The Fukushima Nuclear Reactor Accident: What Happened and What Does It Mean?

so let's uh today's speaker is dr. Robert butlet's he is on a scientific staff at the Lawrence Berkeley National Lab where he works on nuclear power safety and security and radioactive waste management from 2002 to 2007 he was at the Lawrence Livermore National Lab where he worked on a two-year special assignment in Washington DC to assist the director of do E's office of civilian radioactive waste management to develop a new science and technology program prior to the launch national Louis little more National Lab in 2002 he ran a one-person consulting practice in Berkeley for over two decades in 1978 to 1980 he was a senior officer on the staff of the US Nuclear Regulatory Commission serving as deputy director and then the director of the office of the Nuclear Regulatory research from 1967 to 1978 he was on the staff of the Lawrence Berkeley National Lab serving in 1975 to 1978 as the associate director of the lab and the head of the energy and environmental division so let's welcome Bob on this very confident I got two likes here about a foot apart and I've got to fix that okay that one's out of the way okay yeah yeah and I don't eat this stand to the Sun okay welcome I can tell this a lot of interest this topic I've given this talk before and there's a lot of interest in this topic and I'm going to I'm going to try to explain two things stuff as it says what happened and what does it mean now I can't possibly explain what happened in detail it would take too long but I'll try to give you the outlines of what happened and also couldn't possibly explain what it means because that's in the future and none of us really know know what it means in detail but I'm going to try to give you some some overview of that too I'm in the presence of a whole bunch of nuclear engineers from across the just across the other side so I'm not going to get into great detail about the nuclear engineering again it would take more than I could do but I'm going to try to give you the the basic outline of what happened and and why it happened so now hold on it's probably that one no yes that the more frame that goes back okay it's that one so just to start nuclear power is very important in Japan it generates about a quarter of their power they have nuclear power plant sites all over the main island of Honshu and also in the southern and northern islands too and as you can see they're on both the East Coast and the west coast this reactor complex was on the East Coast on the northeast coast of Honshu quite a long ways a couple hundred miles north of Tokyo I'm not exactly sure about those numbers but it was too far away from Tokyo to have affected Tokyo very much and there are altogether 50 odd units on a whole lot of different sites in the northeast coast there are 610 13 units that were affected or one way or another by this very large event it says 40 yes affected by the tsunami but the ones at issue are the ones the six in the middle at what's called Fukushima one now I want you to notice that just south of publishing one or four more units at Fukushima two very closest few kilometers away they are not identical but very similar to the ones on the other site that was damaged and because they retained capability have off-site power that's offset part wasn't lost there those reactors were damaged and we can go and look at those reactors and have and a lot of lessons about what happened what didn't happen at the at the accident are understood because of going to look at the other ones so there are six reactors on the site that got in trouble and serious trouble and you can see where they are I'm just going to go on to the next slide and explain this is an aerial view and the six units the oldest one in 1971 they were all built with 70s the first the the first one is small although all the others are quite large the two three four and five or seven or 16 megawatts electric that's about 2,000 megawatts thermal and then the last unit is bigger still but crucially only three of them were in operation if all six of them ended operation there might have been more there certainly would have been more trouble but only three of them were in operation the other three were an outage there are outages from time to time for refueling but in this case the outages were of longer duration because they were doing some after all these years doing some upgrades and repairs and so on and crucially unit for all of the core was out of the reactor and in a spent fuel pool and that's a very important thing we'll come to later the other three though one two and three they were an operation and all three of those suffered a very serious core damage accident the likes of which we've only seen in a light water reactor once before in the in our history and that was the Three Mile Island where the core the core melted and that's what I'm going to talk about now as everybody probably knows the proximate cause of this was a tsunami tsunami caused by the earthquake so I'm going to talk about that just just briefly I've got a I've got a picture it's not a very good picture but it's sort of a picture of Japan and look at the left-hand picture the stuff up up above don't worry about I I'm not skilled enough to have figured out how to erase it the tsunami break that the earthquake break that causes tsunami was 400 kilometers long more or less sort of north to south not quite but north to south and it was 75 miles offshore and as and there's a picture of the tsunami just after it started to happen now you have to understand how this tsunami work because it was a slump tsunami our place in California goes like this they go on strike slit but there because in the subduction zone phenomena it was a slum and over the whole four hundred kilometers which is 200 more than 20 50 miles there was the snub it wasn't uniformly a same amount all along but in the middle it was a huge slump over 20 meters by talking metric you'll have to figure out that over 20 meters is 60 odd feet and if you do that in your bathtub you get a lot of waves let me get a big light and there was a wave this picture shows it went both ways of course the one that went then when he ended up you know it came to our short hair on the Pacific coast of North America and the other one went the other way and this wave was a huge tsunami and it was caused by that earthquake now of course the earthquake motion got to the gut to the mainland right away because it's traveling and sonic velocities in the the tsunami is travelling and wave velocities the time determined the earthquake got to the mainland and when the wave got there was about 45 minutes 45 50 it varied a little from one to the next but that's that's the time and all in fact it says it there was it's like 1446 and 1538 so you can work that out all right 57 minutes in any event if the tsunami and then that other picture shows is it comes close to shore it's a tsunami that is the cause of this accident not the earthquake although there's quite cause it's enough now I have learned in the last several months that most people who haven't thought about this and don't know much about it think that system is a big wave and there's this very famous picture Hocus I a very famous Japanese artist about 200 years ago in fact it's one of the most famous graphic pictures in the in all of art every everybody in our recognises it that's not what this Nami looks like it's not a wave like that even though that's what a lot of people think in fact that way which is what surfers surf on has nothing to do with this tsunami phenomenon what a tsunami is because of this big slump is way out in the ocean is it causes a wave that more looks like that this is my own handwriting imagine this wave is going from left to right and depending on the height in this particular