Here's sodium.
Who wants to throw it in? Alright go.
Whoo! It lights on fire then it explodes.
Oh, no. I have some good friends in the nuclear industry
that are very big advocates of the fast-breeder reactor. The common name for it now is the
integral fast reactor. Personally, I'm not the biggest fan of a reactor that's full of
liquid sodium. It's stored under an oil to stop air or moisture
getting on it. It reacts very, very quickly with air and also with water. With the hydroxide
there's a white crust on the outside. It's fizzing around because it's generating
lots and lots of hydrogen gas. The heat from the reaction is burning away all of that hydrogen. You don't want to build a reactor out of stuff
that wants to burn, react, anything. You want to go, "Whatever I've made you out of, I want
it to be like the rock bottom of stability. I want there to be no step further down that
is chemically favorable because that's how things burn." The fast-breeder guys that use
sodium, because it doesn't slow down the neutrons. Everybody who is pushed in plutonium said,
"We want a fast reactor. That's the only way to do it." Notion of public being intimately involved
in very complicated technical issues which went way beyond the confidence of any member
of the public. Just in same that that was the right way to do it. The basic question
is, "Can modern intrusive technology and liberal democracy coexist?" The decision that was
acceptable is not something that we, technologists, can make. It's something that the public makes. A lot of people were daunted by new [inaudible
02:21] . There's no way we could learn this stuff. I don't want to do that class. It can
be too hard. These three clones are generally associated
with three different nuclear fuels. Liquid sodium-cooled reactors are fueled by natural
uranium. Water-cooled reactors are filled by enriched uranium. The molten salt reactors
can be fueled by thorium. The reactors deployed commercially around
the world are water cooled. Today, we use water to cool reactors, because we use enriched
uranium as fuel. We use enriched uranium as fuel in today's reactors, because they are
water cooled. Despite sodium's reactivity with both air
and water, it is, in some respects, a safer coolant than water. This is because our enriched
uranium-fueled, water-cooled reactors pressurize the water to raise its boiling point and drive
steam turbines more efficiently. If we didn't pressurize the water, then we'd
be using much more uranium and producing much more nuclear waste per watt of power. In addition to being a thorium guru Weinberg
was also the original inventor of the pressurized water reactor. It was a little bit of a tricky
thing to have the inventor of the light water reactor advocating for something very, very,
very different. As long as the reactor was as small as the
submarine intermediate reactor, which is only 60 megawatts, then containment was absolute. It was safe. But when went you went to 1,000-megawatt reactors, you could not guarantee this. Weinberg never really was crazy about the
light water reactor. He didn't like the fact that it had to run at really high pressure.
He figured there would be an accident someday where you were not able to maintain the pressure or keep cooling it. In some very remote situation conceive of
the containment being breached by this molten mass. A small valve in this collection of pipes
is stuck in an open position letting steam and water escape from the reactor core. It's
critical that the uranium fuel rods that make up the reactor core stay under water. A yellow tag covers an important light. They're convinced that the core is covered by water. A huge bubble of hydrogen is forming right inside the reactor vessel. The hydrogen was generated by reaction between air and the zirconium fuel cladding, and then the hydrogen ignited from some sparks. Kaboom! The whole building shudders. I mean the whole building, the plant building. Kaboom! Somebody says, "What was that?" An explosion had taken place inside the containment building. Those gaseous fission products came out and were released to the environment. Pregnant women and preschool-aged children
leave the area within a five-mile radius. It took a month to shut the reactor down,
but finally unit two was stone cold dead. The biggest environmental release at Three
Mile Island was krypton and xenon, but they don't have an uptake in the body. It scared
a bunch of people, but it didn't hurt anybody. It really comes down to which fission product
is it? I know it sounds particular. Number one, most dangerous is iodine because of the way it's taken up by the thyroid. There was a metallic taste in our mouth, an
acidity. They say radiation has no taste. It was only later we realized it was the taste
of radioactive iodine. Chernobyl was just a bad design in the first
place. Cory Arkin and a fellow engineer wrote an
article in the newspaper "Communist." It criticized the lack of safety in the design of the plants. They had these cylindrical graphite followers;
they called them, that kept the water out of the place where the control rod was in
the core. Well, they pulled it out so that the follower was out of the core, too. Now
all of a sudden they had water turning to steam, and the pumping system capitated. The power's rising, Alex. The power's rising. I only put the turbine in. It
was stable just now. We've had this. Let's stop it. Shut down the reactor! I'm trying to get it towards back in. Sir,
I'm shutting down the reactor. Well, there goes the test. How am I supposed
to explain that? I'm sorry, sir. It wasn't worth it. The power
was gone. I didn't know exactly... What was that? The rods haven't gone in. Well, let them drop in. I am doing it. I just don't know why they
didn't go in in the first place. I pressed the AZ button! They should
have gone in! Maybe... A series of detonations go off in the core
of the reactor. The explosion had thrown the 2,000-ton reactor lid in the air. It fell on edge into the mouth of the reactor vessel. Pieces of the core
were scattered all around. The core just burned for days. A lot of radio-nuclides
were released to the environment. The white flashes on these images are the
results of radioactivity on the film. People in the streets hardly can hide at the masked
soldiers scattered throughout the city. At first I was told there hadn't really an
explosion. The consequences of such false information were particularly dramatic. Windows and doors should be sealed and iodine tablets swallowed to counteract the effects of radioactivity, yet no such orders have
been given. Taking potassium iodide can help the thyroid
not absorb radioactive iodine. It prevents your thyroid from taking up the radioactive
stuff because it will be plum full of the not-radioactive kind. 30 hours after the explosion more than 1,000
buses arrived. The army announces the city is to be completely evacuated. It exploded when you hit the AZ button. Why didn't it stop the reaction? They say there wasn't a design flaw, but
how else do you explain it? They'd know. If they knew, they'd tell
us. They weren't aware of the facts. The potential
neutron surge as the graphite tips reentered wasn't known. Known by whom? Nobody told them. Nobody. Controllers are made of boron, but they're
tipped with graphite. Now in '83 a big lean on a similar reactor we found that in certain
circumstances when the graphite enters the water, it causes a power surge. A power surge. If you do stupid designs, something bad will
happen even after 40 years. A friend of mine was GE's first nuclear safety engineer.
