 Okay, I'm going to propose we go ahead and start up here again. We're a little bit since we have plenty of time for today. I don't think this presentation is going to take an hour and a half. I'd like to make sure we have some time for them discussion afterwards. Before we begin with the final presentation of the day on the containment. Do we have any questions from anybody? Anything you need to clarify for now or as Marco said, we do have a. You know, we have some discussion time built in at the end of each day for which intended to give us an opportunity to have some open discussion about what we talked about during that day so we can open the floor at that point. So all right. So having said that, let's move into the next system that we're going to discuss today, the containment. What I'm going to try to do today is follow a similar pattern to what we've done all day so far. Talk about some of the specific safety requirements. Go through some examples of different types of systems. And then I'll talk about some specific information related to some actual sample calculations that I wanted to show you. And really what I want to try to emphasize there is some of the linkages between the calculations that we do in the reactor itself. Using that information as a source term, if you will, to then calculate the loads that we have to deal with in our containment. So that's kind of how I'd like to structure this presentation today. But so let me begin by going through some discussions regarding the design requirements. You know, this is, I wanted to talk about this just to kind of put a little background overlaying everything I want to talk about this afternoon. We think about radiation protection. It's basically, you know, we can put it in terms of time distance shielding. In this case, shielding is barriers. These are the basic high-level concepts that we use when we think about trying to protect ourselves from radioactive material. Obviously, barriers in this case are shielding or intended to contain radioactive material. Obviously, you know, one such system is the containment. Inside the reactor, as we just learned, we have the reactor coolant system. It is another system which is intended to contain radioactivity. And we talked about the fuel in the reactor core earlier today before lunch. We think about distance. Well, you know, distance is another way we can protect ourselves from the radiation and also time. Some of the philosophies regarding containments are, you know, and in some cases, some people refer to them as, some structures are called a confinement structure. Some of the principles in place are this is, you know, this is with existing plants. This is not a concept that we would apply to a new plant. But some of the existing plants, containment structures, are really more there to give us time for some, you know, for some accident sequences to take necessary emergency protective actions if we, you know, if we had a severe event. But that's not a concept that we're going to apply to a new plant. And we would like to be able to design a containment structure which would function, you know, to actually be able to contain all the radioactive material from a given set of accident sequences. Okay, so think about again, we're always thinking about defense and depth. This is a concept we apply across the board with anything that we do. This is just sort of a summary picture of the different kinds of barriers. We've talked about all of these already. The containment structure is number four. Actually, I guess we didn't talk about the last one yet. I'm at an emergency preparedness or emergency measures in there as a potential, as a potential level of defense and depth, because again, we're always thinking about how we can, you know, how we can take actions to protect the public and the environment. One way we can protect people is to just simply move them out of the way. If we have a situation where, you know, if we go through the emergency plan at a nuclear power plant, they're going to establish a set of what are called emergency action levels. And these are basically what these are, a set of instructions for actions to take given a certain set of plan parameters. If I start losing critical safety functions, which are things that I need in order to be able to provide for core cooling or the long-term integrity of the containment, then my EALs will direct me to evacuate people. And that's, this is another level of defense and depth that we will take. And if you follow the emergency plans as they're described by the IAEA, one will take those actions irregardless of whether or not we actually do indeed have a release from the facility. They're going to be taken based on the conditions in the plant at the time. So again, it's a level of defense and depth. Okay, so getting now specifically to the actual systems that we've talked about. Again, these numbers are intended to be representative of different types of systems. These are not exact numbers. We think about a containment. Typically it's going to be like, you know, roughly a 1 to 1.2 concrete structure or thick walled concrete structure. You know, we could have, and some reactors will have like a biological shield, if you will, around the reactor, which is about approximately one more meter in width. We'll have the reactor pressure vessel itself. And then we get down into the fuel and the fuel rods, which we've already talked about. Okay, so what I've done here, these aren't exact representations of the requirements in SSR 2 slash 1. I wanted to kind of paraphrase them a little bit. But let me just work through this first one here. This is, this states that a containment system shall be provided in order to ensure that any release of radioactive materials to the environment in a design basis accident would be below prescribed limits. Now, when you read that, what does that mean to you? What does below prescribed limits mean? Okay, that's one thing, and yeah, exactly. We have limits in normal operation. We want to maintain the releases of the plant below, you know, below prescribed regulatory limits. Okay, and where I'm getting at here is, we think about a containment. You know, all containments have a design leak rate. It's not possible to build a structure that big, which is going to have zero leakage. I mean, it's just simply not possible to do it. So we always have a prescribed allowed leak rate, which we have to consider. As you said, there are normal operations, for example. You know, the plant has a certain amount of allowed effluent release, which is going to be controlled by national regulatory authority and national requirements. We have to maintain those values below that. Now, we think about an accident condition. You know, those limits, you know, are going to be set by the member state regulatory authority of what they're willing to accept for a given set of accidents, be it an AOO, be it a DBA, be it a DEC condition, for example, you know, but they may have different allowed limits. But the key here is, you know, we're not saying in the safety standards, you know, zero release. I mean, that is just not practical. Because of the way containment are built, the structures are massive, they're huge. It's not possible to have a zero leakage building. So we have to take that into consideration in our standards. You know, what this, depending on design requirements, well, it says leak-tight structures. But again, that's within the design leak rate of the system. Some of the other things we have to think about when we're considering how we design our containment to meet this requirement, we have to think about the associated systems for the control of pressure and temperature. I have some examples of that later on in the presentation. You know, we have to be able to remove heat. We have to be able to, we have to be able to lower the pressure in the containment. If we don't, then it's going to be very difficult to meet these requirements. It's very difficult to build a building which is going to be able to accept and contain all of the energy from the reactor system and the associated decay heat inside this, inside this isolated structure over a long period of time without some mechanism of removing energy from that building. Okay, we have to think about, you know, how are we going to isolate the containment? You know, we, if we look at a containment, you know, it has a bunch of pipes going through it. You know, we have to get the steam from the steam generator to the turbine. So there's a, so there's a pipe penetration. We have to, we have to have pipes coming in from external tanks. We have to have, you know, we have to have the ability to get instrumentation lines through containment. So we have to, you know, we have penetrations in the containment, okay? But in order to have a truly leak tight, again, within the design leak rate of the containment, I have to be able to isolate those penetrations. So I have to have a valving system is what designers typically do on each of those penetrations, which would close, you know, on, well, within a certain set of prescribed conditions which, you know, which have been pre-designed. This is something that, that realistic, there