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I’ve been exploring different types of clean energy generation and storage in my videos
over the past few months, and a topic that has been mentioned a lot in the comments is
Thorium reactors. Thorium is often held up as one of the best paths forward for achieving
a mix of cheap, clean energy for our grid. Even former presidential candidate Andrew
Yang was pushing for Thorium reactors along with wind and solar. So what is it? Why are
there so many people excited about it? And is it really the future of clean energy?
I’m Matt Ferrell … welcome to Undecided.
In recent years we’ve seen a huge increase
in the amount of solar and wind power being added to the grid, which are viewed as the
ultimate clean energy power sources. And there’s a growing movement to provide better grid-scale
energy storage options to capture that energy generation for use at times when they may
not be producing enough energy. But some argue that’s not going to be enough, so nuclear
needs to be a part of the clean energy mix. It’s probably a good idea to quickly go
over nuclear energy, but just like I said on my fusion energy video, I’m going to
keep this higher level because nuclear physics is clearly a very complex topic that’s out
of scope for this video ... and it hurts my brain a little bit. As always, I’ll include
a link in the description to my research if you’re interested, but here’s how it works
at a high level. All fission based reactors use the same exact
process. It’s the result of an extra neutron slamming into a larger nuclide, which splits
it into two smaller nuclide. The splitting of the nuclide releases a massive amount of
energy and produces more loose neutrons. And those neutrons can start a chain reaction
by slamming into more nuclides to continue the process. It’s a nuclear chain reaction,
and that reaction generates heat. Nuclear reactors can then capture that heat to turn
water into steam, which then turns a turbine to produce electricity … all without producing
carbon emissions associated with climate change. But many today are scared off of nuclear energy
because of disasters like The Three Mile Island, Chernobyl, or Fukushima. All of which came
down to a failure in the cooling systems. U-235 is the common fuel source used today
and an out of control chain reaction can cause a catastrophic meltdown. And it’s this fear
around nuclear meltdowns that’s holding back public interest in increasing the number
of nuclear power plants. But what if there was a type of nuclear reactor that still had
no carbon emissions, produces nuclear waste with a dramatically shorter half-life, a fuel
source that's three times as plentiful, and ... oh ... wouldn’t have the same risk of
a meltdown? Enter Thorium So where and why does Thorium come into this?
Thorium is one of the 15 heavy metallic radioactive elements in the bottom row of the Periodic
Table of Elements and goes back to Swedish chemist Jons Jakob Berzelius who first isolated
Thorium in 1828. But it wasn’t until 1898 that Gerhard Schmidt and Marie Curie separately
identified Thorium’s radioactive nature. Th-232 is the most stable of the 27 Thorium
isotopes, which can be found in the minerals thoriate, thorianite, and monazite. For commercial
purposes Thorium is most often found from monazite mining, and is fairly abundant worldwide.
The countries with the highest estimated deposits are India, Brazil, Australia, and the United
States. So what sets it apart from U-235 that’s
used in nuclear reactors today? Well, U-235 is used because it’s highly fissile. The
neutron speeds can be controlled and slowed by using water as a coolant and regulator,
which increases the number of U-235 nuclides that split. Most uranium ore is U-238 and
only contains about 3-5% of U-235. When U-238 absorbs an extra neutron it turns into U-239
and then quickly into plutonium ... the material we use in nuclear weapons. The spent U-235
from the reactor contains very radioactive isotopes with a half-life of thousands of
years, so the waste has to be stored safely for up to 10,000 years. And with today’s
reactor designs, which in the U.S. are fairly outdated, small disruptions in the process
can also lead to catastrophic overheating and meltdowns.
Thorium on the other hand isn’t fissile, which means it’s not a good source for a
fission reaction. While it’s not directly usable in a fission reactor, when it absorbs
a neutron it decays into P-233 (Protactinium). Then it can be chemically separated into U-233,
which in turn can be used in a reactor and is very efficient for fission reactions. Thorium
is able to “breed” U-233. It's the ability to separate the U-233 from the thorium that
sets it apart from U-235 and U-238. We end up with a vast amount of waste from today's
reactors that needs to be stored safely. The waste from a thorium reactor is radioactive
for about 500 years compared to up to 10,000. All of this is what makes Thorium a unique
option for nuclear fuel because it’s more abundant than Uranium, can be turned into
usable fuel, and dramatically reduces the amount of nuclear waste.
