What is the future of nuclear power?

Daniel and Kelly talk about how nuclear reactors work and explore the new techologies that try to limit the risks.

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Episode Transcript

Speaker 1 (00:06):
Nuclear power is kind of a hallmark of the modern age. Finally,
all that nerding out to understand the nature of matter
and how the atom was put together led to some
real applications, and wow, did things get real. Nuclear physics
gave us nuclear weapons and the omnipresent threat of total annihilation,
but it also gave us nuclear energy an incredible way

(00:30):
to generate emission free energy from weird little rocks. Later
this week, we'll dig into the policies and politics of
all that, whether nuclear power is a net good or
bad for the environment, and talk to a journalist who
explored the new pro nuclear environmental movement. But today we're
going to dig into the science and make sure our
next conversation is well informed by the science. How does

(00:53):
it all work? What about salt reactors and pebble fuels?
What is the future of nuclear technology? Genium? Welcome to
Daniel and Kelly's Extraordinary Powerful Universe.

Speaker 2 (01:19):
Hello. This is Kelly Waider Smith. I'm a parasitologist who
also studies space, and we are recording this episode on piden.

Speaker 1 (01:28):
Hi. I'm Daniel. I'm a particle physicist, and I will
judge anyone who says nuclear instead of nuclear.

Speaker 2 (01:34):
Oh, I mean that's fair. Yeah, or nuclear yeah? Ye,
Judge away, man, Judge Away.

Speaker 1 (01:41):
I heard a lot of them Texas when I lived there.
Nuclear power.

Speaker 2 (01:45):
Oh man, how long were you in Texas?

Speaker 1 (01:47):
I went to Rice in Houston. Yeah, and that's where
you know one of our presidents came from, and he
said nuclear every single.

Speaker 2 (01:54):
Time Bush went to Rice.

Speaker 1 (01:56):
No, but he's from Texas.

Speaker 2 (01:57):
Oh yeah, got it? Okay, right, But one of.

Speaker 1 (02:00):
The Bushes went to Rice with me? I think with
George P. Bush, son of Jeb Bush, was a Rice
with me. Yeah.

Speaker 2 (02:06):
Oh were you two BFFs?

Speaker 3 (02:07):
No?

Speaker 1 (02:08):
Definitely not. Oh all right, I mean just that he
was very political and I very much wasn't. I don't
know the guy at all.

Speaker 2 (02:15):
Yeah, got it, got it. What is the most that
you've ever leaned in too? Celebrating a particularly nerdy holiday?

Speaker 1 (02:26):
I don't know if it counts as celebrating a holiday.
But during the pandemic, some of our friends and neighbors
challenged us to a bake off competition who could make
the most interesting cake with movable parts, which was a
big engineering challenge. And when we showed up at their house,
we had to measure the width of their door to
see if our cake would fit. Because I made this

(02:48):
enormous landscape with a boat that would go down a
river and a windmill with pieces that turned. I think
I took like a week off of work and I
bought all the marsh mellows and all the rice crispies
at the grocery store to make this ridiculous landscape.

Speaker 2 (03:05):
Yeah did you win?

Speaker 1 (03:06):
Oh yes, we absolutely destroyed them just by sheer size.
You know, I was going for like, this thing has
got a pop. So yeah, it was pretty impressive. I
gotta say.

Speaker 2 (03:16):
I mean, that's a good way to pass the pandemic.
Did you take a picture?

Speaker 1 (03:19):
We have a picture somewhere. Absolutely. And then it had
other weird downstream consequences because nobody could eat that much
rice crispies, and so we ended up throwing a lot
of it away, which led to a huge explosion in
the neighborhood rat population. And then we ended up discovering
a rat's nest literally, like a mom and ten little

(03:40):
rat babies near our garbage can. And when you discover
a rat's nest, the mom will just abandon the babies.
So then we had like ten cute little rat babies
and they starved to death because the mom wouldn't come back.
And you can't feed rat babies. I don't know if
you know much about rats, but like they have to
be nursed, and also they can't poop on their own.
Like rat babies are a whole thing. And so then

(04:02):
we felt really bad about that, and that's why we
ended up adopting rats.

Speaker 2 (04:06):
That story was a roller coaster ride, Daniel. There are
some real highs and real lows there, I know.

Speaker 1 (04:13):
And because we had such a good experience with having
pet rats, the kids were able to convince me to
get a dog. So the reason and we now have
a dog who is an integral part of our family,
is because I went all out celebrating this crazy engineering challenge. Bakathon.

Speaker 2 (04:28):
Oh my goodness, it is kind of incredible the way
small things in life can lead you down completely different paths. Well,
your story is way more wholesome than mine.

Speaker 1 (04:37):
Yeah, what's yours?

Speaker 2 (04:38):
I was born on Molday. So Avagadro's number is what
six point two three times sent to the twenty third
or something like that, but October twenty third, and so
for my junior and senior year of undergrad I had
chemistry themed birthday parties, and it would be like, uh, yeah, it.

Speaker 1 (04:55):
Sounds really fun. Why didn't I get invited?

Speaker 2 (04:58):
If I had known, you man, you would have been.
But it was, you know, like how many electrons are
in beryllium? Wrong drinks?

Speaker 1 (05:04):
And it was.

Speaker 2 (05:08):
Because you know, no one knows that.

Speaker 1 (05:10):
Nobody knows that, because it's chemistry, it's all exceptions.

Speaker 2 (05:13):
That's right, that's right. And you know, my friends didn't
know chemistry very well either, so it was we had
a really great time.

Speaker 1 (05:20):
But this is high school, so you're what drinking soda
or punch or.

Speaker 2 (05:22):
Something undergrad undergrad?

Speaker 1 (05:24):
Undergrad. Oh, so these were fun parties.

Speaker 2 (05:26):
These were fun parties. We were all of legal drinking age,
and we were careful, we watched out for each other,
but way less wholesome than a cake with a waterfall.

Speaker 1 (05:38):
Well, it does sound like your parties are maybe the
only way to make chemistry fun.

