[00:00] I was asked if I wanted to represent Alabama in a really cool thing called 50 by 50 Science Across America. Basically, there's 50 videos being made, one from every state, about a really cool scientist doing really cool science in that location.
[00:15] I think it's awesome. So, being from Alabama, we have the nuclear plant nearby. So this video is about how a nuclear reactor works, and we're going to get to interview a really cool guy named Bill. It's awesome. So if you want to see some of the other cool stuff that's happening all across America to celebrate 250 years of America,
[00:33] you can do that by going to the link down in the video description after this video and go check out some of the other states and some of the cool stuff that's happening. I'm proud to represent the South. This is a pecan tree, which is why I set my camera up here.
[00:45] And I'm excited about the stuff that's happening here in Alabama, and I'm excited to learn more about the stuff that's happening in other states. Let's go learn about a nuclear reactor. Hey, it's me, Destin. Welcome back to Smarter Every Day. I've got all these boxes here at the house of all the different things that I've made videos of.
[01:02] This one, you might remember, this is uranium. And you might remember this guy, a fast neutron. These are little tools that we use to understand the concepts of nuclear power.
[01:15] So basically, we hit this thing, and we talked about how uranium was kind of like a mousetrap, and it would throw off another fast neutron. we kind of understand, if you've looked at previous videos, how nuclear power works just from an atomic level.
[01:30] Then we took a tour of Brown's Ferry Nuclear Power Plant. We got to see the hardware. Today's video is very special. We're going to actually understand the hardware, the core specifically.
[01:43] So when I started this Nuclear Power Deep Dive series, a guy sent me this book right here. got into Alex, and he said, hey, my granddad wrote this book, and I opened it up, and to my surprise, on this page right here, that is the actual core of the Browns Ferry Nuclear Power Plant.
[02:00] It's called a boiling water reactor, and today we're going to learn all about how that works, and we're also going to learn about these fuel assemblies over here. We're going to get to, like, deep dive into the physical components and understand how that works,
[02:15] because we know we've got hot rocks, and we know we've got steam, and that makes electricity, but I want to understand exactly how the mechanics of the nuclear reactor core work, and that's what we're going to do today, and it's going to be rad.
[02:28] All right, that's it. Let's go jump back into our nuclear power deep dive series here on Smarter Every Day. We've done all kinds of things already. We checked out EBR-1, Experimental Bridge Reactor 1, out in Idaho. We learned about the world's first nuclear power to come online.
[02:42] We learned about nuclear safety and how people that work in the nuclear industry actually approach being around nuclear energy. We've taken the tour. We've learned a ton in this series, and it's been fantastic. Let's go learn about the inner workings of a boiling water reactor, a nuclear reactor core, and continue our series on nuclear power.
[03:02] Let's go get smarter every day. There are two main types of reactors in the U.S. The first is what's called a boiling water reactor, and the second is called a pressurized water reactor.
[03:18] They're pretty similar, but they're fundamentally different. So let's say this is the reactor core of each, and this is the turbine of each. So basically what we want to do is we want to get steam to the turbine on each of them, right?
[03:30] Well, the way a boiling water reactor works is we have water in the reactor there, and it actually starts to boil inside the reactor. So you get steam that goes directly to that turbine,
[03:44] and then it condenses back, and I didn't draw it well, but it turns back into water after it goes through a condenser. You get the idea. But long story short, it boils in the reactor, and that goes directly to the turbine. In a pressurized water reactor, you have water inside the reactor,
[03:59] but the whole loop stays under pressure. So you end up having nothing but water in the reactor loop. Now, you end up having another heat exchanger, That turns that hot water into steam, and that's what goes over to the turbine,
[04:15] and then that goes back through a condenser, and then you put that water back into that heat exchanger. So basically, for a boiling water reactor, you're boiling water inside the reactor itself. For a pressurized water reactor, because you're maintaining such high pressure,
[04:30] you keep it below the boiling point in the reactor, and you use a secondary heat exchanger process to get steam to the turbine. Browns Ferry is a boiling water reactor. Okay, we are here at Browns Ferry Nuclear Power Plant.
[04:44] We're not at the plant, though, are we, Bill? No, we're in the training center right now. We're in the training center. Okay, this is Bill Ball. Bill does instrumentation. You know how the nuclear plant works, all that kind of stuff. I'm a little more smart, yeah. Okay, so we're in a little interesting room here in the training center.
[04:58] There's three models that we're going to look at. The first model is a big overall model of how the whole thing works. We'll look at that here in a second. And then what do you have over here? So over here is just a mock-up of what the actual reactor vessel internals look like, right?
