Daniel and Kelly’s Extraordinary Universe - Can molton salt reactors produce electricity safely?

Episode Date: March 17, 2022

Daniel and Jorge talk about alternative designs for fission plants that could produce electricity much more safely. Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

This is an I-Heart podcast. 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 or 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. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell. And the DNA holds the truth. He never thought he was going to get caught. And I just looked at my computer screen. I was just like, ah, gotcha.

This technology is already solving so many cases. Listen to America's Crime Lab 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 is easier. Complex problem solving takes effort. Listen to the psychology podcast on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Hey, Jorge, are you a fan of molecular gastronomy? Gastronomy. Is that like molecular astronomy, but you eat it? Yeah, exactly. They used chemistry to like transform the texture of your food into foam. So you might get like burrito bubbles, for example. I'm not sure burritos need to give me more gas.

Well, if you're not into spherical sandwiches, then I've got an idea for a new frontier in eating high energy physics gastronomy. Ooh, what's that? Like proton pasta or ozonic burritos? Did you already invest in this startup? No, no. I'm thinking more about. about spices. What if you had a device that accelerated and heated up your spices and shot them out of a gun? Like the large anise accelerator? Exactly. Would you like a little molten salt on your proton pasta? I think you should get your money back, but I wonder what's for dessert. Hi, I'm Jorge, a cartoonist, and the creator of PhD comics. Hi, I'm Daniel.

I'm a particle physicist and a professor at UC Irvine, and I am actually a big fan of toasted spices. Ooh, like toasted spices. Like, you pour spices on your toaster oven. No, when you're cooking, you're supposed to warm up your spices, make them volatile by toasting them in the pan. You know, it like brings them to life. Oh, I see, I see, I see.

Like, if you don't put the spices at the end, you cook with the spices. Yeah, you've got to put the spices in the pan first so they warm up and, like, become alive. Hmm. And then you eat them. And then you eat them, exactly. Interesting. Have you dug into the physics of that?

I've taken a big bite out of it, but I wouldn't say I've understood the science. I see. It's more of an experimental thing, I guess. Hands on. So far, it's just exploratory. But I'm sure my wife, the biochemist, could explain to you why volatile molecules create better reactions in the nose. Why being volatile is tastier. And anyways, welcome to our podcast, Daniel and Jorge, explain this.

the universe a production of iHeart radio in which we spice up the universe by explaining all of it to you we go out there and dig into black holes to understand what's going on on the inside we take apart the core of neutron stars we dig deep into the earth and into all the tiny particles that make it up in order to tease them apart and spice up your life with a little bit of understanding that's right because it is a pretty tasty universe full of amazing flavors and colors and textures and deliciousness to discover, and we like to serve it to you in a three-course meal here. I think there's an interesting and unexplored philosophy question there. You know, some people ask, is it necessary for us to find the universe beautiful? But I don't know if anybody's ever explored the question of, is it necessary for us to find the universe tasty? Could we have evolved in a universe that we just found kind of gross to eat? Well, I don't think it's necessary, but it's certainly nicer that things taste good and look nice.

it would be kind of bleak, I guess, if everything didn't look nice or taste good. Yeah. What if we evolved in a ugly, bland universe? Boy, I'm sure glad we didn't. Or maybe would you just lower our bar and start to appreciate the ugliness of the universe, maybe? Maybe that's what happened. Maybe there's another version of the universe where everything is more beautiful and more delicious. Interesting.

So you think aliens would come to Earth and be like, boy, what a crappy place. Look at all this blue stuff. and the sky gets all red. That's disgusting. Yeah, there's another unexamined frontier. When aliens do come, they wouldn't just teach us about the universe. They might give us tips about how to cook. Hopefully not how to cook us.

Hopefully not a direct lesson. New spices to serve to humanity, not new spices to serve with human. Yeah. I find the heating up humans really sort of makes them more volatile, really activates the flavors. I don't think we'd want to learn about that. Dry aged, exactly. Yeah. But anyway, today is a wonderful universe that we like to talk about and hopefully we'll be here for a long time to sort of appreciate how it evolves and how it changes and how it gets more and more interesting and complex. And in order to stick around a long time, we need to power our lifestyle. We need to provide energy for our burners and for our oven so that we can continue to cook and bake delicious things to eat.

As our society gets more and more complex, we have a larger and larger appetite for. for energy. Yeah. And so far in human history, we've basically resorted to one source of energy for most of, you know, our existence. And that is to basically burn stuff, you know, take wood and sit in on fire or find oil and sit it on fire. And it's kind of dirty and not as efficient as it could be. It's really shockingly inefficient. I mean, the amount of energy you take out of coal when you burn it or when you burn wood is really a tiny, tiny fraction of the energy that's in there. It's like you find Bill Gates' wallet

and you just take a single dollar out of there and then give it back to him. That would be shocking to you. That seems like the right thing to me. No, clearly, you should give Bill Gates his wallet back with all of his billions. But it's, you know, maybe another analogy is like we're thirsty

and we're standing next to a rushing river but we're just like sucking droplets of water from the grass nearby. Yeah, because I guess we've only resorted to chemical means to extract energy out of matter, right? We only sort of release the energy that's trapped in the chemical bonds of materials, but it turns out that if you go deeper and smaller, you can release a whole bunch more