Speaker 2 (05:42):
Ah, we did have a good time. The Benzene ring
and I me and my five friends, six of us total,
because there's six carbons in a benzene ring.

Speaker 1 (05:50):
And today on the podcast, we're going to be exploring
how small decisions can lead to big consequences that also
involve chemistry. Nuclear power is incredible because these tiny, little
weird rocks can lead to incredible influence on our economy.

Speaker 2 (06:05):
I am always impressed by the way you bring our
tangents back to the topic.

Speaker 1 (06:09):
Not always easy, but I'm like, wow, we could do
a whole episode on Kelly's Weird college Parties.

Speaker 2 (06:15):
I think our listenership would go down pretty fast at
that point. But Okay, so today we're talking about nuclear power,
and I'm really excited to be talking about these sort
of advances in nuclear power technology now because when Zach
and I wrote Soonish, which came out in like twenty seventeen,
we did some research on advanced nuclear fission reactors. And

(06:36):
I always have to pause before I say fission and
fusion because I memorized it in the opposite way initially,
and so now I will always pause and have to
think through it.

Speaker 1 (06:45):
But anyway, well, you've got nuclear right. At least you
didn't say nuclear fusion.

Speaker 2 (06:49):
There you go, that's right now. I'm gonna avoid saying
that we're too out of a concern for messing it up.
But we had a chapter on fission and a chapter
on fusion, but I haven't thought about this in about
the decades since we researched the topic, and so I'm
looking forward to your coverage of what the new and
exciting things are in the world of advanced nuclear reactors.

Speaker 1 (07:08):
Yeah, if we're going to talk about nuclear power, we
need to understand how it works and how it's changing,
because it's not a stagnant field, right. Nuclear reactors today
are not the same nuclear technology your grandparents grew up with,
and so there's lots of promising directions, some with more waste,
some with less waste, some with greater risks, some with
smaller risks, and so it's crucial to understand the whole

(07:28):
spectrum of possibilities in order to have an informed conversation
about nuclear politics, which we're going to have in the
next episode. So I was curious what listeners thought about
the future of nuclear technology. What have they heard about
in terms of advanced nuclear reactors. So I went out
there and I asked our group of volunteers what is
the most promising advancement in nuclear power technology. Here's what

(07:52):
they had to say. If you'd like to play for
a future episode of the podcast, we really really really
really wanted to hear your voice on the pod right
to us to questions at Danielankelly dot org. So think
about it for a minute before you hear these answers.
What do you think is the most promising advancement in
nuclear technology? Here's what our listeners have to say.

Speaker 3 (08:13):
Just for Kelly, I've heard of biologists working on microbes
to solve our nuclear waste problem.

Speaker 1 (08:17):
Somehow they eat the nuclear waste.

Speaker 2 (08:19):
No idea how it works, but heyo biology.

Speaker 1 (08:22):
There are a few promising advances, but the most promising
comes in the form of superpowers from what used to
be just ordinary bug bites.

Speaker 2 (08:29):
But where I would like to see more study is
in medical applications such as radiation treatment for cancer.

Speaker 4 (08:39):
Not running redundant systems through the same conduent.

Speaker 1 (08:43):
I think the most promising advance is the potential to
use what used to be waste as fuel for a
whole new set of nuclear reactions, using or repurposing fuel
that has been expent. Reusing the nuclear waste as opposed
to story without a doubt, fusion decreasing the waste.

Speaker 2 (09:03):
People have probably paid a lot of money in PI
to make me think of thorium, So I'm going to say.

Speaker 4 (09:07):
Thorium SMRs, which are those small modular reactors micro nuclear
energy where they're able to go much smaller nuclear power stations.

Speaker 3 (09:20):
I guess to me what seems most interesting is the
liquid thorium salt reactors, which kind of can use up
the material really well from what I understand, or have
beneficial byproducts, and are also seemed a lot safer.

Speaker 5 (09:35):
The very teeny tiny amount of nuclear material that's necessary
now to create vast amounts of energy, which means it's
not as big of a risk of a meltdown and
things like that.

Speaker 4 (09:50):
Perhaps the reactors are more efficient, more manageable, less likely
to melt down in the case of an earthquake or
tsunami or other natural disaster.

Speaker 2 (10:02):
As usual, a lot of fantastic answers. We're not going
to be talking too much about fusion today, but if
you want to hear more about fusion, a little while back,
we recorded an episode on whether or not there would
be enough fuel available to run fusion plants, and we
go through the science of fusion reactors there as well and.

Speaker 1 (10:18):
Throw cold water on that whole industry.

Speaker 2 (10:20):
Well, I remember we were optimistic at the end that
you know, once we got fusion going, maybe we'd get
the technologies needed to make like deuterium and trinium more available,
but maybe maybe maybe, But all right, but now today
we're talking about fission reactors in particular.

Speaker 1 (10:37):
Yes, exactly, and so let's dig in first and make
sure we killing everybody understands the difference between fission and aufusion,
because they're closely related but very very different. Right. So,
fusion is what powers the universe, it's what makes stars bright,
it's where all the energy on Earth comes from. It's
really almost ubiquitous in the universe. Fission is much more

(11:00):
more rare. A fusion is basically when you take light
elements hydrogen, helium, things lighter than iron, and turn them
into heavier elements, so you stick them together and energy
is released. So, for example, if you take hydrogen and
you stick it together to make helium, energy is released
and the mass of that helium is less than the

(11:20):
mass of the hydrogen's combined, so energy is released there
in fusion. So that's fusion is you take light elements,
you stick them together, and energy is.

Speaker 2 (11:29):
Released, which sounds easy but requires super extreme conditions to
make happen, which is why it's been so hard to
make a fusion plant exactly.