[05:13] So this is what we call the reactor pressure vessel. Okay, so that's inside that one. Correct. Okay, and then we have these over here. These are models of the actual fuel rods. That's correct. These are the fuel bundles.
[05:25] And so these are inside that. Yep. And those are inside that. Is that how this works? Yeah, you've got that big gray cylinder in there. is actually that mock-up right there.
[05:39] The gray cylinder. Okay, so I think let's start with the overall context. So this is the nuclear reactor unit here at Brown Strait Nuclear Power Plant, right? Yeah, this is actually a model of our primary containment.
[05:51] The reactor pressure vessel is this gray portion right here, as we said, was mimicked over there. And then the reactor itself is the fuel, which is inside the pressure vessel. Inside that. Correct, which you'll see when we disassemble that 3D mock-up.
[06:05] So this is a beautiful model. This is old, right? This is very old. Been here since before I've been here. I came here in like 2009. I think this is like 1970s, 1980s. Really? So this is before 3D printers. This thing is awesome.
[06:17] But let's look at some pictures of the construction of Brown's Ferry back in the 70s so you get a sense of the scale. This thing is huge. And keep in mind, they have three of these reactors side by side within this plant. This is the reactor, as you said.
[06:29] And you have a sphere under that. Correct. And a torus outside that. What are the different sections of the unit? So this is what we would call the dry well, the outer portion, and the bottom portion here is what we would call the torus and or the wet well.
[06:43] So you'll see a little catwalk where people can walk under here on the torus. The whole purpose of the torus is it serves two primary functions. One, in the event there was an accident where this vessel pressure boundary leaked and it put a bunch of steam in there, like suddenly it would suppress,
[06:58] all that steam would come down into here and suppress all that steam and condense it underwater. right and it also serves as a surge volume for all of our emergency systems if we had to use them to pull the water and inject it back into the vessel so there are pipes like there are water
[07:13] going up into this i guess i guess we need to understand the reactor better don't we i think so okay so you want to go with the reactor so we're doing this a little weird we're going to start give you context and then drill down and then maybe when we go back we'll understand how
[07:27] how it all works. So this is a reactor. Yep. And the real thing would be like tens of feet in diameter. Really big. So this is a 3D model of it? Yep. All right. Go for it. It comes in two pieces. You got the actual reactor pressure vessel here and then the head, which should come off
[07:43] right here. Oh, and these are all the bolts. Those would be bolts, right? That's right. That's right. Those are the bolts that ring on top of it, or the nuts that ring on top of it with the bolts. Of all the things in mechanical engineering that I studied, one of the things that I respect the
[07:55] most is the simple threaded bolt. I mean it's a fascinating thing. It's ultimately about tension in the joint and I could go on a huge just spill about this because I love threaded fasteners.
[08:09] But when we were on the tour we got a closer look at these. This is the lid over to the side and when you look close you can see on the side I'm thinking these are the nuts. This is the part that screws down onto the bolts or the studs and we saw those studs when we looked into the reactor.
[08:24] You can see that these studs are sticking around the outside. I think that's how that works. You can sort of see inside here about what the vessel looks like. So we like to talk about the vessel in two sections. There's actually a downcomber area.
[08:37] A what? A downcomber area or an annulus area. Comber area? Downcomber. What way? C-O-M-B-E-R? C-O-M-E-R. C-O-M-E-R, okay. So I'll explain here in a little bit more detail. But if we start disassembling this thing...
[08:52] Oh wow. What you'll see is the steam dryer here. Oh wow. This is your moisture separator. Again, let's check out this D-roll for scale here. This is the steam dryer and this is the moisture separator in the spent fuel pool.
[09:09] This is where they took it off the top of the reactor so they could refuel the reactor during their outage. And then this is where the actual fuel sits on the inside here. Oh, this is a fuel rod.
[09:21] So this would be the fuel bundle, which we see over here. Uh-huh. This would be your core crate down here, and this would be the top side. Okay, and that's where the square holes, that's where you drop the fuel bundles down into.
[09:35] Yeah, we prefer to insert them instead of drop them. Okay, yeah, that makes sense. Okay. Now, this is looking down into the reactor, where you can see that top guide that Bill was talking about. And here you can see the fuel bundle at the end of a big arm being inserted, not dropped, as Bill pointed out, down into the reactor core.
[09:52] Yeah. So when I talk about the downcomer, you'll see on the side here these things called jet pumps, right? The white thing? Yep. These are jet pumps. And all these are just like big venturis, right? Okay. So what we're doing here is we're injecting water from our feed water system.
[10:08] Excuse me. I'm going to put this together. Into our nozzles here in the downcomer area, right? Uh-huh. And then we have some recessed pumps, which we looked at some variable frequency drives earlier,
[10:20] that pull water out of the downcomer area, push them into the jet pumps. The jet pumps push them under here, right, to where the fuel is. So there's holes in that so it can communicate with the fuel section?