should be an automatic action, you know, to isolate containment. Well, what you typically find required by national regulations is to have a valve inside the containment wall and outside the containment wall for each of these penetrations. Again, that just adds additional level of redundancy to this isolation function, okay? We have to think about the management and, and, and removal of fission products, you know, hydrogen, oxygen, other substances like this, for example, you know, hydrogen, why do I have to worry about hydrogen in a containment? Because, yeah, because it's a potential explosive gas, as, again, as we saw from Fukushima, hydrogen is an extremely explosive substance when the right conditions are present, okay? And that's a key, that's a key qualifier. Hydrogen, just by itself, is not an explosive substance. It has to have, it has to have the right concentration of hydrogen and oxygen under the right pressure-temperature conditions in order to have an explosive mixture. But we're thinking about the design of our containment. We have to consider the possibility that we could have a situation where we have severe core damage. Of course, we all have, you know, we've learned throughout the course of these last couple of days, obviously, that will lead to the production of hydrogen from the oxidation of the zirconium alloy cladding. We have to figure out something to do with that hydrogen. It's really not a good idea to just leave it in the containment. And I have some examples of different design concepts for how these combustible gases have been dealt with by different designers over the years. Okay. The last bullet here is really just sort of a scope question. We have to think about, again, we have to think about a large set of what we call the identified design basis accidents. And that's going to lead to a series of loads in the containment that I have to think about as I'm designing my containment. You know, what is the maximum load that I have to design to? And then we also, again, have to think about severe, well, here it says severe accidents. Again, we're transitioning here to terminology. Nowadays, we refer more to this as a design extension condition. But we also have to consider those conditions in our containment design because we will most likely have requirements on the containment related to those. Okay. So the next requirement that we need to think about is the strength of the containment structure, including access openings and penetrations. An isolation valve shall be calculated with sufficient margin on safety on the basis of the potential internal overpressures and temperatures. We have to think about things like, we have to think about certain things like different kinds of dynamic effects. We have to think about the reactive forces that arise from design basis accidents. Now, let me kind of paraphrase what that means. When I think about this, you know, I think about the fact that if I have a high pressure pipe inside my, inside the containment and we have a whole bunch of them, you know, they're all associated with the reactor cooling system. If one of those pipes should break, again, this is, this is the standard, this is the basic traditional large break loss of cooling accident. What that's going to lead to is basically a jet of water or steam under those conditions because the water will flash into steam, which is going to be coming out of that pipe, which is probably going to be sitting there, kind of flailing around in the containment because there's nothing holding it in place. So I need to think about the effect of the impingement of that extremely high velocity, high temperature steam on internal structures. So that is, you know, that's basically like a jet impact inside the containment. I need to think about that. Is that, is that situation going to damage vital equipment? Is it, you know, is it going to damage the structure? These have to be considered because I don't want that to happen under those circumstances because that is, again, one of our design basis accidents. One of the things that we have to have the containment be able to handle. Okay, we have to consider the possibility of other energy sources inside the containment. For example, in this case, it mentions possible chemical or radiologist or radiologist reactions. I would put this in terms of molten concrete interaction if we heard the term MCCI. If you read anything about Fukushima, you probably read MCCI. Well, what that basically is, is the corium or the molten core drops out of the bottom of the vessel, falls down to the concrete structure under the vessel. It starts a chemical reaction with the concrete. It starts to eat through the concrete. It's an exothermic chemical reaction, creates hydrogen, creates a bunch of carbon monoxide. So we have to think about those effects in our design, especially now because, again, we are now designing for these kinds of situations in our contaminants. Okay. All right, so now we're moving on to the next requirement. Calculating the necessary strength of the containment structure, natural phenomena, and human-induced events shall be taken into consideration and provisions shall be made to monitor the containment and its associated features. So what this means to me is, I need to think about instrumentation. We've talked a lot about instrumentation. I need to be able to measure the conditions inside the containment under potentially extremely hazardous conditions, extremely challenging environmental conditions, is perhaps a better way to put it. What are some of the parameters I need to measure in a containment? Any ideas? During an accident. And what do I need to know as an operator? Pressure. Pressure, yeah, yeah, that's definitely... Anything else? Temperature, yeah. Hydrogen concentration, okay. You're getting the biggies. That's where I was gonna go. So great, okay. You know, that's what I was gonna say. I was gonna say those three, so let's stop there. So again, the idea is you have to sit down and think about it systematically. What do the operators really need to know? And then I'm gonna go to my INC specialists who are gonna design a set of instruments to deal with the expected environmental conditions in the containment. So obviously an instrument is worthless to me if it melts, for example, during the accident or if it gets damaged by a jet stream coming at it from a pipe that is just broken. It's not gonna do me any good. So we have to think about these things, okay. We've already talked about the severe accident or again, I'm going back to old-term and I apologize for that. We have to think about the containment's ability to withstand design extension conditions. One of the things that's very challenging to deal with is this issue of combustible gases. That's another way of saying hydrogen generally speaking, although there are other potential combustible gases. Hydrogen tends to be the worst one. To be quite frank, I don't know of any containment that really has been designed that could handle hydrogen explosion in the containment. I think designers will take the approach. We'd rather avoid that. So we don't have to design against it. So we'll put provisions in place to allow us to ensure that we do not have an explosive mixture inside the containment environment because it's a very, very challenging design problem to solve and it's a very challenging design problem to prove that you've solved. Okay, so capability for... We have to think about capability for testing. Again, as with any system, this is a safety system. We will have requirements in the plant technical specification or in the license of the plant which require me to prove that the containment functions not just during normal operations. There will be times during the operation of the plant where I have to pressurize the containment to its design point and show that it actually works. That's going to be done periodically throughout the lifetime of the facility so I need to design the ability to do that. So that's something I have to think about. That is not an easy thing to do because the containment are really, really big and it's not an easy thing to do. Leakage. Again, we have, you know, this is a building. It is not possible realistically, as I said, to build a building of this size which has zero leak rate. So we have to design in an allowed maximum leak rate and part of the testing is I prove it that it actually meets the leak rate. If it doesn't, the operator has to shut the plant down and they have to find out what's wrong. They have to fix it before they can restart. That's going to be a requirement in the license of the plant. Again, what this really gets back to is demonstrating that I'm staying inside the box of my analysis. You know, one way of dealing with that would be to go back and redo the analysis with a higher leak rate if your regulatory authority would allow you to do that. We have to stay within the boundaries of our calculations because that's how we make the demonstration of the safety of the plant is with the computer models. Alright, penetrations. Talked about this. We have to ensure basically that the penetrations will function just as well as the containment structure