Speaker 1 (11:37):
Those nuclear i do not want to stick together. They
have coolombic repulsion. You need high density, high pressure, all
sorts of stuff to make that happen. If you make
it happen, it releases energy and that helps it happen.
So it's this cool ignition process where the energy released
from fusion helps make the next round of fusion happen.
And you have a sort of similar chain reaction going
on in fission. But fission is the other direction. Fission says,

(12:00):
take a heavy element, break it open to make it
a lighter element, and energy is released. In that case,
you might wonder a whole lot a second, didn't Daniel
just tell us that when you squeeze light elements together
to make them heavy, energy is released. Now he's saying,
if you break elements apart to make them lighter, energy
is released. And yeah, those do sound contradictory. And the
difference is whether you're starting with light or heavy elements. So,

(12:23):
if your elements are light like below iron, specifically, fusing
them together releases energy, making them heavier towards iron. If
your elements are heavy, like uranium, something heavier than iron,
breaking them apart, bringing them again towards iron releases energy.
So basically, anytime you're taking a step towards iron, which

(12:43):
is like the middle of the periodic table, you are
releasing energy.

Speaker 2 (12:46):
Can you remind me? Inside of stars is that where
we get iron and everything up from that? What is
the breakof there?

Speaker 1 (12:54):
Yeah, it's about iron. So inside stars you mostly have hydrogen.
Hydrogen fuses to me helium, and then that fuses to
make neon and carbon and oxygen and heavier stuff silicon, nickel,
all the way up to iron. And that whole process
keeps the star hot because every step along the way
releases energy. What happens when you start fusing iron. If
a star is really big and really hot and has

(13:15):
the high enough temperature tofuse iron, that cools the star.
It takes some energy because it costs energy to fuse
iron together into heavier stuff that cools the star and
kills it. So that's the end of a star's life
when it has enough iron in it that that iron
starts to fuse and cools the star. So you can't
really make stuff heavier than iron in any substantial quantities

(13:37):
inside a star. To make the stuff heavier than iron,
uranium platinum, gold, all that good sparkly stuff. You need
other kinds of events collisions of neutron stars and supernova
for example, very briefly have the conditions to make those.
It costs a lot of energy to make those very
heavy stuff.

Speaker 2 (13:54):
Okay, interesting, all right, So fusion really hard to do
unless you're in the sun. Fission much easier to do
using big stuff.

Speaker 1 (14:01):
Yeah, exactly. So find some uranium, shoot it with a neutron,
for example. The uranium will break apart and it will
release more neutrons, and those neutrons can hit more uranium atoms,
which can release more neutrons. So if you have it
set up correctly, like your fuel is dense enough so
there's a high enough chance for that neutron to hit
another uranium nucleus, and the neutrons are at the right

(14:22):
speed to make that happen, Like really fast neutrons are slow,
neutrons might be more or less likely to make the
uranium nucleus break up. We'll dig into that in a minute.
Then you can get a chain reaction. If it's a
runaway reaction, like the fuel is very very dense and
things are growing exponentially, you get a bomb that's a
nuclear bomb.

Speaker 2 (14:40):
Don't do that, folks, not in your basement.

Speaker 1 (14:43):
If you manage it so that the rates at which
one nucleus is spurring the fission of another nucleus, you
regulate it to be steady, then that's a reactor. It's
releasing energy, but it's not growing exponentially out of control.

Speaker 2 (14:57):
And why is uranium the sweet spot on the periodic
table for stuff you want for your fission reactor.

Speaker 1 (15:04):
It's not really that sweet. It's just something that's around
and for a while, is pretty cheap to mine. As
we'll hear about, there are lots of things that are fissile.
It's just a question of what's present in the Earth's crust,
what's cheap to mine, what's not already being used by
other industries. And so uranium is actually not a great
source for fuel because most of the uranium we find

(15:26):
in the Earth's crust is an isotope that's not great
for fission. It's uranium two thirty eight. Uranium two thirty
five is pretty good for fission, but most of what
we find in the ground is uranium two thirty eight.
Less than one percent of natural uranium is the kind
we want so as we'll talk about there are other
options like thorium that are maybe even better for nuclear fuel.

Speaker 2 (15:49):
Let's dig in then to uranium a bit more. So
you said, we mostly find uranium two thirty eight, but
we need two thirty five. How do you get it
from two thirty eight to two thirty five?

Speaker 1 (15:59):
So what you do is just enrich it. Like remember
chemistry lab when you have like a pilot goo and
you need to separate it out into the elements of
the goo. You can like boil it and one will
boil off, or you can, you know, try to make
them settle or something. There's lots of different tricks in chemistry,
and what they typically do, because one of them is
heavier than the others, they use a centrifuge. So if

(16:20):
you remember, like hearing about Iranian centrifuges as they're trying
to purify uranium, that's a typical strategy because they have
different masses, is use a centrifuge, and so you can
enrich your uranium. Run these centrifuges more and more and
filter out the two thirty eight you get a higher
and higher fraction of two thirty five.

Speaker 2 (16:36):
I've always been unreasonably concerned about USB sticks after hearing
the story about how the virus that messed up the
Iranian centrifuges was brought in by somebody who just had
a USB stick that had the virus and then when
they stuck it into one of the computers, it spread,
which is like amazing, And I'm sure there's a lot
of other things I should be way more worried about,
and of course, like nobody really cares about what I've

(16:57):
got going on in my office. I remember thinking that
was just like such a cool story, and now every
time I see a USB stick, I think, h's on you.

Speaker 1 (17:06):
It's a pretty cool story about engineering, like cyber espionage,
pretty cool stuff. But are you running a uranium centrifuge
and your science form?

Speaker 2 (17:14):
Well, I mean, why would I admit something like that
to you, Daniel on air? That's ridiculous, But you wouldn't
be a good spy at all. But yeah, I mean
the story there is that like this virus messed up
their centrifuges because there was concerned that Iran was turning
two thirty eight into two thirty five so that they
could start making weapons, and by messing up that process,
by messing up all of their super expensive centrifuges, we

(17:35):
at least managed to slow them down.