[10:35] Yes, the under-annulus area. Okay. So the water goes up under the core. Uh-huh. that pushed under there and then and then the water boils right up make some steam and what are these top things these are moisten separators cyclone moisture separators so what they do is make like a torturous path for the steam to come through So we minimize the moisture content of the steam that being come out of the reactor
[11:04] I don't even understand what you just said. I got the torturous path. That's turbulent flow. You're slowing it down to cool it. But you said minimize the moisture of steam. I mean moisture content, right?
[11:17] So you can have wet steam or dry steam. Right. Okay. We prefer to have a dry steam going to our turbine, right? Because the more water that's enshrined in the steam, the more potential we have to damage downstream products like our turbine, right?
[11:29] Okay. So we want dry steam coming out of the vessel. I've never even thought of dry. Every time I thought of, I think of a sauna in Finland. Yeah. You know, like the wet moist steam, but a dry steam is what you want.
[11:41] Correct. Okay. Got it. So this has a tortuous path, and what it does is sort of condenses the... Just like pipes. Yeah, it condenses the steam with the lower enthalpy, right? Okay. Only the high-quality steam is going to come out, and then it goes to some dryers,
[11:56] which is where we're just, again, some more tortuous path from Chevron dryers. And then, if we put it back in here again, it'll come out the top here through our steam lines. All right. Which we'll send off to go to the turbine to spin the turbine.
[12:10] Okay, Bill just said two things that were fascinating. The first thing is he used this big word called enthalpy. Enthalpy is like the internal energy in a fluid or a gas at any time, okay?
[12:23] That involves the temperature and the pressure and what work that fluid can do. So if you have a steam that is really hot at a certain pressure, and then it cools down, but it's at that same pressure, it's going to have less enthalpy.
[12:37] Conversely, if it's at a temperature and it goes to a lower pressure, and it stays at the same temperature versus, you know, lower pressure, that is a gas with less enthalpy. So, enthalpy is like a thing that people throw around to say,
[12:52] this is how much energy this fluid has. The fact that Bill is talking in terms of enthalpy tells me, a mechanical engineer, dude knows what he's talking about. That's just kind of like a signal, okay? Another thing, this concept of wet steam versus dry steam.
[13:07] I find this to be fascinating. So I've never really thought about that, but if you were to whistle, okay, you have just gas coming out of your mouth, right? But if you were to whistle and you got like a lot of spittle and stuff,
[13:21] like, you know, spits coming out of your mouth, that is wet steam. So you have what's called two-phase flow. You have gas and liquid together. So, the way I think about it is this steam dryer separator thing that Bill's telling us about.
[13:39] He says chevrons. I think of like something going one direction and then it has to turn around and keep going. I think of it as trying to get off. This is bad, but I'm just going to say it. Imagine you're on a merry-go-round and you've got a bunch of people on a merry-go-round
[13:52] and then you've got this big kid on the merry-go-round. He's a fat kid. I'll just say it. He's a fat kid. And you're just going to spin the merry-go-round really, really fast and you swing that fat shit off the merry-go-round. That's what they're doing.
[14:05] They're using the momentum properties of fluids and the fact that liquid is more dense than gas to make it so that that liquid gets flung off and it hits the sidewall of the pipe
[14:17] and it drifts back down into the core, which I think is fascinating. Using a momentum property of a two-phase fluid in order to separate the liquid from the gas, that's genius. I don't know that I ever would have thought about that, and it's a fascinating approach.
[14:33] So the two concepts are empathy and the fact that we're using this momentum nature of a toothpaste fluid to separate the liquid from the gas. Awesome. So let me try to understand this.
[14:47] So I'm going to take this apart here. So this is like a big pipe. Everything on the outside of it is designed for pumping water into it, so it goes from the bottom up. Is that correct?
[14:59] Correct. Okay. So the water's going in from the bottom up. I've got this grid that I can slowly and gently insert fuel bundles into. And so depending on the configuration of those fuel bundles, which we'll learn more about that later, right,
[15:16] we're just going to assume that some magic happens at the reactor to make heat. and then when that heat gets, it boils the water and it doesn't boil at like 212 Fahrenheit or 100 Celsius.
[15:28] It boils at a much higher temperature, like 500 something? Yes, that's correct. Okay. And it's because it's under pressure. That's right. It's a big pressure cooker. That's the best way to think of it. Okay. All right. So then we have this right here and this is a bunch of pipes
[15:41] that make the steam zigzag on the way up so only the good steam comes out. And then on top of that, once the good steam comes out, you dry it even more. Is that the correct term? Yes, that's correct.