itself. In other words, they become part of the containment. So they have to meet all the same design requirements. They have to be able to handle all the same loads, all the same concerns such as internal, you know, internal jet forces, pipe whips, you know, all these different situations that we could postulate could exist in the containment during our suite of accidents that we're designing against. The penetrations become part of the containment structure. Seals, again, seals also, you know, if we have a seal around a penetration, you know, I mean, again, it's, I mean, this is a little bit of an oversimplification, but imagine you drill a hole in the wall and you put a pipe through while you have to put some sealant in between the pipe and the concrete. I mean, it's a little more sophisticated than that, but that's a relatively good example. That seal is the containment, becomes part of the containment structure. That seal has to hold. It has to work under the design basis conditions for the whole suite of accidents that I have to consider. Again, not an easy thing to do. All right, isolation, we talked about this again. I'm not going to dwell on this other than to say that this particular point here points out that, you know, we need to have the two isolation valves on each penetration to give us that extra level of redundancy to ensure that this function actually works, and that it should be reliably and independently actuated. Okay, this is more on the requirements related to containment isolation. The requirements state that the isolation valve shall be located as close to the containment as is practicable. Again, the point there is, is we're trying to prevent a, we're trying to prevent a situation where we have a penetration. Let's see here, let me, and Marco, I'm going to get rid of your stick figures here. Sorry. We have a situation here where we have, let's assume this is the containment wall. This is my, this is my pipe. Got an isolation valve here. Got an isolation valve here. Well, if I isolate, let's just say hypothetically that I, you know, that I have an isolation signal. Let's say this valve isolates, but this one fails for some reason. And then let's say I have, you know, if I have a lot of distance between here and the containment penetration, it's possible I could have a break on the inboard side of that valve and then I have a release path. So the point is make them as close as you possibly can. But there are obviously practical considerations that have to be taken into account within the containment structure. Because again, contaminants are very big buildings, but they're full of a lot of stuff. And so you have to move things around very carefully and design the internal configuration. Very carefully. Okay. Okay, this is the containment isolation valve requirement that we talked about already more. And then again, the modern thinking or the latest thinking on our isolation systems is we need to be able to consider the possibility of design extension conditions and that they will still function under those conditions, including all of the environmental challenges that we talked about. All right, so now we're, now we're moving on more to the internal design of the containment. I mean, why do you think it's important to have ample design space inside the containment to allow sort of the free flow of air or gases or whatever it happens to be? I mean, what's the advantage of that in a containment? That is, that's a big one, yeah. If I can, you know, if I'm using, let's say, my fan coolers going inside the containment and they're creating sort of like a recirculation flow, well, one of the advantages of that is, is that can move the material around or the gas in the containment, which can tend to minimize local hydrogen concentrations. If I have a space where the air can't flow and if it just happens to be that's where the hydrogen is, I'm going to have a local large concentration of hydrogen in that structure. So these are things that we have to consider as we're thinking about our containment. This next bullet here is I want to, you know, these internal structures have to, you know, they're not necessarily designed to handle large internal pressure gradients. So I don't want to have a situation where I have a space inside containment which is highly pressurized next to one that's not highly pressurized. You know, the wall could fail if there's a door or some sort of an opening that could blow open on that wall in order to relieve that pressure. I want to try to minimize that as much as I can because the internal structures, again, may not be designed to handle that kind of pressure differential. Okay. Oh, and again, this is going to be a bullet you're going to see a lot during these presentations. We have to consider these design considerations in the presence, again, of what we call design extension conditions. Okay. Residual heat removal. Okay. Now we're going into systems design associated with the containment. I have a little more on this later to actually show some examples of some of the different configurations. But, you know, certainly for existing containment structures, ones that are operating today, you know, that they don't have these new passive heat removal systems that we've seen some pictures of, of these new plants. So I have to have an active system in order to remove heat. Now, one of the things that's done by some designers is, is, well, as you'll see, some of them use existing plant equipment. I've seen some situations where there's a specially designed system intended just for residual heat removal of the containment. The point is, it has to be thought about. I have to have a system in place in order to reject heat from the containment in order to get the pressure down in the containment long term because the containment will most likely not be able to withstand high pressure of a long period of time. That's not really, that's not really structurally something that's going to work for the long period of time. But I always need to be able to get the system down to a safe and stable configuration, which is low pressure and low temperature. In order to do that, I have to be able to remove residual heat from the containment. Okay. And for this particular system, as you see here, we're going to apply the standard traditional design assumption such as a single failure criterion. So it needs to, so we have to think about, you know, just how many different independent systems we need in order to meet that criterion. And then once again, we're bringing in this idea of design extension conditions. Okay, so next system we're going to talk about is we have to think about the internal atmosphere of the containment. You know, what are we going to do in order to try to minimize I'm going to, out of this list, I'm going to pick hydrogen, for example. Because again, we have some examples recently, unfortunately, of why hydrogen is a really, really bad thing. But we have to think about systems that would allow us to minimize the hydrogen concentration, maybe even remove it from the containment, or maybe work on a way to, you know, perhaps we can even like, you know, we can have like an inert gas. You see some containment structures that have been inerted to deal with hydrogen, because there's not going to be a hydrogen explosion or deflagration if there's no oxygen. It's not, that's not possible. So that's, so these are some of the design concepts that have been developed over the years to deal with that. The point about fission product removal is really in order to try to remove the fission products from the containment, so we don't have an uncontrolled release to the environment. What you find here sometimes is you'll see systems where there might be like a filtered release, for example, where you're going to relieve pressure in the containment, but it's going to go through a series of filtration devices in order to capture the fission products. But the point is I'm lowering the pressure and I'm retaining the fission products in a controlled fashion rather than an uncontrolled fashion. Okay. And again, here we're going to be applying the same design assumptions we do for all of our safety-related systems. We're thinking about single failure criterion is one of the examples mentioned here. And I'm not going to say the last one again because I've said it already 10 times, so I'll let you read that at your leisure. Okay, so let me pause here and ask, because I'm going to move on here now into showing some examples of different kinds of containment structures and then I want to go through some example calculations to show you how some of these requirements impact the designs that people have come up with over the years. But I wanted to pause here and ask are there any questions about the requirements? Again, I realize they were more of a paraphrase of the requirements, but I wanted to use more of a more of a discussion approach rather than just reading the requirement that you can do on your own out of the document. So, any questions? Yeah, please. I don't know if we have a mic. I think we're trying to use the mic here still, so let me bring this to you. Sir, regarding this containment pressure