energy. Yeah, at the sort of maximum efficiency would be to take particles and antiparticles and annihilate them into pure energy. If you had a huge source of antimatter, for example, you could generate energy very, very efficiently. You turn 100% of the energy stored in matter into energy. energy. But of course, antimatter not very plentiful, very expensive to make, and so not really a practical choice for energy production. You're not pro-antimatter. I love antimatter. It's wonderful. I wish we

had so much more of it so we could study it and do all sorts of things with it and we could fuel all of our desires and charge up all of our bones with it. But it costs more energy to make antimatter than you get out of the antimatter afterwards. So it's not efficient for commercial industries, for example. Right. Well, I think what you're saying is that if we could somehow take pure matter and transform it into pure energy, there would be a huge amount of energy in even just like a drop of water or even a tiny little raisin. A single raisin has more energy stored in it than a nuclear bomb. It's an incredible amount of energy that's all around us. It's just bound up. It's just tightly contained in the atoms and the molecules that we are surrounded with. And we haven't

been great at figuring out how to tap into that energy. Right. Because I guess the energy inside of a raisin likes to stay there, right? Like a raisin doesn't want to give up its energy or it doesn't want to turn into energy. Like it would take a lot of energy just to unlock that energy. Raisins are not like particles. They don't just decay, right? They just hang out. You take a raisin and you leave it in space. You come back a billion years later, you'll still have a raisin most likely. So raisins are stable elements of the universe, exactly. This is energy locked into a certain configuration. To release it, you have to somehow pry it apart. One way to do it, that is to collide with an anti-raison, but without anti-raisins floating around, it's harder

to crack open that raisin. Right. Well, I guess you could eat the raisin and somehow convert that to energy, maybe. You could, but humans are not very efficient at extracting energy from stuff. You know, most of the stuff in the raisin just passes right through you and the energy stored in its matter. You don't even touch. Humans do like a chemical rearrangement of some of the bonds in the raisin and extract a tiny,

tiny little sliver of that energy, which is why the matrix doesn't make any sense. You know, humans as sources of energy. I mean, come on. That's the part that doesn't make sense. That's the part that drives me crazy. That's the physics of it, right there. You're like, you're so inefficient computers.

And they have to power a hyper-realistic simulated world. There's no way they're doing that with human batteries. They should have used the raisins, maybe. Yes, yes, exactly. Raisins are more efficient. so chemical means have a limit so over the years humans have tried other things right more intricate physical ways to do things and that includes fusion yeah we have looked up into the sky and seen a fusion reactor at work right most of the energy that is here on earth originally came here via the sun the rays from the sun which are in the end the output of a fusion reactor at the heart of the star pushing hydrogen together to form helium it's much more efficient than cal chemical burning, although much less efficient still than matter, anti-matter production. Interesting. And there's also fission, right? I mean, we've sort of done both in terms of

at least nuclear weapons, fusion and fission. But in terms of making energy power plants, we've only really used fission plans, right? That's right. Fusion has a lot of advantages. It's much more efficient. It doesn't produce any waste. You can use water essentially as fuel, but we haven't really managed to make it work yet. There are a lot of efforts in that direction. working on it. We have a couple of episodes on how to make fusion power possible. But fusion is one of these technologies that always seems to be about 25 years off. Whereas vision, splitting atoms in half and extracting the energy when a heavy atom breaks up, that is something we have working. That is part of the electrons that you are probably using come from fission power plants.

Yeah. If you're in Europe, most likely the energy you're using to listen to this podcast came from a fission power plant. And if you're in the U.S., there's a pretty high likelihood also, right? Yeah, it's a significant fraction. Depending on the country in France, for example, they have a very large fraction of their energy comes from nuclear power plants. Yeah, and it's been around for maybe like 60 years, right? A long time.

Like, this is old technology now. Yeah, the first power plants were developed in the 50s, not long after we cracked open the atom and developed the weapons technology in the 40s. So it's been around for a long, long time. Of course, there are significant drawbacks to vision reactors. Yeah. And so people are always looking for a new kind of fission plants that could maybe be safer and cleaner. And one such idea is the one we're going to talk about today, which is this idea of molten salt reactors. Exactly. They stole it from my heated spice accelerator. Maybe you should have filed the patent sooner, Daniel. And so let's talk about that. So today on the podcast, we'll be tackling the question. Can molten salt reactors solve our energy problems? Now, Daniel, I have to say I'm not familiar with molten salt.

Is that the same as Morton salt? That's a brand, right? That's a brand, exactly. No, molten means liquid, like super hot. You know, like molten lead, heat up lead, and it goes from being a solid to being a liquid and it's all glowy. That's molten. So in this case, molten salt refers to taking salts and melting them down. Oh, I see. So it's like melted salt. Like if you heat up salt, they'll melt into liquid.

