Daniel and Kelly’s Extraordinary Universe - What is the future of nuclear power?

Episode Date: April 8, 2025

Daniel and Kelly talk about how nuclear reactors work and explore the new techologies that try to limit the risks.See omnystudio.com/listener for privacy information.

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so you can work, create, and boost productivity all on one device. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then everything changed. There's been a bombing at the TWA. Terminal, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged. Terrorism.

Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back-to-school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone.

Hold up. Isn't that against school policy? That seems inappropriate. Maybe find out how it ends by listening to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome. Avoidance is easier. Ignoring is easier. Denials easier. Complex problem solving takes effort. Listen to the psychology podcast on the iHeart Radio app, Apple Podcasts, or wherever you get your podcasts. 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 to generate emission-free energy from weird little rocks. Later this week, we'll dig into the policies and politics of 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 it all work? What about salt reactors and pebble fuels? What is the future of nuclear technology? Welcome to Daniel and Kelly's extraordinary powerful universe. Hello, this is Kelly Wienersmith. I'm a parasitologist who also studies space, and we are recording this episode on PIDIDA. Hi, I'm Daniel.

I'm a particle physicist, and I will judge anyone who says nuclear instead of nuclear. Oh, I mean, that's fair. Yeah. Or nuclear? Yeah, yeah. Judge away, man. Judge away.

I heard a lot of that in Texas when I lived there. Nuclear power. Oh, man. How long were you in Texas? 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 time. Bush went to Rice? No, but he's from Texas.

Oh, yeah. Got it. Okay. Right. But one of the Bushes went to Rice with me. I think it was George P. Bush, son of Jeb Bush, was that Rice with me, yeah. Oh, were you two BFFs? No, 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. Yeah, got it, got it. What is the most that you've ever leaned in to celebrating a particularly nerdy holiday? Wow. 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 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 marshmallows and all the Rice Krispies at the grocery store to make this ridiculous landscape. Did you win?

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 got to say. I mean, that's a good way to pass the pandemic. Did you take a picture? We have a picture somewhere, absolutely. And then it had other weird downstream consequences because nobody could eat that much rice Krispies. 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 discussing. a rat's nest literally like a mom and 10 little 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 10 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 we felt really bad about that. And that's why we ended up adopting rats. That story was a roller coaster ride, Daniel. There were some real highs and real lows there. I know. 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 we now have a dog, who's an integral part of our family, is because I went all out celebrating this crazy engineering challenge, Bakeathon. 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 me. mine. Yeah, what's yours? I was born on Molday. So Avagadro's number is what, 6.2, 3 times 10 to the 23rd or something like that, but October 23rd. And so for my junior and senior year of undergrad, I had chemistry themed birthday parties. And it would be like, you know, that sounds really fun. Why didn't I get invited? If I had known you, man, you would have been invited. But it was, you know, like how many electrons are in beryllium? Wrong. Drink. And it was. because you know no one knows that nobody knows that because it's chemistry it's all exceptions that's right

that's right and you know my friends didn't know chemistry very well either so it was uh we had a really great time but this is high school so you're what drinking soda or punch or something undergrad undergrad undergrad oh so these were fun parties these were fun parties we were all of legal drinking age and we were careful we watched out for each other but uh way less wholesome than a cake with a waterfall. Well, it does sound like your parties are maybe the only way to make chemistry fun. Ha ha ha, 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. 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. I am always impressed by the way you bring our tangents back to the topic. I know who's easy, but I'm like, wow, we could do a whole episode on Kelly's Weird College parties. 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 the sort of advances

in nuclear power technology now. Because when Zach and I wrote Soonish, which came out in like 2017, we did some research on advanced nuclear fission reactors. And 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. But anyway, well, you got nuclear right. At least you didn't say nuclear fusion. There you go. That's right. Now I'm going to avoid saying that word 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. 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. 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 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 did 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 they had to say. If you'd like to play for a future episode of the podcast, we really, really, really, really want to hear your voice on the pod. Write to us to questions at danielandkelly.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 had to say. Just for Kelly, I've heard of biologists working on microbes to solve our nuclear waste problem. Somehow they eat the nuclear waste.