building, so this is your talk about the severe accident, whatever the pressure release inside the contentment. But in case of severe accident, whatever percussion you may take, there may be a rise of pressure inside the contentment that need to be released. So, what is the requirement regarding venting? Okay, well, within our current set of safety standards requirements, we don't have requirements specifically directed towards venting. Marco, correct me if I'm wrong, but I think we don't have any venting requirements. What we would say within the context of the design requirements, that would be left to the member states and to the designers to decide what's the best strategy. Are we going to have a venting solution? Are we going to have a filtered venting solution? Are we going to design the containment so we don't have to vent? In other words, it has enough free volume and it has the ability to passively remove heat, for example, or even actively remove heat. So we don't have to address that question. I mean, right now I can't directly answer your question within the confines of the safety standards so we don't have specific directions on that. But I know it's definitely an area of active discussion amongst member states and these are the general solutions people that try to come up with. But the point is, what you're trying to avoid is having an uncontrolled release from containment. We don't want the containment to actually crack open and just have a direct release to the environment. That's what the safety standards will be directing you to avoid. Certainly filtered venting or venting is one way to avoid that. If you open the vent, it's a controlled release pathway, something you can monitor it, you can filter it, and it's certainly better than the alternative, which would be to just have an uncontrolled release. Because sir, what I feel if there is a design if the venting provision is not there, then we have not foreseen what kind of accident scenario can happen in future. So in that case, if you would not provide any design future for venting, so in any unfortunate accident condition like Fukushima, there may be some accident situation which could rise the containment pressure so high that if you will not provide the design for venting design, then the situation could be very bad. I can't disagree with that. Anything, we can postulate any number of scenarios here, I expect, which could probably lead to an over-pressurization of containment. But then the challenge becomes from the regulatory authority, from the designer perspective, from the operator is, how do I go from this large population of potential sequences and rule some of them out as things that are just simply not going to happen. We're able to practically eliminate those sequences. And then when I get down to my next level of sequences, then I have to ask this question, can any of those sequences lead to an over-pressurization of containment? If that can be, what am I going to do about it? And again, that's something that the member states have to deal with directly because our requirements do not go to that level of depth. We stipulate that there has to be the provision to maintain the containment below the prescribed pressure and temperature limits. How that's done is a design solution question. And there are several ways of doing it. But it's definitely an area, as I said, of active discussion. People are talking about this. You pointed out that the challenge for an existing plant, and then you can't tear the containment off and build another one. That's just not practical. So you have to think about what am I going to do for a plant that's currently operating? Is the containment big enough? Do I need to add a vent? Do I need to add a filtered vent? Certainly it's easier for a new plant, which I haven't built because then I can try to apply some of these new passive solutions. I can just make it bigger. I can have more free volume inside, et cetera. So again, I'm not answering your question directly. And the reason is because I can't answer your question directly because it has to be determined amongst the member states within their own regulatory requirements. But it's a good question. Very good question. Okay, thank you. Any other questions? Okay, so I'm going to move now, as I said, into sort of, I want to show you some demonstrations of different kinds of containment, and in this demonstration, I'll actually try to talk about some of the features that people have adapted over the years to address these questions of over-pressurization, for example. This is not, by any means, going to be an exhaustive list. So I will just concede that up front. There are many, many different kinds of containment. And, you know, it's just not possible to put them all in one presentation. This is intended, as I said, to show you some examples. And I want to use these to illustrate some various points about different designs. Let's start with some comparisons. I think we've all seen that the BWR Mark I is a pretty small containment. This is the containment that was at the Fukushima Daiichi power plant. It has an extremely high pressure bearing capability. I apologize. These numbers here are actually in British units, not atmospheres. These are in PSIG. But it is a very, it's an extremely high pressure bearing structure, but the free volume is relatively small. The next evolution of BWR containment was called the Mark II. The free volume is a little bigger, but the design pressure is a little lower. Again, they were trying to optimize the design for these containment. But one thing to keep in mind here is what you're seeing here is engineering the containment to meet the DBA requirements. Again, existing containment were not designed for severe accidents. The Mark I containment, for example, was not designed for the accident that it faced. It was designed for the large brake loss of coolant accident. And this is how you see this optimization evolving on this plot where designers tried to optimize the size of the structure versus its pressure bearing capability as they went through the evolution of their thinking. The next one on here is a PWR ice condenser containment. This is an example of a PWR pressure suppression system. So it has a relatively large volume, but it also has a relatively low pressure bearing capability because, again, the design concept was to keep the pressure low within the structure. And I have some pictures of this later on. Next up is the PWR Mark III. This containment is more of a traditional PWR-type structure, a large free volume or larger free volume, relatively low pressure bearing capability. It's a concrete, I believe it's primarily a concrete structure, although I think some of them have actually been steel lined. And then we have PWR sub-atmospheric pressure containment as the name implies during operations. The containment is kept at a small amount of, as a small vacuum in the containment during operations, which is there to help you, which is there to deal with, which is there to help with some of the leak-rate issues in the containment. And the final one here is a PWR large dry, very, very large free volume and a relatively high pressure bearing capability. So, again, this shows the evolution and the thinking of the designers as they work through the different design concepts from the 1960s on. But again, what you see here is structures that were designed for the design basis accident. And then over the years, they've been retrofitted to try to deal with some of the severe accident conditions that we've thought about over the years. They were not included in the original design. Okay, three examples of PWR containment. On the left is the Mark I. In the middle is the Mark II. On the right is the Mark III. The basic concept of the PWR containment designed by GE is to use a pressure suppression system. In other words, we have water inside the containment. It's always going to be low in the containment. This is an area called the wet well. What happens during the design basis accident? Again, we're thinking DBA here. The steam from the reactor vessel is going to be discharged into this structure either here, here, here. And that water is going to condense that steam. In other words, it's going to suppress the pressure. Hence the name pressure suppression containment. Now from a design perspective, in order to meet the DBA pressure requirements, that led to the conclusion that we could have a relatively small free volume. The containment is this inverted light bulb shape structure surrounded by, it's actually a metal structure surrounded by a concrete shield wall. In the Mark II, this is the containment structure here. It's a little bit bigger. And it's a concrete structure. And in the Mark III, again, we see this large open free volume here. So they move to more of like a pressurized water reactor concept with the Mark III design. OK. So this is a blow up of a PWR Mark I. And I think I've already mentioned all these features. So, oh no, I didn't mention the last one here. There was an evolution of thinking on the Mark I concept. Originally, Mark I contaminants were not inerted. They didn't have an inert environment. As the concerns about