[15:53] You dry it even more, and all that is under pressure. And so what's the top here? So this is the bulkhead. Is it called the bulkhead?
[16:06] We call it the reactor vessel head. The reactor vessel head. So that's the thing that contains the pressure, and that's why all these bolts are so important. That's correct. I mean, if you just think of, like, in your kitchen, this is one big pressure cooker.
[16:18] That's what we're making, right? Okay. Got it. Okay, so cool. And then all three reactors here at Brownsford are designed the same? Correct. Now that we understand the reactor itself, what I want to do is I want to understand the fuel rods that are in there,
[16:33] and that's where they go, the fuel bundles, right? And that's what we have over here. Can you explain that to us a little bit? Absolutely. So here's a fuel bundle, right?
[16:46] And you can see sort of what you're looking at are these pieces right here in our 3D model. These vertical pieces. There's 764 of these inside the core. That's a lot. There is a lot. Now, when you say 760, are you looking at these little rods or are you looking at these square pieces of assembly?
[17:02] 764 bundles in the vessel. Okay, that's a lot. Yeah. So the way they're assembled is you've essentially got four bundles per fuel assembly. Okay? So they all sit down here. So is this a bundle?
[17:15] This is a bundle. I'm looking at a bundle. This is a bundle. Okay. This whole thing is an assembly. Okay, got it. So there's four bundles and an assembly. And how many, what do you call the little rods of fuel?
[17:28] Yeah, these are fuel rods. We call this the cladding on the outside. Is there pellets inside that? There are. These are uranium oxide pellets. Uh-huh. And then these are zircaloy cladding around it. So we have pellets in rods in, what do you call that?
[17:43] Inside a fuel bundle? and their bundle goes into an assembly. That's correct. Okay, got it. All right. So how does this work? So you've got four bundles that sit down in a fuel support casting.
[17:58] You can sort of see where they sort of connect down there on the bottom. Uh-huh. You see this little piece down here sort of just sits inside that fuel support casting. Okay. It indexes in there. And then in between it, what you have is a control valve ring.
[18:13] This thing right here. That's right. This is a control. It looks like a cross from the top. That's correct. Okay, can I stand on there? Sure. Okay, I'm going to look straight down. Oh, yeah, so there's a cross down there, and that's the control rod.
[18:29] I always thought the control rod would be a cylinder, but it's actually a cross. Yeah, so it's all about the cross section of absorption, right? So what we want to do with these control rods is these control rods like neutrons, right?
[18:42] And the whole fission process is about controlling how neutrons interact with fuel or the material around them, right? Okay. So the control rods? Like neutrons. Oh, yeah, big time. Okay. So these are made of B4C boron, mostly, right?
[18:56] And boron is a gigantic neutron absorber, right? Okay. So the way the fission process, I guess, ultimately works is you have a neutron that comes out, right? And then the light water reactor, all the fuel.
[19:08] Now, that neutron that comes out, is it a fast neutron? A desert neutron? Woo! A desert neutron? Yep. Okay, it is a fast-distance. Yep. And these fuel bundles are always covered with water constantly, right? So what we're doing is, in order for a light water reactor to work,
[19:25] is the fuel or the neutron will get slowed down by the water. Okay. So the neutron interacts with the water molecules, right? Slows it down to what we call thermalizing. And then it can interact with a multitude of different things, right?
[19:38] But for the most part, it either interacts with the fuel, the fuel pellet, that's in here. Okay. Right? To cause a fission, which would release energy and that energy that's heated when the energy released when the fission occurs
[19:50] heats up the water, which we use to boil. Okay. Right? And make the steam. Yeah. Or it can be absorbed in the control rods which is completely inert. Right. So when I look top down on the core, I'm seeing every four slots
[20:04] right there that goes into an assembly. Correct. Okay. Now, I do notice that there's there's a hole right here and this looks very pipe-like. Are you pumping water vertically through that?
[20:19] So like we talked about earlier over here, the water is technically flowing through here. So what happens is the water gets sucked from our research pumps out of the downcomer here, gets put into the jet pumps here
[20:33] where it goes through the centuri, goes to the bottom of the core, and then there's enough turbulent force with that research that research pump to push water and flow up through the core this way.