He worked on the Fukushima plant, and they would have meetings with the TEPCO officials
and engineers. They would all nod their heads in long meetings and say, "Oh, yeah. We'll
do this. We'll do that." Then they'd go off after the meeting and do
whatever they wanted. That's why you had a 15-foot seawall with a 45-foot wave coming
over it and diesel generators and fuel in the basement. The earthquake that shook the Fukushima Daiichi
nuclear power plant was the most powerful to strike Japan since records began. The Japanese TV station's NHK offices across the country shook. I couldn't keep standing. Fires burned across the northern part of the
country as gas lines ruptured, and this oil refinery was engulfed in massive flames. The skyscrapers nearby were swaying like trees in the wind. The workers stayed calm because they knew
Japanese power plants are designed to withstand earthquakes. The reactors automatically shut
down within seconds, but nuclear fuel rods generate intense heat even after a shutdown.
Backup generators kicked in to power the cooling systems and stopped the fuel rods from melting. High-pressure water coolant reactors have
an abundance of safety systems designed to always keep the core covered with water. We
saw the failure of the Fukushima Daiichi. They had multiple backup diesel generators,
and each one probably had a very high probability of turning on at any given time. They were
there, several of them, so that if one didn't the next one would. If it didn't, the next
one would. Well, the tsunami came and knocked them all
out, and that's what called a common mode failure. At NASA we were always thinking about
how could we have a common mode failure that just trashes our idea of redundancy. Tepco had been warned by a government committee
of scientists in 2009 that its tsunami defenses were inadequate. [background noises] It was more than twice the height of the plant
seawall. The waves were relentless. [sea waves] Zooming everything in their path and watch
as it destroys an entire village while still burning fires ride the waves. Hundreds of
cars were swept along the current. Around 20,000 people were dead or missing.
The coastline was devastated. Most of the backup diesel generators needed to power the
cooling systems were located in basements destroyed by the tsunami waters. The workers
had no functioning instruments to reveal what was happening inside the reactor cores. All of us, we had a car rustic batteries. The [inaudible 11:56] batteries allowed vital
monitoring instruments to work again. The levels caused panic. Pressure was going up and up. Everyone thought,
"Isn't this dangerous?" The rising heat of the fuel rods and the reactor
core was creating massive amounts of radioactive steam and hydrogen. We begin by making these uranium oxide pellets,
and we formed them into fuel rods, plaid in this zirconium. It turns out the zirconium,
in certain conditions, can be quite reactive... With the water that's surrounding the reactor. We have a fuel and a coolant that are inherently
incompatible with one another. That's how we run nuclear today. As night fell, the Japanese government ordered
an evacuation of everyone within two miles of Fukashima Daiichi. Radiation levels were
now rising. This isn't inside the reactor itself. It's
in the office. The engineer suspected something that Tepco
would not acknowledge for months, nuclear meltdown have begun. The prime minister began
to suspect that Tepco was hiding the truth. He decided to go to Fukashima Daiichi himself. The prime minister met directly with the Tepco engineers. The radiation near the vents was at potentially fatal levels. His orders might
condemn the men who went into the reactor to death, but he felt Japan's future was at
stake. The workers found the wheel for opening the
vent. They inched it open. A thin, plume of gas signaled that the pressure on the reactor
core was falling. With the vent incomplete, the workers could focus on getting vitally
needed water into the reactor cores. Suddenly, the ground shook. Leaking hydrogen
had exploded the roof of the reactor building, but the reactor core itself was intact. Iodine tablets were being handed out in the
village. I made my daughter take one. The government widened the evacuation zone,
ordering everyone within 12 miles of the plant to flee. The explosion had already set back
average to get water into the melting cores of reactors one and two. Now, reactor three
was also in meltdown. Another hydrogen buildup meant the reactor three housing could explode
at any moment. Colonel Shinji Irokuma and his team's mission
was to inject water directly into the core of reactor three. Just as we were about to get out of the jeep
to connect the hose, it exploded. Our dosimeter alarms were ringing. Lumps of concrete came
ripping through the roof of the jeep. The soldiers were now surrounded by radioactive
debris. They were injured in the blast but managed to flee the scene before anyone received
a fatal dose. The Japanese prime ministered ordered a desperate
tactic, dumping water on the spent fuel pools from the air. Tungsten plates where in-bolted
to the helicopter to protect the pilots from gamma rays, but the wind was too strong for
accurate aiming. The Japanese government ordered a team of Tokyo fire fighters to park a truck
by the sea to suck up water and lay 800 yards of hose and leave it spraying into the fuel
pool. The route was blocked by tsunami debris. The
firefighters now had to lay the hose by hand. After an hour on site, the hoses were finally
connected. Radiation levels at the plant began to fall. The hundreds of workers who had been
on standby headed into the plant to lay miles of pipes. A steady flow of water at last started
to cool the reactor cores. The workers in the control center began to feel hope. Three Mile Island, Chernobyl, and Fukushima,
were all radically different incidents. What was similar at all three was how poorly water
performed as a coolant when things started to go wrong. This is not to say that water
coolant caused these accidents to occur, it did not. All three accidents were initiated
by different combinations of design and operator error. It was water coolant which allowed
these errors to multiply and ultimately result in the escape of radioactive isotopes into
the environment. At Three Mile Island, water couldn't be pumped
into the core, because some of the coolant water had vaporized into steam. The increased
pressure forced coolant water back out, contributing to a partial meltdown. At Chernobyl, the insertion of poorly-designed
control rods caused core temperature to skyrocket. The boiling point of the pressurized water
coolant was passed, and it flashed to steam. It was a steam explosion which toward the
2,000 ton lid off the reactor teasing and shotted up through the roof the building. At Fukushima, loss of power to the pumps allowed
coolant water to get hotter and hotter until it boiled away. These three accidents illustrate the need
for a coolant with a higher boiling point than water. It's only got 100 degrees of liquid range,
zero to 100 C. That's not really particularly impressive. To jack up water's liquid range,
you have to put it under pressure, because that's the only way to get water to go up
to 300 degrees C without turning into steam. Super high pressure is one of the basic challenges,
difficulties, flaws, whatever you want to call it of the water cooled reactor approach.
