What if I told you that, right now, right here in America, we have lots of a carbon-free fuel that could power our electrical grid for thousands of years to come. What if I told you that a pound of this fuel contains a million times more energy than a pound of coal. In fact, a mere ounce of it contains more energy than a typical American family consumes in an entire year. Would you be interested?
Might it also pique your curiosity to know that if we were to generate electrical power from this abundant resource, we would emit no greenhouse gases to the atmosphere. Well, if you’re like me, I’d like to know: it’s Thorium.
But what’s the catch? Why aren’t we utilizing thorium to help meet our nation’s energy needs? According to the U.S. Geological Survey, America has about one-fifth of the world’s supply of economically mine-able thorium reserves. The energy contained in America’s reserves alone is roughly equivalent to 1 trillion barrels of oil. So, what’s holding things up?
A quirk of cold war history is partly to blame. Since the super-secret Manhattan Project of the 1940s to build an atomic bomb, our government’s atomic energy research has focused primarily on weapons development. Very early on, atomic scientists realized that uranium—thorium’s famous radioactive cousin—can be more readily weaponized into an atomic bomb than can thorium. So, uranium—as well as the highly radioactive elements such as plutonium that can be made from uranium—garnered nearly all our attention. Because thorium doesn’t lend itself for making bombs, and in general has very limited commercial uses, research into thorium was given short shrift for decades.
Before we begin to explore how we can use thorium as a nuclear fuel, here is some background information. Thorium was discovered in 1828 by the Swedish chemist Jons Jakob Berzelius, who named it after Thor, the Norse god of thunder. Monazite, which contains between six to twelve percent thorium phosphate, is the most common source of thorium. Thorium is only weakly radioactive. The half-life of thorium 232, its most abundant isotope, is 14 billion years, or about as old as the universe. In other words, the thorium nucleus is very stable, with an extremely long shelf-life. And very importantly, thorium is not fissile. It cannot sustain nuclear chain reactions, unlike, for example, uranium 235, which is fissile and is used in making bombs and nuclear fuel rods. Furthermore, it very difficult to derive weapons-grade plutonium from thorium; it’s much simpler starting from uranium. So you can see why thorium has languished quietly on the shelves of our National Energy and Defense Laboratories, and in academia, too.
But I believe this neglect is about to change. Why? Molten salt reactors. New advances in this promising nuclear reactor technology are opening the door for thorium to become a major player in safe, reliable, carbon-free power generation.
Unlike conventional nuclear reactors that use solid fuel rods, molten salt reactors (MSRs) operate with the nuclear fuel in the liquid state. Using thorium formulated in liquid nuclear fuel generates less than one percent of the nuclear waste of conventional solid fuel rod nuclear reactors that use uranium. And this thorium waste is much more benign. Conventional reactors generate waste that is highly radioactive for 10,000 years or more. This makes safe storage of the waste very difficult, if not impossible. On the other hand, the radioactivity of the waste from a thorium MSR nuclear reactor dissipates much more rapidly, within several hundred years, making secure storage doable.
MSRs provide other phenomenal safety advantages over conventional nuclear reactors. Without going into great detail, here are a few examples of the advantages of molten salt reactors.
Unlike conventional nuclear reactors, MSRs operate in the absence of water. By eliminating the need for water as a coolant and moderator, the reactor building does not have to be designed to withstand a high-pressure steam explosion that would eject radioactive materials into the atmosphere. Further, water decomposes into extremely flammable hydrogen gas when exposed to the extremely hot reactor core. Eliminating water eliminates the risk of hydrogen gas explosions like those that occurred in the Fukushima nuclear plant disaster.
Perhaps the most important feature of MSRs is that they are “walk-away safe.” Unlike conventional nuclear reactors, the rate of nuclear fission in an MSR is inherently stable. State-of-the-art MSR reactor cores cannot “melt down” like conventional reactor cores when temperatures get too high. Molten salt reactors have passive systems that will shut the nuclear reactions down, without human intervention, when something goes terribly wrong. In the event of a major accident, loss of electrical power and reactor control, or deliberate attack or sabotage, the radioactive molten salts will drain away from the reactor core and solidify in storage tanks buried on site, minimizing radioactive releases to the environment.
Much of the enormous size (and thus the cost) of conventional nuclear reactors is devoted not to power generation but to building mandated safety features. Because MSRs are so much safer, they can be built much smaller, even modular!
I know we have a national phobia about nuclear power, some of which is justified. What is more horrifying than the sight of a radioactive mushroom cloud on the horizon? None of us wants to be exposed to air, water, soil, and food contaminated with radioactive fallout. And we don’t want weaponizable nuclear materials falling into the wrong hands.
According to most climate scientists, burning fossil fuels to power our economy poses an existential threat to our way of life on Earth. Wouldn’t you agree that thorium deserves a fresh look. Thorium itself is quite safe. It cannot, in and of itself, trigger a nuclear explosion. In fact, it itself is not directly a nuclear fuel! It is what nuclear scientists call “fertile,” meaning that thorium can be transmuted into fissile uranium 233. It is uranium 233 derived from thorium 232 that is the actual nuclear fuel used to generate power in an MSR!
In summary, we need safe, reliable, environmentally benign, and cost-efficient ways of generating electrical power. Renewable energy from solar and wind are part of the answer. But solar and wind have a major drawback. They are inherently unreliable. They do not generate energy when the wind isn’t blowing and the sun isn’t shining. In theory, we could store excess energy generated by solar and wind and tap into these reserves later when needed. But in practice, we have nowhere near sufficient battery storage capacity to provide backup power to fill the breach. Today, fully charged, all the batteries in the world would satisfy the global appetite for electricity for less than one hour. After that, the lights would go out.
What are we then to do? I suggest that thorium provides an attractive alternative to fossil fuels worth taking a look at. Others agree, and are doing just that. Four companies in North America have plans to build commercially operational MSRs to generate electricity, and France, Japan, Russia, and China have all shown interest in developing and deploying MSR technologies, technologies that can use thorium.
The biggest obstacle to deploying carbon-free nuclear power in the 21st century is not our lack of scientific knowledge or technological expertise, it’s the difficulty in changing our hearts and minds from fear to hope. Paraphrasing the lyrics of the late John Lennon, I, along with a small but enthusiastic cadre of scientists, engineers, and environmentalist are singing, “All we are saying, is give thorium a chance.”