No idea how it works, but, hey, yo, biology. 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. But where I would like to see more study is in medical applications such as radiation treatment for cancer. Not running redundant systems through the same conduit. 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 reality.

Reusing or repurposing fuel that has been expent. Reusing the nuclear waste as opposed to storing it. Without a doubt, fusion. Decreasing the waste. People have probably paid a lot of money in PR to make me think of thorium, so I'm going to say thorium. SMRs, which are those small modular reactors. Micro-nuclear energy, where they're able to build much smaller nuclear power stations, I guess. 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 seem a lot safer. 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 like a meltdown and things like that. 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. 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 throw cold water on that whole industry. 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 Tridium more available. But maybe. Maybe.

But all right. But now, today we're talking about fission reactors in particular. Yes, exactly. And so let's dig in first and make sure we and Kelly and everybody understands the difference between fission and fusion. Okay. 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, much more rare. 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 mass of the hydrogens combined.

So energy is released there in fusion. So that's fusion, is you take light elements, you stick them together, and energy is 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. Those nuclei do not want to stick together. They have kulombic 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, 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 of second, didn't Daniel just tell us that when you squeeze light elements together to make them heavy, energies 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 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, any time you're taking a step towards iron,

iron, which is like the middle of the periodic table, you are releasing energy. Can you remind me inside of stars? Is that where we get iron and everything up from that? What is the break off there? Yeah, it's about iron. So inside stars, you mostly have hydrogen. Hydrogen fuses to make 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 The star is really big and really hot and has high enough temperature to fuse iron that cools the star and 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 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 cost a lot of energy to make those very heavy stuff. Okay, interesting. All right. So fusion, really hard to do unless you're in the sun.

Fission, much easier to do using big stuff. 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

speed to make that happen, like really fast neutrons or 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. Don't do that, folks.

Not in your basement. 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. And why is uranium the sweet spot on the periodic table for stuff you want for your fission reactor? It's not really that sweet. It's just something that's around and for a while was pretty cheap to mine. As we'll hear about, there are lots of things that are fizzile.

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 in the earth's crust is an isotope that's not great for fission. It's uranium 238. Uranium 235 is pretty good for vision, but most of what we find in the ground is uranium 238. Less than 1% 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. Let's dig in then to uranium a bit more. So you said we mostly find uranium 238, but we need 235. How do you get it from 238 to 235? So what you do is just enrich it. Like remember,

chemistry lab, when you have like a pile of 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 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 the centrifuges more and more and filter out the 238, you get a higher and higher fraction of 235. I've always been unreasonably concerned about USB sticks after hearing this 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 got going on in my office. But I remember thinking that was just like such a cool story. And now every time I see a USB stick, I think, oh, what's on you? It's a pretty cool story about engineering like cyber espionage, pretty cool stuff. But are you running a uranium centrifuge and your science farm? 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 concern that Iran was turning 238 into 235 so that they could start making weapons. and by messing up that process, by messing up all of their super expensive centrifuges, we at least managed to slow them down. And so you need to enrich uranium because you need dense enough source of the good stuff, uranium 235. If you don't have it dense enough, then it makes neutrons when it splits, but then those neutrons don't find other 235 nuclei, and it just peters out.

So you need to be dense enough. You need to enrich it up to like 2 or 5%. It doesn't have to be pure uranium 235 at all. just up to like 2 to 5%. But this is still kind of a problem because you end up mostly just burning the U-235 and the U-2-38 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-2-38 being in the reaction, not being part of it, and then getting converted to toxic stuff. 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. So if you want the neutrons to be going quickly so that they're bumping into the 235,

why would you want to slow them down? It seems like more neutrons is, you know, that's better. That's more energy. Yeah, it seems like fast neutrons are good, right? The whole point is to get energy out. Well, the thing is that U-235 is a little persnickety. Like, if you shoot fast neutrons at it, sometimes they will just go right through. They will not make it fizz. What is the Fission? They will not make it fission. Can one atom fission? That seems weird. They will not fission it. I don't know. I will not stand for that. Anyway, U-235 likes slower neutrons. U-238 likes faster neutrons, but uranium fission doesn't make enough fast neutrons to sustain fusion with 238.