The salts, on the other hand, you have to heat them up to about 300 C before they melt.
Once they melt, they have 1,000 degree C of liquid range. Safety is one of the most important reasons
to consider very seriously molten salt reactors. This is because of the clever implementation
that was demonstrated in the molten salt reactor experiment of the freeze plug and the drain
tank. It was just a small port in the bottom of the reactor that was kept plugged by frozen
plug of salt. To keep the port plugged, they had a blower
that would blow cool gas over it. There's a little plug of frozen salt there. If the
power went out, the blower turned off, and the heat would melt the frozen plug. Guess
what. The fuel drained into this drain tank. The
difference between the drain tank and the reactor vessel was the reactor vessel was
not meant to lose any thermal energy. The only place you want it to lose thermal energy
was to give it up in the primary heat exchanger. The drain tank, on the other hand, is designed
to maximize the rejection of thermal energy to the environment. I'm a mechanical engineer, so all we ever
talked about in school was how to add heat to things and take heat out of things. One
of the hard things about designing nuclear reactors is to design it to not lose any heat
while you're running it, because you don't want to lose a bunch of heat in normal operation,
but then to turn around and try to keep it cool if something goes wrong. There are two conflicting things. The great
thing about liquid fluoride reactors is you can design them completely separately. You
can say, "Here's my reactor and it's designed to make heat, and here's my drain tank and
it's designed to cool in all situations." Better than having what's called deterministic
safety systems or engineered safety systems is to have inherent safety systems that will
work 100 percent of the time, because it is based on the laws of physics. A cooling system
that is completely passive, that does not rely at all on electrical power to manage
the decay heat after shutdown, it is always going to work because gravity is always going
to be turned on. Because it was not operating at high pressure,
this is a system that was tolerant of extraordinary damage. If you wanted to go in and jam a projectile
through the side of the reactor, the salt would still just drain out, now into a pan
but the pan would run back into the drain tank. In that situation, you're not going
to turn the thing right back on again. But it's not going to lead to a dangerous release
of radioactivity. At Three Mile Island, coolant water which
had boiled into steam reacted with the fuel rod cladding to produce hydrogen gas. This
led to several explosions. At Fukushima, steam also reacted with the fuel rod cladding to
produce hydrogen gas. This lead to hydrogen gas explosions at reactors one, two, and three. Let me diss on water a few more times. [laughter]
It's a covalently bonded substance. The oxygen has a covalent bond with two hydrogens. Neither
one of those bonds is strong enough to survive getting smacked around by a gamma or a neutron. Sure enough, they knock the hydrogens clean
off. In a water cooled reactor, you have a system called a recombiner that will take
the hydrogen gas and the oxygen gas that is always being created from the nuclear reaction
and put them back together. It's a great system as long as it's operating and the system is
pumping. Well, at Fukushima Diiachi, the problem was the pumping power stopped. H20 can also react with the fuel cladding
to release hydrogen and damage the cladding, releasing radioactive isotopes. These two
accidents illustrate the need for a coolant which is more chemically stable than H20. A nuclear reactor is a rough place for normal
matter. The nice thing about a salt is it is formed from a positive ion and a negative
ion, like sodium's positively charged and chlorine's positive charged and they go, "We
aren't really going to bond. We're just going to kind of associate one with another." That's
what's called an ionic bond. You're kind of friends. Facebook friends. [laughter] Facebook friends. Turns out this is a really
good thing for a reactor because a reactor's going to take those guys and just smack them
all over the place with gammas and neutrons and everything. The good news is they don't
really care who they particularly are next to as long. As there's an equal number of
positive ions and negative ions, the big picture is happy. A salt is composed of the stuff that's in
this column, the halogens, and the stuff that in these columns, the alkalis and the alkaliners.
Fluorine is so reactive with everything, but once it's made a salt, a fluoride, then it's
incredibly chemically stable and non-reactive. Sometimes people go, "You're working on liquid
fluorine reactors." No, I am not working on liquid fluorine reactors! We talking about fluoride reactors and there's a big difference between those two. One is going to explode,
the other one is super-duper stable. I see moving to molten salt fueled reactor
technology is a way to get rid of all the stored energy term problems that we look at
in today's reactors, whether it's pressure, whether it's chemical reactivity, even the
potential of the fission products and the fuel itself to be released. In fluoride fuel,
which is what we would use in a molten salt reactor, those fission products are bound
up very tightly in salts. Strontium and caesium are both bound up in
very, stable fluoride salts. Caesium fluoride, very stable salt. Strontium bifluoride, another
very stable salt. In light water reactors, cesium is volatile in the chemical state
of the oxide fuel of a light water reactor. That's been one of the concerns about cesium release. Cesium would not release from a fluoride reactor at all. Why are we using water to cool today's reactors?
