While nuclear power raises fear among many of us, it’s considered one of our better options for a reliable, carbon-free future. Alongside small modular reactors, molten salt reactors (MSRs) that use Thorium as a fuel, are considered cheaper, cleaner and safer options to the traditional reactors fueled with the highly radioactive elements and can benefit a nuclear energy expansion. With experimental tests scheduled for a Thorium-reactor in China and US companies developing projects that should be spinning up in the next few years, let’s revisit Thorium energy and molten-salt reactors, and when we’ll be able to see their impact. Could Thorium reactors build a cheaper and safer future for nuclear power?
In 2020, I produced a video on Thorium reactors explaining what they are, why people were excited about them, and if they could really be the future of green energy. But at that time, at least here in the U.S., we hadn’t seen significant progress in projects involving molten salt reactors. For example, in 2019 the construction of the experimental power plant for the traveling-wave reactor (TWR) developed by TerraPower was suspended. That was a significant loss for the company, considering that the cost to demonstrate a reactor like that was about a billion dollars according to the CEO of TerraPower, Chris Levesque. 1
Also, due to the technical and practical challenges of molten salt reactors, Lin-Wen Hu, director of research and irradiation services at MIT’s Nuclear Reactor Laboratory had said:
”There is still a lot of work to be done in terms of demonstrating molten-salt reactor technology, even for uranium-based reactors. Molten-salt reactors need to be demonstrated with a uranium fuel cycle before that system can be used for a thorium fuel cycle. Moving toward a thorium fuel cycle has a lot of unknowns.” -Lin-Wen Hu, director of research and irradiation services at MIT’s Nuclear Reactor Laboratory 2
But since then there’s actually been some progress.
Before we take a deep dive into recent news on thorium and molten salt reactors, let’s quickly review what they are, how they work, and what pros and cons they have. That means getting into the chemical concepts behind the operation of these rectors.
You’re probably aware that nuclear reactors are responsible for containing and controlling nuclear fission, which is a process where atoms split and release energy in a chain reaction. In short, atoms are bombarded with neutron particles, fissioning the atoms into two smaller atoms and some additional neutrons. Some of those neutrons go on to hit other atoms … and this cycle keeps going.
Inside the nuclear reactor is a robust steel vessel containing the reactor core where the fission occurs. It uses a fuel that’s usually a radioactive metal like Uranium-235 (U-235) or Plutonium-239 (Pu-239). Along with the core is a moderator, that’s usually water or graphite, which is used to reduce the speed of the neutrons coming from the fission process in order to feed the chain reaction. The heat generated by the reaction in the core is used to create steam to turn a turbine and generate electricity.3 4
In order to ensure safety in the nuclear reaction, reactors have control systems called “rods” that speed up or slow down or even stop the nuclear reaction if necessary. The control rods are typically made out of neutron-absorbing materials like silver and boron, but the element that’s used depends on mechanical and lifetime characteristics, the neutron energy inside the reactor, and how it resists neutron-swelling.4 5
If something goes wrong while controlling the nuclear reaction, this can cause the reactor’s core to meltdown due to excessive heat produced from the chain reaction. And this can be catastrophic, like what happened with Three Mile Island, Chernobyl, or Fukushima. And all of these accidents haven’t helped public perception, which has held back interest in pushing nuclear power policy ahead.
This is where Thorium-fueled reactors have an edge over other nuclear energy technologies.
Thorium-fueled reactors offer a potentially safer, cleaner, and more abundant alternative to traditional reactors fueled with the highly radioactive elements.
Thorium is a naturally occurring, slightly radioactive metal that was isolated in 1828 by the Swedish chemist Jons Jakob Berzelius. It was 60 years later that the reactive nature of Thorium was discovered by Gerhard Schmidt and Marie Curie. Thorium is found in small amounts in most soils and rocks, where it’s about three times more plentiful than Uranium. The most common source of Thorium is monazite, a rare-earth phosphate mineral that contains up to 12% Thorium phosphate. 6 7
Th-232 is the most stable of the 27 Thorium isotopes, which decays very slowly. This isotope isn’t itself fissile and so it can’t be used directly in a thermal neutron reactor. However, when absorbing a neutron, Th-232 will transmute to Th-233, which beta decays to Protactinium-233 (Pa-233).
