March 28, 2011 • 45 mins
The disasters in Japan severely damaged the Fukushima nuclear power plant. In this episode, Chris and Jonathan break down the tech behind nuclear reactors. Tune in to learn more about nuclear power -- and why preventing meltdowns is so important.
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Episode Transcript
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Speaker 1 (00:00):
Brought to you by the reinvented two thousand twelve Camray.
It's ready. Are you get in touch with technology? With
tech Stuff from how stuff works dot com. Hello again, everyone,
Welcome to tech Stuff. My name is Chris Poulette and
(00:20):
I am an editor at how stuff works dot com.
Sitting across from me as always a senior writer, Jonathan Strickland.
Hey there, Okay, I think we'll probably be a little
subdued for those those of you who are long term fans.
A few weeks ago we recorded an episode of tech
Stuff because of a seismic event in christ Church, New Zealand.
(00:43):
Yet uh did a lot of damage, but hadn't resulted
in a lot of human costs. Since then, of course, um,
you know, we've had the earthquake in Japan nine point
oh earthquake um, which, if you remember in the Seismology podcast,
(01:04):
each each number in the Richter scale is ten times
greater in intensity than the previous number, So a two
is ten times more intense than a one. So nine
is an incredibly intense earthquake. What's what's interesting about that too?
Just as a note, um, I understand that that was
actually an aftershock of a six point two I believe
(01:27):
magnitude earthquake. It was in the sixes. Yeah, it can
sound kind of unusual to some of us that an
aftershock would actually be more powerful than the initial earthquake.
But you just have to remember those those plates that
we talked about in the Seismology podcast are the pressure
is incredible. There's nothing else like it on Earth really
(01:48):
where uh and if if those plates slip against each other,
then your you can get a pretty massive earthquake or
an aftershock. So um, of course, we we touched on
how earthquakes are measured, the different devices have been used
to measure them in the past. Um. And uh, you know,
of course in Japan there were the earthquakes and aftershocks
(02:11):
in the tsunami that followed, resulting in a lot of
property damage and loss of life. We're still not sure
at this point how many people are gone. No, it's
a tragedy that is definitely on a on a huge scale.
We just don't know the extent of that yet. And um,
although no one has really asked about this yet, we're
(02:34):
kind of thinking that maybe people would want to know
about the other major news event that has gone along
with that, which was the the nuclear power plant that
has suffered catastrophic failures as the result of the earthquake. UM,
and we thought it might be interesting to talk about
how nuclear power plants work, and then we'll we'll go
(02:56):
into exactly what the problem is in Japan. Yeah, with this, frankly,
this could be a marathon episode. We could talk about
nuclear power plants for hours because they are very involved.
So we decided to stick primarily to the general type
of nuclear power plant being used in question, but also
some of the others that have had major problems in
(03:18):
the past, notably the Chernobyl reactor and the one in
Three Mile Island in in the United States. So let's
talk first about what a nuclear reactor is and how
it generates power. Uh, of course, it's using a nuclear process, right,
It's using decay. Really, it's we're talking about controlling the
(03:40):
decay of of uranium. Really, it's when you compare it
to a coal power plant, um, and you and you
take the very very basics together, this type of nuclear
power plant is almost exactly the same type. You're using
a new clear reaction to generate heat as you would
(04:02):
for a coal fired power plant, right, exactly, you would
you would burn coal to generate heat in a coal plant? So, yeah,
same thing, you're trying to use heat to generate electricity.
You use that to to generate steam. The steam turns
a turbine and a generator, which generates electricity. It's it's
the nuclear reaction that makes it so very different from
the coal plants that. Yeah, And you might ask, well,
(04:24):
why would you want to use nuclear power in the
first place. Well, there's several reasons. One is that, unlike coal,
it doesn't produce uh, greenhouse gases. That's right, right, So
when you burn coal, you're going to generate greenhouse gases
and essentially carbon dioxide being chief among them, and uh
and that can contribute to lots of environmental problems. So
(04:45):
in some ways, nuclear power, at least from a greenhouse
gas perspective, is greener than coal technology. Also, you don't
need as much fuel to generate power as you would
with coal. It's it's actually an incredible skin you could
be talking about, you know, a few pounds of uranium
versus tons and tons and tons of coal. Yes, it
(05:07):
wasn't that long ago that the uh, those of us
in the United States were talking about the coal mine
the coal miners who are trapped in West Virginia. UM.
And of course people start talking about the pros and
cons of coal. Now of course we're talking about the
pros and cons of of nuclear energy. UM. But yes,
it requires far less uh um raw material to generate
(05:30):
the nuclear reaction as it would for the coal fired
power plants. Now, so you're you're talking about material where
you don't need as much. You aren't genering greenhouse gases UM,
and you can create an intense amount of heat very
pretty simply in the grand scheme of things. But there
(05:51):
are a lot of concerns around nuclear power as well.
For one, I mean, we're talking about radioactive material, and
radioactive material that is harmful to human Yes, it's not
just you know, lots of things radiate energy, and not
all of that energy is harmful. Yes. Just the other
night I was watching, uh the CBS news report on
(06:12):
radio activity, and a lot of people in the United
States have been concerned that, first of all, the governments
of Japan and the United States aren't being truthful with
the amount of radiation being leaked in the atmosphere as
a result of the explosions that took place at the
plant in Japan. UM. But they were One of the
(06:34):
things that I think was interesting was they took a
Geiger counter around to several different They were basically walking
around New York City with a Geiger counter, and they
went to the middle of the park and turned it
on and it was picking up readings of radio activity.
And they walked over to granite, a granite monument as
a matter of fact, and UH and and took the
(06:55):
Geiger counter. A geiger counter, by the way, as a
device that measures radioactivity. You hear clicking sounds and it
has a needle. One of the UH. I think of
it as an old style, but really I guess it's not.
With the needle and it shows you roughly how much
radioactivity is being gendered. And granted is naturally radioactive, and
I didn't know that now. Of course, you can't take
(07:17):
just anything UM and throw it in a nuclear reactor
and have it react. You have to use a very
special UM type of material. Because to generate a nuclear
reaction UM, you're splitting an atom, use a stray neutron
to UH break apart the nucleus of another atom. And
(07:39):
and some some elements are more likely to be are
are are easier to do that with than others. You
need something that's called fistle if you're using a effission
reaction as the one as these reactors do. Fusion power
right now is kind of beyond us as far as
it takes more energy to create a fusion reaction than
we get back, I'll of it. But there is a
(08:01):
lot of hope that in the future fusion will become
the the power source for nuclear facilities. The Sun generates
energy through fusion, not fission, so uh yeah, we haven't
we haven't gotten there yet, but there are a lot
of very very smart people working on ways to create
fusion power plants, and it's quite a bit of research
(08:23):
on on these things from Britannica. I like to to
use that, of course as one of my sources. Um
and uranium two thirty five, according to Britannica, is the
only naturally occurring fistle material that's in a ready state
to be to be split apart this way. Um, there
are other, uh different kinds of materials. We're we're talking
(08:45):
about the nucleides um. Somebody probably correct my pronunciation. I
think that's right, but those some of them basically as
long as the atoms are in an excited state. Uh,
they can be um. When they're hit with a slow
moving neutron, you can you can break them apart. Uranium
two thirty five to thirty three, plutonium two thirty nine
(09:06):
and two forty one um Plutonium two thirty nine. You
actually create with your uranium two thirty eight and then
you bombard it with neutrons. Yeah, materials that are fertile,
uh can be that if you are different kinds of
materials that if you add an extra neutron, you can
they can become fiztle. Uh. Those are thorium two thirty two,
(09:28):
uranium two thirty eight, and plutonium two forty um. So
these are very complex atoms and heavy atoms and very
heavy atoms and um. There are are the kinds of
materials required to be used in a in a core
of a nuclear reactor, and uranium two thirty five will
break apart naturally decays over time. But but that's not
(09:51):
the You know, you want to have a controlled and
a controlled reaction in order to be able to generate power,
and you want to be able to do it at
a good time scale. Because we're uh, we don't have
thousands of years to generate electricity. So with the uranium
two thirty five, you actually would bombard it with neutrons
in order to uh to speed up that reaction. Now,
what that will do is that the the atom splits apart,
(10:14):
it generates a lot of energy in the form of
heat and radiation. The radiation comes in the forms of
gamma radiation, beta radiation, and alpha radiation. Uh So, gamma
radiation is a form of electromagnetic radiation UM. In fact,
there are two major kinds of radiation. Electromagnetic radiation, which
(10:35):
is some form of light. Uh it's it's photon radiation UM.