Speaker 1 (17:37):
And so you need to enrich uranium because you need
dense enough source of the good stuff uranium two thirty five.
If you don't have a dense enough then it makes
neutrons when it splits, but then those neutrons don't find
other two thirty five nuclei and it just peters out.
So you need to be dense enough. You need to
enrich it up to like two or five percent. Doesn't
have to be pure uranium two thirty five at all,

(18:00):
like two to five percent, But this is still kind
of a problem because you end up mostly just burning
the U two thirty five, and the U two thirty
eight is just sitting there, and it sits there and
makes heavy elements which are bad. So this is like
really not a great mixture. A lot of the waste
comes from U two thirty being in the reaction, not
being part of it, and then getting converted to toxic stuff,

(18:22):
so it's not like a great situation. But what you
need to do to make uranium fission happen is to
enrich your fuel. So you have like two to five percent.
Then you also have to engineer the speed of those
neutrons to make things work.

Speaker 2 (18:35):
So if you want the neutrons to be going quickly
so that they're bumping into the two thirty five, why
would you want to slow them down. It seems like
more neutrons is you know, that's better, that's more energy.

Speaker 1 (18:45):
Yeah, it seems like fast neutrons are good, right, The
whole point is to get energy out. Well, the thing
is that you two thirty five is a little personicity,
Like if you shoot fast neutrons added sometimes they will
just go right through. They will not make it fizz.
What is the very many fission? They will not make
it fission. Can want atom fission? That seems weird.

Speaker 2 (19:04):
They will not fission it. I don't know.

Speaker 1 (19:07):
I will not stand for that anyway. YouTube thirty five
likes slower neutrons. YouTube thirty eight likes faster neutrons. But
uranium fission doesn't make enough fast neutrons to sustain fusion
with two thirty eight, So you got to use the
two thirty five, and you've got to slow down the
neutrons untill they're in the sweet spot for making other
uranium nuclei go. So you've got to moderate the temperature.

(19:28):
So you hear a lot about neutron moderation, and so
the way they do this is they use water. So
you have like these fuel rods and then you have
water around them, which is also good for cooling them
and extracting the energy, but it slows down the neutrons
to keep the reaction going. It's a little counterintuitive, but
this stuff is a little bit sensitive.

Speaker 2 (19:47):
I thought the answer because my memory is great. I
know I wrote about this about a decade ago, but
I thought the answer was going to be you don't
want the neutrons to go too fast because you don't
want the reaction to go too fast and overheat. But
that's not the answer. Was misremembering. Okay, so you've got
the water. The water is heating up. How does this
create energy? Does the water turn into steam and turn

(20:08):
a turbine or is the energy being collected in some
other way?

Speaker 1 (20:12):
Yeah, so not directly. The most popular technology is called
a pressurized water reactor. You have uranium rods surrounded by water.
The water moderates the speed of the neutrons, also keeps
the core from overheating, and then you've got to extract
the energy from that water, so it heats up the water.
How do you get the energy out of the water,
typically a turbine. Right. Also, that water becomes radioactive, so

(20:34):
you want to buffer yourself from that. So typically there's
like a heat exchange or with that water well then
heat up other water. You have like these two corkscrews
that interwove with each other. It's sort of like electrical inductance,
but with heat or just basically a radiator. You have
this water pass near other water and the hot, nasty,
radioactive water heats up the clean cold water, which then

(20:57):
boils into steam and then turns a turbine. So that's
the most common steps, and this is called a light
water thermal reactor, sometimes known as a pressurized water.

Speaker 2 (21:07):
Reactor if I'm remembering correctly. The reason that light water
thermal reactors are the most common kind of reactor out
there isn't because we were super careful and we looked
at all the possible reactor designs and there was definitely
none that could be better than this, but because we
sort of happened upon one design because it fit really
well in our submarines that we wanted to have nuclear

(21:28):
powered Is that story correct.

Speaker 1 (21:30):
Yeah, that story is correct. In the fifties that were
exploring lots of different technologies, some of which we're going
to talk about thorium and other technologies. But this was
a good fit for the military because one of the
waste products of this reactor is plutonium, which the military
wanted to produce anyway for their weapons. Also, if you're
on a ship or a submarine places that the military

(21:51):
wanted to put nuclear power, water is plentiful. It's not
so hard to find water. And so these light water
thermal reactors were explored for the military, and the government
basically stopped funding all these other directions. The government's decisions
early on determined like what was explored and what was
made economically feasible. No private industry was like involved in

(22:12):
developing nuclear technology. This is definitely like a public investment
by the government.

Speaker 2 (22:16):
All Right, well, let's take a break, and when we
get back, we'll talk about some of the risks of
this particular kind of reactor. All Right, we just finished

(22:39):
talking about how light water thermal reactors work. Let's talk
about some of the risks of this particular kind of reactor.
Go for it, Daniel, You're turning to be the negative Nelly.

Speaker 1 (22:50):
I don't know how to order them, but you know
it's called a pressurized water reactor. So let's start with
the pressurized water. You got this water that you want
to keep liquid because you want to keep flowing. It's
easiest to control if it's liquid, it's a more efficient
heat transfer. If it's liquid, you got other things like
control rods, graphite you want to dip in the liquid.
So basically, you want to keep this stuff liquid. But

(23:11):
it's also really hot. So how do you keep something
liquid if it's really hot. Chemistry tells us you need
to keep it at high pressure, right, Basically, build really
strong vessel and force the water to have high pressure
so it doesn't turn into steam. We're talking like one
hundred to one hundred and fifty atmospheres of pressure, so
really high pressure stuff. This is kind of dangerous because

(23:32):
very high pressure. Right, if you lose containment, you know,
you can imagine like a rivit pops and steam shoots out. Right,
it's super hot, it's super high pressure. It's going to
burn somebody. Also, as soon as you lose pressure, you're
losing your coolant. Right, This water is crucial to keep
in the core from overheating, right, we don't want the
core to turn into a bomb. We don't want the

(23:54):
energy from that thing to like melt the reactor itself.
So you've got to keep the temperature at a certain
level so it doesn't melt down. That's literally what melting
down happens. But as soon as you lose containment of
your water, then you're losing your coolant and boom you
have an overheating and a meltdown. This is what happened
a three mile island. Like one of the water hatches
jammed at Fukushima. One of the water pumps was knocked out,

(24:18):
and in Chernobyl the water boiled off. And so this
is really important to keeping this whole thing going is
keeping this very high water pressure and that's not easy
to do. And if it fails in any way, boom
you have a disaster.