Mm-hmm. Exactly. And we're not just talking about like table salt, but there's a whole set of compounds and elements that chemists call salts and any of those can be used. Oh. And so the idea is to use these for a fission nuclear power reactor to make them better. Yeah. There are these really interesting designs for nuclear power plants that use molten salts, which sounds, you know, salty and d'am. dangerous and crazy, but it could actually be much safer than traditional nuclear power plants. So this is kind of a new idea. And so as usual, we were wondering how many people out there had heard of melting salt for efficient power. So Daniel went out there into the internet to ask the question, how do you think a molten salt reactor works? And thank you again to all of our cadre of volunteers who answer crazy physics questions without the opportunity to look

anything up. If that sounds fun to you and you'd like to hear your voice on a future podcast, please don't be shy. Email us at questions at danielanhorpe.com for instructions about how to participate. So think about it for a second. What would you use melted salt for? Here's what people had to say. I honestly have no idea. If I had to guess, I would say that it uses some kind of molten salt mixture as a fuel source. I don't know if that's even possible. After I'm done answering this question, I'm definitely going to look it up, though. The word reactor makes me think of power generation, but then molten sodium. The first thing that comes to mind is the reaction between sodium and water and how violent it is. So maybe it's a reactor

that can harness the power of the reaction between sodium and water somehow. A molten salt reactor is a reactor that uses molten salt and maybe something to do with the salt ions to help facilitate reactions? Well, I know that salts typically don't get molten. They have to be very, very hot to become molten. Something to do with their conductivity, probably. I'm not sure how that would work, but I expect it as something to do with the electrical conductivity. of salts when they are in a liquid rather than a solid state. All right. Some pretty cool answers here.

A lot of people seem like they're chemists. Yeah, people thinking about salt maybe as fuel, you know, but none of these are actually even close at all to the right answer of how we use molten salt inside a reactor. And that's not a criticism because to me, the whole design of a molten salt reactor is kind of bonkers. I never would have guessed either. it melts your mind or at least the salts in your mind yeah exactly i prefer the molten pepper

reactors i prefer the melted oreganoes because you know i like my italian energy compressed cinnamon reactors really that's the way i'm going to go it happens if you take like cinnamon and chocolate and you fuse them together inside a reactor do you get some new super spice interesting i think you need to start a new like think tank where it's just spices used for making energy. Well, I think before I think about it, I just want to build an accelerator so you can shoot like cinnamon and chocolate particles at each other and just see what happens. I mean, I'm experimental. It's not a theorist after all. I see. You just want to make like anti-cinnamine maybe or dark cinnamon. Wait, what is anti-cinamen? Is that something you can add to your food

to make it taste less like cinnamon? I don't know. It's intriguing though, right? Like what is anti-ch chocolate taste like? Oh, man. It doesn't sound very good, but I am curious. Or like, anti-salt. It's called sugar. And speaking of salty situations, I want to give a special birthday shout out to one salty listener. Happy birthday to Ben. His girlfriend Natasha tells us that Ben is something of a salt aficionado. So happy salty birthday, Ben. All right, this is an interesting idea to use maybe melted salt. I guess that's the idea, right, to melt salt because if you heat up salt, I've never tried heating up salt. Does it actually melt into a liquid? Yeah, a lot of If you heat them up hot enough, and we're talking like 450C, they'll melt into a transparent liquid.

Can you set like salt on fire? Wow, that's something I want to type into Google, but I don't want my university to have seen me type that into Google. Can he sells? What do you mean he said salt on fire? I think that's the kind of thing that's going to get you on the TSA watch list, like trying to build a bomb on a salt. I think you're thinking of like, can I make a bomb at a salt? Yeah, that's the next thing to Google, right? Exactly.

Salt bombs. Salt bombs. Is that sort of like a bath bomb? You know, like a salt bomb for your food? I think that's what I was thinking. I think those exist already. Bad salt bombs are a thing. Yeah.

And then you can make a reactor. You can convert yourself from a dirty person into a clean person using a bath salt bomb. There you go. You can make clean energy or at least a clean you. I wouldn't recommend dipping your toes into 450C molten salt no matter how much you want to get into the bath. Yeah, it sounds like a bad idea.

But this is all sort of leading towards making maybe nuclear power more efficient, more clean. And so maybe we should start with that. Let's start maybe recapping how a nuclear reactor works, like the kind that we see in our countries right now. Yeah, to understand why molten salt is an attractive idea, you have to understand what it's doing in the reactor and what it's replacing. A lot of current fission reactors use water as an important element of it. Essentially, molten salt will be replacing the water. But you might not be familiar with the role of water in fission. Like, why would you even need water? So, yeah, we should probably break down exactly how fission operates. Yeah, and so fission is like splitting the nucleus of an atom.

And then when you do that, energy gets released. And so if you do that in the right way, you can just get energy from stuff. Yeah, I think it's really quite interesting that for light elements, hydrogen, helium, et cetera, if you squeeze them together, you release energy. Whereas for heavy elements, everything above iron, if you break them in half, you release energy. The reason for that is a bunch of really interesting nuclear physics details, which, as usual, we have planned for a future episode. But the point is that when you do fission, you need to use heavy elements.

Things like uranium or plutonium are good for fission, because of it. when they break up, they produce neutrons, which can then create more fission and they produce some energy. And so the way a fission reaction works is you have like a bunch of uranium, it splits up, shoots off more neutrons, which hits more uranium, which split them up, which shoot off more neutrons. And if you get enough uranium together, then it's going to self-sustain. It's going to keep going. It's going to cause like a chain reaction, right? That's the idea. I mean, that's kind of how a fission bomb works, is that if you put enough of it together, you break one atom, one nucleus, and that breaks other nuclei, and then then you have a runaway explosion.

