Thorium Revolution – Molten Salt Reactors | Armstrong Economics
COMMENT: Martin,
Long time reader and fan. I am a physicist, I’ve spent years proving mathematically what you say about climate change.
It is obvious that humanity must embrace nuclear fission to replace fossil fuels as they slowly deplete and become too expensive.
Solar and wind are a joke, and practical fusion is many decades away. Unfortunately, so few people understand the physics, that a multitude of mis-conceptions cloud this topic, and few even got into your post.
First, Thorium produces roughly the same power pound for pound as Uranium or Plutonium. But Thorium IS NOT FUEL, like Uranium 238 it is FERTILE but not FISSILE: it cannot ‘burn’ by itself. However, Thorium 232 can be bred into the fissile isotope Uranium 233, which burns just like Uranium 235. This breeding process already happens to Uranium 238 in our existing reactors. It absorbs a neutron, and decays into Plutonium 239, which burns even better than Uranium 235.
All our current reactors rely on enriched Uranium to operate, which means they burn only 4% of their fuel. But so-called fast breeder reactors could tap into this vast supply of fertile isotopes, and breed and burn 100% of the fuel. Just burning it up completely also makes the waste vastly less dangerous.
The physics of breeder reactors is well-understood, but we need engineering research to perfect a new generation of practical safe breeder reactors. By far the most promising technology is the Molten Salt Reactor, where the reactor fuel is a liquid that circulates from the ‘core’ through heat exchangers, to produce steam like any reactor. It runs at atmospheric pressure so it cannot suffer steam explosions, and if If anything goes wrong, the fuel can be emptied from the reactor by gravity, shutting it down in seconds.
Interestingly, the man who developed our existing reactors, Alvin Weinberg, immediately saw how unsafe they were. So in the 1950’s began developing the Molten Salt reactor. He built several which worked flawlessly. But the government shut his project down in the 1970’s. Now is the time to resurrect his brilliant design, and build a generation of much safer, less inexpensive and more efficient fission reactors to power humanity’s future.
REPLY:
Pressurized Heavy Water Reactors (PHWRs) fueled by uranium generate plutonium. That plutonium is then used by Deploy Fast Breeder Reactors (FBRs) to create fissile material such as uranium-233. The final stage employs the Advanced Heavy Water Reactor (AHWR) and other thorium-based fuels that are designed to operate on thorium-plutonium and thorium-uranium-233 mixed oxide fuels. Thorium is not fuel, as one reader pointed out, but can become fertile when turned into uranium-233.
Most current nuclear reactors are light water reactors (LWRs) that use enriched uranium (typically about 3–5% U-235) as fuel. These reactors extract less than 1% of the energy available in natural uranium, as they mainly fission U-235 and leave the much more abundant U-238 largely unused. The claim that they burn only 4% is broadly accurate, but the true number is a bit closer to 1% for once-through cycles, and up to 4-5% for certain modern fuel cycles.
Fast breeder reactors (FBRs) are designed to convert fertile isotopes (like U-238 or Th-232) into fissile isotopes (like Pu-239 or U-233), enabling them to extract nearly all the potential energy from uranium or thorium. This can theoretically increase fuel utilization by a factor of 100 compared to LWRs. In practice, FBRs can utilize 60–70% of uranium’s potential energy, with the remainder being fission products and some unconverted fertile material. Breeder reactors can also significantly reduce the volume and long-term radiotoxicity of nuclear waste, as most actinides are consumed, leaving primarily shorter-lived fission products.
Alvin Weinberg led the development of the pressurized water reactor (PWR) and pioneered molten salt reactor research at Oak Ridge National Laboratory in the 1950s and 1960s. The Molten Salt Reactor Experiment (MSRE) operated successfully but was discontinued in the 1970s due to shifting priorities and funding.
Alvin Weinberg believed that light-water reactors (LWRs) were extremely risky and identified issues with loss-of-coolant accidents (LOCA), core meltdowns, and containment breaches, as well as inadequate scaling of containment structures. The complex nature added to the risk of human error. “Can we develop nuclear reactors whose safety is deterministic, not probabilistic, and which, if developed, would meet the public’s yearning for assurance of safety, not simply assurance of the probability of safety?” he asked. His proposed reactor uses liquid sodium as opposed to water as coolant, allowing the reactor to operate at a lower pressure, reducing risk.
Former President John F. Kennedy believed that succeeding in producing a feasible molten salt reactor was “very remote” after the US Air Force spent $1 billion ($7 billion today) from 1946 to 1961 on the Aircraft Nuclear Propulsion program. The US government may have abandoned plans to study molten salt nuclear reactors, but the Canadian, Indonesian, and Chinese governments have invested tens of millions into developing the technology. None other than Bill Gates funded the nuclear venture Terrapower that has produced a molten chloride fast reactor, tying this into his climate change campaign.
China created the first fully operational thorium molten salt reactor in 2024 and remains the only nation to have successfully completed the project. This year, the Chinese government produced a live-refueled reactor and plans to construct a larger 10 MW version by 2030. China announced its thorium discovery one month after scientists announced their groundbreaking achievement.
So I stand corrected—China is not on its way to becoming the world’s leading nuclear super power—China IS the world’s leading nuclear super power.