Speaker 2 (24:31):
So one, you have to worry about the boom, but
do you also have to worry about when the water
gets out it's a steam. Can that steam travel great
distances or does that tend to settle near the plant?

Speaker 1 (24:41):
If you have any loss of containment, then the clouds
can travel great distances, like what happened at Chernobyl is
these clouds of radioactive dust and steam and all sorts
of stuff drifted over Europe and like caused cancers all
over Europe. It was really bad. Yes, it's terrible.

Speaker 2 (24:57):
This pressurized containment problem. Is that only a problem for
light water thermal reactors or is this a problem for
some of the other reactor types we're gonna talk about
as well.

Speaker 1 (25:06):
It's only a problem for light water thermal reactors. For
these pressurized water reactors, and there's lots of designs inspired
specifically by avoiding having high pressure liquid, and we'll talk
about some of those, but this is by far the
most common, Like something like eighty five percent of all
reactors in the world are pressurized water reactors.

Speaker 2 (25:25):
All right, so the pressure part is not great. Let's
move on to another risk.

Speaker 1 (25:31):
Yeah, So the U two thirty eight that's mostly what's
in your fuel rods, is not burning, it's not undergoing fission,
but it does get hit with a lot of neutrons
and it breaks down into other stuff. It can make
things like plutonium, right, plutonium two thirty nine, for example,
or plutonium two thirty eight. Two thirty eight is short
lived and very very toxic. It has a half life

(25:52):
of eighty eight years, but two thirty nine has a
half life of twenty four thousand years. So you got
sort of two different angles here. One is you're making
weapons fuel, right, Plutonium is excellent for making weapons, and
you're creating stuff that has like thousands of years or
sometimes millions of years, like neptunium two thirty seven has

(26:13):
a two point one million year half life. This stuff
is toxic for a long long time.

Speaker 2 (26:18):
So how big is the weapons risk? If you run
one of these plants for a decade, does that give
you enough plutonium to make a big bomb or do
you need to run it for two hundred years or
does it depend on a lot of other factors. How
much weapons grade radioactive material is produced?

Speaker 1 (26:35):
Not a lot, but you don't need a lot to
make a few bombs, right, And in order to have
like geopolitical deterrence, you don't need a huge number of bombs.
Like North Korea started out with like three, four or
five bombs, but that completely changed the politics are dealing
with North Korea. Right, one bomb dropped on Soul is
a huge impact. And so yeah, you can make a

(26:56):
weapons significant amount of plutonium without a huge industry. Absolutely.

Speaker 2 (27:02):
This is one of the things that's so frustrating to
me about nuclear power is it's so clearly a technology
that would be you know, great in this world where
we're dealing with climate change, if only humans weren't so humany.

Speaker 1 (27:16):
Yeah, exactly. And you know, there's two sides to this,
as we'll dig in when we talked to Becca later
this week. Like most of the stuff, when you make it,
you just keep it on site at the reactor, you know,
drive it all around. But there's this question of like
where's it going to go long term? You know, like
can we just bury it in the ground, Can we
put it in Yaka Mountain? Should we launch it into space?
Isn't that a terrible idea? And you know a lot

(27:38):
of people are concerned about that, and the environmental is
very concerned about that. On the other hand, you have
to remember that this stuff has a finite lifetime, right,
This stuff will decay away into something non toxic after
hundreds or thousands of years. But if you're making really
terrible forever chemicals with fossil fuels, that stuff is poisoned forever.
Like literally you come back to Earth in five billion years,

(28:00):
it'll still kill you. And so we should remember that
a long lifetime is still shorter than an infinite lifetime.

Speaker 2 (28:06):
Speaking of sending nuclear materials to space, once there was
a piece of I think it was polonium that was
being sent up, and the rocket blew up and the
radio active materials sort of scattered over the Soviet Union.
And then the Soviet Union also sent up a bunch
of tiny nuclear reactors to power some of their satellites,
and one of those satellites went rogue, and the nuclear

(28:27):
material that powered that reactor scattered over northern Canada. So,
you know, sending the stuff into space could go wrong
and scatter it over a big stretch of land if
anything happens to that rocket. These are complicated problems.

Speaker 1 (28:39):
Basically, each time you do a launch, it's a potential
dirty bomb, right.

Speaker 2 (28:43):
Yeah, yeah, you gotta be really careful about this stuff.

Speaker 1 (28:45):
Nobody wants dirty bombs. I don't want clean bombs or
dirty bombs, but I definitely don't want dirty bombs.

Speaker 2 (28:50):
Yeah, no, thumbs down to dirty bombs. We both agree.

Speaker 1 (28:53):
And there's another factor to this waste, which is the
waste produced in the actual reactions is not that large.
The total amount, the volume of waste produced worldwide in
the history of the industry is not huge. It's like
a football field size, But that's not all of the waste. Like,
in order to get uranium out of the ground, you
have to mine it, and there's a lot of waste

(29:13):
produced in that mining. Some of that is also radioactive
and toxic and much much higher volumes. So when you
hear people talk about the waste from nuclear power plants,
guess the actual waste from the reactions is quite small
and very toxic, But there's a much larger volume of
waste produced in the processing to get the fuel to
the plant. That's not always considered in those conversations.

Speaker 2 (29:36):
And what do we do with that waste?

Speaker 1 (29:38):
Yeah, that waste we store on site near the mines,
and like that's dangerous also when you're polluting water tables
and so yeah, oh.

Speaker 2 (29:45):
Yeah, yeah, no easy answers. Okay, all right, so let's
move on. We've now talked about the benefits and risks
of the light water thermal reactor. Let's move on to
some of the alternative designs that have sort of different
problems and different benefits. Let's start with the boiling water reactor.