case on the middle of the ocean the middle of that thing might have been 10 or 20 meters high and if you had a ship shown on top of that that's the same scale as chips the ship would ride up and ride back and wouldn't see too much about it but it's going that way pretty fast and when it comes up to the shore that's where you get these huge what we call waves on the shore because of this you know the shore has a slope and the size of the wave and the run-up and the size of the water inundation depend on the on the local topography but it's the tsunami impacting the shore that's the key problem but notice if you're on the shore it doesn't look like this wave it's a it's a rise in the sea level that takes place over many seconds it's not just one thing takes place over many seconds rise in the sea level and then it goes back down and that can last for tens of seconds and that goes back down the course goes the other way and there's a whole lot of damage caused by that now at the plant site the height of the wave that rose was 14 meters this slide says estimated more than 10 this is an early slide but it turns out we now believe that it was more than 14 meters and you notice the blue line is where the sea level the normal sea level was they had anticipated tsunamis here and they had built a wall that was about 6 meters high 6 meters about 19 or 20 feet and of course it was more than twice that 14 meters is about 40-plus feet and it just completely went over it as if it didn't see it but it wasn't as I said a wave hitting it it rose up above it and just rose up above it and it pacted as this picture shows it impacted the front building as a turbine building but the water actually went around the buildings to the other side and kept going for some ways because of its of its how high it was and the reactor building was tight to the water but the turbine building wasn't water went inside and the crucial design flaw of these reactors the first crucial area of these reactors is the diesel generators were in the basement of the turbine building now I'll describe why that's important in just a minute you see the earthquake caused the loss of off-site power the grid went down then these reactors like all reactors depend on the grid for electricity it runs all sorts of stuff but because we know that the grid isn't 100% reliable all reactors are required by design and regulation to have on-site power so that power is available when the grid is lost and that worked here there were two diesel generators in each of these six units and a couple more besides there were 14 days your unit diesel generators I understood it on that on that six unit site and they all started up right after the earthquake and that's just as designer if there hadn't been any water things would have been safe so that's good that means they started up fine they survived the earthquake just as they're designed to do because they're designed for earthquakes like this but the water came and knocked them out okay the reason why units five and six didn't get in trouble was one diesel generator every unit six actually survived provided power and save units five and six all the others were lost and the reactors got into a blackout blackout meaning no AC power at all and that's what caused the accident I'll get I'll get into more about that but first I want to talk a little more about that tsunami now I got this slide from somebody else and I can't read Japanese at all but along the along the bottom are a whole bunch of sites from north to south over about a 300 kilometer distance from north to south along that coast and I can't read this but what I was told was the red big red dots are the size of the tsunami height at spot going from north to south and all the other ones are the sizes of various sea walls that were built they have harbors they had industrial facilities they have towns and you notice they built a whole lot of sea walls and a lot of them we're ten meters high or even 15 meters I so they knew tsunamis were coming and a lot of them were five or six or seven you can see the different different squares and triangles or different kinds of facilities but you can see that pretty uniformly from north to south that tsunami was way bigger than they had anticipated and that's the fundamental failure it wasn't the reactors failing alone 26,000 people are dead because of that figure the Japanese are concerned about as they should be and it wasn't just the reactor at all now just going north to south again I'm another picture whoops I guess I didn't okay to shorten it up I had another picture that showed a little more about this but but that's the lesson for you twenty-six thousand people were inundated by this thing by the way as I understand it they have 45 minutes from the earthquake till it tsunami came they have tsunami warning system the horns went off more or less 400,000 people evacuated successfully 26,000 didn't less than 10 percent it was kind of a successful evacuation they got for imagine less than an hour 400,000 people were saved 20,000 were they got left behind there some people are old some people weren't mobile some people got confused various things but it was actually quite a successful evacuation when you considered they did all that in less than an hour but those 20 odd thousand people paid because of this painful payment their lives because of this this failure to protect helping to set up the tsunami was okay let's get back to the reactor as I said the tsunami came to the reactor site completely swamped those diesel generators caused all sorts of other havoc by the way and the earthquake had caused some trouble on the roads and so on - and all sorts of havoc on the site what what's the cause the loss of power was the cause of the the accident I'm going to explain but a lot of other damage also ensue crucially even if the diesels had run the diesels produce power that has to go somewhere in the site it's a distribution system wires and switch gear and control systems alike and most of that was damaged also by the by the it survived the earthquake and most of that was damaged by the Sami also so even if the diesels had come on they work on to distribute power again because it was there was damaged by the water they were below they were below the the height of the water and the cause of that was the what was that blackout so let me go to talk about a boiling water reactor and we're going to get into some reactor stuff here this will be stylized I can't do much more here but if you understand a boiling water reactor simply it's a way of boiling water to make steam thanks electricity on the left-hand side is a large presser vessel with reactor fuel in it and when the chain reaction runs and the control rods are out they come in from the bottom and the quads go in and it cuts the chain reaction to stops in the chain reaction boils water it goes out that line the the light blue line as steam goes to a turbine drives the turbine about a third of the energy in that steam makes electricity about the other two-thirds doesn't because of the efficiency of the of the thermodynamic process and the rest of that is wasting it goes down out of the turbine down to a condenser here which is shown and then it gets condensed back to water and there's a pump pumps it back inside and goes around a little again condenser in turn in this case goes to the sea that's how the ultimate ultimate heat sink for this cooling isn't about two-thirds of the energy and the chain reactions going out to the sea and as you can see there's a generator this is stylized as a generator that's that goes off to wherever the load is you know in the in the grid so that's very stylized but just to explain a couple more things about about how this works the fuel consists of fuel assemblies there were over 500 of them and an assembly as shown