So you've got to use the 235 and you've got to slow down the neutrons until they're in the sweet spot for making other uranium nuclei go. So you've got to moderate the temperature. 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.

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. I 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 a turbine? Or is the energy being collected in some other way?

Yes, so not directly. The most popular technology is called a pressurized water reactor. You have uranium rods. It's 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 you want to buffer yourself from that.

So typically there's like a heat exchanger with that water. Well, then heat up other water. You have like these two corkscrews that interwoved with each other. 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 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 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. 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 powered. Is that story correct? Yeah, that story is correct. In the 50s, they 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 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 developing nuclear technology. This is definitely like a public investment by the government. 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. Ah, come on, why is this taking so long?

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Lenovo, Lenovo. Unlock AI experiences with the things. Inkpad X-1 Carbon, powered by Intel Core Ultra processors so you can work, create, and boost productivity all on one device. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently the explosion actually impelled metal glass.

The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and order, criminal justice system is back. In season two, we're turning our focus to a threat that hides in plain sight that's harder to predict and even harder to stop listen to the new season of law and order criminal justice system on the iHeart radio app apple podcasts or wherever you get your podcasts my boyfriend's professor is way too friendly and now i'm seriously suspicious

oh wait a minute sam maybe her boyfriend's just looking for extra credit well dakota it's back to school week on the okay story time podcast so we'll find out soon this person writes my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate.

Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor? or not. To hear the explosive finale, listen to the OK Storytime podcast on the Iheart radio app, Apple Podcasts, or wherever you get your podcast. I'm Dr. Scott Barry Kaufman,

host of the psychology podcast. Here's a clip from an upcoming conversation about exploring human potential. I was going to schools to try to teach kids these skills and I get eye rolling from teachers or I get students who would be like, it's easier to punch someone in the face. When you think about emotion regulation, like you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome as a result of it if it's going to be beneficial to you because it's easy to say like like go you go blank yourself right it's easy it's easy to just drink the extra beer it's easy to ignore to suppress seeing a colleague who's bothering you and just like walk the other way avoidance is easier ignoring is easier

denial is easier drinking is easier yelling screaming is easy complex problem solving meditating, you know, takes effort. Listen to the psychology podcast on the IHartRadio app, Apple Podcasts, or wherever you get your podcasts. All right, we just finished 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. Your turn to be the negative, Nellie.

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

But 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 a really strong vessel and force the water to have high pressure so it doesn't turn into steam. We're talking like 100 to 150 atmospheres of pressure. So really high pressure stuff. This is kind of dangerous because very high pressure, right? If you lose containment, you know, you can imagine like a rivet 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 keeping the core from overheating, right? We don't want the cord turn into a bomb. We don't want the 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 to three mile island, like one of the water hatches jammed. At Fukushima, one of the the water pumps was knocked out. 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. 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? If you have any loss of containment, then the clouds can travel great distances, like what

happen 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 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 going to talk about as well 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 85% of all reactors in the world are pressurized water reactors.

All right. So the pressure part is not great. Let's move on to another risk. Yeah. So the U-238, 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?

Plotonium 239, for example, or plutonium 238. 238 is short-lived and very, very toxic. It has a half-life of 88 years, but 239 has a half-life of 24,000 years. So you've 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 Neptuneum 237 has a 2.1 million year half life. This stuff is toxic for a long,

long time. 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 200 years? Or does it depend on a lot of other factors? How much weapons grade radioactive material is produced? 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, five bombs, but that completely changed the politics of dealing with North Korea, right? One bomb dropped on Seoul is a huge impact. And so, yeah, you can make a weapons significant amount of plutonium without a huge industry. Absolutely. 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. Yeah, exactly. And, you know, there's two sides to this, as we'll dig in when we talk to Becca later this week. Like, most of the stuff, when you make it, you just keep it on site at the reactor, you don't 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 Yucca Mountain? Should we launch it into space? Isn't that a terrible idea? And, you know, a lot of people are concerned about that, and the environmentalist 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 poison forever. Like literally, you come back to Earth in five billion years, it'll still kill you. And so we should remember that a long lifetime is still shorter than an infinite lifetime. 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 of active material 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 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 land if anything happens to that rocket. These are complicated problems. Basically, each time you do a launch, it's a potential dirty bomb, right? Yeah, yeah. You've got to be really careful about this stuff. Nobody wants dirty bombs.