severe accidents mounted or grew, it was determined that the Mark I free volume was a little on the small side. So one of the solutions that was developed to address potential hydrogen issues was to inert the atmosphere with an inert gas. I believe it's argon or maybe even nitrogen. I can't recall the exact gas that's used. But the point being, if I release hydrogen into that free volume, there's no oxygen. So it cannot have a deflagration or hydrogen explosion. That was the design solution that was developed to deal with the potential of combustible gases. OK. And what we see actually from the Fukushima example, it's interesting. Again, I caution that this is not information that we know with absolute certainty, because again quite a bit of the information from the accident we still quite frankly do not know because we have not been able to access the reactor buildings to go take a look and see what the current situation is. But all the indications are is that structurally the containment actually held. In other words, there was no hydrogen explosion or hydrogen deflagration inside the steel structure. Now, as we know, there were hydrogen explosions, what's been theorized, what's been calculated, some evidence that has been able to be gathered strongly suggests that there were leakage pathways from the containment structure into the reactor building. One of the most popular leakage pathways is this flange. This is just a dome that sits on a bolted flange, which can be lifted off to allow access to the containment and the reactor below. It's been theorized that this flange yielded under the high pressure conditions and leaked the hydrogen into the reactor building into this upper space, which then led to, as we saw, the combustible mixture. But again, this is theory at this point. We don't have any facts to back this up. Well, we don't have many facts. We have some, but not enough to draw definitive conclusions. But all indications are, to this point, like I said, that the inerting feature actually did its job. OK, so I think I've said enough about Mark I designs, Mark II and Mark III. So let me move on into the Mark III here. They continue to maintain the pressure-suppression concept, but they came up with a significantly larger free volume. From a design perspective, that meant that they did not have to inert the atmosphere, because it was argued, based on calculations, that for the design-basis accident, we would never be able to achieve a combustible mixture. So these contaminants are not inerted. In some cases, they have hydrogen igniters in them, as you see here, in order to deal with the possibility of hydrogen or other combustible gases. So as we move on, this is a picture. I'm going to move past this, if I show this to you. OK, now these are different. These are BWR containment that were designed by the Siemens Company in Germany. The real thing I wanted to point out here is that you see some very similar features. They use a pressure-suppression concept. These are the different evolutions of the containment. And that's a concept that's been adapted to my knowledge by most of the BWR designers around the world is to use a pressure-suppression concept. That was the point that I really wanted to make on that slide there. OK, so let's stop for a minute here and talk about residual heat removal systems. So this is an example of a very high-level schematic of a layout of a residual heat removal system in a boiling water reactor. Now, as you can see here, it has multiple functions. And they're listed here. Now, it can function as an ECCS system, emergency core cooling system, where I'm drawing water from either the external refueling water storage tank, or I'm drawing water from the suppression pool when I'm in a recirculation mode, as you think about how the system can function. So it can form part of ECCS. It also can be aligned to provide cooling to the various spaces in the containment. I can use the RHR system to provide my dry well sprays, which are there to cool and also help. They also help to condense and remove certain gases in the system and get them down into the suppression pool. I can apply the residual heat removal system as a wet well spray. In other words, this is a spray system which is on top of the pool of water, which is at the bottom of the containment. Or I can also use it to provide cooling from the suppression pool. This is a closed-loop cooling system fed to a heat exchanger in order to keep the suppression pool down below design limits. So this is just an example of a lineup. It's not the only way this is done around the world. But I wanted to make the point that we have systems, active systems, in order to meet the design requirements of pressure, temperature, and the containment. And this is just one example. Again, this system is designed to meet all of the design requirements that are necessary, single failure criterion, et cetera, that we've already talked about throughout the last couple of days. So can-do systems. I wanted to show some pictures here of the different kind of designs they have. Really all I wanted to point out here, whoops, is that, as Marco said, the can-do system is a different reactor design. It doesn't have a pressure vessel per se. The pressure, the reactor cooling system boundary are a series of horizontal pipes, which are fed into a header, which are then fed into a steam generator, which is pretty similar to a typical pressurized water reactor system. OK. So I just wanted to leave this with you again as an example. This is an example of a VVER-1000 containment. The features here are pretty similar to what I call a large, dry containment. It has very similar features. Very large, free volume up and above. You see they've given, they have different spaces in the containment. But the designers would have given consideration to, again, the ability to have the free flow of air between these spaces. So we're not building up high pressure areas. As you can see in this schematic, containments have quite a bit of equipment in them. We have the reactor itself. We're going to have the pressurizer over here. We're going to have the steam generators around like this. We're going to have our ECCS pumps and stuff. We're going to be really low in the building in order to give us the highest possible net positive suction head during their demand. All of this equipment has to be considered within the spaces in terms of environmental qualifications. What kind of pressure or temperature am I going to see over the long term for this equipment? So again, this is the point here. They're very large structures, but they're very busy structures. They have quite a bit of equipment inside of them. VVR-440, this is an example of a pressure-suppression structure. This feature over here is the pressure-suppression feature of the 440 containment design. That's really all I wanted to point out on this here. It's just another example of how you can achieve that pressure suppression function. OK, if we think about PWR containments, generally speaking, we have the large dry versus pressure suppression. I mentioned a couple of those already. I have some pictures in the next couple of slides. For the structural configuration, you're going to find various approaches. Some will have a steel structure surrounded by concrete shield wall. Some will have reinforced concrete, which actually have these really large cables running through that we then secure to the base mat. You actually put tension on these cables to keep the dome held down under these situations. All these various kinds of design concepts have been developed over the years. These are an example to show you a contrast between the two different ideas. This is a large dry containment on the left. Again, what we see here is a very, very large open space. This again allows, this is the volume to allow the containment to be able to hold and retain the energy released from the accident. Plus it also has the advantage of giving us quite a bit of room inside to work. When we're doing work inside the containment structure, we're going to have a crane structure on top to move heavy equipment around inside as we're doing refueling work or other maintenance. You see here the reactor vessel sets in and here this shows the instrumentation lines for the in-core instrumentation. We talked about this. These are going to actually go up to a containment penetration, which is going to go outside of the containment in order to allow the instrumentation to be fed ultimately into the control room. All these penetrations again would have to meet the design requirements that I talked about earlier because they form part of the containment boundary. OK, this is an example of an ice condenser containment. I don't know if you've ever heard of an ice condenser. Have you ever heard of an ice condenser? Well, this is a fairly unique concept. It's a very unique concept. I think there's only maybe one or two of these that were ever built. It's a pressure suppression containment. The way it does it is it has a series of actual ice baskets, which are kept as ice in the containment structure during operation. So you have to have a series of refrigeration systems to keep the ice as