That's a bomb. But for a reactor, you do the same thing, but you do it in a, I guess, more controlled way. Yeah. Naturally occurring uranium will just spontaneously decay, and that doesn't always start a chain reaction. Although we did have a fun episode about a dense deposit of uranium underground in Africa, which did create a natural self-sustaining reaction. But in general, naturally occurring uranium can't set off a chain reaction,

those neutrons just go into whatever other material. But if you get uranium that's dense enough and you have it pure enough, then it can reach critical mass. And so it sustains itself. And as you said, if you have the right kind of fuel, it can create a runaway explosion or very rapid release of energy. That's a bomb. You can slow it down and moderate it a little bit so that, for example,

every neutron creates one more uranium net split, which creates one more. And rather than growing exponentially, it'll just keep going at the same level, producing some heat. Right, because each time the atom splits, it releases it sort of like other particles or, you know, like light or heat in some way that you then capture through another means. Exactly. Usually, you capture that in like water, which then you boil into steam and you can feed it through some turbine and that generates electricity. So that's the basic idea, but it turns out to be

a little bit more complicated in a crucial way because there's different kinds of uranium. And the different kinds of uranium. Some of them are really good to use infusion and some of them are not very good to use in fission. You've got to get the right blend. You've got to get the neutrons going at just the right speed. So there are a couple of details there. Yeah. And there have been a couple of problems in history in making these things work. And so let's get into all of those details and all that history. But first, let's take a quick break. 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 2, 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 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 professional. 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. A foot washed up a shoe with some bones in it. They had no idea who it was.

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Get fired up, y'all. Season 2 of Good Game with Sarah Spain is underway. We just welcomed one of my favorite people. and an incomparable soccer icon, Megan Rapino to the show, and we had a blast. We talked about her recent 40th birthday celebrations, co-hosting a podcast with her fiancé Sue Bird, watching former teammates retire and more.

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just to shit talk. We've got more incredible guests like the legendary Candice Parker and college superstar AZ Fudd. I mean, seriously, y'all. The guest list is absolutely stacked for season two. And, you know, we're always going to keep you up to speed on all the news and happenings around the women's sports world as well.

So make sure you listen to Good Game with Sarah Spain on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Presented by Capital One, founding partner of IHeart Women's Sports. All right, we're talking about melting salt to make vision power more efficient. Now, is this sort of a new idea, Daniel, or something you just came up with this morning? Or has this been around for a while? No, this is fascinating history because it's an idea that has been around for a while

and it was explored early on, but then was put aside because it didn't have enough weapons applications. It wasn't good for developing fuel for nuclear weapons. So it's basically ignored. And now that's actually an advantage. And so it's being looked at again. Right. Interesting. And it might make our food tastier somehow.

Exactly. Don't you want your kid to have molten salt sprayers so they can shoot their own eggs with molten salt? I want my kids to eat food that's not glowing probably. But you said there are some details here about fission that are important to understand. And they sort of have to do with the fact that basically to do fission and to make fission reactors, you need uranium. Now, I guess maybe step me through here.

Like, why do we need uranium? Like, you know, everyone has probably heard of uranium for movies or TV shows because, you know, it's related to making nuclear energy. But, like, why uranium? Why not the next material over? Or why not, you know, chlorine? Well, you can do fission with lots of different kinds of stuff. And we'll talk a little bit later in the program about alternative fuels.

You can use plutonium. You can use all sorts of different heavy elements. Uranium has been used traditionally. because it satisfies a lot of the requirements, like it is physile, meaning if you hit it with a neutron, it will split in half and produce more neutrons. And also because it's abundant. Like there's a lot of uranium around. There's more uranium than plutonium, for example, which is almost non-existent in the Earth's core. Interesting. So it's like, and is there a reason why it's more abundant? It's a really interesting and deep question actually about just like why various elements

exist in the universe in their various proportions. Typically, there's a trend that like, the heavier elements, there's less of them because it's harder to make them. You need like collisions of neutron stars and also the heavier ones are less stable. So uranium is a bit of a sweet spot there in terms of being heavy enough to be fizzile, but also long lived enough to still be around in the Earth's core. I see. Maybe there were other kinds of physical materials, but they just naturally split by themselves over time. And so they're not that material anymore.

Yeah. And some of the heavier ones, there's just harder to make because the heavier they are, the more neutrons you need to get together in the core of a neutron star to make them. So there are just less of them. And so uranium is around and I guess there's enough of it around right now that we use it for nuclear reactors. And so like what's the process of using uranium for fission? So uranium comes in two flavors in the Earth's core. There's uranium 235 and uranium 238.

And they are the same element. They have the same number of protons. Both of them have 92 protons in the nucleus. but uranium 238 has three more neutrons. So that doesn't change, you know, what element you are. It doesn't change the number of electrons. It just changes how many neutrons are in the core, so it's a different isotope. But uranium 235 and 238 are really quite different.