Speaker 1 (30:01):
So the most obvious things they do is to focus
on the pressure of the water. Can you make a
design for a nuclear reactor core that doesn't require high
pressure water. So there's a boiling water reactor that says, hey,
let's just let the water boil and turn into steam.
That makes the heat transfer less efficient, so you have
to build it larger so you can have like more
of this steam and the water of course is less

(30:22):
dense because now it's steam, but it lets you lower
the pressure down to like seventy five atmosphere because now
you can just have the water turn into steam and
then you use that steam directly to generate energy, basically
what you were saying earlier. So instead of having this
like weird heat exchanger system where the hot water boils
other clean water, you just use the dirty water directly

(30:43):
to make your steam.

Speaker 2 (30:45):
So that seems clearly better than the other method. Is
there a downside to this reactor?

Speaker 1 (30:52):
Downside is now you are using irradiated water and steam
to generate your energy, and so it's a little less
contained like now involved in these turbines and stuff like that,
So you haven't decoupled the energy production and the electricity production,
so there's some risks there. Also, it has to be larger,
and so for example we're talking about later the benefits

(31:13):
of small modular reactors. Those require technology that has very
dense fuel and very small reactor core, and you can't
do that with a boiling water reactor. You need a
large core because this steam isn't as dense and the
heat transfer is less efficient.

Speaker 2 (31:26):
I think I'm still a little confused about the decoupling thing.
Is the point that you're going to at some point
also need to replace the turbine and now you have
a radioactive turbine and that's the problem.

Speaker 1 (31:37):
Yeah, exactly.

Speaker 2 (31:38):
Okay, so about what percent of our reactors right now
are boiling water reactors.

Speaker 1 (31:42):
These are like fifteen percent, so a good number of
these and this has proven technology, right. I mentioned this
because some of the stuff we're talking about later is
like a little bit more speculative. But these are reactors
that are running, we know how they work. We have
people out there in the world with experience running these reactors.
It's not speculative, it's not experimental technology. This is like
it's been proven. And then the last piece are heavy

(32:04):
water reactors like five percent of the reactors out there,
say well, let's just take the pressurize water and replace
it with heavy water. So heavy water is not just
like water that feels heavier. It's water where some of
the hydrogen has been replaced by an isotope of hydrogen.
So instead of just having like a proton as for
the hygen, you have like a proton and a neutron together. Basically, deuterium,

(32:26):
one of the important fuels for fusion, can be used
as an alternative moderator in your reaction and a heavy
water reactor.

Speaker 2 (32:35):
And you had told me in that fusion episode that
there's not a lot of deuterium. Is that right? Is
getting enough deuterium one of the difficult things of running these.

Speaker 1 (32:44):
Reactors, Yeah, exactly. Deutarium is not free and it's not
that easy to filter out. I mean, there's a lot
of it out there, but it's a little bit rare.
And so heavy water is an excellent moderator because it
will slow the neutrons down to the speed that U
two thirty five needs it, but it never captures them right,
and so if lets them fly through. Basically it's perfect
at converting fast neutrons to slow neutrons without ever gobbling

(33:07):
up the neutrons, and so you can actually run a
heavy water reactor without using enrichment. You can have a
much lower density of you two thirty five in your
fuel for a heavy water reactor. So there's pros and
cons there.

Speaker 2 (33:20):
Okay, so it's good to use more two thirty five.

Speaker 1 (33:24):
Lets you use less two thirty five. Usually you need
more two thirty five so the neutrons can find other
two thirty five nuclei. But here heavy water converts all
the fast neutrons into exactly the right neutrons that U
two thirty five needs, so that even if you don't
have an enriched fuel, those neutrons will find enough two
thirty five nuclei to get the reaction to keep going.

Speaker 2 (33:46):
But two thirty eight is the stuff that turns into
the nasty byproducts, right, yeah, exactly. So now you've got
the same kinds of waste and you have the same
confinement issues as the light water reactor.

Speaker 1 (33:59):
Yeah, you still have to keep high pressure here because
you have the same issues. You want to keep the
water liquid, et cetera. So the heavy water reactor is
one variation on the pressurized water reactor. It's not a
boiling water reactor.

Speaker 2 (34:11):
Okay, so you still have the same problems with waste
and the same problems with pressure, but you don't have
to start the process by enriching the uranium as much exactly. Okay,
all right, so we've gone through the main kinds of
currently existing nuclear fission reactors that are out there. Let's
take a break, and when we get back, let's talk
about some of the more advanced designs that are being

(34:32):
researched at the moment. And we're back, all right. So
we talked about the most common nuclear reactor designs that

(34:55):
we've got at the moment, and now we're going to
talk about some more advanced designs that are being researched.
So Daniel tell us about gas cooled reactors.

Speaker 1 (35:01):
Yeah, so these are super cool ha haha. The idea
is to use something like helium to cool your reactor.
Helium is excellent because it's a noble gas. It hardly
ever reacts, It likes to ignore everything, so it's basically inert.
It's a very high heat capacity, so it will absorb
a lot of heat. So take your water out and

(35:22):
replace it with helium. But the water also is doing
two jobs. Right. The water was not just keeping your
reactor from overheating, it was also moderating the neutron speed.
So they were just right forgetting the U two thirty
five to do its thing. So now you need something
else to do that moderation, and so they use graphite,
either rods of graphite that you insert between the rods

(35:42):
of fuel, or you can take the uranium and code
it in graphite. Graphite is awesome because it will moderate
the temperature and it's like almost indestructible. You cannot get
a nuclear reactor up to high enough temperatures to melt
this graphite. So, for example, you cot your uranium in graphite.
It does the moderation and it's basically impossible to have

(36:05):
a leak or a meltdown or to lose containment because
the graphite is really going to wrap it up forever for.

Speaker 2 (36:11):
This hot stuff that's happening. Do you have a container
of water that makes the steam that turns the turbine?
Is that where the power part happens.

