Welcome to Nuclear Update.

This week, I’m writing to you from my honeymoon in South Africa, currently posted up in Cape Town, where the wine is excellent and the nuclear debates are still raging (in my inbox, anyway).

But you didn’t think I’d skip a chance to nerd out about thorium, did you?

So today, we’re cutting through the hype and breaking down what thorium reactors actually are, how they work, and whether they live up to the buzz.

But first let’s see how much you know about thorium already:

Last week, I asked: What does “TRISO” stand for in nuclear fuel technology?

You said: 

🟨🟨🟨🟨🟨🟨 TRi-reactive ISOtopic oxide (28%)

🟨🟨🟨🟨🟨🟨 Thermally Resistant Isotropic Sphere Object (27%)

🟩🟩🟩🟩🟩⬜️ TRi-structural ISOtropic particle (25%)

🟨🟨🟨🟨⬜️⬜️ TRIple-layered radioactive Silicon Oxide (20%)

Now, let’s dive into the good stuff!💥

⚛️What’s the Deal with Thorium Reactors?

Thorium is often described as “the better uranium.” It’s more abundant, less radioactive, and doesn’t come with the same proliferation baggage. So why isn’t the world running on thorium already?

Let’s rewind a bit.

Thorium (element 90, Th) is a naturally occurring radioactive metal, and unlike uranium-235 or plutonium-239, thorium isn’t fissile on its own. That means it can’t sustain a chain reaction by itself.

But! It is fertile. Which means if you hit it with neutrons, it transforms into uranium-233, a highly fissile isotope that can fuel a reactor. And that’s the whole idea behind thorium reactors.

It’s not a one-step process. It’s a fuel cycle.

Thorium Fuel Cycle 101

1. Start with thorium-232

2. Bombard it with a neutron

3. It becomes thorium-233, which then decays to

4. Protactinium-233, and finally into

5. Uranium-233, which can fission and release energy

Thorium reactors are basically U-233 production machines that then burn the U-233 they create. Pretty neat.

Thorium fans love to say it’s safer, cleaner, and more abundant. And they’re not wrong:

Abundant: Thorium is about 3–4 times more common in the Earth’s crust than uranium.

Efficient: It converts more of the fuel into energy, meaning less waste overall.

Proliferation-resistant: Produces less plutonium than traditional fuel cycles.

Passive safety: Most thorium designs are based on liquid fuel, which can be drained in an emergency to stop reactions instantly.

But there are challenges

No existing supply chain: Unlike uranium, there’s no infrastructure for thorium mining, fuel fabrication, or reprocessing. It’s a “chicken and egg” situation: no thorium reactors means no thorium fuel demand, which means no incentive to build thorium fuel supply chains.

U-233 purity issues: U-233 is a great fuel, but it can also be weaponized if isolated. To prevent that, many thorium cycles intentionally “contaminate” the U-233 with uranium-232, which emits intense gamma radiation, making it hard to handle and unattractive for weapons use. Still, it complicates fuel management.

Delayed gratification: The Pa-233 intermediate has to sit quietly for weeks while it decays into usable U-233. If the reactor is still running, it can absorb another neutron and turn into something useless. This means online chemical separation is often needed, which adds complexity.

💡Enter: Molten Salt Reactors

If thorium is the fuel of the future, molten salt reactors (MSRs) are the machine to burn it.

Instead of relying on solid uranium rods and pressurized water coolant, MSRs dissolve nuclear fuel directly into a circulating liquid salt. This design lets them run at atmospheric pressure and much higher temperatures, opening the door to safer, more efficient operation.

There are two main flavors. Liquid-fueled MSRs dissolve thorium or uranium in molten fluoride or chloride salts, so breeding and fission can happen in real time, fuel is created, burned, and replenished in a continuous cycle that generates little waste. Solid-fueled MSRs, on the other hand, use salt purely as coolant while the fissile material stays in TRISO particles or other solid forms.

The technology’s appeal comes from a set of unique advantages. If a liquid-fueled MSR overheats, the molten salt expands and naturally slows the chain reaction, providing built-in stability. Most of these designs also feature a clever safety feature: a “freeze plug”, a cooled section of pipe that melts at high temperatures, draining the liquid fuel into a passively cooled storage tank where the reaction stops instantly.