That may not be visible light, but it is. It
falls under the photon radiation. Then you have particulate radiation,
which is when you're talking about an unstable uh atom
particle shoots off essentially from the the atom. And uh
(10:57):
So with alpha radiation uh uh or well, I'll start
with beta radiation. With beta radiation, you've got electrons being released. Right,
alpha radiation, it's protons and neutrons being released. Now, protons
and neutrons are much much much larger in comparison to electrons,
(11:17):
and they move slower than electrons do. So alpha radiation,
you get the protons and neutron splitting off. That's a
particulate radiation that moves slowly. It can actually depending upon you,
know how how you're being exposed to it. Your skin
can sometimes block alpha radiation just because your skin is
thick enough where it's the particles are not moving at
(11:40):
a speed sufficient to be able to penetrate the skin. Um.
The beta radiation is different because those electrons are very
tiny and they're moving really really fast and uh, and
this is the sort of radiation that the sort of
particular radiation that can actually cause pretty nasty deep tissue
damage if it hit to you. And then of course
(12:00):
gamma radiation is really really high energy electro magnetic radiation,
and that stuff is serious business. Uh. You know, gamma
radiation can cause lots of problems in both immediate acute
problems and chronic problems over time. So why would you
want to use this, Well, it's because it gives off
this this amount of energy, this this kind of intense energy.
(12:24):
It's really good at converting water into steam. So if
you can control this reaction, uh and generate the right
amount of heat, you're going to generate a lot of
steam that's going to move through the system and eventually
turn the turbine which is going to uh provide the
power to the generator, and then you you create power
(12:45):
for the power grid. And some countries rely very heavily
on nuclear power to create to to supplement their power grid.
Countries like like France, it's nearly seventy of their power
that comes from nuclear power. In the United States, it's
more like it's funny because there are two, um, two
different things to consider that you might not consider with
(13:07):
some of the other forms of electricity generation. Here UM
atomic reactions are deal with probability UM and they deal
with chain reactions. UM. I remember watching in one of
my science classes a long long time ago an experiment
that they did where they had set up we're not
an experiment, but an an illustration. They had a plexiglass
(13:31):
or clear plastic box and across the floor of it,
the entire floor was covered with mouse traps set mouse traps.
Each mouse trap had two ping pong balls on top
of it and everything was still. So this is the
normal state of the atoms that's supposed to represent the
(13:51):
normal state of the atoms inside the fuel. UM. And
then there was a small hole at the top of
the box, and the person said, Okay, this is what
happens when you add the neutron. The stray neutron is
another ping pong ball in this illustration, and the person
dropped the ping pong ball into into the box, and
of course it hit one of the mouse traps, setting
(14:14):
it off. The other two ping pong balls representing neutrons again, uh,
jumped up from the mouse trap in different directions, and
each of those set off more mouse traps, and each
of those set off more mouse traps. Exponential growth. Yes. Now,
of course in the nuclear fuel uh, you know, in
that particular illustration ended and very quickly within a matter
(14:36):
of you know, probably two or three seconds, because they
were you know, forty mouse traps or something like that.
In nuclear fuel, this continues on UM, but they have
to control that. They have to look at the probability
that a neutron will continue, that there will still be
stray neutrons able to generate more heat energy release UM.
(14:57):
So when they want to what they call a slightly
super critical uh level of reaction, because there's that means
that there is more more than one fission per neutron
so you're you're you don't want it to be a
little bit. You don't want to be underneath that. When
it gets subcritical, that's when there are a few there
are fewer neutrons available to make the nuclear reactions, which
(15:22):
means that you would actually have to pour more power
into the system to to shoot more neutrons into it
in order to generate power. And of course, you know,
the whole goal here is to make it as efficient
as possible when you're generating electricity. Otherwise you're actually consuming
far more power than you are able to convert into electricity. Yes,
when it's one spare neutron to a reaction, that's or
(15:44):
to a nucleus of another atom, that's critical. That literally,
that is what they call critical, and that's the reactive
state of the the reactor core um. From what I understand,
they do want it to be slightly super critical, but
only lightly, and so controlling the reaction is very important,
and it's done in a number of different ways. Sure,
(16:07):
let's talk a little bit about the way the fuel
is put together and then we can talk about how
that control happens. Yeah, I think that that would be
excellent because that is a big part of how they
control the reaction. Yeah, so, so the uranium is enriched
with uranium two thirty five right now for a nuclear facility,
I was gonna say, we should might maybe explain what
(16:29):
that means, because uranium two thirty five is naturally reactive,
but there's only so much of you two thirty five
found in a chunk of uranium. So enriched uranium is
basically they've added more uranium two thirty five to the
uranium overall to make it, to make it more reactive
so they can use it as nuclear fuel. And so
(16:50):
for UH, you have to for for fuel for a
nuclear power plant, you need to have added enough you
two thirty five, So it's got two to you two
thirty five and the overall fuel now you two thirty
five is the same element that you're going to find
in UH in nuclear weapons. But nuclear weapons require a
(17:14):
much higher percentage of you two thirty five to thirty
five within the uranium in order for it to be
weapons grade. So that's a pretty easy way to tell
if someone's making weapons grade uranium is you measure how
how the percentage of you to to thirty five in
the fuel itself. If you've been following the news and
(17:34):
you've seen pieces on where some countries are concerned about
Iran enriching uranium. This is why you can enrich uranium
for a nuclear power program, or it can also be
used in weapons. Right, So if you're enriching beyond that
two to three percent, then that's a good indicator that
you're looking at something more uh dangerous than the nuclear
(17:57):
power plant. So the what the bits of uranium are
actually formed into what what is called pellets, and they're
about an inch long. They're about the diameter of a dime.
So you can think it's kind of like a cylinder
right now. These pellets are stacked together to form rods.
Yes they are. They are contained within a metal rod, yes, yes,
(18:21):
so yeah, you can think of like a there's like
a sheath, a metal sheath, and these uranium pellets are
stacked within that sheath. Now, these rods are then grouped
together into a collection called a bundle. And if if
that's all it was, if that's all you had and
then you started introducing neutrons into it, you would have
no way to to modify to moderate that at all.
(18:43):
It would just the reaction would would increase and increase
until either you would spent all the fuel or you
had had a melt down. And meltdown essentially is when
the fuel itself gets so hot that it melts um.
So in order to control this, they have control rods.
And control rods are made of material that are that
absorbs neutrons, because as we were talking about, you know
(19:06):
these neutrons that that fly off and hit uranium two five,
that's what initializes this reaction. So if you have material
that absorbs neutrons, it's like taking you know, you're you're
you're putting the brakes on things, and the control rods
tend to be you can you can insert them either
all the way down where they are going to control
(19:28):
the reaction as much as possible, keeping in mind that
there's still some decay heat that's going on here. It's
not like it's not like you immediately switch it off.
It's just slowing it down to the point where you
call it a nuclear shut down, but there's still heat.
Or you can raise them all the way up and
then just let the UH reaction go to full full blast.
(19:52):
Cadmium and boron are two elements that are very good
at absorbing stray neutrons, and you may have heard about
born being introduced into the Japanese facility along with sea water.
We'll talk about that in a minute too, um, but
those are those are also uh, those are useful because
they're basically fighting over who gets the stray neutrons and
(20:14):
that just slows everything down and helps right keep it
under control. Now, inside this nuclear reactor, you also have
to have coolant because and actually the coolant is what
heats up to go and then usually you have a
you have a coolant that then runs through another system
that will heat up water and the water becomes steam
and that's what drives the turbine. Some nuclear power plants,
(20:37):
and these are the ones that are kind of particularly dangerous,
have the coolant system also driving the turbine, which means
that you have radioactive material pushing that turbine because the
coolant that encounters the actual rods is going to pick
up radioactive material itself, will become radioactive. It's gonna have
(20:59):
radioacti particles running through that cooling system. So most of
these cooling systems are are self contained and they do
not cross over into the water system that drives the turbine.
They just they just you can think of it as
it runs up against the water system, and the heat
from the cooling system is what generates the steam in
(21:20):
the water system. Um. So, but you have to have that.
If you don't have that again, the uh, the core
can reach a temperature that's so high that the uranium
begins to melt. And there there's a lot of scary
guesswork as to what would happen if you had a
true meltdown, like a full on meltdown to the point
(21:43):
where we're not really sure if the material would get
so hot, like the reaction would continue to a point
where it would just burn right through the reactor. Um
that's a theoretical possibility, although we haven't actually seen that
happen in real life yet, Thank goodness us that's true. Well,
the the movie The China Syndrome is about that, and
(22:06):
I think most scientists would probably tell you that that's
a bit hysterical for what might actually happen. Uh. The
the premise being that the core melts down, the fuel
is melting, and it melts all the way through the
center of the Earth again, from the United States to China,
(22:27):
all the way through the the Earth that might be
a little I think that's probably I mean, I'm not
a scientist obviously, but I think that's a little extreme.