ice during operations. The concept is the hot steam, the hot gas is going to be fed through these ice baskets, which will then melt. That's going to condense the steam, so it's going to suppress the pressure. Plus it also gives me a source of internal water inside the containment, which I can then recirculate from the sump after I've exhausted my external tanks of water. It also allows me to have a slightly smaller free volume, because again, it's a pressure suppression concept. As I said, I only know one or two examples of this around the world that have been built. So it's a fairly unique containment idea, but I wanted to show it to you. This is an example of a large, dry, reinforced concrete containment. What we wanted to point out here, again, is just some of the features. You see the basic design concept is we have this very, very large open space. Again, we're trying to allow enough free volume to be able to handle the energy from the design basis accident and stay below the limits. Plus it has an added advantage to giving us quite a bit of room to work inside containment. We can set a polar crane up on top so we can move heavy loads around as needed in order to do maintenance during outages, et cetera. These spaces down here below in the containment, we're going to tend to house our equipment. That's where we're going to have our ECCS pumps and whatnot, because we want to have them very low in order to have the necessary net positive suction head during a demand as needed during the design basis accident. All right, this is a large pre-stressed or pretension concrete containment. The point I wanted to make here is that actually what happens here is to reinforce concrete structure. And then inside the structure, I have a series of what really amounts of very large wires that I feed through the containment structure all the way around. And I secure down on the base mat here. And then I actually take those wires and actually pull them down. That's intended to add this kind of pre-stressing to the containment, which gives it added strength. So this is a concept that you'll see. Again, I don't think this is one of the more common, but it is out there. So I'm going to move on. To the next discussion about different kinds of systems, any questions on the pictures? I know some of them are a little different. There are some unique concepts out there. Again, these are for existing plants. As we've shown, as you would see, if you go to the internet, as Marco said earlier, you're going to find a lot of fancy pictures of a lot of new concepts. Most of them are going to employ passive technologies. They're going to have larger free volumes. They're going to have the added advantage of being able to be designed upfront to deal with design extension conditions, not have to be retrofitted to deal with these kinds of conditions. So moving on here, residual heat removal system. What I wanted to point out here is how the heat removal systems work in general for the containment. We have a source of water. We talked about this. If we think about the ECCS systems, or the emergency for cooling systems, or our heat removal systems, our safety requirements stipulate that we have to think about how much water I need. I'm going to have a big tank somewhere. I'm going to have a reservoir somewhere. I have to have an external source of water that I can use to inject into the reactor if I have a design basis accident. Now, that water is not unlimited. I mean, there's no way to have an unlimited supply of water in the reactor. That's just not possible. You'd have to have a huge tank farm or some huge source of water that you can access. So the concept is I'm going to inject water either through ECCS or through one of my containment injection systems. In this case, this uses the refueling water storage tank, which is a pretty typical source of water that you're going to find designers are going to use. ECCS systems for containment heat removal will be aligned during normal operations with their suction source aligned to this tank. So what happens when this tank runs dry when it's out of water? I mean, what are you going to do? Recirc mode, yeah. You're going to shift out of recirculation. Now, there's going to be instrumentation. Again, this brings in the instrumentation part. It has to be safety-related instrumentation because it's actually waiting a safety function. It's going to be assumed in my safety analysis. I need to know when this water gets low enough in this tank that I've got to start thinking about switching over through recirculation. Because if I don't do that, all my pumps are going to be sucking air. And pumps don't like to suck air. OK, the pumps will cavitate. The pumps could damage themselves. So this is a very critical action that has to be taken, either manually or automatically, depending on the configuration, to make sure that I can shift my water source over to the sump. And I'm going to start recirculating. OK, but now I have another problem. I'm no longer injecting water inside the reactor or inside the containment. It's now this isolated system. I have to be able to figure out how to get heat out of it. Or the pressure is just going to keep going up and up and up. So we see here, we have a heat removal system. In this case, it's shown as I have a fan that draws air into a heat exchanger, out to my heat sink. This is another example of how this could work. I could draw from the sump into the heat sink. And then I'm going to put water back in through some sort of recirculation mode with the containment sprays. It's just various examples of how a designer could approach this. The point being, it has to be thought about because in order to meet the safety requirement on maintaining pressure-temperature limits, I have to have some kind of means of removing heat. And I also have to have a means of doing it long term. I can't just think about the first 5, 10, 15 minutes of an accident. I need to have water supplies for a time period prescribed by the regulatory authorities. And then I have to have the ability to shift over to recirculation. And I have to have the ability then to reject heat from the containment atmosphere. Or it's just going to keep heating up. Ice condensers, I'm going to move past this because these are a very specialized system. I'm not going to spend a lot of time on this. OK. All right, so now we're moving into safety analysis. So let me pause here again and ask if there are any questions about what I've talked about so far. No questions. OK. All right, so what you're going to find here, a lot of this is pretty typical. We've talked about some of this already, the kinds of things we have to think about when we're setting up to do a deterministic safety analysis. I need to think about, obviously, my series of postulated accidents. That's going to be DBAs. It's going to be deck conditions, depending upon requirements, and how I'm going to set up the number of sequences that I'm going to analyze. But then on top of that, as we do typically, I have to think about what other initiating events can I have to worry about in the containment structure? Some of these can be equipment failures. Like, for example, I could have a DBA in the containment, which is related to a failure of a particular piece of equipment, which could then lead to damage in the reactor, which could then lead to a load inside the containment. This could be, for example, some sort of like, well, I guess, really, the large, big loss of coolant accident is really the best example of an equipment failure. With the human errors, we've talked about this already. Other internal events, these are some of the unique events that I think about in the containment loading structure, fires, internal explosions. If I have an internal flood, for example, we think about the design of my containment or how I'm going to analyze it and what equipment is available. If you walk into a containment, there's a lot of pipes running around in the containment for various systems, some of them that carry in steam, some are carrying hot water, some are carrying cold water. Well, if I walk into a space and I look down and I have, let's say, hypothetical, I have a space where I have the equipment I need to operate my containment cooling system and I have a huge pipe running through the upper part of that containment, that space, well, I have a flooding hazard there, right? If that pipe breaks, that equipment's going to be flooded and it's not going to work. So I have to think about these things as I set up my analysis for what kind of equipment I'm going to have available to me to mitigate the consequences of the event. For containment, I think about external events. I have to think about high winds. High winds can create missiles, can lift things up, they can actually hit the side of the containment structure. Obviously, we have to think about seismic events. We have to think about flooding, obviously, we've seen that. All of these things can challenge the containment. One of the things we're learning or that we've learned as a result of Fukushima is we have to think about the combination of external events. The combination of a seismic event leading to a tsunami, which