there its twelfth the active area is 12 feet active height is about 12 feet high it's about this big around these boxes and consists of 64 8x8 fuel rods it says 62 because they're a couple of control rods that's an instrument tubes in there but it's 64 4x4 and each of those fuel rods on the left 12 feet long has a whole lot of little pellets that look with like aspirin tablets kind of that's the uranium fuel uranium oxide fuel that's in there and the fuel rods than 33,000 and 500 assemblies comprise this great big machine that if you want to know how big that is I'm going to show you a picture in a minute this is a huge huge pressure vessel in a huge huge building next now I'm just going to go on and show you now just to show how big it is this is this is a reactor very similar to the large Fukushima the largest of the Fukushima reactors this is under construction in Alabama this is a TV a plan under construction in the 70s and to show you how big this is this is all going to be inside the building that you're going to see got damaged so there's something this thing is that great big donut at the bottom which we call the torus or the suppression pool I'm going to come to later there's a that's the containment structure this this thing that sort of looks like a light bulb and the lid of its found here in front and just to show you what the scale is there's a woman sitting right up there in the edge but I don't know if it's a woman but you can see a person sitting up there so this is you should just see how big this is a huge huge dobby next picture oops yeah we see yeah oh no I got one more here it is now here it is stylized this is this containment that sort of looks like an upside down light bulb and it has these channels there are half a dozen channels to this great big torus at the bottom is suppression pool and up above is a spent fuel pool I'll come to in a minute that's but when they when they refuel they take the fuel out of there out of the reactor core and they put it in that spent fuel pool that's that pink thing that's stylized in the fuel and it stays there for a few years while it cools down radioactively and thermally before can be moved and the way this is designed is this large inverted light bulb is the containment that's designed to retain the radioactivity if the reactor and inside the pressure vessel gets in trouble okay this large torus I'll talk about they keep going cuz I now here's a picture of it remember how big that picture was with that a woman sitting at the top of that thing well this is inside that building and there's a cranes and stuff but this just just to show you in the reactor vessel is that long thing that's sort of red or ochre colored there and this is just a way if this is a GE picture just a way to show show the kind of scale of these things next one and here's the spent fuel pool empty way up in the top of the building it looks like a swimming pool except it's about 30 feet deep and it's probably 50 feet on the side and the reason it's 30 feet deep is those things are 12 feet long the spent fuel and they they're sort of 15 or 20 feet underwater as they're stored there now here's the normal operating configuration before they got into trouble and I saw this before but it this has a little more the reactor in the middle boils water the steam goes out that red line going to the turbine the turbine spins the generator makes electricity off site okay then the exhaust from the turbine goes down to the condenser which condenses that's the seawater condenser and this red pump pumps it back into the reactor all of that the red pump and so on is run by electricity and that's the normal operating operating configuration and the electricity that runs this it also comes from the grid but if you lose the grid the diesels which there's a diesel shown up there the diesels are supposed to run all this stuff too and in fact they do although when you lose the grid you shut down just as a safety measure so let me go on whoops no I'm gonna I got it back up whoops so here's what happened they lost the diesels they have lost the grid there was no on-site electricity at all the reactors are actually designed to be safe for some time even when that happens the way they're safe is that there are other systems I'll describe it in a minute that can function to keep it safe for a while even when you lose electricity now here's the crucial thing you need to remember problem with a reactor is that even when it's shut down and the control rods are in it generates a whole lot of heat it's the case gradually but in the first moments it generates a whole lot of heat many percent of the primary power because there's a lot of thermal energy and there's also a whole lot of radioactive decay heat inside the core and that heat sitting there would blow all the water in the reactor right away so in order to keep it safe you've got to keep putting water into the pot and as long as you can keep water in the reactor in the pot and keep it covered and remove the heat that it's generating because that's tripping generates me it will be safe and the principle after shutting the chain reaction down which happened here and is not generally a problem the principle design problem for reactors to keep them safe is making sure that the water never goes down so the core is uncovered that's the thing you got to do that's the that's the main thing in these reactors that keeps them safe the loss of which causes trouble so as long as there's electricity even when the shut down this works fine but the the actually an alone of power doesn't go to the turbine it bypasses it to a to it to another system because they're not making electricity at when to shut down but it goes to the condenser it's going around keeping water in there it's fine you lose electricity AC power there is in fact and this is by design a system in these reactors that can keep water in that pot keep putting it in even though there's no AC power and I'll describe that here there's this very large suppression pool that great big torus that I showed you a lot of water and there's a pump shown in green which runs on the steam that the reactor itself is making the reactor is making steam some of its bled off drives the pump as long as that steam is there and as long as that pumps running as long as there's water in this pressure pool the green path injects water into the into the core and as long as you can keep doing that and we can remove the decay heat why the reactors under water and things are safe now of course in this configuration with no in this configuration with no place for that for that steam to go where does the steam go well there are valves at the top of the reactor relief thousands of top reactor that go out and the steam that's generated by the river it's underwater we hope with the green system the steam goes out the top and goes back down into the suppression pool this great big torus where it is condensed and then the water is available to keep going around of course as you do that that's fresh involves heating up a little bit and if you do it forever that special is going to heat up too much so there's only a certain amount of time in which the system will work before you've got to find some other way to get water in there or some other way to remove decay so there are systems to remove the K heat from the expression pool but they need power the power was gone so the pressure boat was heating up so this will only run for a certain number of hours before you get in trouble and I'll talk about that more in a minute but as long as this green system is working and the steam is driving that pump why this thing remains safe but here's the problem if the green system stops you're not putting any water in the level goes down very fast as it's boiling and right away in just no time I mean you know an hour