There’s a whole chemistry class in here, which goes beyond the scope of this video … and my brain, but anyway …
After Th-233 beta decays once, it undergoes a second beta decay to become Uranium-233 (U-233), which is an excellent fissile fuel material. This fuel cycle is very important to molten salt reactors because most of the proposed reactors rely on this cyclical process.7 8 9
One big benefit of Thorium reactors is the much smaller half-life of the nuclear waste. U-233 can be separated from the Thorium, which sets it apart from U-235 and U-238. It’s U-235 that contains very radioactive isotopes with half-lives of thousands of years. A standard nuclear reactor’s waste needs to be stored safely for up to 10,000 years until the isotopes decay. On the flip side, the waste from a Thorium reactor is radioactive for about 500 years.10
Another benefit of Thorium breeding Uranium-233 is that it can be used in other types of nuclear reactors like Heavy Water Reactors (PHWRs), High-Temperature Gas-Cool Reactors (HTRs), Boiling Water Reactors (BWRs), Pressure Water Reactors (PWRs), and more. Even so, the main reactor type that’s being explored for Thorium is Molten Salt Reactors (MSRs).7
There are many different types of MSRs, including the Molten Salt Breeder Reactor, which is commercially known as a Liquid Fluoride Thorium Reactor (LFTR). While conventional nuclear reactors use solid fuel, LFTRs use a liquid fuel in the form of very hot fluoride salt that also serves as the coolant, and also operates at low pressure. In these reactors, rather than solid fuel rods, Thorium is dissolved into the liquid fluoride salt before sending it into the reactor chamber at temperatures above 1,112ºF, equivalent to 600ºC.11
A great benefit of these reactors is that they can self-regulate the process to maintain the temperature within an appropriate range. As the temperature in the reactor goes up, the rate at which the fission reactions occur goes down. In addition, the liquid fuel is run through a reaction chamber filled with graphite rods that reduce the speed of neutrons, and if these rods are removed, the chain reaction stops. It’s a more reliable emergency braking system than traditional nuclear reactors.
Another benefit is the increased fuel efficiency in LFTRs. Because there is no cladding, there is little neutron loss, meaning all neutrons are used in the reaction, not for crashing into the cladding. This increases overall efficiency and the life of the fuel.
In order to make MSR even safer, there’s a freeze plug safety mechanism built into the reactor plumbing. So if this plug is taken out, the reactor salt goes down the drain … so to speak. Imagine that a natural disaster happens, and the nuclear power plant undergoes a blackout, the reactor would safely power down without the need for any human intervention. 12 13
The interest in Thorium isn’t just for its potential safety. Although we don’t have a commercial reactor operating currently, it’s expected that Thorium-fueled reactors will have a lower price than traditional fission reactors. From the economics perspective, Thorium-fueled reactors make sense for several key reasons.
First, these systems operate at low pressure and high heat capacity, which means the containment vessels can be smaller and thinner. Also, Thorium-fueled reactors require fewer components for fuel assemblies; they’re basically composed of just vats of fuel, making them simpler and cheaper to build. To make it better, due to their operation at high temperatures, the heat losses are lower, so the efficiency goes up. Finally, while conventional reactors need to be shut down for refueling, LFTR can be refueled while operating at full power.14
While there are some major advantages to Thorium-fueled reactors, they aren’t perfect and there are several challenges that have been holding back their mainstream adoption.
The main concern with MSRs is that radioactive fission products could potentially leak from the containment vessels. They are just in a big, sealed vat. Traditional reactors keep their fuel in solid pieces surrounded by cladding. On top of that, these nuclear plants will require periodic maintenance, but all of the equipment will contain high levels of radioactivity, which can make maintaining the components harder and riskier. Also, there’s a proliferation risk because Thorium makes Uranium-232, which emits gamma rays. This irradiation process can be altered slightly by removing Pa-233, forming U-233, which could be used in nuclear weapons. Another concern is that while Thorium is more plentiful than Uranium, it is more expensive to mine. 15 14
Despite these challenges, the several pros of Thorium reactors have resulted in some projects being developed around the globe. Let’s take a look at what’s changed since my last video on Thorium energy.
Some countries like France, India, Japan, Norway, and the U.S. have reported some development on Thorium nuclear reactors, but there are no plans for their commercialization yet.