I would definitely call that the worst case scenario. Yeah,
I don't I don't know that it could actually go
that far. But yes, that that is an exaggeration of
what Jonathan's talking about, the idea that it would melt
(22:47):
through the reactor. So the the problems that we could
conceivably face with a nuclear power plant would involve something
going wrong with the ability to insert or remove the
control rods, really to insert them, because because if they're
stuck there, all you really have is a dead nuclear
power plan. And yes, that is terrible and that it's
(23:09):
gonna cost billions of dollars to fix, but it doesn't
pose an immediate threat to the surrounding area. UM. You
also have the problem with if if the water system,
if the cooling system is UH in any way compromised,
then you have the chance of the nuclear reactor overheating,
which unfortunately we have seen happen before, and that can
(23:30):
cause UH massive problems down the line. Now, what happened
with Japan is that the earthquake actually did not UH
did not damage the reactors to the point where they
were inoperable. In fact, what happened was that the control
rods descended, as they should have in that instance to
(23:51):
control that reaction. But again there's decay heat. It's not
like it can shut it off immediately. It's just that
the reaction is no longer continuing, right, but still generating heat. Right. UM.
Another thing to consider with regard to the Japanese reactor
is that, uh, there were containment devices set up. When
(24:15):
you build a nuclear power plant like this, this light
water plant, UM, it is ideal to build a containment
area around the reactor course. UM. This is usually made
with concrete, UH, very thick concrete in the case of
the Japanese plant, UM, which for has has so far
(24:39):
as of the time we're talking right now, prevented a
major release of radiation. UM. The problem comes from what
happens with spent nuclear fuel, which to this point we
haven't mentioned. At some point, when the fuel becomes subcritical
and it cannot continue producing a nuclear reaction sufficient enough
(25:02):
to continue the the electrical output of the plant, UM,
they're going to want the people running the plan are
going to run and replace it with fresh fuel. This
can take weeks. Usually they do maintenance on the plant
at the same time, because it's a good time the
plant shut down. So what they'll do is they'll remove
the bundle of rods and replace it with new rods
(25:24):
of with fresh fuel. But what do you do with
the old rods. That's the tricky part because the old
rods are very hot and they are very very radioactive. Yeah,
it's just like it like Chris was saying, it's kind
of like, you know, it's just that they're not generating
the amount of energy necessary to run the plant, but
they're still generating tons of like of energy and not
(25:44):
really tons. Don't write me and um, the they are
very much dangerous to people and here's eventually they will
be inert. But but eventually I'm talking like ten thousand years. Yes,
we can't wait around that long. And because they're generating
so much heat and so much radioactivity, they tend to
corrode pretty much any container you put them in. This
(26:07):
is one of the aside from the potential for an accident. Uh,
this is one of the things that can that makes
nuclear power so controversial, is that this is the flip
side of the green coin. Yes, Storing the nuclear fuel,
the spent nuclear fuel is very, very difficult. Uh. Nobody
wants nuclear fuel in their backyard. Um, and there's not
(26:31):
even there's not a good answer for that. Storing it
in caves is one solution. The question is whether or
not people will go in there. Um. You know, a
thousand years down the road is still very radioactive. Um.
You could say, well, why don't we shoot it off
into space. Well, that's fine, except there's the potential for
(26:54):
an accident. Rockets are not foolproof, and if you have
an accident with the rocket, there's the potential that radioactive
waste could be scattered across the roth's atmosphere in that again,
is something that no one wants to happen. So one
of the first things they do when they remove the
fuel from what I understand from the reactor core, is
(27:16):
they put it in a containment pool. Water, as it
turns out, is a natural shield against radioactivity. Uh. Not
only is it cooling the very very hot rods with
the nuclear fuel inside, but it also is shield doing
some shielding against radioactivity. Well in the Japanese plant, when
the power was shut off, ironically enough, Uh, the water
(27:41):
began to evaporate. It was boiling off. And that's the
problem is that there when there's no more water surrounding
the spent fuel. It wasn't the reactor cores, it was
this the spent fuel. Uh, and the reaction is allowed
to continue that generates hydrogen when the hydrogen is explosive. Yeah,
(28:01):
it's It's a process called thermolysis. It's when heat turns
water into hydrogen and oxygen breaks up the molecules into
their into their component atoms, and you can you can
do the same thing with electricity, that's electrolysis. So it's
the same sort of thing. It's just you pour enough
energy into a molecule and you can break those molecular bonds.
And that's exactly what happened. Hydrogen built up. But before
(28:24):
we get to the hydrogen problem, I should also mention
there were a lot of fail safe procedures in place
at the Japanese plant. It's none of the Japanese were
not doing due diligence with safety. It's just that was
the perfect set of terrible situations for this to happen.
And it and it from what I understand, not to
interrupt him, um, from what I understand, the plant was
(28:46):
intended to survive and eight plus UH point Richter scale earthquake. Yeah,
it was the tsunami that really hit them. Because here's
what happens. They lost power from the power grid, well
the power plant had and they need power to pump
water through the system in where to keep it cool.
(29:07):
So the pumps run on electricity. So they switched to
their diesel generators. But then the tsunami hit and the
diesel generators were not above the tsunami levels, so they
were flooded and could no longer work. They also had
battery power, but the battery power was only meant to
last you know, I think it like a day, because
(29:28):
the idea was that, well, we won't be without power
for longer than that. But they could not get supplemental
power in place to uh to cover the gap between
the battery power and when they could get some other
form online. And so the water stopped pumping and the
temperature kept building and the hydrogen built up. Um and
(29:49):
hydrogen is incredibly flammable. It's explosive, and there was the
hydrogen collected at the top of the facility. UH. Something
set it off and there was that's what that big
explosion was when we first you know, and there's been
a uh, there's been other ones since then, but that
(30:10):
initial explosion, people were worried that the reactor had exploded.
That's not what happened. It was the pocket of hydrogen
that it exploded. And as uh, if you've been through
a certain level of science, of course we have some
younger listeners. The three things that you need for fire
are you know, heat, a source of fuel, and air,
and you would certainly have that with very hot fuel rods,
(30:34):
air in the in the area, and then you know
the source of hydrogen. So um, it was a very
dangerous situation. Now uh people have said, uh, you know,
this is going to be another Chernobyl. But Chernobyl was
a different situation. They did not have any containment in place,
or what they did have some containment that it was
not designed to prevent the kind of release that that occurred.
(30:58):
Chernobyl was interesting. So when we're talking containment, like Chris
was saying, you're talking about a very thick concrete liner,
usually there's a steel a steel like you can call
it like a furnace, I guess, but it's a steel
container that is lined with concrete, and then you have
a big concrete building around that, so you've got two
(31:19):
barriers of concrete and a barrier of steel in order
to contain the nuclear reactions. Chernobyl only had the basic container,
did not have a secondary container, so if there were
a failure, then there you have much more chance of
nuclear fallout. And in fact, the Chernobyl incident happened ironically
during a procedure where they were trying to test out
(31:41):
a safety feature because what Chernobyl was going to have
was having some similar issues to the japan facility and
that Chernobyl um they were worried about what would happen
if power were lost, If they lost power from the
power grid and they can no longer pump water through
their system, so they uh they had these diesel backups,
(32:01):
but the diesel backups would would not really kick in
until about a minute after the initial power loss, and
that minute is a long time for these nuclear reactions
to go unchecked, right with no water cooling them down.
So one of the things that we're looking at doing
was using the turbine as it slowed down to generate
enough electricity to keep the pumps running for that one minute.
(32:24):
Before the diesel backups could kick in, and they were
running a test and it was like the perfect set again,
a perfect set of situations going wrong for that test
to fail. There was a power spike, and then while
they were trying to react to the initial power spike,
there was a second power spike, and that's when you
had another explosion and release of steam and nuclear steam,
(32:50):
and then there was the terrible fallout that happened in
a huge radius around your noble Belarus in particular was
hit really really hard by that radio and it was UH.
And there there are levels of nuclear disaster. We give
them a numeric UH assignment for how bad it is,
and it goes from one to seven. Chernobyl was a
(33:12):
seven three mile island which happened in the United States
nineteen seventy nine. That was a five, and the Japan
incident right now is is listed as six. Of course,
that can change over time and things get worse. Um
hopefully it will not so, but yeah, because Chernobyl was
(33:32):
was not as protective as it needed to be. That's
why the it was ended up being a seven. Like
if it had had the right protections in place, it
may still have been a terrible, terrible accident, but it
may not have been as bad as it turned out
to be. Three Mile Island was interesting and that uh,
it was a combination of user error and mechanical failure.