can then cause damage to facilities. That's kind of a new style of thinking, things we hadn't really thought about before in our approach to safety analysis. As with any good calculation, I need a lot of data. I have to know the specifications of the containment. I need to know the general configuration. I need to know things like what is the radius of this arc of the dome? What's the free volume? I have to know down here, I'm going to have to know what kind of structural material am I using? Is it steel? Is it welded joints? Is it concrete, reinforced concrete, stainless steel, carbon steel? These things all matter when I'm doing a structural analysis of containment. I have to know all of those details. I have no details about the penetrations. Again, we talked about seals. Every penetration has to have a seal on it. What's the seal design? Is it something that maybe be susceptible to high temperature? It's going to fail under high, it's going to fail in high temperature conditions. Is it going to fail under high pressure? What's the actual material itself? I need to consider that in my calculations. Obviously in a structure, welded locations are going to be your weak points. I need to know where they are. When I'm doing any kind of structural loading calculation, I have to think about the welded joints. Is that's a possible failure location? Getting down a little more detail here, it actually matters what kind of concrete I have. What's the aggregate of the concrete? What's the size of the rebar and the reinforcing concrete? How are they placed in the concrete? These are things that matter when I'm thinking about a structural analysis. What type of steel type, for example, showed you a picture of what we call the pretension containment, the ones that have those big tensioning wires going through the dome down to the base mat where they're secured and then pulled tight. What's the pretension? What's the size of the wire? And again, sealed design and composition. And obviously, I'm going to feed my results of testing into my calculations. If I have a test that shows that the containment has a certain type of performance, well, I'm going to use that in my calculations. One such example would be leak rate, for example, when I'm thinking about source term. OK, definition of potential loads. These are two examples. The one on the left, I would call an impulse load. If you look at the time scale here, this is over what? This is less than a second. This pressure load here. What could lead to something like this? We talked about it already. This kind of rapid pressurization. What could lead to that in a containment? We talked about it during Marco's last presentation. Any ideas? Talk about, pardon? Not really, those don't happen that fast. I'm thinking about direct containment heating. Let's say I have a high pressure ejection from the reactor vessel of molten corium into the containment atmosphere. It will lead to this kind of an impulse load on the containment structure. It's possible if the containment fails, it's possibility. I don't know the details of this exact calculation, but most likely maybe at this point they predicted a containment failure and then the pressure went down. It's possible. I'm not sure. I don't know the exact details of this calculation. This is intended to be an example. That's a good question, though. You're going to have that energy in the containment. Probably what I would expect would happen is you're going to have this impulse load. It's going to drop back down. And then it's going to equilibrate at some higher elevated pressure if the containment survives. That's an if, because you don't know. Again, this is why we want to avoid that. On the right-hand side, you see a more traditional, typical calculation of pressure in containment. This happens over the series of from 10 to 40 hours to a very, very long event. As the containment just sits there and heats up, it takes a long time for the containment to heat up and pressurize. It's a very large structure. There's a very large amount of internal volume. Most likely what happened under these conditions when you see this rapid drop was they predicted a failure of the containment in these calculations. And the containment just dropped back down to atmospheric pressure. So that's probably what you're seeing there in these simulations. OK. We talk about, again, we can't talk about a computer code calculation without talking about uncertainties. I mean, they go hand in hand. Because we have to do that in order to have a reliable answer. We have uncertainty about the free volumes in the containment. We have a design of containment. But realistically speaking, unless someone goes out and sits in the containment space with a laser and sits there and physically maps the actual location of every wall and every curve and every corner, probably the design volume is not going to exactly match the as-built volume. It'll be close, but it's not going to be exactly the same. So there's uncertainty there with your source of data on the volume. The heat structures, this really is internal walls and structures. What are the thicknesses of the containment? The exact material composition, again, we have a design specification. It'll be really close, but it's probably not going to be perfect as we built it. We have uncertainty about the initiating and boundary conditions. Again, you'll find if we go back to the design basis accident analysis situation, we have the large break loss of cooling calculation. One of the most challenging things to model in that calculation is the rate of flow of steam from the reactor cooling system. Even today, that's a very challenging thing to model. We have ample data sources out there. There's still uncertainty. What happens in the pipe nozzle itself after the pipe breaks, the steam will achieve a sonic velocity at that point. It's a condition called choked flow because it cannot exceed that velocity because that is the maximum velocity under those conditions. But the ability to calculate the sonic velocity of steam under those conditions is very challenging. And we can't calculate it from first principles in our codes, so we have to use a series of models to model it with empirical data taken from experiments. Again, it's pretty good, but it's a source of uncertainty. Heat transfer conditions, again, we're talking here about heat transfer along the various internal structures. Am I going to have an evaporating wall? Am I going to have a condensing wall? Am I going to have rain falling inside from an upper structure that has water on it, which is then condensing inside the structure? Are the surfaces of the inside of the dome going to be wet? They're going to be dry? All of that affects the heat transfer. Under these conditions, it's very, very complicated. All right, so now we move on to the codes themselves. I listed three of the more common examples that I'm personally familiar with. There are others. These are not the only codes out there that do this kind of calculation. These are some examples of some of the phenomena that I have to worry about. But again, unfortunately, these are examples of phenomena that are very difficult to predict with a code. I cannot model these from first principles. What I need then is data. I need test data to be able to verify and validate that the code works. Now, we have a particularly unique problem in the containment is that it's just so big. I'm not going to go build a containment to take test data. It's just not possible. We always have to do scale testing. And what happens when we introduce scale into a test facility? I have to make it smaller. I have to shrink it because there's no way I can build a containment structure to run test data. It's just not possible. So the effects of scale have to be considered. This is something that the basic problem that we talked about in our basic engineering courses is the same here. It's impossible to scale both velocity and buoyancy forces correctly at the same time. It's just not physically possible. It cannot be done. So I have to compromise in my experimental design. What am I more interested in? Buoyancy forces, viscosity, et cetera, in order to have a facility that I can actually build and that I can actually take data in. There are several examples of these around the world. I know there's some in the Russian Federation. There's some testing in France. There's some test facilities in the US. There's some test facilities in Germany. All of these facilities have been built. They're an excellent source of data for us. But the point is we have to understand what the data means when we use it in our code verification and validation. User effect, oh boy, we've talked about that. That's me sitting behind the computer typing. If I make a mistake, I choose a bad model. That's user effect. It happens. This is an example of how these codes are going to link together again. The point I wanted to make here is relap5. In this case, this again is an example. It's not the only code that does this. There are many codes around the world that calculate the design basis accident in the light water reactor. Effectively, it becomes a source term for the containment calculation. In