Uranium 235 is great for fusion. It splits nicely. It produces more neutrons. It's excellent. But most of the uranium we find in the earth is uranium 238, the one that's not good for fission. In fact, it's like more than 90. 9% of the naturally occurring uranium. And I guess for those of us who don't remember high school chemistry, the 235 and the 238 means

it's like the sum of the number of protons and neutrons in the nucleus, right? Like you said, it has 92 protons and 143 neutrons. If you add those up, that gives you the 235. And so uranium 238 has just three more neutrons in it. Exactly. And uranium 235 is the one that is really good for fission. Wait, why is 235 better? Like what is adding those just three neutrons to the nucleus due to the whole thing?

It makes it more or less stable. So uranium 235 is a little bit less stable. If you hit it with a neutron, it's more likely to split up than uranium 238. And that has to do with like how the neutrons are arranged. Remember we talked once about super heavy elements and how the protons and the neutrons inside the atom arranged into these shells, sort of the same way electrons do in their orbits. And if you have the right number, then they're much more stable. stable. It's like completing an arch, like a Roman arch. If you have all the pieces, it's much

more stable than if you're missing one or two. So uranium 238 is harder to split than uranium 235. Right, which is weird because it just has three more neutrons, which are neutral. But I guess they also sort of contribute to the, you know, general stickiness of the nucleus, right? Like through the gluons and quarks. Yeah, neutrons are neutrals. They don't have electromagnetic forces, but they do have the strong force because they're made of quarks and it's the strong force that holds the nucleus together. So the fact that neutrons are neutral doesn't mean they don't play a role in the strong force. They totally participate just as much as protons. Both of them have three quarks. And so just adding those three makes a huge difference. And so that's why we prefer uranium 235,

but it's like the minority and the uranium we find. It's the minority. And also uranium 235 likes a very particular kind of neutron. It likes slow moving neutrons. Fast moving neutrons. are much less likely to cause uranium 235 to split. So the problem with naturally existing uranium as we find it is that there isn't enough uranium 235 and when it splits, it produces neutrons that have too much energy. They're going too fast to be effective

to split more uranium 235. Right. So it's rare. So that's why people talk about enriching uranium, right? It's like you're sort of sifting through the uranium and you're separating the 235 with the 238. Exactly. So to solve these two problems,

to like get more uranium 235 and to fix the neutron speed with two solutions. One is enrich it. And so we use centrifuges and all sorts of other technologies to get uranium 235 to be a larger percentage so that there's enough in there to do the fission. And then we do things to slow down the neutrons that are produced so that they are much better at causing fission. And that's where the water comes in in traditional reactors. We bathe these uranium rods in water, which is really good at slow.

down neutrons so they go from the fast speed to the slow speed where they're much better at causing fission. Right. So you make like a bar of this enrich uranium. And if you just leave it there, it's going to decay, right? It's going to glow. It's going to give off heat. And so the idea is that you sort of put a bunch of these bars sort of together.

And like the neutrons from one bar then cause the atoms from the next bar to split up. And then that one releases more stuff. And that then causes the atoms and the other bars to split up. That's how you get the chain reaction. Exactly. And the water plays a crucial role between the bars there and slowing down the neutrons because slower neutrons are much more likely to cause fission. You need to enrich the U-235 component and you need to slow down those neutrons.

And so that's called a light water thermal reactor. Thermal there just means the neutrons are slow and water means the thing you're using to moderate the neutrons and also to provide coolant for the whole thing and to suck off the heat to create electricity is water. So that's the traditional structure of a fission reactor. Right. You just take a bunch of rods of enriched uranium and you dip them in water basically, right? But it's interesting, I think, too, because the way they control the reaction is they control

how much you dip the rods in water, right? Exactly. If you over moderate it, for example, then you'll slow down the reaction. You'll slow all those neutrons down so that they can't even provide fission anymore. Right. And so why is it called light water thermal reactor? Oh, as opposed to heavy water. Sometimes they use like deuterium water.

and that has different properties. There's like a thousand different varieties of these reactors. And this is the one that uses like normal water, the kind of water that we can drink. I see. All right. So then you dip the rods in water. That's how you get a reactor.

But there are problems with that, right? There are a bunch of problems with these reactors. Number one is that you're only really burning the uranium 235, which is a tiny fraction of your fuel. So the uranium 238 that is in there, you're just sort of wasting it. Like, it could maybe be turned into fission, but you don't use it. And so uranium, depleted uranium is uranium where you've burned the uranium 235.

You're just like leaving most of the uranium gone. Sort of like, you know, you try to burn a campfire and you only burn the pine needles on the tree. You don't burn like the real core of the tree. So most of the energy is wasted. It's not even used. Wow. And then that becomes nuclear waste, right? Because this stuff is still like breaking down, shooting off dangerous particles.

and that's why it's radioactive. Exactly that U-238 doesn't burn. It doesn't participate in fission, but all the neutrons that are flying around will convert it into really dangerous stuff like plutonium and all sorts of other stuff. And that stuff has half-lives of like tens of thousands of years. So most of the stuff in your fuel doesn't contribute in a useful way

and then turns into like poison, which will kill people and ruin the environment for like, you know, thousands and thousands of years. Wow, not good. Definitely not good. Yeah, and it's also a little bit, you know, risky too because if you don't control the reaction well enough, you can have a big meltdown. Yeah, one problem with water is that it boils at a pretty low temperature, right? 100C.

