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

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

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

that has 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 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 that of 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 fueld 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

now 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 fueled reactors and i was interested and asked if i could borrow it

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 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

fluorides are remarkably chemically stable

they do not react with air and water you have to heat them to 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 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 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 to prevent a meltdown as we saw in japan

but in this reactor if you lose the power to the reactor it shut 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 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 a 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 can 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

the 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 and 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 can 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

when area the size of a football field would produce enough thorium each year

to power the entire world

using the LFTR 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 much 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 LFTR 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 web site where a growing enthusiastic community

of thorium advocates is working to tell the world

about how we can realize the clean safe and sustainable energy future

based on the energies of thorium thank you very much