Nearly everyone in the world is part of some community whether large or small and all of these communities have similar needs. They need light, they need heat, they need air conditioning. People can’t function very well when it’s too hot or too cold. They need food to be grown or provided distributed and stored safely. They need waste products to be collected, removed and processed.
People in the community need to be able to get from one place to another as quickly as possible and a supply of energy is the basis for all of these activities. Energy in the form of electricity provides light and air conditioning. Energy in the form of heat keeps us warm and energy in chemical form provides fertilizer, drives farm machinery and transportation energy.
Now I spent 10 years at NASA and in the beginning of my time there in 2000 I was very interested in communities but this is the kind of community I was thinking of — a lunar community. It had all of the same needs as a community on earth would have but it had some very unique constraints and we had to think about how we would provide energy for this very unique community. There’s no coal on the moon. There’s no petroleum. There’s no natural gas. There’s no atmosphere. There’s no wind either.
And solar power has a real problem: the moon orbits the earth once a month. For two weeks the sun goes down and your solar panels don’t make any energy. If you want to try to store enough energy in batteries for two weeks it just simply isn’t practical. So nuclear energy was really the only choice.
Now back in 2000 I really didn’t know too much about nuclear power, so I started trying to learn. Almost all of the nuclear power we use on earth today uses water as the basic coolant. This had some advantages but it has a lot of disadvantages. If you want to generate electricity you have to get the water a lot hotter than you normally can. At normal pressure water will boil at 100 degrees Celsius. This isn’t nearly hot enough to generate electricity effectively. So water-cooled reactors have to run at much higher pressures than atmospheric pressure.
Some water-cooled reactors run at over 70 atmospheres of pressure and others have to run at as much as 150 atmospheres of pressure. There’s no getting around this. It is simply what you have to do if you want to generate electricity using a water-cooled reactor. And this means that you have to build a water-cooled reactor as a pressure vessel with steel walls over 20 centimeters thick. If that sounds heavy that’s because it is.
Things get a lot worse if you have an accident where you lose pressure inside the reactor. If you have liquid water at 300 degrees Celsius and suddenly you depressurize it, it doesn’t stay liquid for very long. It flashes into steam. So water-cooled reactors are built inside of big thick, thick concrete buildings called containment buildings, which are meant to hold all of the steam that would come out of the reactor if you had an accident where you lost pressure.
Steam takes up about 1000 times more volume than liquid water, so the containment building ends up being very large relative to the size of the reactor.
Another bad thing happens if you lose pressure and your water flashes to steam. If you don’t get emergency coolant to the fuel in the reactor it can overheat and melt. Now the reactors we have today use uranium oxide as a fuel. It’s a ceramic material similar in performance to the ceramics that we use to make coffee cups or cookware or the bricks we use to line fireplaces. They are chemically stable but they’re not very good at transferring heat. If you lose pressure you lose your water and soon your fuel will melt down and release the radioactive fission products within it.
Making solid nuclear fuel is a complicated and expensive process, and we extract less than 1% of the energy from the nuclear fuel before it can no longer remain in the reactor.
Water cooled reactors have another additional challenge. They need to be near large bodies of water where the steam they generate can be cooled and condensed. Otherwise they can’t generate electrical power.
There’s no lakes or rivers on the moon, so if all this makes it sound like water-cooled reactors aren’t such a good fit for a lunar community I would tend to agree with you.
You see I had the good fortune to learn about a different form of nuclear power that doesn’t have all these problems for a very simple reason: it’s not based on water cooling and it doesn’t use solid fuel. Surprisingly it’s based on salt.
One day I was at a friend’s office at work and I noticed this book on his shelf Fluid Fuel Reactors and I was interested and asked him if I could borrow it. Inside that book I learned about research in the United States back in the 1950s into a kind of nuclear reactor that wasn’t based on solid fuel or on water cooling. It didn’t have the problems of the water-cooled reactor. And the reason why it was pretty neat. It used a mixture of fluoride salts as a nuclear fuel, specifically the fluorides of lithium, beryllium, uranium and thorium.
Fluoride sales are remarkably chemically stable. They do not react with air and water. You have to heat them up to about 400 degrees Celsius to get them to melt but that’s actually perfect for trying to generate power in a nuclear reactor.
Here’s the real magic: they don’t have to operate at high pressure and that makes the biggest difference of all.