to the core gets uncovered and then you get in trouble really fast and the trouble goes very fast I'll describe that in a minute and you get and the core melts and you really cause a serious serious problem so the crucial thing about this green system this injection system that runs on steam is that it to needs electricity but it only needs batteries the control system for its system requires DC power batteries so the reactor is equipped with these very large battery banks they kind of look like automobile batteries except there's hundreds of them gang together that produce DC power to provide control for these systems and the way the reactor got in trouble was that they couldn't restore AC power I can restore any AC power the batteries ran out the injection system stopped and they lost level in the course melted okay that's really quick more complicated than that for one of the units which has a slightly different system for it but ultimately all three of those reactors that were running had that scenario they couldn't eject because the batteries ran out and then one of the others would you know what it was a little different but this is the same general scenario and the cores melting what after the other but remarkably in unit 2 that green system which we call reactor core isolation cooling lasted for 20 hours and in unit 3 and actually lasted for 70 hours almost three days which is longer than the then people speculated it could've but these designs are predicated on restoring some sort of power and they didn't restore the power they couldn't restore off-site power because of the earthquake they couldn't restore the on-site power because the diesels were swamped and even if they weren't the distribution systems from the diesels were swamped too so knowing that now we can look back and say that when when the tsunami caused the trouble it did they were going to get a core damage accident and all three of those sooner or later and it happened sooner in one medium for another one later in the other one but by three days all three of them were in trouble all three of them had had a level decrease than the chorus melted okay now when a core melts there's a phenomenon which is really another thing important for you to understand I won't go into gory detail but I just want to sort of describe it to you so you'll see so you'll see this idea here here's a stylized picture they sort of acute things as well the batteries ran out okay and it killed that that green line and they got in trouble but let me keep going what happens when the water goes down below the top of the core it isn't even all the way down is the the car that the fuel rods are made out of uranium but they're surrounded by a zirconium cladding which is chosen for its Neutron properties and it's other mechanical and metallurgical properties but as soon as this happens and there's a lot of steam around and it's hot it's just hotter than the blazes the reaction I've shown takes place with the zirconia so coating reacts with water oxidizes the zirconium oxide releases hydrogen and crucially it's exothermic which means that that reaction creates more heat which drives reaction more once it gets started it's really hard to stop unless you pour a whole lot of water in there which they didn't so gradually it gets up it heats up need something eats right so the uranium eutectic actually melts at that very high temperature that's a very high temperature but that happened here because they lost level and then they finally got up there but that's the source of the hydrogen that caused trouble and I'll talk about a minute but as this reaction proceeded and they lost the decoding cladding the pellets there they look like aspirin tablets they crumble and gradually they collected in the bottom of each of these reactors as a rebel bed a pile of rubble now the Three Mile Island about half or more of the core did that this was 1979 in Pennsylvania and a certain fraction of the core remained intact up at the top in these channels and the rest of it was a rubble bed at the bottom and I have to say that today here's some about seven months later we don't really not eat six months later we don't really know yet how much of the core is at the bottom how much of the core is still there but we know a whole lot of it's at the bottom of each of these three so let me go on metal water reaction here releases energy makes it go faster the core slumped it's at the bottom of the vessel not all of it but a lot of it here's a kind of a stylized picture of this sort of debris bed at the bottom of the lower head of the vessel we don't really know that it looks like this this is sort of a stylized cartoon picture but that sort of sort of idea and of course if you can't keep that rubble bed cool it will ultimately damage the steel vessel which is eight inches of steel and will go down through outside the vessel and go into this this lower containment as best we can tell in two of these three reactors there's been some compromise of the vessel at the bottom and we don't really know nobody knows how much or where but we think that only one of those three vessels is still intact although we don't know for sure no this is a rubble bed but if it gets hot enough and keeps them there's no way to get the heat out it sort of becomes molten here's a picture of molten pool we call it corium that's sort of a junk but a jargon in the industry but here it is before it has melted and here it is after smell this is a molten pool which is hotter still because there's energy from the from the decay heat and so on continues if you don't remove the heat and this sort of phenomenon is at the bottom of each of those three X two reactors unit 1 in a 2 in unit 3 again we don't know the community the Japanese themselves they don't know how much it is we have some speculations a whole lot of indirect evidence but but not not really knowing how much of its melted but we know it did in all 3 now let's go back to this picture because I want to show you a couple other things ok if that happened and it did at Three Mile Island essentially no radioactivity got out of treatment because it stopped injection was restored that core stuff at the bottom was cooled it was molten and then solidified at the bottom the vessel wasn't compromised and almost nothing got out except a little bit of radioactive gas but here we know a good deal got out by the way several percent not 10% but several percent um and some of it was gas and some of it was liquid I'll describe both and then I'm going to go on some was gases that was liquid III mentioned to you that when the when the pressure inside the primary vessel gets too high their relief valves they go back down with the suppression pool where the suppression hold is this torus is supposed to condense and does condense as long as it works but if they're non-condensibles hydrogen is an example but co2 also their non-condensibles why they're not condensed and and it pressurizes that and so there's a relief system that's supposed to relieve that that relieve that and relieve it to the outside ok but that system in fact didn't work properly and nobody is really sure why and that system actually relieved the hydrogen not to the outside but to this but to the the building around it the hydrogen in unit 1 unit 2 and unit 3 built up in the building and in one and three actually caused these large hydrogen explosions that you've heard about in unit 2 it didn't because by a fluke a window a window nice thing maybe a few meters about the size of this ceiling panel a blue out of the side of the building I'll show you a picture of a neck invented it so it didn't accumulate enough to to to explode that's our interpretation of what happened there but in units one in unit three there was a very large explosion attributed to hydrogen and here are pictures of unit