Speaker 1 (36:19):
Yeah, So the uranium is wrapped in graphite, that whole
thing is surrounded by helium. Then the helium has a
heat exchanger to water and then that water turns turbines.
We should do a whole episode about like why we
still use steam driven turbines, Like we have this incredible
modern age technology, and in the end it's basically a
steam engine. Yeah, I think that's super fascinating. But yeah,

(36:40):
so uranium surrounded in graphite covered in helium, and then
the helium heats water, which turns the turbine, which generates
electricity which powers your phone.

Speaker 2 (36:49):
Okay, so I've got graphite in my pencil, and when
I go and I draw something and I shade it in,
I always have to like brush away the graphite because
it's all like dusty and stuff. Do you have a
similar problem with like the uranium pebbles rubbing up against
each other and graphite becomes a powder. Do you have
to worry about that powder?

Speaker 1 (37:05):
Graphite is really complex stuff and there's lots of different
forms of it, and so the kind that's in your
pencil is like a very very soft kind of graphite.
You can also make a very very durable, very hard graphite,
and that's the kind they use. So nobody is like
going to be drawing portraits of people with graphite pebble fuel.
But you're right, there is some graphite dust produced, and
we do have to worry about that. But this is

(37:27):
very cool technology. They call it pebble fuel. Basically, there's
no meltdown risk here at all. It's really amazing.

Speaker 2 (37:34):
So why don't we have these yet?

Speaker 1 (37:35):
Then, so we do have some of these. There are
seven of them that have been ever made. It's sort
of experimental. It's a little tricky because in order for
it to work, you have to have very highly enriched fuels.
They call these h al EU highly enriched fuels, and
that's like five to twenty percent enrichment, and so this
is much more enriched than the typical stuff. But it

(37:56):
allows for very small, very dense reactor core, and it
allows for small, modular reactors. The idea is like, don't
build this like huge plant that takes an enormous amount
of space and produces energy for like half of California.
Shrink the reactors, make them like the size of a
shipping container, and then you can produce them at scale,

(38:19):
so now they become modular. Every reactor we've ever built
is basically a one off bispoke design, which is one
reason why they take like twenty years to build and
to regulate and to check and to verify that it's
actually going to work. Right, if you had a plant
to pump these things out, and you knew every single
one was the same, you could develop once the technology

(38:41):
and then pump them out. And the idea is that
you could distribute them to lots of places where otherwise
there isn't the market for nuclear energy remote places, rural places,
so you'd have fewer bigger plants and more small plants.
That's enabled four technologies to have a very small core.

Speaker 2 (38:58):
Okay, awesome, you've got these cheaper modular reactors. You still
have to worry about bad byproducts being made with those
uranium pebbles eventually, right you do.

Speaker 1 (39:10):
The pebble fuel itself is fascinating because you can use
it over and over again. It doesn't use up all
the fuel immediately, so the pebble remains in the core
for like three years, and then they circulate it in
and out several times to burn it up, so like
a single pebble, you can use it for decades and
then in the end, all the fuel is still encased
in your graphite, right, so all the bad stuff is

(39:30):
also inside the graphite, so basically it comes out already sealed.

Speaker 2 (39:34):
That's amazing. Do you not have to worry about the
helium because it doesn't get radioactive the same way water
does because it doesn't react.

Speaker 1 (39:39):
To stuff exactly, it's inert.

Speaker 2 (39:42):
Awesome, Okay, so it makes less bad waste that's also
easier to clean up while not having this explosion risk.

Speaker 1 (39:49):
Yeah, exactly. And so this is very promising and there's
a bunch of private industry developing this technology. It's like
exploding right now. And I talked to a nuclear chemist
here ECI and asked, like, is this real or is
just just like private industry hype? And she said, no,
it's real. The tech has been demonstrated. We know this works.
It's really just a question of getting it regulated and

(40:10):
getting the economics to work.

Speaker 2 (40:12):
All right, So it sounds like it's all upsides for
this particular reactor. Are there any downsides?

Speaker 1 (40:18):
So you know, this is a newish technology. There's still
developing it. There's only seven that have ever been made.
Two of them are operating now in China. And in
some cases there were issues, like there's a reactor in
Germany where they had exactly the problem that you were
talking about. The graphite pebbles were rubbing against each other
and they made dust, and the dust is radioactive. It
has caesium, has strontium. It's not good, and so there's

(40:40):
always risks there. But you know, people are working on
this technology. It's new, it's promising, it's definitely not perfect.

Speaker 2 (40:46):
Okay, awesome, So let's move on to the last kind
of new reactor that we're going to be talking about today,
which is liquid metal salt, which is definitely the most
awesome sounding of the reactors.

Speaker 1 (40:57):
I know, it's super cool and it sound that is
much more dangerous. And the idea is, let's avoid again
having very high pressure water. That seems bad, so let's
replace the water with something else that doesn't need to
be super high pressure in order to stay liquid. So metal,
for example, metal is a very high heat capacity. It
can remove heat very quickly, and it doesn't need to

(41:20):
be a super high pressure to stay a liquid. Right,
It's not going to want to turn into gas because
this boiling point is much much higher, and so you
can have, for example, liquid metal flowing through your reactor
at basically one atmosphere. It's still super duper hot, but
now it's liquid metal instead of liquid water, which you're
forcing to stay liquid. It's like very happy to stay

(41:42):
a liquid.

Speaker 2 (41:43):
Wow. So if the reactor cools off, is it hard
to get that metal to be liquid again or no,
you just get the reaction going and it melts happily.

Speaker 1 (41:52):
That's actually one of the safety mechanisms, right, is they
have a plug at the bottom made of metal that
melts at a slightly higher temperature, and if the core
or ever overheat past a certain temperature, it melts the
plug and all the metal just drips out and then
it cools, and now you have this big solid so
it's not like exploding everywhere. It can't melt down anymore, right,
because the fuel also is dissolved into the metal. In

(42:16):
the case of the water, you have like the water
flowing around the fuel rods. Here, you take the uranium
directly into your liquid metal. The reaction is happening within
the metal, but if it ever overheats, it breaks the
containment and just drips out and then cools, and so
it's all good. So it's much safer.