If water coolant prohibits us from completely consuming uranium or thorium as fuel, why
did we start using it in the first place? The association between different nuclear
fuels and their respective coolants is because some nuclear fuel requires slow neutrons and
some nuclear fuel require fast. There really were three options for nuclear
energy at the dawn of the nuclear era. Only one of the materials in nature is naturally
fissile and that's uranium-235, which is a very small amount of natural uranium, about
0.7 percent. This was the form of uranium that could be utilized directly in a nuclear
reactor. Most the uranium was uranium-238. This had to be transformed into another nuclear
fuel called plutonium before it could be used. Then there was thorium. In a similar manner
to uranium-238, it also had to be transformed into another nuclear fuel, uranium-233, before
it could be used in a reactor. Nein, nein, nein, nein, nein, nein! This was wartime. They're plan was to make
bombs. They took natural uranium and they separated those two isotopes. They would highly
enrich uranium-235 from less than 1 percent up to like 90 plus percent. Too big factories,
very difficult to do isotopic enrichment, but this is how they made the uranium for
the first nuclear weapon used in war. This was the bomb at Hiroshima. It was called "Little
Boy." Then they said, "What could we do with all
this junk uranium-238, the 99.3 percent of it?" You could expose it to neutrons and you
could make it into plutonium. Now, plutonium is a different chemical element than uranium,
so they can be chemical separated. Uranium-235, uranium-238 are identical chemically. There's
no chemical difference between them. There is a chemical difference between plutonium
and uranium, so it was a lot easier to do a chemical separation of the plutonium you'd
made. That's how they made the Nagasaki bomb, which was called "Fat Man." Maybe we can do the same thing with thorium.
Maybe we can expose it to neutrons and we can make it into uranium-233, uranium will
be chemically separable from thorium, and we can go make a bomb out of it. Sounds great. It's a really bad idea because, as you made
the uranium-233, you were always making uranium-232. You didn't make a lot of it, you only made
a little bit of it, but uranium-232 is much more radioactive than uranium-233. In addition
to that, here's the decay chain that uranium-232 is on. It jumps down to bismuth-212 and thallium-208. These two decay products put out very, very
strong gamma rays. These gamma rays are just super bad news if you want to go and build
a practical nuclear device, because they tell everybody where the stuff is and they kill
you. Really quickly, they were going, "We can work with uranium-235. That seems OK.
We can work with plutonium. That seems, OK. But this uranium-233 stuff, that's bad news
for making a nuclear weapon." Thorium was just set aside. Run! "The Wolverine," PG-13. After the war, they picked up on this again
because now they were thinking, "Let's talk about making power instead of making nuclear
weapons." This is the fast region. This is the thermal region. Squiggly lines, blah,
blah, blah, and you could probably tell the entire history of the development of nuclear
energy in this one graph. I'll tell you why. How much energy did the neutron have that
you smacked the nuclear fuel with? How much energy did it have and then how many neutrons
did you kick out when you smacked it through fission? Two is a very significant number in breeder
reactors. You need two neutrons. You've got to have one to keep your process going, and
you have to have another one to convert fertile material into fissile material. Look at plutonium. Eh, it's that dip below
two right there. That's what makes it so you cannot burn up uranium-238 in a thermal spectrum
reactor like a water cooled reactor. You just can't do it. The physics are against you.
The reality is you do lose some neutrons. You can't build a perfect reactor that doesn't
lose any neutrons. They looked at this and they said, "Man, we
just can't burn uranium-238 in a thermal reactor. It just can't be done." These guys aren't
deterred. They said, "Here's what we'll do. We'll just build a fast reactor because look
how good it gets in the fast region. Wow, it gets above two. It gets up to three, wow!
This is really good!" There's a powerful disincentive to doing it
this way, and it has to do with what are called cross-sections. These are a way of describing
how likely it is that a nuclear reaction will proceed. Look how much bigger the cross-sections
are in thermal than they are in fast. How many of these little dots are we going to
need to add up to this size? We're going to need a lot. This is why it was a big deal
to be able to have performance in this region of the curve. Those little bitty dots, they're
up here in this part of the curve. This is the fast region. This is the thermal region. Thorium is more abundant than uranium. All
we're consuming now is that very, very, very, very small sliver of natural uranium. But this is not the big deal. No. It's not
a big deal that natural thorium is hundreds of times more abundant than the very small
sliver of fissile uranium. The big deal about thorium is that we can consume it in a thermal
spectrum. That's the big deal of thorium is that it can be consumed in a thermal spectrum
reactor. When you're talking about a thermal spectrum
reactor of any kind, you have to have fuel and you have to have moderator. They're both
essential to the operation of the reactor. The moderator is slowing down the neutrons. When the neutrons have been slowed down, we
call them thermal neutrons or a thermal spectrum. On a water cooled reactor, we use water, specifically
the hydrogen in the water, to slow down the neutrons through collisions. The graphite in the molten salt reactor, is
that a moderator? Yes, that's the moderator in the reactor. Same idea, except we have graphite as the
moderator instead of water. Neutrons go in the graphite, hit a carbon
atoms, they lose energy, they slow down. Why slow it down? That's the difference between
you're going from that little bitty dot to the big dot. That's why you want to slow it
down. You want the big dot, not the little bitty dot. A thermal spectrum molten salt reactor has
to have the graphite moderator of the core in order to sustain criticality. If the vessel
ruptures, recriticality is fundamentally impossible. The drain tank does not have any graphite
in it. If something happens where that fuel drains
away from that graphite, criticality is no longer possible. The reactor is subcritical,
fission stops, and there's no way to restart it without reloading the fuel back into the
core. This is such a remarkable feature, and it
really is unique to having this liquid fuel form and to having something that can operate
at standard pressure. You can't do this in solid fuel. If you do this in solid fuel,
that's called a meltdown. That's bad. Now, in a fast reactor on the other hand,
you don't depend on moderator. You put enough fuel in the reactor so the criticality is
possible even without moderator. In those scenarios, if there is a drain or a spill
or something, you need to be careful about what geometries it can get into because recriticality
is not from first principles impossible. It may be impossible in the design you design
but that becomes design-specific, whereas in thermal reactor, it is just impossible.