(33:53):
There was a valve that was open, and then the
power to the valve was shut off, which normally would
mean the valve would close. The valve would only open
when powered. There's a mechanical failure. The valve did not close,
and because um the indicator on the console said that
there was no longer power going to that valve, all
(34:14):
the operators assumed that the valve was closed, but their
readings were showing that the pressure and temperature were off,
like the pressure and temperature of the core should not
have been what it was. Well, the reason why there
was a problem was because the water was boiling off
and there was this open valve and so there was
an open you know, the pressure was not building the
right way. But it took hours for them to figure
(34:36):
out what the problem was. Actually, there was a shift change,
and it was when someone from the new shift was
looking at the problem that they figured it out. And
then by then the scare had really hit. Unfortunately, Three
Mile Island wasn't as bad as it could have been.
There was no There was only I think there's a
partial melt down, which was scary, but it could have
been so much worse if someone had not picked up
(34:58):
on that mistake. Now as far as Japan goes, Uh,
we talked about the boron uh and the seawater. Well,
dumping seawater into the reactor is pretty much a last
step because the seawater is going to ruin that reactor.
You're not gonna be able to use it again. Um.
And the boron is there to help absorb those neutrons,
like Chris was saying. Yes. Another another one of the
(35:21):
problems that they were mentioning on the news yesterday as
that the day we're recording this is that Um there
they are currently this. This will show you probably when
we're recording this. Uh. They were talking about the pumps
that are in place. They wanted to be able to
restart them. They've had trouble doing that and they're going
to have more trouble doing that now. Uh. They're hoping
(35:43):
to again as at the time we're recording, to restore
electricity to the plant so that they can go ahead
and shut the pumps back on. But for the reactors
UH in which they have introduced seawater, this is an
issue because the seawater also clogs those pumps, so it
is going to be even more difficult for them to
contain the situations in those damaged reactors UH today than
(36:09):
it would have been a few days ago when the
problem was first getting out of hand. Yeah, the issue
was just that if they did not introduce the seawater,
there was there was an increased danger of a meltdown because,
like we said, this temperature just keeps on going. It's
not even with the control rods in place, which the
system did do UM, it does not eliminate that heat.
(36:31):
You have to be able to circulate the coolant through
there in order to to maintain the temperature. And UM,
because there was no way to circulate the coolant, they
had a choice either they introduced the seawater and boron
into the reactor core, or they take a chance on
a meltdown. And and clearly the second option is not
one that anyone wants to take. That that is not
an option, right. So there's a lot of concern actually
(36:55):
that this this UH will really set Japan back quite
a bit because they are very reliant on nuclear power
and that um losing this facility, which it's quite possible
that they will lose at least, uh more than half
of the reactors in this facility, that it will really
(37:16):
impact their ability to create electricity. And the quake in
general has really um, I mean, it seems it seems
weird to say this because there are so many more
important tragedies that are connected to the quake, But the
quake itself could actually set back everything from electronics to computers,
(37:38):
just because so much of it is manufactured in Japan
and those manufacturing facilities were damaged in in the quake.
That that's true. Um, Even places that weren't directly hit
by the tsunami are still suffering problems. Um. And from
what I understand, the majority of flash memory used in
(37:59):
all kinds of electronic devices cell phones, smartphones, tablets, MP
three players, and all kinds of other things, the majority
of it comes from Japan. Uh So this is likely
to u to cause problems in the supply chain and
disrupt um electronics manufacturers the world over. And of course,
you know, those those people who who weren't directly hit
(38:21):
probably would like to get back to work. But this
is going to be difficult for them to be able
to move on and and do things that they want
to do again. You know, even even people who weren't
directly affected by uh, you know, losing their homes and
losing friends and loved ones. Um, you know, this is
this is difficult for for them as well. It's a
(38:41):
major catastrophe. It's all. It's I was gonna say it's
almost unimaginable to me, but no, I think I have
to say it's unimaginable. I I cannot comprehend the level
of catastrophe this is. I mean, I see the pictures,
and I see the video, and I hear the testimonials
and it's all heartbreaking. But it's just there's I can't
(39:02):
grasp it. It's beyond my ability. Um, and guys, I
want to say this before we before we start wrapping up.
We have some amazing articles on how stuff works dot Com,
about nuclear reactors, about radiation, and about the Japanese crisis.
There's how nuclear power works, how Japan's nuclear crisis works,
(39:23):
how radiation works. These articles are fantastic. I read through
all of them in prep for this UH, this podcast
and the writing on these are amazing. I mean, you
get the Marshall brain and Robert Lamb and uh and
and Deborah Ront's all did fantastic jobs. And my hat
is off to them because they took a very complex,
(39:46):
dense subject and they broke it down in a really
understandable way. So if you want to learn more, I
highly recommend you check them out. Yeah. There there are
so many other types of uh nuclear energy to the
haven't touched on and talk anything about, uh some of
the other new technologies that people are trying out now, um,
(40:07):
one of them being the pebble bed reactor that they're
starting to roll out in China, which, from what I understand,
maybe to some degree safer there's less chance of something
like a meltdown occurring because it uses a different method
of nuclear reaction, and that might be maybe we can
look at that again when when this uh these issues
aren't so fresh and we can uh uh you know,
(40:29):
look at some of those. And I'm also interested in personally,
and something that I read about and wired um a
couple of years ago now or maybe about a year
and a half ago, thorium using thorium, which is not
nearly as radioactive as uranium. Of course it will carry
for some people, probably for a lot of people, the
stigma of being labeled nuclear energy. But from what I understand,
(40:51):
you can hold the piece of thorium in your hand
and you should not suffer any ill effects because it's
not the same kind of it's not as radioactive as
as uranium or plutonium, and can be used on a
smaller scale with uh, you know, the possibility. Like I said,
I'm only reading this, but it doesn't look like there's
nearly the possibility of uh, the kind of disaster that
(41:14):
we're talking about here. So there might be other kinds
of technologies that will use in the future that can
still harness the power of the atom without being so
dangerous in the event of an act of you know,
a nature event like this. And I imagine that this,
this disaster will definitely make countries around the world rethink
(41:34):
their their approach to nuclear power. Well, that's already that's
already happening in the United States. President Obama has ordered
um a look at all the nuclear reactors currently in
service to to just as a check up to see
how they're doing. Germany, I think has taken all of
theirs offline, um with the idea that they will evaluate
(41:56):
their safety. There were bills in many countries or laws
already passed to extend the life of aging nuclear reactors
that from one understand, are being rescinded one by one
as people are rethinking the possibility that older reactors and
this the reactor in Japan was older too. Yeah. Um so,
I mean there you know, as as we complain about
(42:18):
very often, technology changes very quickly and it's hard for
us to keep track of It's also changing in the
nuclear industry as well, and there are new safe safety
measures that might be implemented in a in a new
reactor that wouldn't have been implemented in the nineties, seventies
and eighties. It's just the question of will it be
politically feasible to implement nuclear power, because uh, it's one
(42:38):
thing to to tell people that safety measures have improved
and that, uh that we've learned lessons from these events
that we can, um we can implement in the future.
But there's it's such an emotional issue and uh it
has it does have problems. I mean, the nuclear waste
is still a very very big and uh, there's not
(43:01):
an easy solution to that, and as long as those
still exist, I think we're going to see increased resistance
to implementation of nuclear power, which I mean that's gonna
be very frustrating for some people, although you have to
admit that, um that the we've seen examples of things
going wrong, and sometimes it's because people did not react
(43:23):
the right way, and sometimes it's just that the perfect
set of circumstances hit in order for something to go
terribly wrong. And you know, there there is the argument
you could make that the likelihood of that happening is low,
but there's also the argument of any likelihood is too much, right.
(43:44):
So it'll be interesting to see where the future of
nuclear power goes. It'll be interesting for me to see
if the the projects that are trying to make breakthroughs
infusion power suffer as a result, because that is another
form of nuclear energy, and uh, it's a frame form
of nuclear energy. It's not the same as vision at all.
But it could very well be that just because it
(44:05):
has that association, that these programs could start to lose funding.
So we'll have to keep our eyes open see what happens. Uh.
Our thoughts go out to everyone in Japan. And all
those who are affected by this disaster. And it's absolutely
a tragic event. And uh and we really feel for
you guys. Um, if you guys want to talk to
(44:27):
us about nuclear power, if you have your own thoughts
you would like to share, please do so. You can
contact us on Twitter and Facebook. That handle is tech
Stuff hs W, or you can write us an email.
That email addresses tech stuff at how stuff works dot com.
Chris and I will talk to you again really soon.