And so you need to keep it at a very high pressure in order to keep it liquid because it has to be liquid to play this role to flow through your reactor and to pull off the energy and to be a moderator. And so a lot of these reactors operated extremely high temperatures, like 100 atmospheres. which is, you know, dangerous. And it means that these things are big and bulky. They have to have like thick, thick layers of steel to contain them. And it takes work to maintain this, you know, to keep this thing flowing and to keep it under pressure and for it all to be safe. And you can also have accidents which have happened in the past, right? Notably like Fukushima and Chernobyl, those were sort of like failures in controlling the fission reaction.

Exactly. And all those failures are linked to the water. You know, in Chernobyl, that water boiled because it got too hot. In Fukushima, the water pumps were knocked out by the tsunami. In Three Mile Island, an earlier disaster, the water hatch was jammed, and so the water didn't flow. And so, like, this water, it can work. And, you know, more modern reactors have more and more layers of safety, but it's complicated. It's interesting from an engineering point of view, I think, that as we learn to do fission reactors with water,

the time it takes to build and get one of these things up and running gets longer, not shorter, right? because we're learning how to do it safely. We're just like adding layers and layers of precaution as we develop new reactors. Right. Because I guess, you know, when they built Fukushima, they probably didn't think like, hey, what if there's an earthquake in the middle of the ocean and that causes a giant tsunami wave that then hits our water pumps, right? Like, you have to think of everything.

And that's really hard. Why didn't they think of that, though? Like, who builds a nuclear power plant near an earthquake line or near the ocean? You know, it doesn't make any sense to me. you're expecting this thing to be there for decades and decades like sheesh put it far away from everything that could potentially cause it any damage but i guess there's always something unexpected i guess you know even if you put it in the middle of the mountain then something else is going to happen right there's always something unexpected that's true yeah and you know

that's the danger here we're dealing with very high pressure very high temperature environment and it needs to maintain that or it's going to melt down and cause a disaster and so it's a bit fragile. And I think that's one main concern of these water reactors. All right. Well, let's talk about then how to make things better, how to make them cleaner and safer. It seems like water is kind of a problem here because water boils too easily, maybe. And so you have to be very careful with it because if it evaporates, then you don't have anything controlling the reaction. Yeah. And that's why people think about using molten salt, right? You take fluoride, for example, and you heat it up to 450C. It melts into.

a transparent liquid. It looks like water, right? It flows. It's clear. Sort of weird to think about it, but that's what happens. That's the chemistry of it. And so you can use molten salt in your reactor instead of water. And the advantage is that this thing stays liquid at much higher temperatures. It doesn't boil, right? And so you don't need really high pressure. You can keep it at like one atmosphere and you can still do the same job that water does for you. So you're talking about like a salt that uses fluorine and then melting it and then using that like bathing the uranium rods in that liquid? Yeah. And here when we say salt again, we're talking about it in the chemical definition of what a salt is, right? The same way like

astronomers consider everything heavier than helium to be a metal, chemists have a specific definition of salt. And so fluoride is one example. And so yeah, you melt it. And then you can use this to cool your reactor to pull the energy out of it. And you don't even have to wrap your rods in it. You can dissolve the fuel itself into the salt. So you just have this like mixture of molten salt with your fuel flowing around your reactor. Whoa. So you mix the fuel into this salt that's at 450 degrees Celsius. Is that the idea?

So you have this boiling hot stew of radioactive uranium and salt. And then how do you get the energy out? Or like what happens to it? Does it just stay hot forever? Does it start to heat up? If you leave it alone, what do you got to do? Well, you have the reactor. and you pump some of this salt out into a heat exchanger.

So then you can like, you know, take the heat out and spin turbines, et cetera, et cetera. And there, you know, you could transfer it to water or whatever you need to do. But there's lots of really cool options because it's much hotter. Because molten salt stays liquid at higher temperatures, it's much more efficient, actually, for energy generation. And it gives you other options like creating hydrogen fuel, it's a sort of chemical battery to store all this energy. So, yeah, you have this molten salt flowing around in your reactor. and some of it gets pumped out into a heat exchanger so that you can pull the energy out. Well, that's intense because you pump it out, but it's radioactive too, right?

Yeah, it is radioactive. It still has your fuel in it, so fission is happening in it. And so I guess what happens if you just have a vat of this dissolve fuel, does it eventually just heat up to like a million degrees or I guess it eventually would melt whatever container it's in? Well, you're pulling the heat out of it, right? Because you're using it as a reactor. And there is also sort of a safety valve, which is at the bottom of this thing, they have a plug, which is made out of another frozen salt. And so if the whole thing overheats, if it gets too hot, then it'll melt this frozen plug and it'll just all sort of like drip out of the reactor and it'll cool down fast enough to become solid.

And then the reaction will stop. The reaction only happens when it's liquid. Oh, that's a good mechanism for safety. So if the salt solidifies, then that stops the reaction. like the reaction only works if the salt is melted. All right, well, that's sort of one idea to make vision safer and cleaner. And so let's get into another one that it may or may not be related to the Avengers. But first, let's take another quick break.

All right, we're talking about making fission energy safer by maybe, some new ideas to make the fission reactor process safer. And one of them we talked about was melting salt or a kind of salt as the sort of mediator between the fuel, the enriched uranium. And so that's a pretty good idea, right? It seems safer. It does. Exactly.