Outside of the lattice of moderator, you can't have a criticality set up. A thermal regent, look who's doing the best.
Look at uranium-233. Look at that. Look at plutonium. Eh. It's that dip below two right
there. You just can't do it. The physics are against you. But uranium-233 on the other
hand, yeah, it gets a little better in the fast but, dang, it's still pretty dang good
right there in the thermal. Big targets, lot easier. This fact was not well known probably until
about the '70s. There was some data that indicated it, but there was enough uncertainty, even
as late as 1969, that the Atomic Energy Commission did not feel like it was a safe bet to go
with thorium. Everybody who was pushing thorium said we
like thermal. This is the kind of reactor we want to build. Everybody who was pushing
plutonium said no, no, no. We want a fast reactor. That's the only way to do it. What
happened is they put resources into the plutonium breeder reactor almost from the get-go. They
built the experimental breeder reactor one in 1951. This was the first reactor that made
electricity. Four little light bulbs here. This is a mock-up of the core. This size was
giving off megawatts of thermal energy. How tall is this? How many meters? Eight inches. This is actual size? No, it's scaled down. No, that's full size. EBR-1. This was a breeder reactor. It was designed
to convert plutonium into energy while making new plutonium. This was not a light water.
This pre-dated the light water reactor by years. It was a fast creator. 1951. This is
a gen four reactor. No kidding. Early nuclear pioneers like Enrico Fermi and
Eugene Wigner saw the future quite a bit differently. Fermi believed that because of the performance
of plutonium, an especially because it could have a substantial breeding gain, in other
words, it could make more fission material than it was consuming, that we should really
focus our efforts on the fast breeder reactor. Eugene Wigner, on the other hand, looked at
these same pieces of information and reached a different conclusion, which was that thorium
was the superior fuel and that it should be realized in a thermal spectrum in a thermal
breeder reactor. This opened up a number of possibilities with coolants and reactor configurations. Thorium, in another way, was a rather unforgiving
fuel. It did not have a great breeding gain like plutonium had the potential in the fast
spectrum. You had to make sure you were very careful and conserving of your neutrons. You
couldn't waste a lot to losing neutrons to structural materials or losing them to leaks
out of the reactor or losing them to absorptions in the daughter products of fission. The thorium also had another challenge. It
took about 40 days, once it absorbed a neutron, to turn into uranium-233. There was a time
delay there between when it absorbed a neutron and when it became new fuel. Fermi wondered
how it would be the thorium would overcome this problem of the delay from when it absorbed
the neutron to when it became new fuel. Wigner had already seen a possible path forward,
which was to do something rather revolutionary. Build a nuclear reactor out of liquid fuels
rather than out of solid fuels. I believe part of this came from Wigner's educational
background. He was the only person, or almost the only person, who combined a great skill
as a nuclear physicist with great skill as an engineer. Wigner, of course, was a chemical engineer by training. He was the only one that commanded both of
those attributes. He was able to see both the engineering and physics aspects. He was
a chemical engineer by training and he knew that in chemical processes the reactant streams are almost always liquids and gases. They're fluids. In fluids, complete mixing is possible
and completion of the various chemical reactions are possible. He looked at the nuclear problem and wondered if the same principle might not apply. With a fluid fueled reactor, it would be possible to isolate protactinium-233 as it was formed and to allow it to decay and prevent it from
being destroyed before it could complete its transition to uranium-233. Wigner was not successful in convincing the
bulk of the nuclear community to take the thorium approach. They, by and large, said
we're going to go the plutonium route. One of the reasons why was they had developed
a great deal of understanding about plutonium from the weapons program. They had made the stuff, they had worked with its chemistry, and they had made fuel out of it. They go,
"We get this. Thorium, we haven't really messed with thorium. It would be like starting over." That propensity there was to go and do what
you already knew how to do. The plutonium was so much better developed than the thorium. Wigner was not terribly successful in making converts in the nuclear community, but he
did make one convert. This guy, Alvin Weinberg. He was a student during the Manhattan Project. Of course I had heard of Eugene Wigner as
this great particle physicist. I gradually became his assistant in charge of the nuclear
design. Weinberg got it. He got the big picture. He
got we need thorium, we need thermal reactor, we need liquid fuel. I see it. I see what
we've got to do. We visited with Mr. Rosenthal after we met
with you. He spent time in Washington DC with Milt Shaw, and that Milt actually had quite an affinity for Knoxville and Oak Ridge, but he wanted Alvin Weinberg and Oak Ridge to get on the
fast breeder funding wagon and Weinberg wanted to stay on with thorium and Walton Salts. It was pretty obvious that Shaw was completely convinced the LMFBR (liquid metal fast breeder), with its sodium cooling system, was going to be successful. If we
have a winner here, why spend money on what we know is going to be the loser? Everyone was so euphoric about the idea of
a fast breeder? That's the way it appeared to me. The Baroness has got a bunch of people over there from GE saying you've got to go build a fast breeder. The Russians are building them and we've built a couple of them. We've had a couple problems with them, actually. In principle, I guess you could go that route. But relative to the molten salt reactor, you've got a lot of fuel cycle infrastructure
you wouldn't need if you went with the molten salt reactor so I wouldn't do it. I wouldn't
build fast breeder reactors if I was the one deciding. In the US nuclear Navy program, they started
out with two reactor systems, one water cooled and one sodium cooled. It didn't take very long for the Navy to decide that they didn't want to deal with sodium cooling. They built a reactor and put it in a sub and
they ended up cutting the reactor out of the sub and putting the LWR in it. They became disenchanted with sodium cooling rather quickly. What happens if there's a leak? Sodium reacts with the air and the water. You haven't got air next door to the sodium
services. You can handle it with a freeze pads. You're not getting stuff from the core getting out into the air. People normally can't walk around the surface of this. If I've just got a little, tiny, thin pipe that can't let very much flow out you'll
have a different access availability than a big sodium pipe that's two feet in diameter
with several hundred pounds per hour flowing through it. What about the sodium? They're not dumb. You've got it, brother. You've got it. What's their answer? Fire suppression system.