[20:48] The real big thing about this, because I think it's important to know, is this reactor is always trying to shut itself down. What do you mean? The hotter the water gets, the less reactive the reactor is. So think about it. We talked about the only way we can interact with the fuel with these neutrons
[21:02] is to thermalize them. You mean you slow them down with water? Correct. So the hotter the water is, how close are the molecules together? the hotter the water is it expands water expands so if you have
[21:14] if you have less molecules close to each other right in the water would your thermalization neutrons go up or down you'd have less reactions right I'm assuming I don't know this to be true but this is something
[21:26] you understand like natively I don't right so you're saying the hotter the water the more it takes energy away from the neutron the hotter the water the less likely a neutron is to collide with Water molecules therefore the less likely it is to thermalize Oh I see therefore Therefore the less neutral thermalize Therefore less neutrons interact with the core therefore power goes down Got it
[21:51] It has to do with, there's a term, it's the cross-section. It has to do, like, as neutrons are flying out, the cross-section of the water changes is what it sounds like. Yep. You're saying. Yep. I love how Bill just understands all this stuff intuitively.
[22:05] I have to slow down and think about it, and if you'll permit me, I'm going to do that real quick. So the fuel inside the reactor is uranium-235, right? In a previous video, we talked about this concept of the fast neutron.
[22:19] Whee! Right? The fast neutron zipping around, right? Well, the fast neutron is less likely to interact with uranium-235 than a slow neutron. And so the slow neutron is what Bill is referring to as a thermalized neutron.
[22:35] It's going slow. The way you thermalize a neutron is by a moderator. Now, water is a moderator for neutrons. And so if you have a fast neutron, when it hits water, it has to bang around on all those hydrogen bonds,
[22:51] and it slows down and it becomes thermalized. So what Bill's saying is fascinating. He says if you have water that's hot, the density of the water gets lower.
[23:03] It starts to expand. And so as it's on one straight path, it's going to hit less water molecules. So the heat of the water actually affects how much the neutron is thermalized. And when you moderate the fast neutrons less, they remain fast,
[23:19] and they are less likely to interact with the uranium. So what this means for us is a really big deal. In the book, it has this graphic, which is amazing. It is the boiling in the water column in the reactor itself.
[23:34] You'll notice that down here at the bottom, that's where the gas starts to nucleate, the bubbly flow. And as it starts to become more gaseous, you can see up at the top, there's nothing but gas.
[23:46] But down here in the middle, you've got like this mix, this halfway between gas, halfway between liquid. And so what that means, and I think this is amazing, this means that down in the bottom of the column, you have water.
[23:59] And so those neutrons are thermalizing. They're slowing down. whee! Ooh, it slows down and it reacts with the drain. Up kind of midway, you're like thermalizing some of them, not thermalizing the other ones,
[24:11] but up at the top of the reactor, whee! They're just zipping around if there's a neutron up there. It remains fast. And I'm talking about through the fuel rod, right? So what this means is if you have a runaway
[24:25] and you boil all the water, all of your neutrons are going to be fast and the reactivity of the whole dang thing is going to go down. So the fact that you are turning all your water into steam,
[24:39] you think that would be catastrophic, but actually that has a self-correcting factor to the reaction itself, which I did not know. And when I understood this, I started to realize,
[24:53] oh, the engineers that made this are smart. They made it, this BWR, They made it such that as the steam starts to happen, you no longer have as much reactivity.
[25:05] And I thought that was really cool. We call it the negative temperature coefficient of reactivity. Okay. And all it's really saying is if the water molecules are further apart, less neutrons
[25:18] thermalize, therefore less reactions occur in the core, therefore power drops. So the hotter the water is, power wants to go down. Interesting. That's interesting. So is the reactor designed so it ramps up to a certain place and kind of rides there?
[25:33] For the most part, we'll set it somewhere. So we'll set a place with these control rods, i.e. how much fuel do we want to expose, right, to be able to have interactions with neutrons, right?
[25:45] And then we'll use the research pumps to put flow up here to move what we call boiling boundary, right? So where's the water, where's the latent heat of vaporization really going to occur on these rods, right?
[25:57] In the vertical dimension. Correct. So is there a part of the fuel rods or the assembly that's ever exposed to air? No, these rods are always covered.
[26:10] However, this is where the boiling point is for the steam to come off and go up to the steam dryer. So it's boiling and going up. So you've got levels like you see in a tea kettle.
[26:22] Correct. The core is always covered. So these little things inside here, that's the actual fuel, right? This is like a tube. These are uranium oxide pellets. Okay.
[26:34] And you have one of those out over here. Yeah, we do. So it's not a real one. It's a mock-up. We wouldn't let it that easily out here. But this is something that the NEI uses. What is the NEI? They're a nuclear energy institute.
[26:47] Okay. But what they do is they help interpret some energy guidelines, et cetera. But the NEI created sort of a mock-up, and in the back here, you're like, what it's equivalent to.
[26:59] You should be able to see, like, how many tons of coal it's equivalent to, one ton of coal. So this little pellet has the same energy in it as one ton of coal. Correct. Wow. Okay. So the energy density of nuclear is just off the charts.