It seems like a cool idea. Another version of that is using molten metals. Like you can have liquid lead in your reactor instead of water. And it's actually maybe even safer than water because, again, it doesn't have to be at such high pressures. Right. And that's good because I guess

high pressure things that are radioactive are kind of danger. Yeah, exactly. It's just less likely to blow if it's not at high pressure.

All right. So melting salt is one way. Another way is to use something called thorium. Exactly. And I'm desperate to hear about your Avengers connection with thorium.

Well, I'm just wondering if it's related to Hulkeum in Iron Man. 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 see. Day. 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 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.

A foot washed up a shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA right now in a backlog will be identified in our lifetime. A small lab in Texas is cracking the code on DNA. Using new scientific tools, they're finding clues in evidence so tiny you might just miss it. He never thought he was going to get caught, and I just looked at my computer screen.

I was just like, ah, gotcha. on America's Crime Lab we'll learn about victims and survivors and you'll meet the team behind the scenes at Othrum, the Houston Lab that takes on the most hopeless cases to finally solve the unsolvable. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Get fired up, y'all.

Season two of Good Game with Sarah Spain is underway. We just welcomed one of my favorite people and an incomparable soccer icon Megan Rapino to the show and we had a blast. We talked about her recent 40th birthday celebrations co-hosting a podcast with her fiance Sue Bird, watching former teammates

retire and more. Never a dull moment with Pino. Take a listen. What do you miss the most about being a pro athlete? The final. The final. And the locker room. I really, really like you just, you can't replicate, you can't get back. Showing up to the locker room every morning

just to shit talk. We've got more incredible guests like the legendary Candice Parker and college superstar AZ Fudd. I mean, seriously, y'all. The guest list is absolutely stacked for season two. And, you know, we're always going to keep you up to speed on all the news and happenings around the women's sports world as well.

So make sure you listen to Good Game with Sarah Spain on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Presented by Capital One, founding partner of IHeart Women's Sports. I see. Thorium, right? How can I have missed that? No, thorium is an element. It's something that exists in the earth. It's actually more plentiful than uranium. And it's something that we produce as a byproduct already of rare earth mining. You know, when you're trying to get like cobalt or Namibium or whatever you need for your new batteries, when you're doing the rare earth element mining, you already are just like digging through lots of thorium to get it. And so thorium is something we have a lot. of and it turns out to be an excellent fuel for nuclear reactors. Wait, what?

So there's something else that's not uranium that could also be used for fission reactors. Is it like lighter or heavier or what's different about it? The cool thing about thorium is that it can't actually do fission on its own. But when you hit it with a neutron, it turns into uranium 233. So now another version of uranium. See, it is kind of like the Hulk. Like it turns green and more volatile. Sounds like the Hulk.

Yeah. And uranium 233 is not something that exists in the earth crust in anything but trace amounts. But it's an excellent fuel for fission. It's very fissile and it can operate with slow neutrons. If you just hit thorium with a neutron, it turns into uranium, which is then fuel. So the reactor can turn thorium into fuel for itself. Wait, what? Like, wait, so you take thorium, you somehow bombarded with neutrons.

it becomes uranium 233. And then when that splits, it splits back into thorium. Is that the idea? No, when that splits, it splits into lighter stuff, releases energy and neutrons. And those neutrons, it produces enough neutrons not just to split other uranium 233 atoms, but also to hit thorium and turn it into uranium 233. So it like breeds its own fuel. Whoa, interesting.

I see. Like the process of the fission reaction would actually make more fuel in the process. if you put more thorium in it. Like, it's not making stuff out of the blue. No, it's not just generating it. But if you pour thorium into the reactor, it will turn thorium into the fuel that it needs and then burn that fuel, turning more thorium into the fuel that it needs.

So you need to keep adding thorium, but thorium by itself is very stable. It's not fissile. So it's not like dangerous the way uranium is. Right. And it's also better because it's not as wasteful, right? Or dangerous when it gets used. Exactly.

It burns up a lot of the uranium. And it doesn't produce crazy. dangerous things that last tens of thousands of years. I mean, it produces very dangerous byproducts. Cizium 137 is very, very poisonous. But it has a half-life of like 50-ish years, not 10,000 years. So you need to put this stuff in a barrel and wait a couple hundred years before anybody goes near it, but you don't need to wait 50,000 years.

Wow, this sounds great. Why don't we use that? Like, why are we still using uranium? Regular uranium. Let's switch to the Avengers. Exactly. It's a much better idea. But historically, it hasn't been pursued in the United States because it doesn't produce plutonium and other heavy elements. Those things which are very dangerous and last forever. Those are also excellent for building nuclear weapons. And so the Department of Energy, for example, yeah, they wanted to promote atomic power, but they also wanted to develop facilities which would generate fuel for nuclear weapons. And so burning uranium 235 was very inefficient, but the uranium 238 that was there, some of it turned into plutonium so you could make weapons grade fuel. Wait, are you saying that most nuclear power plants are also secretly like weapons,

weapons factories? Not secretly. A lot of nuclear power plants can produce plutonium, and it's certainly an issue. You need to also enrich it, right? It doesn't like come out with pure plutonium, but a lot of the uranium 238 gets converted into very dangerous, long-lived waste, and some of that waste is excellent fuel for, weapons. Wow. So I guess maybe they saw it as like a twofer, like a bonus, like, hey, if we use this kind of fuel, this uranium 235 to 38, then as a byproduct, we have kind of kind of a steady