On the other hand, China is closing in on Thorium energy. It launched its molten-salt reactor program in 2011, investing $500 million. The Chinese government has been developing an experimental reactor based on an MSR technology developed by researchers at Oak Ridge National Laboratory (ORNL) in the 1950s. Originally designed for aircraft propulsion in the Manhattan Project, the ORNL’s 7.4 MWth (Megawatt thermal) output experimental reactor ran for over four years. The project was closed due to a corrosion problem and cracked pipes caused by the hot salt, as well as the weak radioactivity of Thorium. These issues made fission reactions unsustainable without adding Uranium. China has put modern technology to use with better materials, instrumentation and controls in order to build its reactor. 16
The experimental prototype generates 2 MWth, enough to supply 1,000 homes, and should have started in September 2021 in the Gobi Desert near the city of Wuwei. However, researchers working on the reactor haven’t confirmed whether the tests have already started. If the prototype works as designed, China has plans to build a commercial 373MW version by 2030. 17 18
In the U.S., the California-based Kairos Power plans to have a 50 MW demonstration reactor operational in Oak Ridge, Tenn. by 2026. The company received $303 million from the U.S. Department of Energy for the design, licensing, and construction of the Hermes low-power demonstration reactor.19 16 Kairos Power’s application for building the reactor will go through a review process with federal regulators. The reviews regarding safety and environmental impact should be completed by September 2023. 20
Also, in November 2021, Southern Company and the Department of Energy (DOE) came to an agreement on designing, building and operating the Molten Chloride Reactor Experiment, which will push forward the Molten Chloride Fast Reactor that has been developed by TerraPower. 21
By the way, TerraPower has announced that it will build its Molten-Salt Reactor in Kemmerer, Wyoming, where the coal-fired Naughton Power Plant has been closed. This 345MW reactor has been developed jointly with GE Hitachi Nuclear Energy, combining liquid sodium cooling and a molten-salt heat-storage system that will better integrate renewable energy. 22
According to the Thorium Reactor Market research report, the global Thorium market is expected to grow at a CAGR of 11.1% between 2021 and 2027. In addition, the global molten salt reactors market is projected to reach $18.7 billion by 2031 according to Visiongain Research Inc.23 24
When it comes to the levelized cost of electricity (LCOE), a study published in the International Journal of Sustainable Energy showed an LCOE of a Thorium molten salt reactor at $53.51/MWh with a 30-year lifespan. Comparatively, the study showed an LCOE for a pressurized water reactor (PWR) at $63.08/MWh for a 30-year lifespan, so according to the study, Thorium-based reactors could be a cheaper option among nuclear technologies. 25
There’s one added bonus that nuclear energy can bring us, and this was mentioned a lot in the comments on my nanotechnology and water desalination video I put out a little while ago, and that’s … water desalination. The heat generated by nuclear power plants combined with electricity can be used for water desalination, which means removing salt and minerals from seawater and turning it into potable water. Because molten salt reactors don’t use water to cool down the core, they don’t need a large water supply to run.26 27 Aquacraft, Inc and Terrestrial Energy made a study for the Kingdom of Jordan in order to build a MSR power plant that could produce 6.3 million MWh of electrical energy and 112,000 acre feet of water (137 million cubic meters).28 27
So it sounds like Thorium might be a win. But do we really need nuclear power to build a renewable energy future?
When compared to solar and wind, nuclear energy is still more expensive. The Levelized Costs of New Generation Resources in the Annual Energy Outlook 2021 from the EIA showed that for new resources entering service in 2026, onshore wind had an LCOE of $31.45/MWh, while solar was at $29.04/MWh without energy storage. With a four-hour battery system the price goes up to $42.18/MWh. It’s also important to consider that the cost for storing energy in batteries has been steadily decreasing, falling from $187/MWh in 2019 to $150/MWh in 2020 for a four-hour discharge time, which benefits intermittent power sources like solar and wind. 29 30
Even though nuclear power can provide stable electricity generation for the grid, these power plants are usually expensive, complex, legally challenging and take longer to build compared to solar, wind, and hydropower. With an average construction time of 6 years and the issues regarding nuclear waste storage,31 there are some hurdles to overcome. New investments and progress in Thorium and molten salt reactors make a compelling case for their potential benefits. However, there’s still a long road ahead in order to verify how they’ll perform in real life.
- Bill Gates’s Experimental Nuclear Power Plant Halts Construction in China↩
- Andrew Yang Wants a Thorium Reactor by 2027. Good Luck, Buddy↩
- NUCLEAR 101: How Does a Nuclear Reactor Work?↩
- How does a nuclear reactor work?↩↩
- Control rod↩
- Facts About Thorium↩
- Thorium fuel cycle↩
- Definition of beta decay↩
- The Thing About Thorium: Why The Better Nuclear Fuel May Not Get A Chance↩
- China is gearing up to activate the world’s first ‘clean’ commercial nuclear reactor↩
- Molten Salt Reactors↩
- Liquid Fluoride Thorium Reactors↩
- Molten Salt Reactors↩↩
- Thorium-based nuclear power↩
- China Says It’s Closing in on Thorium Nuclear Reactor↩↩
- China prepares to test thorium-fuelled nuclear reactor↩
- NEXT: A Thorium-fueled Nuclear Future?↩
- Governor Lee, Commissioner Rolfe Announce Kairos Power to Establish Low-Power Demonstration Reactor in Oak Ridge↩
- Southern Company, DOE to lead demonstration of molten-salt reactor↩
- China shows us the path to the nuclear future↩
- Bill Gates’ nuclear power company selects a site for its first reactor↩
- Thorium Reactor Market Research 2021 Global Impact Analysis Report With Terra Power, Thor Energy, Flibe Energy, General Electric↩
- Global Molten Salt Reactors Market is projected to reach at a Market value of US$ 18.7 Billion by 2031: Visiongain Research Inc↩
- Safe, clean, proliferation resistant and cost-effective Thorium-based Molten Salt Reactors for sustainable development↩
- Nuclear Desalination↩
- Molten Salt Reactors and Thermal Desalination to Transform Jordan↩↩
- How Molten Salt Reactors and Thermal Desalination Could Transform Jordan↩
- Levelized Costs of New Generation Resources in the Annual Energy Outlook 2021↩
- Behind the numbers: The rapidly falling LCOE of battery storage↩
- Economics of Nuclear Reactor↩