I don't want clean bombs or dirty bombs, but I definitely don't want dirty bombs. Yeah, no, thumbs down to dirty bombs. We both agree. And there's another factor to this waste, which is the waste produced in the actual reactions is not that large. You know, 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 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, yes, 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. And what do we do with that waste? 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, 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 alternative designs that have sort of different problems and different benefits. Let's start with the boiling water reactor.

So the most obvious things to 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 dense because now it's steam. But it lets you lower the pressure down to like 75 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 weird heat exchanger system where the hot water boils other clean water, you just use the dirty water directly to make your steam. So that seems clearly better than the other method. Is there a downside to this reactor? The downside is now you are using irradiated water and steam to generate your energy. And so it's a little less contained.

You have it like now involved in these turbines and stuff like that. So you haven't like 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 of small modular reactors. Those require a 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 the steam isn't as dense and the heat transfer is less efficient.

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? Yeah, exactly. Okay, so about what percent of our reactors right now are boiling water reactors? These are like 15 percent, so a good number of these, and this is 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 water reactors. Like 5% of the reactors out there say, well, let's just take the pressurized 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 hydrogen, you have like a proton and a neutron together. Basically deuterium. one of the important fuels for fusion can be used as an alternative moderator in your reaction in a heavy water reactor. 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 reactors?

Yeah, exactly. Deuterium 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-235 needs it, but it never captures them, right? And so it lets them fly through. Basically, it's perfect at converting fast neutrons to slow neutrons without ever gobbling up the neutrons.

And so you can actually run a heavy water reactor without using enrichment. You can have a much lower density of U-235 in your fuel for a heavy water reactor. So there's pros and cons there. Okay, so it's good to use more 230. It lets you use less 235. Usually you need more 235 so the neutrons can find other 235 nuclei. But here, heavy water converts all the fast neutrons into exactly the right neutrons that U-235 needs so that even if you don't have an enriched fuel, those neutrons will find enough 235 nuclei

to get the reaction to keep going. But 238 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 can. confinement issues as the light water reactor? Yeah, you still have to keep it at high pressure here because you have the same issues. You don't 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. 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. Yeah, 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.

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predict and even harder to stop. Listen to the new season of Law and Order criminal justice system on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Oh, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her.

Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him?

Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about exploring human potential. I was going to schools to try to teach kids these skills and I get eye rolling from teachers or I get students who would be like, it's easier to punch someone in the face. When you think about emotion regulation, like you're not going to choose an adaptive strategy

which is more effortful to use unless you think there's a good outcome as a result of it if it's going to be beneficial to you. Because it's easy to say like go you, go blank yourself, right? It's easy. It's easy to just drink the extra beer. It's easy to ignore, to suppress, seeing a colleague who's bothering you and just, like, walk the other way. Avoidance is easier. Ignoring is easier.

Denial is easier. Drinking is easier. Yelling, screaming is easy. Complex problem solving. Meditating. You know, takes effort. Listen to the psychology podcast on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. And we're back.

All right. So we talked about the most common nuclear reactor designs that 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. Yeah. So these are super cool. Ha-ha-ha. 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'll absorb a lot of heat. So take your water out and replace it with helium. But the water also was 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 for getting the U-235 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 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 coat your uranium in graphite. It does the moderation. And it's basically impossible to have a leak or a meltdown or to lose containment because the graphite is really going to wrap it up forever. For 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?

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, so uranium surrounded in graphite, covered in helium, and then the helium heats water, which turns a turbine, which generates the electricity, which powers your phone.

