Re-thinking thorium

14 March 2024

Thorium advocates have not always helped the nuclear cause, but despite this we should embrace the possibility of thorium contributing to a diversified and more resilient nuclear fuel cycle in the future.

Have you heard of thorium!?” said the internet commenter, said the friend of a friend, said just about every contrarian whose interest in nuclear energy had led them to Google what was wrong about it, and then latch on to the first magic solution they stumbled across. A decade or so ago this was a big problem and made it difficult to have serious conversations about the need for nuclear. At that point in time, in the aftermath of a major accident, the nuclear renaissance had stalled and dialogues on nuclear energy were not exactly top of the political agenda. Thorium was an ideological, technological distraction from problems which primarily needed political will and policy-based solutions – or so the nuclear industry mostly believed.

Whenever public discussion did take place and the classic nuclear objections invariably arose – safety, waste, proliferation – up would pop a thorium fan to convince you that some kind of cold-war conspiracy had led to the widespread adoption of uranium-based light water reactor technologies. They would then tell you that meltdown-proof, non-weaponisable thorium reactors were already proven, and all that was needed was someone brave enough to break free of big uranium and lead a bold new design to market.

While nominally nuclear advocates, thorium fans would typically argue that countries would be crazy to invest further in today’s uranium-based reactors when tomorrow’s thorium technologies were just around the corner and capable of solving every problem. They were happy to throw the existing nuclear industry under a bus and seemed to genuinely believe that the challenges of conventional uranium-fuelled nuclear power were both serious and essentially unsolvable.

At the same time thorium fans were incredibly willing to believe outrageous things about the technical readiness of their own chosen reactor technologies and fuel cycle, and equally ready to gloss over any limitations. To question just one talking point, how proliferation-proof is thorium really when you need to breed it to fissionable U-233 before you can even get energy out of it? To question another element of thorium lore, how easy can it be when the one country still recently championing a thorium fuel cycle and with the largest thorium reserves, India, has experienced well-known difficulties and seems to be changing course? It is probably for the best that thorium fans came across as fringe, as such assertions lack credibility.

Without having plants in operation all the associated problems that come with real infrastructure, fans of paper-based thorium technologies were of course free to imagine away any and all such limitations. They were in essence techno-utopians, an early and extreme version of the mindset that characterises the innovators which have since swept the nuclear industry, and which most of us now feel quite comfortable with. Will tomorrow’s reactors be fundamentally better than today’s reactors? Why of course they will! Only a terminal cynic (or an anti-nuke) believes that the future will be worse than the past.

Indeed, it feels natural now to talk about thorium fans in the past sense not because they no longer exist, but because most of us have our own preferred advanced nuclear reactor technology now – and that’s ok. Eyes have been collectively opened to the potential of nuclear energy, an energy source that is still in its infancy, to evolve beyond what it is today. Thorium fans have simply melted into the crowd of the 80 or more advanced reactor and SMR designs that are now being developed globally, and which industry should be immensely grateful for.

The default thorium fantasy reactor – the molten salt reactor – is being actively advanced now by private interests such as Moltex and Terrestrial, but these companies are at least initially working towards uranium-fuelled designs. Thorcon springs to mind as a start-up that is actively pursuing thorium from the get-go.

It’s fair to say that most people in the established nuclear industry are not die-hard uranium-fans, they are simply fans of what works. Pragmatists don’t care whether uranium is theoretically better than thorium, or vice versa, according to some arcane metric, we care that uranium-fuelled designs have a proven track record of constructability and safe operations, with existing assets capable of operating for 60 years or longer. Uranium simply out-competed thorium in the same way that VHS out-competed beta-max, by being first and not necessarily better.

But things keep changing. Just as VHS has long since given way to DVD, Blu-ray and digital files, we can expect nuclear technologies to change profoundly in the future. We can be confident that things will change, although can only guess at what that distant future holds.

Thorium could well make a come-back and there are good reasons why it should. Imagine what an immense improvement it would be to the overall resilience of the nuclear sector if utilities had the flexibility to switch between uranium and thorium as a hedge for resource availability and price volatility. In a world where the different kinds of fossil fuels – coal, gas and oil – have all been phased out and nuclear plays a greater role in meeting overall energy demand, this diversity of nuclear fuel resource becomes even more essential.

To build on a theme raised in previous columns appearing here in NEi, the nuclear industry needs to improve its offering significantly if it is to meet the needs of a fossil-free, triple global nuclear generation capacity and truly equitable future.

Given the zeal of the thorium fan, it is somewhat ironic that uranium seems to be a prerequisite for the development of a thorium fuel cycle. This is the case with India’s forward-planned fuel cycle at least, while the Chinese experimental molten salt reactor that started operating in 2023 does so with enriched uranium core and about 50 kilograms of thorium loaded. Pressurised Heavy Water Reactors are perhaps the most versatile reactor designs currently operating, and thorium-based fuels have been designed and tested in AECL’s Chalk River laboratories – hybrids with uranium oxide or plutonium oxide. As so often turns out to be the case with many superficially divisive topics within the nuclear community, the reality is that thorium could be as much a complement to uranium as it is competition.

Ultimately, those annoying thorium fans may have done more good for future nuclear prospects than is appreciated. Despite recent improved public acceptance globally it is true that many people are reluctant to embrace nuclear energy the way it is presented today. The nuclear industry’s reputation has been tarnished by a litany of over budget, late construction projects and a mainstream media focus on accidents and near-misses. People need a bright shiny aspirational technology to initially accept the possibility of new nuclear energy, and only then to become more familiar with the issues and to look past what they think they know. Advanced nuclear technologies, including thorium and fusion, are the gateway-drug that encourage people to understand nuclear energy more deeply and become less afraid of it.

It is genuinely exciting to see thorium R&D advance. If and when thorium technologies reach maturity, the global nuclear industry should not hesitate to integrate this fuel. Respect is owed to the researchers and visionaries that continue to defy the status quo and work diligently to make this happen.

Author: David Hess, Senior VP, DeepGeo

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