Because MSRs operate at low pressure, they avoid the explosive failure risks of conventional reactors.

And whether they use solid or liquid fuel, MSRs can achieve high burn-up, squeezing out more energy and producing less long-lived waste.

Some designs even support online refueling, letting operators add or remove fuel without shutting down, a major boost to uptime and efficiency.

🇺🇸 The U.S. Had One In the 1960s

This isn’t new sci-fi stuff. The U.S. built and ran a working molten salt reactor at Oak Ridge National Laboratory from 1965 to 1969. Known as the Molten Salt Reactor Experiment (MSRE), it proved the core technology and demonstrated thorium breeding using uranium-233.

It ran for over 13,000 hours without major incident. But the political and military priorities of the time, namely plutonium production for bombs, meant thorium never got funding momentum. The MSRE was decommissioned, and uranium stayed king.

Still, the engineering foundations were solid. And today’s private sector startups are building directly off those designs, with modern upgrades for passive safety, digital controls, and scalable deployment.

🌍 Who’s Working on Thorium Right Now?

While thorium isn’t commercially mainstream yet, there are serious developments unfolding across several countries:

🇮🇳 India: The Long Game

India has the world’s largest thorium reserves, and it’s been planning a three-stage nuclear program around it since the 1950s. The current focus is on developing the Advanced Heavy Water Reactor (AHWR), a 300 MWe design that will use thorium-232 and plutonium-239.

Progress has been slow, but steady. The Bhabha Atomic Research Centre (BARC) continues to run thorium test reactors, and Indian policy circles still see thorium as a long-term strategic asset.

🇨🇳 China: Quietly Scaling

China began operating a 2 MW thorium molten salt test reactor in the Gobi Desert in 2021, developed by the Shanghai Institute of Applied Physics.

The country has plans to scale up to a 100 MW commercial unit, within the next five years. If successful, this would be the first real-world test of thorium-fueled MSRs at commercial scale.

Beijing sees thorium as part of its long-term diversification strategy, particularly for desert regions and remote installations where SMRs make more sense than large LWRs.

🇺🇸 United States: Private Sector Momentum

The U.S. doesn’t have a government-backed thorium program, but startups are pushing the envelope.

Flibe Energy is working on a thorium molten salt reactor designed to operate with passive safety features and onsite fuel recycling.

ThorCon (with U.S. roots and operations in Southeast Asia) is pitching a 500 MWe thorium MSR design, backed by shipyard manufacturing to reduce costs.

Several U.S. national labs have also supported R&D on thorium fuel cycles in cooperation with DOE funding, though uranium remains the near-term focus.

🇳🇴 Norway: Thorium Tests in LWRs

Thor Energy has tested thorium-MOX fuel in conventional light water reactors, a hybrid approach that could help bridge the transition between uranium and thorium cycles.

The idea is simple: if you can run thorium fuel in existing infrastructure, the barrier to entry drops dramatically. Early results are promising, and further tests are underway.

🔮Is Thorium the Future?

One of the most common questions I get from Premium readers is: “If thorium is so promising, is uranium becoming obsolete?”

Short answer: nope.

Thorium is exciting, especially when paired with advanced reactors like MSRs.

But it’s not a silver bullet. It doesn’t fix the real deployment bottlenecks: permitting, financing, and global supply chains.

It’s a better fuel, sure, but we still need the machines to burn it, and the infrastructure to scale it.

Thorium isn’t going to “replace” uranium anytime soon.

We already have nearly 500 commercial reactors around the world running on uranium. Many are being extended past their original 40-year licenses, and others are being restarted or uprated. All of them need a steady supply of uranium fuel, and they’ll continue to run for decades even after thorium reactors become standard.

Meanwhile, of the 60+ large-scale reactors currently under construction, none are thorium-fueled. Every single one is a uranium-based design.

If anything, the real answer is: we need both. Thorium may play a growing role in the long-term future, but uranium is the foundation of the nuclear fleet we already have and the one still being built.

📈 Tracking the Future of Fuel, Including Thorium

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DISCLAIMER: None of this is financial advice. This newsletter is strictly educational and is not investment advice or a solicitation to buy or sell any assets or to make any financial decisions. Please be careful and do your own research