[27:13] That's right. And that's why we like it. It's expensive up front, right, because it costs a lot of money to get all the fuel in one location and all that other type of stuff. But once we have it, we're good for two years.
[27:26] We don't have to continue to buy coal or buy oil or anything like that. It's all sitting right there. So it's a reliable source of energy. So if you think about it, a lot of people talk about nuclear being a green energy.
[27:38] There's obviously waste associated with this that we'll talk about in another video, I'm sure. But there's a lot of energy that went into making the fuel as well. So if you think about the whole balance equation, you have to consider making this. and you have to consider all the stuff.
[27:52] Where are you at on nuclear in terms of, do you think it's a green energy or what's your? Yeah, well, obviously I'm a big fan of it, right? It's very green. There's no carbon monoxide released with it. Any waste that we produce, right, we know exactly where it is.
[28:07] It didn't go somewhere and then we're trying to figure out, you know, years later where in the air it is or how it affected the public. I can point to it and say it's right over there. And we know exactly how much it is, where it is, and how we're tracking.
[28:20] Interesting. So you're saying, yes, there is waste, which is one of the big criticisms of nuclear. It's like, look, there's the waste. But your point is, you know where it's at. It's not in the air or in the water. That's right.
[28:32] I've never heard that point. That's pretty interesting. There's a lot of stuff that just goes away from most power plants into the atmosphere. But with a nuclear plant, it's right there. That's fascinating. They have a storage area there.
[28:45] So in a future episode, we're actually going to look at this. We're going to meet some people that are preparing these nuclear fuel rod caps. It's really fascinating, and I look forward to sharing that with you. So I have been working on my school stuff for quite a long time,
[28:59] and this computer right here is very important to me because I have some very complicated simulations set up in a program called ANSYS LS Dyna.
[29:11] So this is one of the simulations. This is a bullet hitting a bullet. It's really cool. So the way this works is I have to run these simulations, and I've got all these hard drives hooked up to this computer,
[29:25] and it takes a long time to run these things. Well, I need to check on those simulations when I'm not at home, and sometimes I need to tweak some stuff. And so I've actually been doing that for a long time with the sponsor of today's video,
[29:38] which is AnyDesk. So AnyDesk is like remote desktop software that you can use from anywhere, and all you do is you pull up any desk on your computer and you host it here and then you can
[29:51] use a password to get into your computer from somewhere else. So for example, this is some footage of me in a train in England checking on simulations. Also, here's me at the New York
[30:03] Public Library. I really like to work there. I've been doing stuff there. You can also use your phone to log into the computer. Here's some footage of me doing that and checking on the simulations. This one blew my mind. Now that I have Wi-Fi in airplanes, I've been doing work on these simulations in airplanes.
[30:21] Apparently, we live in the future now. So if you have a need to let somebody access your computer or you want to access your own computer remotely and password protect it and all that stuff, you can do that by going to anydesk.com slash smarter.
[30:36] And the way it works is there's a freeware version, and they're banking on you liking this software so much that you're going to get a corporate version at wherever you work, and that's how they're going to make their money. So it's a really good tool.
[30:48] It's helped me a lot. Actually, I recently got this paper published, which is fantastic. So if you want to see this paper, you can go to Royal Society Open Science, and you can check out the paper.
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[31:25] That's it. Anydesk.com slash smarter. Try it. You need it. You don't. Whatever. Okay, let's go back and talk to Bill about the fail-safe design characteristics of the nuclear reactor itself. So it's the configuration of multiple bundles in the water that allows you to go critical.
[31:40] Correct. Correct. No one assembly will go critical on itself. In fact, we have a calculation we make, the way these things are designed, that you could delete a control rod. A control rod.
[31:53] Aggregately in a big core, right? And the core will still remain shut down at all times. So something happens. So are the control rods controlled independently or are they all together on one plate? Independently. Independently. Correct. Really? And so if one of them were to drop, I would assume that would make the reactivity in this part of the reactor go up.
[32:11] Yeah, yes it would. But the way the overall core, nothing would quote-unquote latch. There's not enough reactivity in this area to cause a critical reaction in the core. Wow.
[32:23] So there's a lot of probability and statistics and geometry, frankly, that goes into all this. Correct. A lot of differential equations. Yeah, absolutely. Everything's balanced. Yeah. Yeah so steady state is your friend in a nuclear reactor Absolutely Okay When you hear a nuclear engineer say the word critical it sounds like a scary thing but it actually not
[32:44] Let's graph a nuclear reaction, and let's see what this is all about. If we have number of neutrons on the y-axis here, and we have time on the x-axis, let's say we have zero right there, we have one neutron here, we have two neutrons there.