unit one there's unit two with a hole in the hole in the side and by the way you wanna know how big these buildings are remember that great big thing I showed you with a woman sitting on the top there inside here these are big buildings these are six and eight story building and you a tree they have an explosion - okay and that was that came we understand from the hydrogen okay now we had a really tough dilemma the whole nuclear engineering community around the world had a tough dilemma trying to understand what happened here before there was no fuel in the reactor uniform it was all the fuel in the court was in the spent fuel pool it blew it stopped off for more than a month all of us were convinced that what happened was the spent fuel pool lost water level because they couldn't restore it and they had explosion to do that that was our scenario more than a month later Japanese went in there looked at the uniform all the fuels in the pool it's all underwater that wasn't so our best understanding is that the lid the explosion unifor came because hydrogen from unit 3 somehow came across collected there and and caused that explosion we're not sure exactly how that work there are lines there there gas in vent lines connecting them perhaps that what it was it seems very unlikely but you know Sherlock Holmes said that if you ruled out the everything else the unlikely is it not that was it sort of the idea of this poem that was in Baskervilles and so we kind of think that that that that that that explosion here was not the spent fuel pool but hydrogen coming from unit 3 but you can see that building has been destroyed - even though it's spent fuel pool there with all of coordinate is intact okay let me go back just to talk about this for a minute I'm going to now talk about the water in Three Mile Island there was no release of anything except gases outside the the reactor vessel here early on there was radioactive water that escaped from the primary it escaped actually this lightbulb thing went into turbine building went into a trench and went into the sea I'm sure you read about that if you paid attention to the news and contaminated the sea it was a percent or two of ala radioactivity which is not trivial but it's not you know as huge as it might be and to this day no one is really absolutely sure how that path went but the best explanation is that there are blue lines here you can see two of them on the side of this reactor vessel in normal operation those are research pumps so the recirculation pumps those blue pumps run on electricity and they recirculate water in normal operation just to keep the rip keep the water in there from becoming stratified and keep it stirred up sort of and it's probably the flanges in those research lines that failed they shouldn't we don't understand why the design shouldn't have and let that water out none of us know why that is no one's been able to go in there to inspect to see why but that's probably the scenario now if it happened in some one flange somewhere we'd say oh that was just a something bad but it happened in all three units so it's more systematic than that if that's what it isn't the sort of the scenario we think so just to just to recoup before I go on with the implications the water pathway that way into the turbine building ultimately into the sea was a little more than one percent of the other activity the airborne pathway that went out those well after the building's exploded there wasn't any way to hold it but if we went out those airborne was several percent it varied from one unit the next but less than ten in every case one of what one it was four or five percent when it was six or seven percent and just to contrast that with where the accident at Chernobyl which I which in 1986 was a very different design a Soviet design in the Ukraine there was way more higher percentage than that when airborne this is a parcel far smaller release but nevertheless it contaminated a whole lot of the countryside so before I talk about the implications we're going to go back and explain just to recoup what happened they lost off-site power from the airplane 45 50 minutes later the tsunami came knocked out the outside power the diesels that green system kicked in ran for a while until the batteries were exhausted then they lost level in each of the reactors in each of them melted okay as quick as that now the melting had they been able to restore some water would have stabilized and they wouldn't have had these releases so as perhaps you know one other thing to say they struggle they didn't have any other sources of water on-site so ultimately they decided to inject water from the sea they brought in a mobile mobile fire trucks they ran fire lines of the sea they took seawater they injected them into the vessel and finally stabilized a few days later each of those three reactors with with seawater and that stopped what would have otherwise been a continuing progression until they got some sort of water in there and then that and that was a wonderful thing to do because it stopped but then because seawater is corrosive they had a long-range problem for three months trying to gradually get the seawater out of there and replace it with fresh water as other sources came in okay a couple other things they tried to bring in emergency power right away but they didn't get it in in time and when they did they couldn't distribute the power because the distribution systems from the deep where the diesels distributed had been destroyed by the tsunami too so they had to actually run separate lines to all the different loans rather than have a distribution place to do it because that had been destroyed - okay they didn't get the on-site power they didn't get that off-site power in in time to prevent the cars from damaging but they could have stopped things earlier had they had they not had that problem and then one other thing to emphasize as best we can tell the earthquake didn't cause this reactor the is this trouble as best we can tell everything functioned fine after the earthquake for the first 45 minutes there are four reactors just a few miles south very similar to these and because they kept on side power they weren't heard a full inspection of those four has been done and they don't see anything that looks like it's seismic caused damage so the general feeling is that the seismic design of these stations was adequate and that's nice to know if you're a seismic engineer because that's not where the issue is the earthquakes here exceeded the the design basis by a little bit but everything performed fine in the earthquake there are a lot of little stuff but nothing nothing serious on the safety side and so I'll just leave you with those those last couple of things and I'm going to talk briefly about the implications because I'm running out of time so let's talk about the implications and I can tell you I'm about as good at predicting the future as anybody else in the room which is I can't even tell you what I'm what I'm going to do a week from week from Thursday maybe I do nobody really knows for sure there are fundamental problems with what happened there that have to be fixed not only here but perhaps at our reactors too until some of the things that I mentioned are understood better we're not going to know whether some of those problems affect our reactors or only affect theirs we're not going to know whether they're only in fact there's on that site or there's elsewhere in Japan we're not going to know whether they affect just that design or other reactors out of that design probably some of each so all around the world different task forces have been trying to understand these things I'm trying to to get to the bottom of what lessons there are in the amp then if the regulatory Commission had a task force for 90 days that issued a report