(44:47):
For more on this and thousands of other topics. Is
it how stuff works dot com. To learn more about
the podcast, click on the podcast icon in the upper
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(45:10):
Are you
Brought to you by the reinvented two thousand twelve Camray.
It's ready. Are you get in touch with technology? With
tech Stuff from how stuff works dot com. Hello again, everyone,
Welcome to tech Stuff. My name is Chris Poulette and
(00:20):
I am an editor at how stuff works dot com.
Sitting across from me as always a senior writer, Jonathan Strickland.
Hey there, Okay, I think we'll probably be a little
subdued for those those of you who are long term fans.
A few weeks ago we recorded an episode of tech
Stuff because of a seismic event in christ Church, New Zealand.
(00:43):
Yet uh did a lot of damage, but hadn't resulted
in a lot of human costs. Since then, of course, um,
you know, we've had the earthquake in Japan nine point
oh earthquake um, which, if you remember in the Seismology podcast,
(01:04):
each each number in the Richter scale is ten times
greater in intensity than the previous number, So a two
is ten times more intense than a one. So nine
is an incredibly intense earthquake. What's what's interesting about that too?
Just as a note, um, I understand that that was
actually an aftershock of a six point two I believe
(01:27):
magnitude earthquake. It was in the sixes. Yeah, it can
sound kind of unusual to some of us that an
aftershock would actually be more powerful than the initial earthquake.
But you just have to remember those those plates that
we talked about in the Seismology podcast are the pressure
is incredible. There's nothing else like it on Earth really
(01:48):
where uh and if if those plates slip against each other,
then your you can get a pretty massive earthquake or
an aftershock. So um, of course, we we touched on
how earthquakes are measured, the different devices have been used
to measure them in the past. Um. And uh, you know,
of course in Japan there were the earthquakes and aftershocks
(02:11):
in the tsunami that followed, resulting in a lot of
property damage and loss of life. We're still not sure
at this point how many people are gone. No, it's
a tragedy that is definitely on a on a huge scale.
We just don't know the extent of that yet. And um,
although no one has really asked about this yet, we're
(02:34):
kind of thinking that maybe people would want to know
about the other major news event that has gone along
with that, which was the the nuclear power plant that
has suffered catastrophic failures as the result of the earthquake. UM,
and we thought it might be interesting to talk about
how nuclear power plants work, and then we'll we'll go
(02:56):
into exactly what the problem is in Japan. Yeah, with this, frankly,
this could be a marathon episode. We could talk about
nuclear power plants for hours because they are very involved.
So we decided to stick primarily to the general type
of nuclear power plant being used in question, but also
some of the others that have had major problems in
(03:18):
the past, notably the Chernobyl reactor and the one in
Three Mile Island in in the United States. So let's
talk first about what a nuclear reactor is and how
it generates power. Uh, of course, it's using a nuclear process, right,
It's using decay. Really, it's we're talking about controlling the
(03:40):
decay of of uranium. Really, it's when you compare it
to a coal power plant, um, and you and you
take the very very basics together, this type of nuclear
power plant is almost exactly the same type. You're using
a new clear reaction to generate heat as you would
(04:02):
for a coal fired power plant, right, exactly, you would
you would burn coal to generate heat in a coal plant? So, yeah,
same thing, you're trying to use heat to generate electricity.
You use that to to generate steam. The steam turns
a turbine and a generator, which generates electricity. It's it's
the nuclear reaction that makes it so very different from
the coal plants that. Yeah, And you might ask, well,
(04:24):
why would you want to use nuclear power in the
first place. Well, there's several reasons. One is that, unlike coal,
it doesn't produce uh, greenhouse gases. That's right, right, So
when you burn coal, you're going to generate greenhouse gases
and essentially carbon dioxide being chief among them, and uh
and that can contribute to lots of environmental problems. So
(04:45):
in some ways, nuclear power, at least from a greenhouse
gas perspective, is greener than coal technology. Also, you don't
need as much fuel to generate power as you would
with coal. It's it's actually an incredible skin you could
be talking about, you know, a few pounds of uranium
versus tons and tons and tons of coal. Yes, it
(05:07):
wasn't that long ago that the uh, those of us
in the United States were talking about the coal mine
the coal miners who are trapped in West Virginia. UM.
And of course people start talking about the pros and
cons of coal. Now of course we're talking about the
pros and cons of of nuclear energy. UM. But yes,
it requires far less uh um raw material to generate
(05:30):
the nuclear reaction as it would for the coal fired
power plants. Now, so you're you're talking about material where
you don't need as much. You aren't genering greenhouse gases UM,
and you can create an intense amount of heat very
pretty simply in the grand scheme of things. But there
(05:51):
are a lot of concerns around nuclear power as well.
For one, I mean, we're talking about radioactive material, and
radioactive material that is harmful to human Yes, it's not
just you know, lots of things radiate energy, and not
all of that energy is harmful. Yes. Just the other
night I was watching, uh the CBS news report on
(06:12):
radio activity, and a lot of people in the United
States have been concerned that, first of all, the governments
of Japan and the United States aren't being truthful with
the amount of radiation being leaked in the atmosphere as
a result of the explosions that took place at the
plant in Japan. UM. But they were One of the
(06:34):
things that I think was interesting was they took a
Geiger counter around to several different They were basically walking
around New York City with a Geiger counter, and they
went to the middle of the park and turned it
on and it was picking up readings of radio activity.
And they walked over to granite, a granite monument as
a matter of fact, and UH and and took the
(06:55):
Geiger counter. A geiger counter, by the way, as a
device that measures radioactivity. You hear clicking sounds and it
has a needle. One of the UH. I think of
it as an old style, but really I guess it's not.
With the needle and it shows you roughly how much
radioactivity is being gendered. And granted is naturally radioactive, and
I didn't know that now. Of course, you can't take
(07:17):
just anything UM and throw it in a nuclear reactor
and have it react. You have to use a very
special UM type of material. Because to generate a nuclear
reaction UM, you're splitting an atom, use a stray neutron
to UH break apart the nucleus of another atom. And
(07:39):
and some some elements are more likely to be are
are are easier to do that with than others. You
need something that's called fistle if you're using a effission
reaction as the one as these reactors do. Fusion power
right now is kind of beyond us as far as
it takes more energy to create a fusion reaction than
we get back, I'll of it. But there is a
(08:01):
lot of hope that in the future fusion will become
the the power source for nuclear facilities. The Sun generates
energy through fusion, not fission, so uh yeah, we haven't
we haven't gotten there yet, but there are a lot
of very very smart people working on ways to create
fusion power plants, and it's quite a bit of research
(08:23):
on on these things from Britannica. I like to to
use that, of course as one of my sources. Um
and uranium two thirty five, according to Britannica, is the
only naturally occurring fistle material that's in a ready state
to be to be split apart this way. Um, there
are other, uh different kinds of materials. We're we're talking
(08:45):
about the nucleides um. Somebody probably correct my pronunciation. I
think that's right, but those some of them basically as
long as the atoms are in an excited state. Uh,
they can be um. When they're hit with a slow
moving neutron, you can you can break them apart. Uranium
two thirty five to thirty three, plutonium two thirty nine
(09:06):
and two forty one um Plutonium two thirty nine. You
actually create with your uranium two thirty eight and then
you bombard it with neutrons. Yeah, materials that are fertile,
uh can be that if you are different kinds of
materials that if you add an extra neutron, you can
they can become fiztle. Uh. Those are thorium two thirty two,
(09:28):
uranium two thirty eight, and plutonium two forty um. So
these are very complex atoms and heavy atoms and very
heavy atoms and um. There are are the kinds of
materials required to be used in a in a core
of a nuclear reactor, and uranium two thirty five will
break apart naturally decays over time. But but that's not
(09:51):
the You know, you want to have a controlled and
a controlled reaction in order to be able to generate power,
and you want to be able to do it at
a good time scale. Because we're uh, we don't have
thousands of years to generate electricity. So with the uranium
two thirty five, you actually would bombard it with neutrons
in order to uh to speed up that reaction. Now,
what that will do is that the the atom splits apart,
(10:14):
it generates a lot of energy in the form of
heat and radiation. The radiation comes in the forms of
gamma radiation, beta radiation, and alpha radiation. Uh So, gamma
radiation is a form of electromagnetic radiation UM. In fact,
there are two major kinds of radiation. Electromagnetic radiation, which
(10:35):
is some form of light. Uh it's it's photon radiation UM.