[32:58] if I put in one neutron and I get less than one neutron out, even if it's 0.999, over time, my nuclear reaction is going to go down. It's going to dissipate and stop reacting at some point.
[33:13] If, however, for every one neutron I put in, I get one neutron out, then that is said to be critical. I am in a steady state situation, and that's good. I can generate power indefinitely like this.
[33:26] However, if I get more than one neutron out for every neutron I put in, that's called supercritical, and that can get out of control. We do not want that. What we want is a critical reactor. The word critical is a good thing.
[33:40] So when you're bringing a reactor up, is that the most critical time, pun intended, to watch everything? Well, it is, really, because I told you before that the reactor is always trying to shut itself down, not just with the temperature of the water trying to, you know,
[33:55] cause less reactions as it heats up. So these rods actually, what's holding these rods back from inserting the core is what we call trans-folio pilot valves. So these are energized, right, to hold air on the control rod to withdraw it.
[34:13] So if at any point in time we lose air or the trans-folio pilot valve is de-energized, you automatically insert. it automatically inserts, right? So then all of our instrumentations that monitor reactor power,
[34:26] like our SRAMs, IRAMs, APRMs, if at any point in time it sees a value that is non-conservative, it automatically trips them and causes the air to pour off and then trip the control off.
[34:38] So the way the control theory works, or just the theory of operation of a reactor, it's a privilege from the reactor standpoint for it to run. Correct. It has to say, mother, may I? Mother, may I? Mother, may I? Yes, you may.
[34:52] And then it can run. If at any point in time anything goes weird, it is not given the permission to run. Correct. Okay. Tell me about these levels of containment you were telling me about. Yeah, so we've got five basic levels of containment, right?
[35:06] So the first one is our fuel pellet itself, right? All the fission products we really want to contain in the fission itself, or the pellet itself, right? Okay. So then our second barrier is actually this clad. Now as this pellet reacts, it's going to swell a little bit, right?
[35:22] So you'll actually see, I don't know if you can tell, Like physically it'll grow. Right. And we call the spacing between the pellet and the clad, the pellet-to-clad interaction process, right? So we actually highly monitor it,
[35:34] and that's why we come up with a power real nice and easy, because this clad is really the primary thing we want to contain everything in inside the cladding of these fuel cells. What's this made out of? Zircaloy. Zircaloy.
[35:46] That's correct. So it's really anti-rust and all that other type of stuff. Very, very heavy duty material. Is it invisible, the neutrons? For the most part, yes. Okay. So this is our second boundary. In fact, when we go through our emergency procedures later
[35:58] in the simulator, you'll see that the cladding, that's what they're always trying to protect. And the way we protect most of the cladding is by keeping the core covered with water, keeping it nice and cool. Okay. In order to minimize the amount of pellets and clad interaction that can potentially occur.
[36:12] Okay. So the first level of containment is the Zircaloy tube. First of all, it contains the pellet, the pellet itself. That's correct. Okay. Then it's the drickle or tube. Okay. Correct. Then, if all that else fails, we contain it here inside the vessel.
[36:28] All this, we can shut everything off and isolate it and contain everything inside the vessel itself. So this is a mechanical pressure vessel that's designed to withstand a certain pressure, and that's a lot of bolts for a pressure vessel.
[36:41] Yep. So it can handle crazy pressures. Well, it can handle up to about 1,250 pounds. Okay. So normally when we shut down, we operate somewhere around 1,000 pounds. Normally when we shut down, the pressure will decay off pretty quickly.
[36:54] Okay. And then if that fails, that's when we come into where our primary containment is. Okay. So for some reason, the vessel becomes compromised. We can contain everything in here.
[37:07] So everything in here can be shut off, and it's actually self-sufficient. We talked about the emergency cooling pump. Yes. We're taking suctions from down here. Uh-huh. It's just one big loop that feeds back into itself. I asked, though, what this part of the reactor is made of,
[37:20] and if you go back to those original photos where they were creating the plant, you can see it's a combination of steel and it has concrete on the outside of that. Bill said there's a specific reason they do this. There's usually two different types of material.
[37:33] We can call it what I'll call a tense thickness, right? That has a lot to do with radiation. We can explore that a little bit later, but effectively it's how much thickness of a material you'll need to reduce the radiation in an area
[37:46] down to a tenth of what it was. Okay, so you've got steel and then steel and then concrete. And all this stuff down here is steel as well? Correct. Okay, got it. And so you can contain pressure on this one.
[37:58] Does this have any kind of pressure capability? It's a larger volume, right, so lower pressure. But this can maintain up to approximately 54 pounds. We normally try not to limit it past 56 pounds.