that I can I can tell you how to find and came up with a whole lot of lessons at which the most important is that we really have to be sure that all of our reactors can survive a blackout like that for a lot longer than some people thought by the way we have reactors off in our country they can only survive a blackout for a few hours others that can survive for a very long time black out meaning loss of AC power all this for a very much longer time and that's a fundamental lesson and the second fundamental lesson is we to be sure that the design basis for our reactors for things like these very unusual large large natural hazards is really much stronger than the Japanese had here as best we can tell that particular site has had two or three tsunamis roughly this size in recorded history in Japan not really sure going back and faded history but it's probably many hundred years recurrence roughly and we're really adamant and making sure that our reactors are designed so that the sort of event that occurs like that shouldn't come around September 10,000 years or even even more remotely than that so we're confident that we have a better design than they had here but nevertheless another lesson is to go and look and that's going on in the US now so let me just go briefly to the US and I'll talk about the radioactivity and then stop and ask questions we have 104 reactors in the US I think it's hundred four yeah twenty-three of them are mark one boiling water reactors signed by GE by the way gen electric they're pretty similar to this I mean they're different to have a pretty similar this and and most of our reactors are old there's an age distribution most are between 20 and 40 years old not too many younger than that and these hundred and four reactors produce about 20% of the power in the u.s. averaged over a year now I want to talk about doses before I come to the Japanese doe situation and then I'll stop and ask for questions I hope you understand the significance of these doses before I go to the Japanese doses but this is a typical dose in the US averaged over the whole population in a year and that we measured dose in rem or in this case milligram the natural radioactivity the natural radioactivity on the left-hand side comprises about 300 milligram per year it varies from from place to place in Berkeley it's a couple hundred in Denver it's four hundred but that's an average over the US and and a lot of it comes with rocks and soil but some of it comes from cosmic rays and and the human body itself is radioactive in various things and then we get some from food and the other half of our exposure today 300 odd is because on average everybody in the country gets about 300 per year for medical now you may not have got it and somebody else is getting 800 but that's the average and the average in the u.s. is about 620 million per year of which about half is is natural and the other half is comes comes from come to medical and and in fact some of the is a little bit from consumer products and not very much it's about half an amp now I want you to keep that 300 in that 600 in context when I go to the next slide because we're going to describe about how much radioactivity there is in Japan okay this is a picture from about the 1st of April and so it's not you don't look at the numbers in detail because things have decayed but this is to show you and there's the site up there this is to show you where the radioactivity went the the circles there are 20 kilometers about 12 miles 30 kilometers about 18 miles and 80 kilometers about 50 miles and and on this particular by then at the end of March all that had been dispersed had been dispersed about airborne and what I want to show you here is the distribution you see the yellow area this sort of orange area and then the sort of yellow area that goes in north west of the site and goes out to about 15 or 20 miles that's the area of significant contamination there's rather less contamination in the area that's kind of green and less still in the area that's kind of blue and by the way these these blue lines here are flight patterns of a particular aircraft I took this off the web just because it was a good meeting showing the you know where they are radioactivity went and although they evacuated the all they've activated this very large area out to 30 kilometers which is the second of those three circles they pack into the whole area reoccupation is possible in all but that area that's sort of orange or yellow now the Japanese have selected as their criterion for reoccupation that if at a particular spot the radioactivity in a year is 2000 or more they're not gonna let people back in till they clean it up it's less than 2000 and remember the natural background is about 300 and then you get by another 300 and if you live in Denver you get twice as much natural stuff and so on so there's a range here but they've selected 2000 as the criterion and they are now in the process where they can of reoccupying the zones that aren't in that in that nasty area that goes north and north and west now that area has about 40,000 had about 40,000 population and those people are out of Houston home and are going to be for a long model because a lot of those homes can't be cleaned they're going to have to be taken down and the reactivity buried and rebuilt although some of them can be clean and a lot of the soil there can be clean and some of it can't be the Japanese have a very major program now half a year later of figuring out what to do and going out there and starting to do it and in the meantime reoccupation is starting in the in the rest of that zone so the impact of this is that although a couple hundred thousand or more people evacuated originally about forty thousand are stuck out of house and home now just to put that in context ten times as many as that lost their homes to the tsunami or their businesses or their place of work you've seen the pictures they look like my childhood gang pick up sticks ten times as many lost their homes tsunami twenty six thousand died but about forty thousand I'm not sure the exact number because they're they're doing it now and people are assessing who can go back a new camp are going to be out for a while the recovery from this is liable to cost many tens of billion recovering the reactor is thought to be between ten and twenty bill just cleaning it up ten and twenty billion for that complex and several times that to recover all the rest of this but the damage from the tsunami is going to cost them almost ten times that again so economic impact is necessary the human impact it's a tsunami of course the headlines unless you live there are the reactor which is fine we understand and there was rather little came down came down south if you're living in Tokyo all that time you really really can get anything that matter so I'm going to leave you with this slide and and stop and take questions before I do I just have one thing really important to say about the implications none of us know besides the safety improvements that are liable to be required and hope urgently at the plants that need them none of us know whether this is going to have a long-term impact on the on the deployment of nuclear power in the world we just don't know in our country or in Japan or in Europe or the new countries building and we can't know because predicting the future is still a few years before this plays out okay and as it plays out a whole lot of a whole lot of it's going to be economic and a whole lot of it will be justifiable fear radioactivity because look what happened and a whole lot of it is just going to be the interplay between various various other kinds of electricity in this so I'll close by just saying I'm a as long as you want answer as many questions as you have thank you thank you Matt open up loaded questions and