That may not be visible light, but it is. It
falls under the photon radiation. Then you have particulate radiation,
which is when you're talking about an unstable uh atom
particle shoots off essentially from the the atom. And uh
(10:57):
So with alpha radiation uh uh or well, I'll start
with beta radiation. With beta radiation, you've got electrons being released. Right,
alpha radiation, it's protons and neutrons being released. Now, protons
and neutrons are much much much larger in comparison to electrons,
(11:17):
and they move slower than electrons do. So alpha radiation,
you get the protons and neutron splitting off. That's a
particulate radiation that moves slowly. It can actually depending upon you,
know how how you're being exposed to it. Your skin
can sometimes block alpha radiation just because your skin is
thick enough where it's the particles are not moving at
(11:40):
a speed sufficient to be able to penetrate the skin. Um.
The beta radiation is different because those electrons are very
tiny and they're moving really really fast and uh, and
this is the sort of radiation that the sort of
particular radiation that can actually cause pretty nasty deep tissue
damage if it hit to you. And then of course
(12:00):
gamma radiation is really really high energy electro magnetic radiation,
and that stuff is serious business. Uh. You know, gamma
radiation can cause lots of problems in both immediate acute
problems and chronic problems over time. So why would you
want to use this, Well, it's because it gives off
this this amount of energy, this this kind of intense energy.
(12:24):
It's really good at converting water into steam. So if
you can control this reaction, uh and generate the right
amount of heat, you're going to generate a lot of
steam that's going to move through the system and eventually
turn the turbine which is going to uh provide the
power to the generator, and then you you create power
(12:45):
for the power grid. And some countries rely very heavily
on nuclear power to create to to supplement their power grid.
Countries like like France, it's nearly seventy of their power
that comes from nuclear power. In the United States, it's
more like it's funny because there are two, um, two
different things to consider that you might not consider with
(13:07):
some of the other forms of electricity generation. Here UM
atomic reactions are deal with probability UM and they deal
with chain reactions. UM. I remember watching in one of
my science classes a long long time ago an experiment
that they did where they had set up we're not
an experiment, but an an illustration. They had a plexiglass
(13:31):
or clear plastic box and across the floor of it,
the entire floor was covered with mouse traps set mouse traps.
Each mouse trap had two ping pong balls on top
of it and everything was still. So this is the
normal state of the atoms that's supposed to represent the
(13:51):
normal state of the atoms inside the fuel. UM. And
then there was a small hole at the top of
the box, and the person said, Okay, this is what
happens when you add the neutron. The stray neutron is
another ping pong ball in this illustration, and the person
dropped the ping pong ball into into the box, and
of course it hit one of the mouse traps, setting
(14:14):
it off. The other two ping pong balls representing neutrons again, uh,
jumped up from the mouse trap in different directions, and
each of those set off more mouse traps, and each
of those set off more mouse traps. Exponential growth. Yes. Now,
of course in the nuclear fuel uh, you know, in
that particular illustration ended and very quickly within a matter
(14:36):
of you know, probably two or three seconds, because they
were you know, forty mouse traps or something like that.
In nuclear fuel, this continues on UM, but they have
to control that. They have to look at the probability
that a neutron will continue, that there will still be
stray neutrons able to generate more heat energy release UM.
(14:57):
So when they want to what they call a slightly
super critical uh level of reaction, because there's that means
that there is more more than one fission per neutron
so you're you're you don't want it to be a
little bit. You don't want to be underneath that. When
it gets subcritical, that's when there are a few there
are fewer neutrons available to make the nuclear reactions, which
(15:22):
means that you would actually have to pour more power
into the system to to shoot more neutrons into it
in order to generate power. And of course, you know,
the whole goal here is to make it as efficient
as possible when you're generating electricity. Otherwise you're actually consuming
far more power than you are able to convert into electricity. Yes,
when it's one spare neutron to a reaction, that's or
(15:44):
to a nucleus of another atom, that's critical. That literally,
that is what they call critical, and that's the reactive
state of the the reactor core um. From what I understand,
they do want it to be slightly super critical, but
only lightly, and so controlling the reaction is very important,
and it's done in a number of different ways. Sure,
(16:07):
let's talk a little bit about the way the fuel
is put together and then we can talk about how
that control happens. Yeah, I think that that would be
excellent because that is a big part of how they
control the reaction. Yeah, so, so the uranium is enriched
with uranium two thirty five right now for a nuclear facility,
I was gonna say, we should might maybe explain what
(16:29):
that means, because uranium two thirty five is naturally reactive,
but there's only so much of you two thirty five
found in a chunk of uranium. So enriched uranium is
basically they've added more uranium two thirty five to the
uranium overall to make it, to make it more reactive
so they can use it as nuclear fuel. And so
(16:50):
for UH, you have to for for fuel for a
nuclear power plant, you need to have added enough you
two thirty five, So it's got two to you two
thirty five and the overall fuel now you two thirty
five is the same element that you're going to find
in UH in nuclear weapons. But nuclear weapons require a
(17:14):
much higher percentage of you two thirty five to thirty
five within the uranium in order for it to be
weapons grade. So that's a pretty easy way to tell
if someone's making weapons grade uranium is you measure how
how the percentage of you to to thirty five in
the fuel itself. If you've been following the news and
(17:34):
you've seen pieces on where some countries are concerned about
Iran enriching uranium. This is why you can enrich uranium
for a nuclear power program, or it can also be
used in weapons. Right, So if you're enriching beyond that
two to three percent, then that's a good indicator that
you're looking at something more uh dangerous than the nuclear
(17:57):
power plant. So the what the bits of uranium are
actually formed into what what is called pellets, and they're
about an inch long. They're about the diameter of a dime.
So you can think it's kind of like a cylinder
right now. These pellets are stacked together to form rods.
Yes they are. They are contained within a metal rod, yes, yes,
(18:21):
so yeah, you can think of like a there's like
a sheath, a metal sheath, and these uranium pellets are
stacked within that sheath. Now, these rods are then grouped
together into a collection called a bundle. And if if
that's all it was, if that's all you had and
then you started introducing neutrons into it, you would have
no way to to modify to moderate that at all.
(18:43):
It would just the reaction would would increase and increase
until either you would spent all the fuel or you
had had a melt down. And meltdown essentially is when
the fuel itself gets so hot that it melts um.
So in order to control this, they have control rods.
And control rods are made of material that are that
absorbs neutrons, because as we were talking about, you know
(19:06):
these neutrons that that fly off and hit uranium two five,
that's what initializes this reaction. So if you have material
that absorbs neutrons, it's like taking you know, you're you're
you're putting the brakes on things, and the control rods
tend to be you can you can insert them either
all the way down where they are going to control
(19:28):
the reaction as much as possible, keeping in mind that
there's still some decay heat that's going on here. It's
not like it's not like you immediately switch it off.
It's just slowing it down to the point where you
call it a nuclear shut down, but there's still heat.
Or you can raise them all the way up and
then just let the UH reaction go to full full blast.
(19:52):
Cadmium and boron are two elements that are very good
at absorbing stray neutrons, and you may have heard about
born being introduced into the Japanese facility along with sea water.
We'll talk about that in a minute too, um, but
those are those are also uh, those are useful because
they're basically fighting over who gets the stray neutrons and
(20:14):
that just slows everything down and helps right keep it
under control. Now, inside this nuclear reactor, you also have
to have coolant because and actually the coolant is what
heats up to go and then usually you have a
you have a coolant that then runs through another system
that will heat up water and the water becomes steam
and that's what drives the turbine. Some nuclear power plants,
(20:37):
and these are the ones that are kind of particularly dangerous,
have the coolant system also driving the turbine, which means
that you have radioactive material pushing that turbine because the
coolant that encounters the actual rods is going to pick
up radioactive material itself, will become radioactive. It's gonna have
(20:59):
radioacti particles running through that cooling system. So most of
these cooling systems are are self contained and they do
not cross over into the water system that drives the turbine.
They just they just you can think of it as
it runs up against the water system, and the heat
from the cooling system is what generates the steam in
(21:20):
the water system. Um. So, but you have to have that.
If you don't have that again, the uh, the core
can reach a temperature that's so high that the uranium
begins to melt. And there there's a lot of scary
guesswork as to what would happen if you had a
true meltdown, like a full on meltdown to the point
(21:43):
where we're not really sure if the material would get
so hot, like the reaction would continue to a point
where it would just burn right through the reactor. Um
that's a theoretical possibility, although we haven't actually seen that
happen in real life yet, Thank goodness us that's true. Well,
the the movie The China Syndrome is about that, and
(22:06):
I think most scientists would probably tell you that that's
a bit hysterical for what might actually happen. Uh. The
the premise being that the core melts down, the fuel
is melting, and it melts all the way through the
center of the Earth again, from the United States to China,
(22:27):
all the way through the the Earth that might be
a little I think that's probably I mean, I'm not
a scientist obviously, but I think that's a little extreme.