[38:10] normal operation we intentionally inert this dry well right because we don't want any explosive gases or anything in there so it's filled with nitrogen and we keep about a pound of pressure in here. Positive pressure. Positive pressure correct.
[38:22] And you do that so that well why do you do that? Well for multiple reasons one it puts a pressure boundary on the water down here in the torus right so it provides net positive suction head for our pumps and emergency pumps if it's needed okay
[38:34] And then two, it ensures that we have an inert gas inside the dry well so that in case something did leak like, you know, there's potential for hydrogen or something like that, there's no potential for explosion inside there.
[38:49] Got it. Everything's inert. That's correct. Got it. So this is the ultimate. But you've got pipes and stuff going to this, and you've got water coming out of this. So how do you contain that? Like let's say something happened in like,
[39:01] I'm going to use the word dirty water comes out. or like what's the correct way to say that has radiological contaminants where does that go so are you asking like in the event of an accident yeah yeah so no normally we'd want to contain
[39:17] it all right within here so it would probably come out the vessel fall onto the bottom of the drywall down there and then fill up and eventually make its way down to the torus where we just circulate that water back into the reactor now you're right there are pipes that come in here we have to be
[39:31] be able to add water sometimes or add nitrogen like we talked about but we have what we call primary containment isolation valve everything is double valve okay so we have an inboard valve and an outboard valve and both of them will close on the event that we get a signal just like we talked
[39:46] about with the with the permissive for running the reactor and running the core how it has to be safe to operate yeah that's the same thing with the containment in fact we have um a ac valve inside
[39:58] the dry well right no sparks dc valve on the outside so multiple power sources so when one of them fails the other one's going to come back behind it and close i didn't know that there's an ac that an ac valve has no sparks yeah as far as i'm aware yeah the dc valve actually runs on
[40:14] our dc motor will run on brushes right yeah that's right so your carbon brush the commutator will cause uh a lot of the spark yeah you have to think about all that yeah interesting what are people much concerned about with a meltdown well i think it's the corium that's generated right so what
[40:30] that what that is is in the event something were to happen with the meltdown right the the crab and the fuel and the reactor vessel would have to melt to the reactor that's all that stuff combined into one thing and there's just this highly um highly contaminated potential piece of metal right that
[40:49] is really hot that is unable to cool one of the things that's really important for a fuel bundle is what we call coolable core geometry. If you go back over here and look at them, water easily flows to cool off this cladding everywhere.
[41:05] It's a convection. That's right. So if for some reason, you know, the core operated and all that stuff started melting together, that coolable core geometry wouldn't be there for us. And that's some of the catastrophic stuff that you saw like at Chernobyl.
[41:19] But Chernobyl and everything, they're not like water reactors, right? Chernobyl didn't have what we call the negative temperature coefficient of reactivity, right? They weren't self-governing like we were.
[41:32] They were all about making power as quick as possible with those RMBK reactors. So it's a completely different core design than what we have here. This one's designed more for safety? Yes, I think so, yes. Did we incorporate the lessons learned from Chernobyl into this?
[41:47] Well, this was designed well before Chernobyl. Oh, really? Well, I don't know when Chernobyl was designed, but Chernobyl happened in 1906, I think. Got it. The thing I love about this Nuclear Power Deep Dive series is I wanted to learn about nuclear power for years.
[42:01] I wanted to get every resource I could get my hands on and just dig into it, but I didn't do that because I wanted to authentically learn this with you on camera, and that's what we're doing, and it's awesome.
[42:14] I'm asking questions I don't know the answer to while in a nuclear plant. Talking to smart people, it's awesome. I hope you are really enjoying this like I am. I am not the knower of all things.
[42:27] I am the asker of all questions, and I hope you enjoy being right there with me because I'm having a blast. Bill Ball, however, does know a ton about this nuclear plant, and he's sharing that knowledge with us. So huge thank you to Bill Ball at PDA for taking the time to teach us all this awesome stuff.
[42:44] We're grateful. so yeah a big thanks to everybody that supports Smarter Every Day at patreon.com slash smarter every day your support is allowing me to do the things I want like I want to ask
[42:56] these really interesting questions in these really interesting ways you're helping me do that so thank you so much patrons I am grateful more videos to come in the Nuclear Power Deep Dive series we're going to talk about Bill Williamson we're going to talk about nuclear cross section
[43:09] I'm excited to learn that with you and there's so much more we went back out to Idaho National Labs. There's a ton here. So big thanks to you for being here. Please consider subscribing to Smarter Every Day. If not, no big deal.
[43:22] I'm Justin. You're getting smarter every day. Have a good one. Bye.