuel into a fissile isotope before it can produce any power.
As you can imagine, this requires an entirely different reactor design. Firstly, a thorium reactor requires an external source of high-energy neutron radiation to ‘turn on’ its fuel. Thorium’s fission happens most efficiently at far higher temperatures than typical reactors can stand, so they use a different design known as a Molten Salt Reactor (MSR). In a typical reactor, you have fuel rods and water as a coolant. In an MSR, the fuel and coolant are combined in a superheated salt bath with nuclear fuel dissolved into it. MSRs have exceptional thermal stability, which enables the safe high-temperature and low-pressure reactor operation that thorium fission relies on.
So, that is the technical differences between the two. So, what is the advantage of the far more complex thorium reactor?
Well, a thorium MSR is basically nuclear accident-proof. The thorium fuel only needs to be transmuted into U233 when required, not all at once. As such, you can ensure there is only a tiny amount of fissionable fuel in the reactor at any one time. When the radiation breeding the U233 is turned off, the reactor can run out of fissionable fuel and completely shut down in just two milliseconds. This makes it nigh on impossible for thorium reactors to have incidents like Chernobyl or Fukushima.
Thorium fission is also far more efficient than U235 fission. This is partly due to the fact that it produces more energy for each reaction, even if you consider the added energy required to turn thorium into U233. But it is also because a thorium reactor can actively recycle nuclear fuel while it is still operational, meaning it can react 100% of its nuclear fuel. Meanwhile, typical uranium reactors only use 5% of their nuclear fuel before the fuel rods need to be replaced.
Thorium reactors are also far cleaner. U233 has far fewer radioactive and toxic fission by-products than U235. This, combined with the high efficiency and ability to burn through all its nuclear fuel and higher energy yield of thorium fuel, means thorium reactors produce a quarter of the nuclear waste as uranium reactors do per unit of energy. What’s more, the waste they do produce is only radioactive for 5% as long as uranium waste is, and is far less toxic. In fact, Chinese scientists have claimed that waste from thorium will be a thousand times less hazardous than that from uranium.
This, in turn, has some serious knock-on benefits. Firstly, environmental. Thorium and Th232 are far more abundant and far easier to mine than uranium and U235. This, combined with the fact we need less of it to produce the same amount of energy, significantly reduces the environmental impact of thorium nuclear fuel over uranium nuclear fuel. The reduced volume of nuclear waste per unit of energy also means that more expensive, permanent, and far safer nuclear waste storage solutions, such as deep geological storage (read more here), will become viable, solving the problem of nuclear waste altogether. The higher safety factor and easier-to-handle nuclear waste also significantly reduce operational costs, and the higher fuel efficiency means that, theoretically, a thorium MSR is cheaper to build than an equivalent uranium reactor. In fact, a recent study found that energy from a thorium reactor would cost $0.014 per kWh, which is 80% cheaper than current nuclear power and more affordable than solar power, the most inexpensive form of energy humanity has ever had!
Simply put, thorium seems like the perfect nuclear technology. Super efficient, incredibly cheap, far easier to manage, way safer, and drastically less nuclear waste worries.
It’s no wonder China and India are rapidly developing their own commercial thorium reactors. Both countries have no uranium deposits, so they have to rely on importing nuclear fuel from abroad, leaving them vulnerable to market swings and energy blackmail, especially as Russia is the world’s largest exporter of uranium nuclear fuel. India already has an experimental thorium-converted nuclear reactor and is in the process of developing commercial thorium MSR. China finished building a thorium MSR in 2021, which was recently granted a 10-year operating licence. This reactor will be used to develop the protocols and industry required to use this technology across China, with a goal of widespread thorium MSR deployment in the early 2030s.
So, you might be asking, why isn’t the West using thorium reactors? Well, this technology isn’t perfect.
Firstly, thorium reactors don’t produce the nuclear by-products necessary for nuclear weapons or medical nuclear material. This is a serious secondary industry for the West, as the governments tend to subsidise the industry heavily in return for these valuable materials. Secondly, while MSRs and thorium reactors have been around since the 60s, they have yet to be developed commercially. You see, the process of getting a reactor design licenced for commercial use takes years of work, extensive testing and billions of dollars, and even after that, your design might not get licensed due to political whims. Even if you get the design licensed, scaling up a thorium-based nuclear industry will be eye-wateringly expensive and take many decades. So, companies have opted to optimise the reactor technology we already have rather than push this new technology.
The West has plenty of uranium deposits in Canada and Australia, and while they currently rely on Russia to turn raw uranium into nuclear fuel, they have the technology and the know-how to bring that industry back to their shores in a few years. So, unlike China and India, the West has no geopolitical motive for going through all the pain and risk of developing commercial thorium reactors, even if the end payoff is potentially a far cheaper, cleaner and safer form of energy than anything we currently have. For the West, the risk is too high and too far into the future for the reward to be worthwhile.
So, thorium nuclear power is a truly promising energy that could herald a breakthrough nuclear revolution over the next few decades. But, because we in the West are so dependent on our nuclear deterrent and are wedded to our capitalist doctrine that can’t accept long-term payoffs and is increasingly risk-averse, we won’t be a part of this revolution. Instead, players in the East are set to unlock this technology, and we will have to scramble to import their designs or desperately develop our own at light speed just to keep up.
Thanks to David Binner who suggested I should cover this technology. Let me know in the comments if there is anything you’d like me to cover in the future.
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Sources: WNN, SCMP, The Guardian, Stiffed, WNA, NCPA, The Hindu, IAEA, Terrestrial Energy, The Telegraph, Forbes, The Bulletin