If you've got a hot, liquid, combustible metal in your iPhone, lithium, why are you allowed
to walk around with it? Because lithium is in a stable compound. Actually, there's some YouTube videos of lithium
not being in a stable compound. [laughs] If I had a lithium battery and I expose it
to air it's not going to immediately catch on fire. Sort of uneventful. Oh well. A lithium battery catches on fire because
it shorts out. It shorts out. The point is, there's a known history of lithium
accidents, which are pretty bad. We don't ban them. I agree. I don't think the IFR was
the best possible solution in the world, but they did have a history of proving that it
could shut itself down. Total plant blackout. Simulated a complete blackout so the power
was lost to all cooling systems. For fast sodium reactors, you've always got
two separate loops. The primary gets radioactive from the core. You clean your dirty sodium? Yeah. Then it's the clean sodium that goes
to the steam generator. If you get a failure in the steam generator wall you haven't got
radioactive sodium. I got that. This thing here, there's lots
of heat sink test would be turning off the power to the secondary so you're not drawing
the heat out of the core/ You would shut down the tertiary, the water
system. The tertiary, OK. The sudden loss of flow
test, is that shutting down the intermediate? The loss of flow test is shutting off the
pump, just turning off the primary pump in here. The pump for the primary sodium? Yeah. It turns off the pump that's somewhere
in there. These two tests are turning off the primary
and turning off the tertiary? Yeah. At all times, the core was still bathed in
sodium? The sodium is turned on at all times. The
only thing you're doing is you're also doing it without SCRAM. Right, without control rods going in. Without control rods going in. This gets so
warm the fuel assemblies expand, the pins lengthen, they expand sideways, pressurizing
up against the core rigidity structure. Achieving a strongly negative temperature
coefficient in a thermal reactor is a much more straightforward proposition than in a
fast reactor. It can be done, but it's easier to do in a thermal spectrum reactor. There's
a lot of options. A lot of those options are connected with the process of moderating neutrons.
You change something about that process and it helps you achieve a strongly negative temperature
coefficient. The fuel expands, the [inaudible 41:50] expand,
the fuel assemblies expand, the core support structure expands, the core plate underneath
expands. This is at the molecular level in the salt
reactor because it expands. The salt expands. This is the same thing, except this is done
at the physical level and so in the salt it's easier to have this happen. Right. I just wanted to drill down and get
some questions. Great. That was very informative. Thank you, sir. The trouble is these tests were done about
two weeks before Chernobyl. Yes, I was aware of that. No one even knew about this, which is a shame.
Bob? My question was this was not commercialized,
right? We were going to. It was called Clinch River.
I was working on Clinch River. Then Al Gore, who thought plutonium is nasty, wicked, and
evil and we shouldn't have anything to do with it, persuaded Clinton to shut the program
down. I've actually been to the site where the Clinch
River fast breeder was supposed to be built. I hopped the fence and trespassed on federal
property and walked out to the river and it's an empty field. The country thought the liquid metal fast
breeder reactor was going to be the future. We've now done three of them. Two have had
unintentional core melts. The last one happened in 1972 where the plant manager had to call
the mayor of Detroit and say, "Prepare to evacuate Detroit." How is that Detroit reactor from here? The [inaudible 43:09] Fermi fast breeder reactor
was built by Detroit Edison, made with metallic fuel like this. Actually, it went online about
the same time as this one. The AEC said, "What happens if you get a meltdown?" They said,
"OK, we'll put some zirconium plates underneath." The trouble is, when they put them in they
only tack welded them and the vibration tore one of them off and it went up and flattened
underneath, blocked out the sodium. So that's a significant meltdown, but they cleaned it
all up. Milt Shaw, insisting on oxide fuel for Clinch
River, wouldn't help give them some money to buy another core load. For want of a couple
of million dollars, the plant went down. Good old Shaw. He's the guy who is really
responsible for our trouble. Milt Shaw is quite infamous in the molten
salt community. I had no idea until I read "Plentiful Energy" that Milt Shaw is infamous
to the IFR crowd, as well. Boy, he was just infamous to everybody. The folks who were in support of Clinch River
fast breeder reactor had very sharp elbows. Guys who were working on the integral fast
reactor have just as much heartache with the focus on the oxide fueled loop reactor at
Clinch River as you do. I agree. You're absolutely right. Fast reactor does not equal fast reactor.
