By Trent Griger
Energy scarcity is arguably considered to be one of the largest problems we face today. Oil and gas will likely be gone within our lifetimes. Coal will last a short while longer, but as energy demands rise with a growing global population and the expansion of AI, this estimate may shorten to a concerning degree. What, then, is the answer to our looming demise?
While green energy is on the rise, infrastructure bottlenecks hold it back from being the sole solution for now. I propose instead a solution that has been well researched for half a century, one that has shown tremendous promise in recent years, and is finally deserving of a chance. I propose Thorium Molten Salt Reactors (TMSRs).
TMSRs are not a new technology. As far back as 1956 the United States had been prospecting for the key component thorium for the express purpose of using it as a nuclear fuel. While originally considered for more traditional solid-fuel reactors, the material quickly showed promise as a primary fuel in the Molten Salt Reactors that were in development in the late-1960s to early-1970s.
There are several factors that make thorium such an attractive element to use for these nuclear projects. One of the most talked about benefits is its relative abundance compared to other nuclear fuels, mainly uranium. While thorium is only about three to four times more abundant in the earth’s crust than uranium, it is almost always found in its pure, usable state of Th232. When you consider that only about 0.7% of the world’s uranium is the usable U235, it works out that thorium fuel is about 500 times more abundant than uranium fuel. Additionally, thorium can breed more usable uranium via the Thorium Fuel Cycle. In this process, Th232 is seeded with a small amount of fissile material (uranium or plutonium) and then captures a neutron to become Th233. This isotope then degrades into Pa233 which itself degrades in U233, a uranium isotope that functions as fissile fuel. Interestingly, this U233 has the capacity to split off 2.35 neutrons as part of its reaction. This is significant because one of those neutrons can be used to perpetuate the thorium-to-uranium cycle, while another can trigger the next uranium atom in the chain reaction. The cycle leaves 0.35 extra neutrons, meaning the ideal reactor is capable of producing slightly more fuel than it is consuming. This makes TMSRs vastly more economical than any other form of nuclear energy generation.
Another major benefit is the measurable reduction in radioactive waste. Traditional Pressurised Water Reactors (PWRs), which are the most common type of nuclear reactor today, must shut-down every 12 to 18 months to remove spent fuel and replace it with more usable material. Not only do these shut downs interrupt power output, they also produce many people’s largest gripe with nuclear power: the waste.
Henceforth, “waste” will only be referring to the 3% of total waste that is designated as “high-level”, where the radioactive uranium and plutonium is no longer usable in that specific type of reactor. Waste and what to do with it has plagued nuclear programs since their founding. The US originally planned long term storage of nuclear waste under Yucca Mountain, but that was struck down by the Obama administration in favor of dry-cask storage under constant guard. That plan has worked thus far, but the sheer quantity of waste produced by uranium-based PWRs cannot be ignored and is putting mounting pressure on those experts working to find a permanent solution.
TMSRs grant two potential answers to this problem. First, they may be capable of using spent fuel from PWRs to power their own reactions. The high-grade waste that is traditionally put in casks and forgotten is actually about 94% uranium. That uranium is not useless, and can be reprocessed into functional fuel to seed TMSRs. Second, TMSRs themselves produce vastly lower quantities of waste. Since they utilize a liquid fuel, they do not need to be shut down and disassembled to refuel like traditional PWRs. That means no gaps in energy production, and no mass quantities of waste being taken out and stuck underground somewhere. TMSRs provide answers to some of the biggest problems plaguing current nuclear policy.
TMSRs have long fallen by the wayside in nuclear infrastructure. Early investments into traditional PWRs globally handicapped investment into alternative reactors. However, they have recently seen a resurgence of interest in the scientific community. As China seeks a foothold in the emerging TMSR sector, it has seen an incredible first success: the first large scale conversion of thorium-uranium fuel in their new Gansu Province-based TMSR-LF1. While still highly experimental, these promising results in the early stage spell good fortune for the researchers of the Shanghai Institute of Applied Physics. The Chinese are not alone in their pursuit of widespread TMSR technology. The Danish company Copenhagen Atomics is pursuing mass produced, modular TMSRs designed for optimizing the neutron economy. The company expects to have a reactor online by 2030. Having made massive leaps in lowering input costs for TMSRs, Copenhagen Atomics seems well-positioned to lead Europe into a new age of widespread affordable energy.
In a world facing mounting demands for affordable, clean energy, new solutions may be found in old ideas. It is time to revisit the Thorium Molten Salt Reactors of the early nuclear era. The fuel is plentiful, the waste is minimal, and new advancements in the field have led them to be more affordable to construct than ever before. With further research, TMSRs could easily be the solution to AI energy demands and more. While the far future may be in wind, hydro, or solar, we need something for the present. And the answer is thorium.
The views expressed in this article are the author’s own and may not reflect the opinions of The St Andrews Economist.
Image Credit: New Atlas