source of nuclear weapons. Exactly. And so if on the other hand, you would like nuclear power without creating weapons fuel and without creating environment poisoning waste that last tens and thousands of years, you can do both at the same time by switching to thorium. Wow. Well, well, it seems like countries that, you know, don't have nuclear weapons. Like, does France have nuclear weapons? Like, why wouldn't they switch to thorium? Well, it's just not something that's been as developed, you know? We did some research in the 50s and 60s and developed these reactors,

but uranium turned out to be kind of cheap and plentiful, and people didn't really care about the fact that you were wasting most of it, and it had these nuclear weapons benefits. So it was largely just sort of abandoned for decades and decades and just not really pursued. Oh, I see. So now it's maybe more of like a historical inertia. kind of like, this is what we know what to do. This is what we know how to do it.

We know how to make the safe. But Thorium, who knows, right? Like, who knows? We don't know enough of it. Nobody has done it enough to really kind of meet the same safety standards, maybe. Could that be an obstacle? Yeah, it's a regulatory issues. You know, you're a company and you're deciding to invest $1 billion into a nuclear power plant.

What are you going to do? You're going to use the plans for one that was recently approved that already sailed through the approval process and is working well. Instead of like, yeah, we're going to do. work on development of some new technology. It requires the government to take the lead in terms of research and developing and making sure these things work. And so outside the United States, some governments are doing this. China, for example, recently completed a fluoride thorium reactor. And they were supposed to turn it on at the end of 2021. I haven't heard if that thing has been turned on yet and works. But, you know, a lot of other countries are looking into this.

Wow. Maybe they can't find a Thor's hammer to start the reaction or something. Every time you've got to reboot it, exactly, you've got to call Thor up. And not just China, India also. India is home to 25% of the world's thorium deposits. So it would be a great place to rely on this kind of energy. And so they're developing a thorium nuclear power program as well. Wow, interesting. I guess it just takes out a long time, right?

I mean, you can't just like do this in a rush. You got to do this very carefully. You do. And there are some challenges to salt reactors that don't exist for water reactors. For example, molten salt is kind of corrosive. Like you have that in the inside of a chamber for a long time. It's going to eat away at the inside. So that was an obstacle a long time ago.

But these days, we have fancy new materials that can be basically hardened to the salt. And so it's no longer really a challenge. So with the help of new technologies to overcome some of these technical challenges, there's lots of places that are looking into this. There's a company in Denmark actually called Copenhagen Atomics, and they have a strategy to build one of these thorium reactors, and they want to make them into shipping containers. The whole thing is just totally self-contained. You never have to open it up or do anything. You just turn it on.

It runs for like 50 years, produces energy, sedately for 50 years, and you can like stack them. You're like, oh, we need 10 of those. We need five of those. And to the self-contained? What do you mean? Like they produce the waste, but it's the waste stays inside. The waste stays inside. just like bury it for 200 years and then it's done. So that's a pretty cool idea. It's a company

called Copenhagen Atomics. And for the record, you're not, you haven't invested in this company, have you? You're not like Elon Musk trying to game the markets. No, but you should buy Daniel coin, really. It's my new cryptocurrency. Dancoin. Dancoin. There you go. Exactly. It's going to fund all of my heated spices. For your other, the other arm of your subsidiary corporation right spicy damn exactly working on development of anti-choccalate technology all right so those are two pretty interesting ideas using melted salt molten salt and also maybe switching up the fuel to do something that's maybe cleaner it sounds like people are working on it and maybe we should too because it sounds like other countries are working on it it's definitely promising technology and if you think that nuclear power

is an important part of a clean future then definitely thorium is a better choice than you're uranium. It's a question, you know, whether or not even the waste produced by thorium is worth the risks, but it's definitely all better than burning fossil fuels. Right. And it's much better than Hawkeyeeum. Yeah, maybe you should just take the Avengers and grind them up into fuel. Well, they definitely make enough money to self-sustain its own reaction there. Yeah, exactly. We'll mint avenge coins out of ground-up offenders. There you go. Marvel coin. They might as well have their own economy, right? They're basically just printing money.

All right. Well, this is kind of hopeful news to know that maybe people are working on cleaner and more efficient energies and to get humanity into the stars maybe and into the far future. So we can learn more about the universe and discover more of it. Exactly. And it's always fascinating to learn about the history of these things and how like political choices that were made decades ago really changed the direction of research. And it's not always for a good reason, not always for a good reason. and not always for reasons that we would agree with today. And so the things that people are working on currently are just sort of the things people have been working on. And they're often really promising directions

that were overlooked for silly reasons. All right. Well, we hope you enjoyed that. Thanks for joining us. See you next time. Thanks for listening. And remember that Daniel and Jorge Explain the Universe is a production of,

IHartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. 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. Every case that is a cold case that has DNA right now in a backlog will be identified in our lifetime.

On the new podcast, America's Crime Lab, every case has a story to tell. And the DNA holds the truth. He never thought he was going to get caught. And I just looked at my computer screen. I was just like, ah, gotcha. This technology's already solving so many cases. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.