I went over thank you just a clarification you go to your last slide I just want to clarify my understanding of the last slide sure that green area not the teal not the yellow green area a quarter to one point one nine milli REMS per hour oh by the way that's the dose on April 3 okay that's not the dose no okay I just put this up to show the the geographical area okay I said this slide was that April 3 or maybe April 4 I'll consider down your um yeah April 3 okay but thank you so it perhaps is declining presumably it's declining oh yes oh yes okay but that if that's one on average let's say the green area just on average maybe I'm a little pessimistic here is one milligram per hour no let's point two-five to 0.1 no no no that was then no no black that time though the green areas outside the green areas got to be roughly outside the 2000 per year let me ask my question for okay so 2003 years is the criterion where they're not going to allow to reoccupy and that's sort of the orange and the yellow that's my question thank you if we take point the average just round numbers 0.25 to 1.19 just call it for the sake of argument for the moment one milligram per hour right all right so that's 24 million per day or 8,000 per year exactly that's my point I just want I just want to clarify my own state yes sir because the limit as you point out the natural or the limit if that is 2,000 okay so by the way there thank you very much little s the 9,000 hours in a year so yes okay hi hi thank you for your thorough presentation today I on that slide also the last liar there you know I find that it's not an even comparison apples to oranges I've screwed up go ahead of course it's not when you talk when you're talking about the tsunami event and the number of people that were affected and the evacuation and the death rate and then at the in the case of the nuclear material escaping into the environment because the the tsunami of course is a short event that only takes place in a certain amount of time and hours within hours but the caesium that was the bulk of what was released you know has that the effect is through the food chain and the people for a hundred years or sure is that right for sure the sea the season 137 has a 30-year half-life and the season 134 has a four year half-life that's right I mean I didn't mean it to be anything but just to point out that there are 26,000 dead from the tsunami and there's no way that anything approaching that can possibly happen from the radioactivity is just not you can't conjure a scenario in which you purposely fed this to people to kill that many it's just not as bad as it is Sasha there was some talk after the accident about speculation that there had been a reality accident in spent fuel pool number three and the alleged evidence was the distribution of isotopes of fission products can you speak to that has there been yes yes that the evidence the evidence by looking in those polls has discount as well as that isn't so okay there was not any recruit Akali in any of the polls none of them lost level there was always plenty of mileage out of a absorber okay we didn't know that at first you bet what are the new standards likely to be in terms of backup power in the future um the NRC has asked every our our NRC has asked every reactor to do it a new assessment to make sure that the reliability of what we we have on every single site is what what is claimed and to assess what upgrades might be appropriate and you ought to know that within a few weeks our nearest plant I have no Canyon near the San Luis Obispo brought in another diesel of a different kind and has had extra arrangements to make sure that fuels the fuel can be can be assessed and that's going on around the country so it's now case-by-case and the NRC is likely to have a rule making it to establish different criteria but how that's going to play out is still a few months away okay if if the place is designed create energy why is it necessary to have external grid energy to power the place Oh because after you shut the reactor down which is when you when you need it okay okay yeah you can't use they still generating heat yes it's still generating heat but that heat that heat doesn't make electricity and you don't want it to you don't want the operators to be it just doesn't work okay thank you with it with with in almost no time there's nothing to drive the turbines good I've heard it said that one of the reasons Fukushima to survive better was because the reactor designs were more modern but from what you said it just seems that you think it was just because I didn't lose on-site power oh how do you want they weren't more about surely the last the last one came out in 79 and like a lot of ours there hasn't been a lot of moderns they by the way they've replaced specific pieces of equipment you know there's better electric distribution systems it's better cabling the fire protection system is new but the fundamental design is is from the 70s okay they're not more modern we have really wonderful modern designs but never built any of them yet here so are you saying with the spent fuel pool that the way they were designed implies that the ones we have in the United States even the one in Vermont that has an enormous amount of spent fuel is probably safe or something no that the NRC is going to be looking at no no um the way I've spent fuel pool gets in trouble is if because there's there's heat in the core it's the fuel and it could boil the water off if you can't take that you got to take the heat out with a heat exchanger and you can do it by boiling but so they kind of keep putting water back in so the design is to assure that those pools always have water in there that depends on the reliability of those systems especially after an event like this rather than just the regular it's sitting there every day and it might be unreliable we and that happens too but these events are a principal cause of trouble and although the NRC has said based on analysis and understanding that our current pools are safe for now I'm going to bet you a nickel that there's going to be some improvements I'm sure to win this nickel there's going to be some improvements that are going to be put in everywhere even though they're thought to be safe just because it doesn't cost much to have a whole lot of extra margin okay um hi ever the question dudes I sure think during that time I read some article that saying that they should have pumped in the the seawater earlier yes they were they were sort of trying not to because sort of like a last resort thing yeah and it would be extremely costly as well yes is that something that that could have been done much earlier and yes and if I helped a lot they know I I don't think in any of them they could well maybe in unit 3 possibly which was the one where Ritchie lasted for almost three days that they could have got seawater in there in time to have saved the reactor core but had they put seawater in earlier they could have had less trouble less damage less more heat taken out made em cooler and this goes to a very difficult problem with the Japanese decision process as I understand it and I think we now understand it we understood it early on but until the Japanese owned up to it themselves we were very careful not to accuse them of anything but they've owned doctrine of themselves up all these plants have procedures for all sorts of things and if you're in the control room and there's a procedure that you're supposed to do you're empowered of your power you're required follow those procedures but in Japan if there's no procedure for the what's happening the control room operators aren't empowered to take action on their own they have to ask supervisors in this case Tokyo Electric Power headquarters in in Tokyo and TEPCO and the TEPCO people although they had the authority