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  • 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

  • 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

nearly everyone in the world is part of some community whether large or small

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【TEDx】TEDxYYC - Kirk Sorensen - Thorium (【TEDx】TEDxYYC - Kirk Sorensen - Thorium)

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    阿多賓 發佈於 2021 年 01 月 14 日
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