I would definitely call that the worst case scenario. Yeah,
I don't I don't know that it could actually go
that far. But yes, that that is an exaggeration of
what Jonathan's talking about, the idea that it would melt
(22:47):
through the reactor. So the the problems that we could
conceivably face with a nuclear power plant would involve something
going wrong with the ability to insert or remove the
control rods, really to insert them, because because if they're
stuck there, all you really have is a dead nuclear
power plan. And yes, that is terrible and that it's
(23:09):
gonna cost billions of dollars to fix, but it doesn't
pose an immediate threat to the surrounding area. UM. You
also have the problem with if if the water system,
if the cooling system is UH in any way compromised,
then you have the chance of the nuclear reactor overheating,
which unfortunately we have seen happen before, and that can
(23:30):
cause UH massive problems down the line. Now, what happened
with Japan is that the earthquake actually did not UH
did not damage the reactors to the point where they
were inoperable. In fact, what happened was that the control
rods descended, as they should have in that instance to
(23:51):
control that reaction. But again there's decay heat. It's not
like it can shut it off immediately. It's just that
the reaction is no longer continuing, right, but still generating heat. Right. UM.
Another thing to consider with regard to the Japanese reactor
is that, uh, there were containment devices set up. When
(24:15):
you build a nuclear power plant like this, this light
water plant, UM, it is ideal to build a containment
area around the reactor course. UM. This is usually made
with concrete, UH, very thick concrete in the case of
the Japanese plant, UM, which for has has so far
(24:39):
as of the time we're talking right now, prevented a
major release of radiation. UM. The problem comes from what
happens with spent nuclear fuel, which to this point we
haven't mentioned. At some point, when the fuel becomes subcritical
and it cannot continue producing a nuclear reaction sufficient enough
(25:02):
to continue the the electrical output of the plant, UM,
they're going to want the people running the plan are
going to run and replace it with fresh fuel. This
can take weeks. Usually they do maintenance on the plant
at the same time, because it's a good time the
plant shut down. So what they'll do is they'll remove
the bundle of rods and replace it with new rods
(25:24):
of with fresh fuel. But what do you do with
the old rods. That's the tricky part because the old
rods are very hot and they are very very radioactive. Yeah,
it's just like it like Chris was saying, it's kind
of like, you know, it's just that they're not generating
the amount of energy necessary to run the plant, but
they're still generating tons of like of energy and not
(25:44):
really tons. Don't write me and um, the they are
very much dangerous to people and here's eventually they will
be inert. But but eventually I'm talking like ten thousand years. Yes,
we can't wait around that long. And because they're generating
so much heat and so much radioactivity, they tend to
corrode pretty much any container you put them in. This
(26:07):
is one of the aside from the potential for an accident. Uh,
this is one of the things that can that makes
nuclear power so controversial, is that this is the flip
side of the green coin. Yes, Storing the nuclear fuel,
the spent nuclear fuel is very, very difficult. Uh. Nobody
wants nuclear fuel in their backyard. Um, and there's not
(26:31):
even there's not a good answer for that. Storing it
in caves is one solution. The question is whether or
not people will go in there. Um. You know, a
thousand years down the road is still very radioactive. Um.
You could say, well, why don't we shoot it off
into space. Well, that's fine, except there's the potential for
(26:54):
an accident. Rockets are not foolproof, and if you have
an accident with the rocket, there's the potential that radioactive
waste could be scattered across the roth's atmosphere in that again,
is something that no one wants to happen. So one
of the first things they do when they remove the
fuel from what I understand from the reactor core, is
(27:16):
they put it in a containment pool. Water, as it
turns out, is a natural shield against radioactivity. Uh. Not
only is it cooling the very very hot rods with
the nuclear fuel inside, but it also is shield doing
some shielding against radioactivity. Well in the Japanese plant, when
the power was shut off, ironically enough, Uh, the water
(27:41):
began to evaporate. It was boiling off. And that's the
problem is that there when there's no more water surrounding
the spent fuel. It wasn't the reactor cores, it was
this the spent fuel. Uh, and the reaction is allowed
to continue that generates hydrogen when the hydrogen is explosive. Yeah,
(28:01):
it's It's a process called thermolysis. It's when heat turns
water into hydrogen and oxygen breaks up the molecules into
their into their component atoms, and you can you can
do the same thing with electricity, that's electrolysis. So it's
the same sort of thing. It's just you pour enough
energy into a molecule and you can break those molecular bonds.
And that's exactly what happened. Hydrogen built up. But before
(28:24):
we get to the hydrogen problem, I should also mention
there were a lot of fail safe procedures in place
at the Japanese plant. It's none of the Japanese were
not doing due diligence with safety. It's just that was
the perfect set of terrible situations for this to happen.
And it and it from what I understand, not to
interrupt him, um, from what I understand, the plant was
(28:46):
intended to survive and eight plus UH point Richter scale earthquake. Yeah,
it was the tsunami that really hit them. Because here's
what happens. They lost power from the power grid, well
the power plant had and they need power to pump
water through the system in where to keep it cool.
(29:07):
So the pumps run on electricity. So they switched to
their diesel generators. But then the tsunami hit and the
diesel generators were not above the tsunami levels, so they
were flooded and could no longer work. They also had
battery power, but the battery power was only meant to
last you know, I think it like a day, because
(29:28):
the idea was that, well, we won't be without power
for longer than that. But they could not get supplemental
power in place to uh to cover the gap between
the battery power and when they could get some other
form online. And so the water stopped pumping and the
temperature kept building and the hydrogen built up. Um and
(29:49):
hydrogen is incredibly flammable. It's explosive, and there was the
hydrogen collected at the top of the facility. UH. Something
set it off and there was that's what that big
explosion was when we first you know, and there's been
a uh, there's been other ones since then, but that
(30:10):
initial explosion, people were worried that the reactor had exploded.
That's not what happened. It was the pocket of hydrogen
that it exploded. And as uh, if you've been through
a certain level of science, of course we have some
younger listeners. The three things that you need for fire
are you know, heat, a source of fuel, and air,
and you would certainly have that with very hot fuel rods,
(30:34):
air in the in the area, and then you know
the source of hydrogen. So um, it was a very
dangerous situation. Now uh people have said, uh, you know,
this is going to be another Chernobyl. But Chernobyl was
a different situation. They did not have any containment in place,
or what they did have some containment that it was
not designed to prevent the kind of release that that occurred.
(30:58):
Chernobyl was interesting. So when we're talking containment, like Chris
was saying, you're talking about a very thick concrete liner,
usually there's a steel a steel like you can call
it like a furnace, I guess, but it's a steel
container that is lined with concrete, and then you have
a big concrete building around that, so you've got two
(31:19):
barriers of concrete and a barrier of steel in order
to contain the nuclear reactions. Chernobyl only had the basic container,
did not have a secondary container, so if there were
a failure, then there you have much more chance of
nuclear fallout. And in fact, the Chernobyl incident happened ironically
during a procedure where they were trying to test out
(31:41):
a safety feature because what Chernobyl was going to have
was having some similar issues to the japan facility and
that Chernobyl um they were worried about what would happen
if power were lost, If they lost power from the
power grid and they can no longer pump water through
their system, so they uh they had these diesel backups,
(32:01):
but the diesel backups would would not really kick in
until about a minute after the initial power loss, and
that minute is a long time for these nuclear reactions
to go unchecked, right with no water cooling them down.
So one of the things that we're looking at doing
was using the turbine as it slowed down to generate
enough electricity to keep the pumps running for that one minute.
(32:24):
Before the diesel backups could kick in, and they were
running a test and it was like the perfect set again,
a perfect set of situations going wrong for that test
to fail. There was a power spike, and then while
they were trying to react to the initial power spike,
there was a second power spike, and that's when you
had another explosion and release of steam and nuclear steam,
(32:50):
and then there was the terrible fallout that happened in
a huge radius around your noble Belarus in particular was
hit really really hard by that radio and it was UH.
And there there are levels of nuclear disaster. We give
them a numeric UH assignment for how bad it is,
and it goes from one to seven. Chernobyl was a
(33:12):
seven three mile island which happened in the United States
nineteen seventy nine. That was a five, and the Japan
incident right now is is listed as six. Of course,
that can change over time and things get worse. Um
hopefully it will not so, but yeah, because Chernobyl was
(33:32):
was not as protective as it needed to be. That's
why the it was ended up being a seven. Like
if it had had the right protections in place, it
may still have been a terrible, terrible accident, but it
may not have been as bad as it turned out
to be. Three Mile Island was interesting and that uh,
it was a combination of user error and mechanical failure.