Sodium loops with pumps. That flavor, that was the project. People who wanted to do metal
fuel and a pool reactor, they wanted to do molten salts, they wanted to improve the light
water reactor, they wanted to prove that the light water reactor could do breeding, as
well. All of those projects were put on back burners or de-funded completely. Making solid nuclear fuel is a complicated
process and we extract less than one percent of the energy from the nuclear fuel before
it can no longer remain in the reactor. Kurt makes a big deal about the fact that
he wants to us thorium because it's 200 times better than using uranium, but using uranium
is about 10,000 times better than using oil. Let's make the big jump first. The nukes,
though, need to stop fighting amongst each other and compare their power plants to the
real competition that holds 85 percent of the market, which is the fossil fuel companies. Nobody saw the light water reactor as the
machine on which we would power our civilization using nuclear power for thousands of years.
The only question is which breeder and how fast do we get to it? I got a 1962 report
to the president and right in there it states this is a stop gap technology. I think these
earlier nuclear pioneers would be absolutely floored to show up today in our nuclear world
and go, "Oh my gosh, you're still using light water reactors? Come on, guys." We should have seen more technology advancement
by now. We should have seen something better. A pressure water reactor has to take 2,000
PSI, which is a really thick pipe. It's typically four to eight inches, depending on the diameter
of the pipe. We're doing new things with light water. The
core, the pumps, the control rod drive mechanisms, the steam generators, the pressurizer all
in one steel pressure vessel. No piping penetration is in excess of about three inches in diameter.
I'm working on that exact reactor. The light water reactor is still the safest,
most efficient energy source we have on the planet right now and it's a real thing. We
have a big, worldwide fleet of these things that should have been bigger. We have like
400 some reactors running. All we are saying is that in the very near future we could have
something that's even yet safer and even yet more efficient. If someone said all you can have are water
cooled reactors of some type or a vast array of fossil fuel and so-called renewable energy,
I'd rather all my energy was created by light water reactors any day. Nuclear right now means water cooled reactor,
uranium oxide solid fuel, poor fuel efficiency, and steam turbine. That's what nuclear power
means right now. How do you tell people this isn't your father's nuclear or this is different? It's a much better way to utilize our resources
in every way. Molten salt reactors reignited my passion
in nuclear because, to me, it solves the waste problem. People look at Fukushima and they go is this
the end of nuclear power? I go, no, it's not the end of nuclear power. There's a zillion
other ways to do nuclear power. I think this is the best way. Maybe I'm wrong, though.
Maybe there's a better way. I've been looking for it. I tell everybody I've got a standing
invitation. You can figure out how to do this better, I'd be happy to go to whatever it
is that's better. I'm always looking for it. Show me a system that is superior to a molten
salt reactor and I'll say yeah, but, to this day, there isn't one. It's not based on nothing that people have
spent their careers and many, many successful long term tests. This is not a theoretical
technology. This is a proven technology that just needs to be commercialized. It's just
by dent of a solid fuel supply chain having gotten started that we don't have molten salt
supply chain in place. While molten salt reactors allow previously
unattainable levels of passive safety, this does not mean that pressurized water reactors
present any greater danger than coal, solar, wind, or natural gas. Despite Three Mile Island,
Chernobyl, and Fukushima, existing nuclear power is already the safest form of energy
available to mankind. This is because every source of energy has
risk associated with it. Molten salt reactors and other modern reactor designs, such as
the AP1000, minimized the impact of any error by improving passive safety mechanisms. Any
incident at a newly constructed reactor is much less likely to disburse radioactive isotopes,
but the key to reducing errors in the first place is having a well-regulated industry. Hey, Barney? Yo? Open 14 and 15. You can't do that, Jack. Open them, Barney. Jack, you can't do it. The book says you can't
do it. Screw the book, we're almost up to the steam
lines. [pause] It just may be a feed water leak. Which valve? Can't really tell. Shut the isolation valves. You're going to need that feed water later. You want to go down there and do it by hand?
Do it. [pause] Barney, give me feed water. Damn it. We'll probably never know the full extent
of how badly Soviet nuclear power was managed. I sat before the world in Vienna and blamed
those young men at the controls and made no mention of the role I played in their ignorance.
I did not speak out. [inaudible 50:41] suicide caused shockwaves
throughout the Soviet nuclear industry. Design flaws in the graphite tips of Chernobyl type
RBMK reactors were finally admitted to and changes hurriedly made. We do know that Japan's nuclear industry has
seen a steady stream of fatalities. This does not happen in France, this does not happen
in Germany. [pause] Over a 10 year period, United States nuclear power was responsible
for a single fatality. From 2003 to 2012, a uranium miner died when a support beam collapsed. Because every single source of energy has
caused at least one fatality during this period and we know how much electricity was generated
by each energy source, we can express how safe each form of energy is as a quantity
of watts per human life. For nuclear power, because there was only a single fatality,
we divide by one. Almost eight million gigawatt hours of electricity per human fatality. The next safest form of electricity is hydroelectric
power. Hydro produced about half as much electricity than nuclear, for which six people died during
that same period. Next is natural gas. We've all seen natural gas explosions on the news.