Speaker 2 (42:33):
That's such a cool passive solution. Like if something catastrophic
happens and all the humans need to leave it sounds
like it solves the problem on its own with no
humans there to help. That's fantastic exactly.

Speaker 1 (42:42):
So the pressurized water reactor needs active containment, and this one,
if it fails, it just basically cools itself down, so
no risk of overheating or melt down. And it's liquid
metal or salt, because you can do the same thing
with what we call salts in the periodic table, you
know whatever. It's just another l element which, if you
heat it enough, turns into a liquid and has all

(43:03):
the right chemical properties you can dissolve uranium into it,
has the right boiling and melting points, et cetera, et cetera.
So they have these experimental reactors using liquid metal or salt,
and this is one of the designs that was explored
early on in the history of nuclear power and then
ignored because the military wanted to use pressurized water reactors.

Speaker 2 (43:22):
Oh boo. Okay, so we've talked about the benefits here.
Does it have downsides?

Speaker 1 (43:28):
I mean, I think it's mostly upsides. The only downside
here is that we don't have as much experience, so
it's not as proven like we've been using pressurized water
reactors for decades we know how they work, we know
how they fail. Liquid metal and salt reactors are just
much more experimental, but they have a lot of other
potential upsides. For example, you can use other fuels than
just uranium. You can use for example, thorium. Thorium is

(43:51):
awesome because it's not fissile on its own right. You
need to start off with some neutrons to hit the thorium,
and then the thorium will convert into uranium two thirty three.
Urinium two thirty three is another isotopic uranium. It's much
better for these reactions, and then you don't produce any
weapons half life. You can also use thorium reactor to

(44:13):
burn fuel from other reactors. So you take like the
byproducts of a light water reactor, you can put it
into your thorium reactor and it will burn it. It
will use up some of that fuel. Remember that we
talked about light water reactors mostly burn the uranium two
thirty five. The two thirty eight turns into all this
other stuff. You can take all that stuff and put
it into a thorium reactor and it will burn it.

Speaker 2 (44:36):
It will burn the nasty stuff and turn it into
not nasty stuff.

Speaker 1 (44:40):
It turns it into less nasty stuff. Exactly. The waste
here has much shorter half lives, so you can take
stuff that starts out with millions or thousands of years
of half life and turn it into stuff with tens
or hundreds of years of half life. So that's really good.
And it can't make plutonium, so there's no weapons byproduct.
And thorium already is a product of rare earth mining,

(45:02):
like you're digging for a zinc and cadmium and all
sorts of other stuff you need for fancy technologies. Thorium
is a waste product. We're already producing huge amounts of
thorium in our industry, so thorium is a really an
excellent direction for nuclear technology.

Speaker 2 (45:17):
You said it's a waste product, so it's stuff we're
currently just throwing out.

Speaker 1 (45:20):
Yeah, exactly, and with huge deposits of it. India has
massive access to thorium, for example, and so a lot
of it. Countries around the world, China, India are developing
these thorium reactors, again more experimental, so there could be
things we don't understand about them yet because we just
haven't spent thirty years watching them fail, but it's definitely
a good direction.

Speaker 2 (45:40):
Okay, all right, So we've talked about some new designs,
we've talked about the old designs. Let's back out and
take a big broader picture. I feel like I'm hearing
more about nuclear reactors as the impacts of global climate
change are sort of becoming more day to day and
bearing down upon us. And so what do you think, Daniel,
do we need advanced nuclear reactors to deal with global
climate chain.

Speaker 1 (46:00):
I think it's going to be part of the future.
I mean, currently nuclear power provides like five to ten
percent of the worldwide energy use. It's like twenty ish
percent in the United States. Some countries like France, it's
a much much higher fraction. A lot of those reactors
are really decades old, like the United States has really
old reactors, as our rate of turning on new reactors
is dropped basically to zero. But nuclear power is also

(46:23):
very attractive for lots of reasons, like it's very constant.
You turn on nuclear power plant, it's going to pump
out energy day and night, rain or shine, wind or
no wind doesn't really matter. And so on one hand,
that's great to supplement things like wind and solar, which
do fluctuate obviously day to night and windy to not windy.
What you actually want, though, to supplement renewables is not

(46:45):
something like nuclear that's hard to turn on and off,
but something you can turn on and off very quickly,
because you don't want to be running a nuclear power
plant when you already have too much energy on the
grid from solar. You want to shut it down then
and then turn it back on during the night. But
nuclear power plants are hard just to turn on and
hard to turn off, so they're very constant.

Speaker 2 (47:03):
One of the things I really loved about atomic Dreams,
and one of the things that we don't end up
getting into in our interview with Becca, is that you
can take those times when you don't necessarily need the
nuclear power and you can do things like run a
desalination plant, which would be very helpful in California that's
having all these issues with fresh water. So there's things
that you can do to make up for the fact
that nuclear power is not easy to turn on or

(47:24):
off to you know, still make it beneficial.

Speaker 1 (47:27):
Yeah, exactly, And it seems like definitely part of our
portfolio in the future. The UN has all these different
pathways to limiting the warming of the planet to one
point five degrees, and every single one of those pathways
includes nuclear power and expanded nuclear power on top of
what we already have. So I think it's an important
quiverent in our arsenal. It's definitely not perfect and the

(47:48):
definitely issues with it, And boy do I wish we
just had fusion around the corner.

Speaker 2 (47:52):
That's the man.

Speaker 1 (47:53):
But you know, we're in an imperfect situation. We have
imperfect options. And next time we'll talk all about the
pluses and minus and whether nuclear power is good or
bad for the environment on the whole.

Speaker 2 (48:04):
All Right, So in the next episode we're going to
be talking to Becca, and in particular, we're going to
be talking about how public perception is impacting the rollout
of nuclear power, things like fear from the reactor meltdowns,
what to do with the waste, problems with licensing, etc.
So we look forward to seeing you on Thursday for
that conversation. Daniel and Kelly's Extraordinary Universe is produced by

(48:33):
iHeart Reading. We would love to hear from you, we
really would.

Speaker 1 (48:36):
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