this case, I chose to talk about a code called Gothic. It's just another example. So I take that energy from the reactor. I put it in the containment. I use Gothic to calculate what I want to know, pressure, temperature, hydrogen concentration, vision gas, locations, et cetera, to demonstrate that I can meet my safety requirements for the design basis accident or whatever the requirements might be for design extension conditions. This is an example of a nodalization for another code called MAP. The point I wanted to make here is, I mean, this is the actual calculational scheme that's in the code. And I think I can probably count the nodes here. Maybe I'm going to be on two hands and maybe have a finger or two left over. This kind of shows you the level of detail that you model in these containment codes. The practical reality of this is we think about our basic numerical methods. What do we do in numerical methods? We take a space. We break it up into small chunks to allow us to create a series of ordinary differential equations that we can then easily solve by linking them together. We break it down into a series of nodes. Basic numerical methods. We do the same thing here, except we set a node which is the size of the containment free volume. It's huge. So what that means is there's a lot of physics that's going on inside that node that I cannot model. The length scale of some of these processes I have to worry about are on the order of millimeters. I want to think about evaporation on the wall. It's a very small length scale. I don't have anywhere near the amount of nodalization that comes grips with that phenomenon from first principles. So as any good code developer would do, they go back and put in empirical models, data, to make the code work. The point is, is these codes, in order to have a practically solvable problem, one that's going to not take months and months and months of computer time, I have to set up this kind of nodalization scheme. So these are some examples. Whoops, didn't work. Example calculations of the large break loss of coolant accident, for example. I'm not going to go through the details here. I just wanted to show you. This is kind of a typical result you're going to find for the various variables of interest. I start with my upper left-hand side, the actual reactor. I build my relap5 model in the upper right-hand side. And then I use that model to predict that in the bot. For my containment, I'm going to do the same thing. I have my containment, my plant layout here on the left. I build my containment model. You see a series of nodes and junctions and volumes. And I do my calculation in the bottom. The point here is I need to link this to this. This is the source term for this calculation. And so they're linked together. And another point here is you'll note the very large different degree of refinement in the calculation. Reactor system, I have a pretty detailed set of nodalization in order to allow me to get a pretty good resolution on the answer. In the containment, I do not. Now again, there are codes that have a higher level of resolution in the containment calculation. But in the end, there are practical limits on what we can do. We're simply never going to be able to model, with current technology, the containment down to the level of the reactor system. It's just not practical on computers to do that. Because the space is just way too big. OK, DBA pressure analysis. I don't want to dwell on this other than to say these are some of the kinds of sequences I have to worry about. And this also shows how the various chapters of the FSAR or the PSAR will link together to give me the information that I need to do a reliable calculation. OK, DBA containment pressure analysis. This is just more detail on one particular sequence. So I'm going to go past this. DBA pressure analysis, again, this is just more detail on that. I'm going to leave this for your reference. You'll have this information. Because I wanted to get to one particular point here, which is, I think this is it, which is right here. This just shows an example, again, of some detailed calculations inside the containment. But the point I wanted to make here is in this lower right hand plot here. You'll see where it says in this box. It says I'm doing a switchover to recirculation. Now, this is probably one of two things. It's going to be driven either by an assumption of the analyst, or it'll be driven by the time when the refilling water storage tank is beginning to run dry and you get a low level alarm, and the operator either has to take manual action or has to rely on the automatic actuation to function. The point is you see the impact here. This is a change in how the system functions and how it's modeled. And you can see that if you follow that curve along after that, you'll see that it actually changes the characteristics of the plot. And there's a point I wanted to make there. Equipment qualification is the next, and I believe the final point I wanted to make in this presentation. The point here is I'm not going to walk through this entire logic chart here, because it's very detailed. And again, you'll have it. If you walk through this logic chart, you're going to get to a series of questions on the right-hand side here where you would estimate for any high pressure component in the reactor. I'm going to ask myself questions of, am I meeting these criteria? In other words, if I have a high pressure pipe in the space in the containment where I also happen to have a piece of equipment, I assume that pipe breaks. What are the conditions? What are the radiological conditions? Pressure, temperature, et cetera. If I meet these series of conditions on the right-hand side, then, as it says here, SSC requalification not required. If I don't meet them, I've got to go back to my INC technician, to my pump designer, to whatever that particular component is, and say, hey, look, here's my new equipment. These are the new environmental conditions. Will the equipment survive? Do I need to buy a new piece of equipment? Do I need to re-qualify it, et cetera? This is an example of a logic chart that I wanted to show you. This is kind of a higher level pictorial of what I just told you, so I'm going to pass through this. And this, again, is a specific example for a VVR reactor, generic VVR reactor, which links from the particular high-energy line break on the left-hand side, or HGLB, talks about the specific node in the relapse five code, where that line is. It lines it up with the node in the Melcore code, have a calculation reference on the far-right-hand side, and then the bottom chart gives me the actual results. And so from this, one could deduce whether or not the equipment that's in that particular space will meet the environmental requirements that are necessary from the calculated results. This is just an example of the calculations of some of these calculations shown in this table. OK, and here, again, is another set of examples. This particular one is for hydrogen. And this is an example picture of hydrogen distribution calculations. I believe this is code is this. This is Gothic, again, which is applied to the Kurskoe reactor, which is a Westinghouse two-loop pressurized water reactor. And these kind of calculations here, again, I apologize for going through this kind of quickly, but I wanted to leave some time for questions here. These calculations I do for hydrogen. Again, this is an example of the hydrogen distribution as a function of time in these various spaces. On the right-hand side, you see the actual containment itself. Left-hand side, you see the mathematical representation in the Gothic code. In the next plot, I see the results. This is on the traditional hydrogen distribution plot. And it shows, as long as I stay outside of this triangle here, which is the red results, it shows that I should not have a hydrogen deflagration or hydrogen explosion. This is a result of a hydrogen calculation. OK, this explains those results in some detail. But again, the bottom line is, as you can see from these plots, for that particular sequence, those particular set of equipment and the particular set of assumptions, I'm able to demonstrate that I should not have a hydrogen deflagration concern based on that simulation. OK, and summary. As we saw, containment design features very considerably. I mean, I showed you some. That's not all. There are even others out there. And the details are important to understanding the containment response during the design basis or what we now call design extension conditions. And those kind of details are things like the source term from the reactor system during the event. What are the specific design parameters of the containment? How is it made? What's it made of? What are the free volumes, et cetera. So with that, let me ask if there are any questions. I think I'm sorry for rushing a little bit at the end, but I wanted to leave time for questions. Wow, everybody must be tired. Maybe that's it. No questions? OK. Any questions about anything? On the schedule, we have a discussion session here set up for the next half an hour. And I wanted to just open it up for any thoughts? Any ideas? No. OK.