This means that they don’t have to be in heavy thick steel pressure vessels. They don’t have to use water for coolant and there’s nothing in the reactor that’s going to make a big change in density like water. So the containment building around the reactor can be much smaller and close fitting. Unlike the solid fuels that can melt down if you stop cooling them, these liquid fluoride fuels are already melted at a much, much lower temperature.
In normal operation you have a little plug here at the bottom of the reactor vessel. This plug is made out of a piece of frozen salt that you’ve kept frozen by blowing cooled gas over the outside of the pipe. If there’s an emergency and you lose all the power to your nuclear power plant the little blower stops blowing, the frozen plug of salt melts and the liquid fluoride fuel inside the reactor drains out of the vessel through the line into another tank called a drain tank. Inside the drain tank it’s all configured to maximize the transfer of heat so as to keep the salt passively cooled as its heat load drops over time.
In water-cooled reactors you generally have to provide power to the plant to keep the water circulating and to prevent a meltdown as we saw in Japan. But in this reactor if you lose the power to the reactor it shuts itself down all by itself without human intervention and puts itself in a safe and controlled configuration.
Now this was sounding pretty good to me and I was getting excited about the potential of using a liquid fluoride reactor to power a lunar community. But then I learned about thorium and the story got even better.
Thorium is a naturally occurring nuclear fuel that is 4 times more common in the Earth’s crust than uranium. It can be used in liquid fluoride thorium reactors to produce electrical energy heat and other valuable products. It’s so energy dense that you can hold a lifetime supply of thorium energy in the palm of your hand.
Thorium is also common on the moon and easy to find. Here’s an actual map of where the lunar thorium is located. Thorium has an electromagnetic signature that makes it easy to find even from a spacecraft. With the energy generated from a liquid fluoride thorium reactor we could recycle all of the air, water and waste products within the lunar community. In fact, doing so would be an absolute requirement for success.
We could grow the crops needed to feed the members of the community even during the two-week lunar night using light and power from the reactor. It seemed like the liquid fluoride thorium reactor or LFTR could be the power source that could make a self sustainable lunar colony a reality.
But I had a simple question. If it was such a great thing for a community on the moon, why not a community on the earth? A community of the future self-sustaining and energy independent, the same energy generation and recycling techniques that could have a powerful impact on surviving on the moon could also have a powerful impact on surviving on the Earth.
Right now we’re burning fossil fuels because they’re easy to find and because we can. Unfortunately they’re making some parts of our planet look like the moon. Using fossil fuels entangles us in conflict in unstable regions of the world and costs money and lives.
Things could be very different if we were using thorium. You see in a LFTR we could use thorium about 200 times more efficiently than we’re using uranium now, because the LFTR is capable of almost completely releasing the energy in thorium this reduces the waste generated over uranium by factors of hundreds and by factors of millions over fossil fuels. We’re still going to be liquid fuels for vehicles and machinery but we could generate these liquid fuels from the carbon dioxide in the atmosphere and from water much like nature does. We can generate hydrogen by splitting water and combining it with carbon harvested from CO2 in the atmosphere, making fuels like methanol, ammonia and dimethyl ether which could be a direct replacement for diesel fuels.
Imagine carbon neutral gasoline and diesel sustainable and self produced, do we have enough thorium? Yes, we do. In fact, in the United States we have over 3200 metric tons of thorium that was stockpiled 50 years ago and is currently buried in a shallow trench in Nevada. This thorium if used in LFTRs could produce almost as much energy as the United States uses in 3 years. And thorium is not a rare substance either. There are many sites like this one in Idaho where an area the size of a football field would produce enough thorium each year to power the entire world.
Using the liquid fluoride thorium technology we could move away from expensive and difficult aspects of current water-cooled solid fuel uranium nuclear power. We wouldn’t need large high pressure reactors and big containment buildings that they go in. We wouldn’t need large low efficiency steam turbines. We wouldn’t need to have as many long distance power transmission infrastructure, because thorium is a very portable energy source that can be located near to where it is needed.
A liquid fluoride thorium reactor would be a compact facility, very energy efficient and safe that would produce the energy we need day and night and without respect to weather conditions.
In 2007 we used 5 billion tons of coal, 31 billion barrels of oil and 5 trillion cubic meters of natural gas, along with 65,000 tons of uranium to produce the world’s energy. With thorium we could do the same thing with 7,000 tons of thorium that could be mined at a single site.
If all this sounds interesting to you I invite you to visit our website where a growing and enthusiastic online community of thorium advocates is working to tell the world about how we can realize a clean safe and sustainable energy future based on the energies of thorium.
