Thorium, an alternative nuclear fuel

Kirk Sorensen shows us the liquid fuel thorium reactor -- a way to produce energy that is safer, cleaner and more efficient than current nuclear power.

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;

it drives farm machinery
and transportation energy.

Now, I spent 10 years working at NASA.

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 had 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 didn't really 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 a basic coolant.

This has 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 pressures, 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's simply what you have to do
if you want to generate electricity

using a water-cooled reactor.

This means 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 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 1,000 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.

The reactors we have today
use uranium oxide as a fuel.

It's a ceramic material
similar in performance

to the ceramics we use to make
coffee cups or cookware

or the bricks we use to line fireplaces.

They're 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 one percent
of the energy for 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.

Now, there's no lakes
or rivers on the Moon,

so if all of 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.

(Laughter)

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 the shelf,
"Fluid Fuel Reactors."

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 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 was pretty neat.

It used a mixture of fluoride salts
as a nuclear fuel,

specifically, the fluorides of lithium,
beryllium, uranium and thorium.

Fluoride salts 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 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 cool 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

and into another vessel
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 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 four 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 could 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.

And 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 need 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 could 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 3,200 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 three 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 liquid fluoride thorium technology,

we could move away from
expensive and difficult aspects

of current water-cooled, solid-fueled
uranium nuclear power.

We wouldn't need large,
high-pressure nuclear 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
five billion tons of coal,

31 billion barrels of oil

and five 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.

Thank you very much.
(Applause)