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? 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 very cool technology. They call it pebble fuel. Basically, there's no meltdown risk here at all. It's really amazing. So why don't we have these yet, 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-A-L-E-U highly enriched fuels, and that's like five to 20 percent enrichment. And so this is much more enriched than the typical stuff, but it allows for very small, very dense reactor cores, 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. So now they become modular. Every reactor we've ever built is basically a one-off bespoke design, which is one reason why they take like 20 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 that pumped these things out and you knew every single one was the same, you could develop once the technology and then pump them out.

And the idea is that you could distribute them to lots of places where otherwise there isn't a market for nuclear energy, remote places, rural places. So you would have fewer bigger plants and more small plants. That's enabled for technologies that have a very small core. Okay. Awesome. All right. So 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. 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 circulated 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 also inside the graphite. So basically comes out already sealed. 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 to stuff. Exactly. It's inert. Awesome. Okay, so it makes less bad waste that's also easier to clean up while not having this

explosion risk. 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 at UCI and asked her like, is this realistic or is 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 getting the economics to work. All right. So it sounds like it's all upsides for this particular reactor. Are there any downsides? So, you know, this is a newish technology.

They're 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 then dust is radioactive.

It has cesium, has strontium. it's not good. And so there's always risks there. But, you know, people are working on this technology. It's new. It's promising. It's definitely not perfect. 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. I know. It's super cool. And it sounds 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 be a super high pressure to stay a liquid, right? It's not going to want to turn into gas because its boiling point is much, much higher. And so you can have, for example, liquid metal flowing through your reactor at basically one atmosphere. 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 a liquid. 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? 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 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 the 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 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. 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. 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 meltdown. 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 element which if you heat it enough turns into a liquid and has all the 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 that ignored because the military wanted to use pressurized water reactors. Oh, boo. Okay, so we've talked about the benefits

here. Does it have downsides? 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 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 233. Uranium 233 is another isotope uranium.

It's much better for these reactions. And then you don't produce any weapons half-life. You can also use the thorium reactor to 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 235. the 238 turns into all this other stuff.

You can take all that stuff and put it into a thorium reactor, and it will burn it. But will burn the nasty stuff and turn it into not nasty stuff? 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. Like you're digging for 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 excellent direction for nuclear technology. You said it's a waste product. So it's stuff we're currently just throwing out?

Yeah, exactly. And there's huge deposits of it. India has massive access to thorium, for example. And so a lot of 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 30 years watching them fail. But it's definitely a good direction. 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 change? I think it's going to be part of the future. I mean, currently nuclear power provides like 5 to 10% of the worldwide energy use.

It's like 20-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. There's a rate of turning on new reactors is dropped basically to zero. But nuclear power is also very attractive for lots of reasons. like it's very constant. You turn on a 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 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 your 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 to turn on and hard to turn off. So they're very constant. 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 off to still make it beneficial. 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 1.5 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 quiver in our arsenal. It's definitely not perfect and definitely issues with it. And boy, do I wish we just had fusion around the

corner. That would be awesome. But, you know, we're in an imperfect situation. We have imperfect options. And next time we'll talk all about the pluses and minuses and whether nuclear power is good or bad for the environment on the whole. 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, et cetera. So we look forward to seeing you on Thursday for that conversation. Daniel and Kelly's Extraordinary Universe is produced by IHeart Radio.

We would love to hear from you. We really would. We want to know what questions you have about this extraordinary universe. We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you. We really mean it. We answer every message. Email us at questions at danielandkelly.org.

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Then everything changed. There's been a bombing at the TWA terminal, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot.

He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want her gone. Hold up. Isn't that against school policy? That seems inappropriate. Maybe. Find out how it ends by listening to the OK Storytime podcast on the IHeart Radio app. Apple Podcasts, or wherever you get your podcasts. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, we're not going to choose an adaptive strategy

which is more effortful to use unless you think there's a good outcome. Avoidance is easier. Ignoring is easier. Denials easier. Complex problem solving takes effort. Listen to the psychology podcast on the iHeart Radio app, Apple, podcasts or wherever you get your podcasts. This is an IHeart podcast.