There’s no shortage of reactor designs and concepts that can take advantage of Thorium
as a fuel source. Some of the reactor types you’ll find are Heavy Water Reactors (PHWRs),
High-Temperature Gas-Cool Reactors (HTRs), Boiling Water Reactors (BWRs), Pressure Water
Reactors (PWRs), Fast Neutron Reactors (FNRs), and Accelerator Driven Reactors (ADS). And
that’s still not all of them. But you can really narrow it down to two major categories
of reactor designs leading the way: Water (thermal) Reactors and Molten Salt Reactors
(MSRs). Probably the reactor type that gets the most
focus are Molten Salt Reactors, like the Liquid Fluoride Thorium Reactor (LFTR), which uses
Thorium fluoride in a salt-mixture that’s melted into a liquid. This is often referred
to as a “breeder” reactor design: Thorium goes in, fission products like U-233 come
out. It’s the liquid nature of the fuel that makes this type of Thorium reactor special.
It’s both the coolant and the fuel, so it can self-regulate the process to keep the
temperature from getting out of control. The simplest way to describe the how and why is
that the liquid fuel is run through a reaction chamber filled with graphite rods. These graphite
rods are acting as a fission moderator because they’re slowing down the speed of the neutrons,
which increases the probability of a fission reaction. Remove the graphite rods from the
equation and the fission chain reaction stops. This is the biggest safety benefit over the
traditional nuclear reactors we have in use today. Thorium-based reactors are safer because
the reaction can easily be stopped and they don't operate under extreme pressure. In the
event of a catastrophic incident in a Liquid Fluoride Thorium Reactor, it will automatically
drain the liquid fuel into a tank away from the graphite … stopping the reaction. There’s
essentially a walk-away safety factor to thorium reactors like this.
So why aren’t we seeing Thorium reactors everywhere? In fact, why aren’t we seeing
ANY Thorium reactors in commercial use at all? There’s varying levels of interest
and investment into Thorium reactors around the world. While the principles have been
understood for a long time, there are still a lot of technical and practical challenges
to overcome, like finding materials that can contain the corrosive molten salts. Lin-Wen
Hu, from MIT’s Nuclear Reactor Laboratory said in a Wired interview:
”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 Countries like the U.S. haven’t viewed thorium
as a leading candidate for nuclear power historically, so there hasn’t been a lot of funding towards
the research. And looking at the history of why the U.S. settled on uranium as a fuel
source instead of on thorium goes back to the cold war with the Soviet Union. As I mentioned
before, uranium-fueled reactors produce plutonium, which can be refined into weapons-grade material,
which is used to make nuclear bombs. So the path the U.S. ended up going down has been
set for a long time, and shifting from a uranium-based infrastructure to a thorium-based one will
take time. But countries like China and India, that don’t have a long standing uranium
infrastructure, have been investing heavily into thorium. In 2009 China demonstrated the
potential of thorium-based fuels and has the first high temperature experimental fluoride
salt loop in operation. India has one of the largest thorium reserves in the world, and
has a 3-stage plan that focuses on reaching thorium reliance by the 3rd stage. In both
cases, it’s about countries establishing self-reliant forms of clean energy generation
to support massive populations. Solar and wind alone won’t be able to support the
rapidly growing baseline energy needs, which is why they’re investing so heavily into
next-gen nuclear reactors and thorium. While countries like the U.S. have been lagging
behind on thorium research compared to others, there is still interest. During his presidential
run, Andrew Yang made the case to invest $50 billion in the development of molten salt
nuclear reactors … wanting to get them online by 2027. And Bill Gates has been investing
heavily into next-gen nuclear. He invested in TerraPower in 2011, which is working on
a next-gen nuclear reactor called a traveling-wave reactor (TWR). The biggest game changer for
this reactor is the ability to use fuel efficiently without uranium enrichment, so it can use
depleted uranium and nuclear waste as a fuel source. We'd be able to reuse that waste we're
storing for 10,000 years. And the design could also work for thorium. Sadly, the test facility
they were building in China has been put on hold. The Trump administration has put a lock
on the potential for the Gates Foundation to keep nurturing China’s nuclear innovations,
but Bill Gates remains convinced that nuclear energy is our single greatest weapon to combat
climate change in the immediate future and requires significant investment into new designs.
And while not directly related to thorium, In May 2020, the US Department of Energy just
started a new project called the Advanced Reactor Demonstration Program (ARDP), which
is funding $230 million into next-gen nuclear. There's worldwide recognition that while solar
and wind are great and viable sources of clean energy, by itself they aren’t enough to
get us to a 100% clean grid quickly. A mix of solar, wind, energy storage, and nuclear
can help the world achieve that goal. There’s a lot of exciting potential around thorium,
and it’s going to be interesting to watch how this evolves in the coming years.
If you’re like me and enjoy puzzling through how this all comes together, and maybe even
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supporting the channel. And if you liked this video be sure to check
out my video on the truth about solid state batteries. There’s been a lot of hype around
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