(33:53):
There was a valve that was open, and then the
power to the valve was shut off, which normally would
mean the valve would close. The valve would only open
when powered. There's a mechanical failure. The valve did not close,
and because um the indicator on the console said that
there was no longer power going to that valve, all
(34:14):
the operators assumed that the valve was closed, but their
readings were showing that the pressure and temperature were off,
like the pressure and temperature of the core should not
have been what it was. Well, the reason why there
was a problem was because the water was boiling off
and there was this open valve and so there was
an open you know, the pressure was not building the
right way. But it took hours for them to figure
(34:36):
out what the problem was. Actually, there was a shift change,
and it was when someone from the new shift was
looking at the problem that they figured it out. And
then by then the scare had really hit. Unfortunately, Three
Mile Island wasn't as bad as it could have been.
There was no There was only I think there's a
partial melt down, which was scary, but it could have
been so much worse if someone had not picked up
(34:58):
on that mistake. Now as far as Japan goes, Uh,
we talked about the boron uh and the seawater. Well,
dumping seawater into the reactor is pretty much a last
step because the seawater is going to ruin that reactor.
You're not gonna be able to use it again. Um.
And the boron is there to help absorb those neutrons,
like Chris was saying. Yes. Another another one of the
(35:21):
problems that they were mentioning on the news yesterday as
that the day we're recording this is that Um there
they are currently this. This will show you probably when
we're recording this. Uh. They were talking about the pumps
that are in place. They wanted to be able to
restart them. They've had trouble doing that and they're going
to have more trouble doing that now. Uh. They're hoping
(35:43):
to again as at the time we're recording, to restore
electricity to the plant so that they can go ahead
and shut the pumps back on. But for the reactors
UH in which they have introduced seawater, this is an
issue because the seawater also clogs those pumps, so it
is going to be even more difficult for them to
contain the situations in those damaged reactors UH today than
(36:09):
it would have been a few days ago when the
problem was first getting out of hand. Yeah, the issue
was just that if they did not introduce the seawater,
there was there was an increased danger of a meltdown because,
like we said, this temperature just keeps on going. It's
not even with the control rods in place, which the
system did do UM, it does not eliminate that heat.
(36:31):
You have to be able to circulate the coolant through
there in order to to maintain the temperature. And UM,
because there was no way to circulate the coolant, they
had a choice either they introduced the seawater and boron
into the reactor core, or they take a chance on
a meltdown. And and clearly the second option is not
one that anyone wants to take. That that is not
an option, right. So there's a lot of concern actually
(36:55):
that this this UH will really set Japan back quite
a bit because they are very reliant on nuclear power
and that um losing this facility, which it's quite possible
that they will lose at least, uh more than half
of the reactors in this facility, that it will really
(37:16):
impact their ability to create electricity. And the quake in
general has really um, I mean, it seems it seems
weird to say this because there are so many more
important tragedies that are connected to the quake, But the
quake itself could actually set back everything from electronics to computers,
(37:38):
just because so much of it is manufactured in Japan
and those manufacturing facilities were damaged in in the quake.
That that's true. Um, Even places that weren't directly hit
by the tsunami are still suffering problems. Um. And from
what I understand, the majority of flash memory used in
(37:59):
all kinds of electronic devices cell phones, smartphones, tablets, MP
three players, and all kinds of other things, the majority
of it comes from Japan. Uh So this is likely
to u to cause problems in the supply chain and
disrupt um electronics manufacturers the world over. And of course,
you know, those those people who who weren't directly hit
(38:21):
probably would like to get back to work. But this
is going to be difficult for them to be able
to move on and and do things that they want
to do again. You know, even even people who weren't
directly affected by uh, you know, losing their homes and
losing friends and loved ones. Um, you know, this is
this is difficult for for them as well. It's a
(38:41):
major catastrophe. It's all. It's I was gonna say it's
almost unimaginable to me, but no, I think I have
to say it's unimaginable. I I cannot comprehend the level
of catastrophe this is. I mean, I see the pictures,
and I see the video, and I hear the testimonials
and it's all heartbreaking. But it's just there's I can't
(39:02):
grasp it. It's beyond my ability. Um, and guys, I
want to say this before we before we start wrapping up.
We have some amazing articles on how stuff works dot Com,
about nuclear reactors, about radiation, and about the Japanese crisis.
There's how nuclear power works, how Japan's nuclear crisis works,
(39:23):
how radiation works. These articles are fantastic. I read through
all of them in prep for this UH, this podcast
and the writing on these are amazing. I mean, you
get the Marshall brain and Robert Lamb and uh and
and Deborah Ront's all did fantastic jobs. And my hat
is off to them because they took a very complex,
(39:46):
dense subject and they broke it down in a really
understandable way. So if you want to learn more, I
highly recommend you check them out. Yeah. There there are
so many other types of uh nuclear energy to the
haven't touched on and talk anything about, uh some of
the other new technologies that people are trying out now, um,
(40:07):
one of them being the pebble bed reactor that they're
starting to roll out in China, which, from what I understand,
maybe to some degree safer there's less chance of something
like a meltdown occurring because it uses a different method
of nuclear reaction, and that might be maybe we can
look at that again when when this uh these issues
aren't so fresh and we can uh uh you know,
(40:29):
look at some of those. And I'm also interested in personally,
and something that I read about and wired um a
couple of years ago now or maybe about a year
and a half ago, thorium using thorium, which is not
nearly as radioactive as uranium. Of course it will carry
for some people, probably for a lot of people, the
stigma of being labeled nuclear energy. But from what I understand,
(40:51):
you can hold the piece of thorium in your hand
and you should not suffer any ill effects because it's
not the same kind of it's not as radioactive as
as uranium or plutonium, and can be used on a
smaller scale with uh, you know, the possibility. Like I said,
I'm only reading this, but it doesn't look like there's
nearly the possibility of uh, the kind of disaster that
(41:14):
we're talking about here. So there might be other kinds
of technologies that will use in the future that can
still harness the power of the atom without being so
dangerous in the event of an act of you know,
a nature event like this. And I imagine that this,
this disaster will definitely make countries around the world rethink
(41:34):
their their approach to nuclear power. Well, that's already that's
already happening in the United States. President Obama has ordered
um a look at all the nuclear reactors currently in
service to to just as a check up to see
how they're doing. Germany, I think has taken all of
theirs offline, um with the idea that they will evaluate
(41:56):
their safety. There were bills in many countries or laws
already passed to extend the life of aging nuclear reactors
that from one understand, are being rescinded one by one
as people are rethinking the possibility that older reactors and
this the reactor in Japan was older too. Yeah. Um so,
I mean there you know, as as we complain about
(42:18):
very often, technology changes very quickly and it's hard for
us to keep track of It's also changing in the
nuclear industry as well, and there are new safe safety
measures that might be implemented in a in a new
reactor that wouldn't have been implemented in the nineties, seventies
and eighties. It's just the question of will it be
politically feasible to implement nuclear power, because uh, it's one
(42:38):
thing to to tell people that safety measures have improved
and that, uh that we've learned lessons from these events
that we can, um we can implement in the future.
But there's it's such an emotional issue and uh it
has it does have problems. I mean, the nuclear waste
is still a very very big and uh, there's not
(43:01):
an easy solution to that, and as long as those
still exist, I think we're going to see increased resistance
to implementation of nuclear power, which I mean that's gonna
be very frustrating for some people, although you have to
admit that, um that the we've seen examples of things
going wrong, and sometimes it's because people did not react
(43:23):
the right way, and sometimes it's just that the perfect
set of circumstances hit in order for something to go
terribly wrong. And you know, there there is the argument
you could make that the likelihood of that happening is low,
but there's also the argument of any likelihood is too much, right.
(43:44):
So it'll be interesting to see where the future of
nuclear power goes. It'll be interesting for me to see
if the the projects that are trying to make breakthroughs
infusion power suffer as a result, because that is another
form of nuclear energy, and uh, it's a frame form
of nuclear energy. It's not the same as vision at all.
But it could very well be that just because it
(44:05):
has that association, that these programs could start to lose funding.
So we'll have to keep our eyes open see what happens. Uh.
Our thoughts go out to everyone in Japan. And all
those who are affected by this disaster. And it's absolutely
a tragic event. And uh and we really feel for
you guys. Um, if you guys want to talk to
(44:27):
us about nuclear power, if you have your own thoughts
you would like to share, please do so. You can
contact us on Twitter and Facebook. That handle is tech
Stuff hs W, or you can write us an email.
That email addresses tech stuff at how stuff works dot com.
Chris and I will talk to you again really soon.
(44:47):
For more on this and thousands of other topics. Is
it how stuff works dot com. To learn more about
the podcast, click on the podcast icon in the upper
right corner of our homepage. The How Stuff Works iPhone
app has a ride Delmode It today on iTunes, brought
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