Somewhere between 26 and 27 people were killed during that same 10-year period. It is a fractional
number, because the natural gas was dual used. Only a portion of it was for generating electricity. Now that we're burning fuel, we have air pollution
to consider as well. 144 fatalities can be reasonably associated with the pollution caused
by burning natural gas over than same 10-year period. Even with the cleanest burning fuel, air pollution
kills more people than explosions. Natural gas gives us about 52,000 gigawatt hours per
human life. The safest renewable is wind, about 21,500
gigawatt hours per life. Wind fatalities are due to maintenance. Just like nuclear power,
this could easily go up or down depending on how the industry is regulated in the future,
but there are a lot of turbines all requiring regular maintenance, each one producing a
moderate amount of electricity. To improve the watts-to-life ratio and try
to make it as safe as nuclear power, it is reasonable to expect the cost of wind turbine
maintenance to go up, driving up the cost of wind power. 27 people died maintaining
wind turbines over that 10-year period. Natural gas comes out ahead of wind because it produced
far more electricity. Solar is 2.5 gigawatt-hour per human life.
There are a whole lot of rooftop solar panels, and each one only produces a tiny fraction
of the energy that a wind turbine does. Of all renewable energies photovoltaic solar
power is the least competitive in terms of price, but it also offers the biggest opportunity
for improvement if panels can be made more efficient. Such an improvement in panel efficiency would
also improve solar safety standing since more watts could be generated for the same amount
of maintenance. In the United States from 2003 to 2012 average number of watts generated
per fatality is 300-gigawatt hour per human life. How is our average so much lower than
any number we've looked at so far? Because of coal. Let's not forget electricity
produced by burning coal. Coal mining killed 298 Americans over 10 years. Coal mining fatalities
dwarf all other forms of accidental death in the United States. The big numbers are
in air pollution. In one decade, burning coal has killed over
130,000 Americans. Largely due to the release of tiny solid particles
that we inhale causing the respiratory illness. Burning coal also exposes us to mercury poisoning.
This is how America's consumption of electricity kills people, by coal. Every other source
of electricity is safer per watt. On the other end of the spectrum, no other source of power
has the potential to meet all of our electricity demand with such a small impact on human lives,
disruptive ecosystems, and future costs projected from greenhouse gases being pumped into our
atmosphere. Nuclear hardware is [inaudible 55:32] from
degrading effects of sun, wind, and rain. All safety systems are focused on a small
area and handful of highly-trained individuals. Nuclear has the advantage that the amount
in energy per atoms is about a million times better than coal or natural gas. You start
with this huge advantage, and yet, given the complexity of the plants and the things you
have to do, you more than wipe out your [inaudible 56:01] advantage. Today's nuclear plants are
terribly expensive, at least the way they're built outside of China. They're pushing the
state of the art and they're standardizing the signs and things like that. Nuclear is one of the directions that we should
innovate it. Nuclear innovation stopped in the 1970s. We basically have this sub-design
thing that was put into shipping port for the first power generator. We basically built
400 of those that are all kind of custom but not many interesting way. The reactors used in the United States had
40, 50 percent up times. They're horrible. They standardize everything they could - pumps,
valves, motors. That's how crazily one off these plants. They would get custom nut and
bolts for the pressure vessels. Part of that, [inaudible 56:58] Three Mile
Island. After Three Mile Island, they realize that training was that good and we're not
uniform or process with companies. Forced all the companies and utilities to get together
to share their training and procedures. Three Mile Island, what an indictment how
poorly managed the industry was back then. Choosing nuclear power does not guarantee
safety. It is possible to make an unsafe reactor, to staff it with poorly trained individuals,
and it is possible to respond to release of radioactive isotopes by doing nothing at all
to protect the public. The only equipment we have to measure it,
the control room Geiger counters, and everything 3.6 nitrogen per hour. Well, I thought that is 3.6. The scanner goes up to 3.6, and it's off that
scale. It could be 3.6. Yes, it could be 3.6. Exactly. I have no intention of telling Moscow it's
worse than it is, OK? If it says it's 3.6, it is 3.6. The other five reactors in the Fukushima Prefecture
were built just a few years later, and all the reactors at Fukushima Daini, none of them
had significant damage. We figured it out how to prevent that problem sometime around
1971-72. The one thing the Japanese didn't do is go back and fix the early systems because
they thought, "You know, we've operated the plants for 40 years. It's not been a problem
before." We have three standard examples of what not
to do, and decades of safe operational experience from hundreds of nuclear reactors around the
globe to learn from as well. What choices can we make today so that nuclear power can
even safer? Very few people understand all the options
that are available in nuclear energy. It's a complicated subject. It's a subject that
is actually quite new. The first chain reaction experiment was December of 1942. My mother
was a teenager in 1942. She's still alive and kicking. This is the only part of the energy business
that anything close to a Moore's Law capability for improvement. We're still at the very early
stages of figuring out best to put that energy inside the atomic nucleus to use. At the time when society had its most optimistic
view of science, it had the view that if that was the form it took, then it must be the
right form. We still have this view that society can't shape technology, that the form that
the technology takes is the form we must accept. What science and technology gives you is a
range of possibilities, and those possibilities can take you in any number of directions. I'm Bert Wolfe. I had General Electric's peaceful
nuclear power program. General Electric and Westinghouse took the
simplest form of nuclear reactor, originally designed for submarines, and redesigned it
on a gigantic scale often to power companies at knock-down prices. We would sell one at a time, and each time
we sold one, we'd have a celebration. I can recall when we'd have meetings, and someone would come in and said, "We sold the plant to somebody." We'd all stand up and shake hands and go out for lunch and have wine and toast each other. It was a great celebration.
We began selling these by the 10s, so it became a real business. The history of nuclear power is a history
of political and economic and social decisions being made about a technology. The key decisions weren't made by the technologist. They were done in the business room.