didn't exercise that authority without asking the government and that took a whole there were two different times in which the one was has two inventing an oven has new seawater in which many hours were lost seeking that authority now with everybody that's thought about this now understands that's a terrible situation and the Japanese have now taken steps to reverse it let me describe - from Chicago yesterday now I got to tell you if the plane gets in trouble I want that pilot to be empowered to take whatever actions are necessary to save that plane now we want the pilot to get on the phone and talk and get advice if there's time I want the pilot to seek other opinions of course he's got a co-pilot so on but the power to do what's necessary is in the hands of that pilot and in our reactors it's in the hands of the senior operator in the control room the dome has five or six senior operator can do whatever is necessary in that person's judgment to save the reactor whatever it is in Japan it's not so they had to go outside they lost precious time and between you and me and they know it now that's dumb I mean you know it's just had they thought in about in advance and now understand it and they they're feeling very bad about it although it didn't cause the core melt that happened anyway but they lost precious time in a couple of occasions because they had to seek approval outside the reactor site for things that the people inside knew there was one case in which one of the senior operators took an action he asked for authorization hadn't come true yet he did it anyway risking his life his pension his job and Shane okay and saved one of those reactors more trouble he's now a hero but you know you don't do that it's really hard it's about it's hard for us it's even harder there but that happened once and now they have they say change that so that if god forbid there's anything like this happens again person in the control room will have the authority okay Bob a hood a comment a of Greenspan from they own the department or engineering yeah yeah very important to know that there nowadays we have over after designs designs that are arm called passively safe meaning that they can maintain their safety without having to you to rely on any power from the outside or well inside their own they had the means to remove the decay heat are basically and we hope that such advanced reactors will be developed to be commercial and will be used in the future yeah by the way it's it's not only a fair comment but if you're a nuclear engineer like I am an exciting one but let me describe everybody in this room I hope understands that the modern aircraft are way way safer than the ones that were forty years old but I came yesterday on a 737 and I felt safe enough but I can tell you those brand new planes are way way safer because they're 30 or 40 years of better controls better materials better better better that they're just safer in commercial aircraft accident rates have gone down and down and down and down and down so they're they're they're a factor of a hundred safer than they were when when you know I was a I was opposed doc but we're still running the old ones right I came on a 737 by the way it's better than the ultra seventy sevens it's got a whole lot of this new stuff but it doesn't have all of it these reactors are old a lot of upgrading has been done on them and the ones like them but there's no way that these reactors have the features that they had just described a professor Greenspan in nuclear engineering is working on along with several other colleagues here and elsewhere weirding out a whole lot of clever designs that if we could deploy them would be immune from a whole lot of this trouble doesn't mean they can't get in trouble but a whole lot of things are just just won't happen actually as a fairly direct follow-up to that I was struck in your talk the number of times you said we thought we understood something and now realized we really don't yes and so it's pretty humble yes well so I am actually curious about what this incident tells us about the limits of our knowledge and how we should build that into how we think about nuclear power for the future very low so that we're not in ten years saying well we thought we understood these passive systems perfectly and thought they were safe and then you know whatever accident happened Walter words I agree and in fact our designs are intended to have backups for the backups okay and mostly that works very well we've had hardly any have hardly any big accidents but it doesn't always work and the problem is that the engineers challenged to identify and overcome something like this which is a we call a common cause failure a whole lot of things were caused by one thing and we think we've done a good job on all that but you never know and anybody that would say otherwise is just more confident than engineers should be but you know their note there there's a lot of evidence to tell us that that these reactors are actually pretty safe in fact let me tell you something interesting I'm am convinced that's a fleet of 400 light water reactors out there today but the exception of a few in funny places that don't know what they're doing is way way these reactors are way way safer than they were 20 years ago at the same reactors a whole lot of safety improvements have been built in operator training learning from experience fixing things something happens over here it fixed everywhere I'm absolutely convinced of that I can show you the evidence I gave a talk about that a year ago about wire for this why our reactors are safer than they were now I want to tell you that's still true despite this in the same sense that if we had a plane crash tomorrow it doesn't mean that the fleet of planes isn't safer than it was 20 years ago it is ok it's not perfectly safe of course and that's our trouble we're worried about that are we on the nuclear engineer you bet it's deeply troubling but on average there's absolutely firm evidence and I can show you about all the things that happen that don't happen very much and just to cite one piece of evidence if you got a minute to explain back at the time of Three Mile Island this is 30 years ago well let me back up whenever some small thing happens in any of these reactors that that's reaches a certain threshold there's an automatic signal or the control room operators are told to scram the reactors put the rods in and shut it down okay back at the time of Three Mile Island every reactor in the US had one of those about 10 times a year the average over the whole country about 10 times a year we had about 100 reactors there about a thousand of them every year where some way wrong we actually ought to be shut down they figured out what it was they fixed it and so on okay no by the middle 80s that had decreased to where it was about one or two per year per reactor okay last year there was a handful in the whole country okay a handful of times in the whole country less than ten I think in which something about what went wrong isn't a safety problem it's just prudent it's as if you know you're driving your car taillight goes out you shut down to fix it you don't drive to the garage you shut down to fix it all right things like I don't mean that's sound trivial but it's not taillights are important for safety things like that prudently demand a shutdown and the number of those mostly minor things is a handful year and it was a thousand at Three Mile Island and the three my life I was a full-grown grown-up professional like damn right I was 40 and you know I was I thought I was some you know full grown professional and I got to tailor in thirty years we've done that how do we do it know one thing six hundred little things fix this fix that train this don't do that observe that pay attention to this experience look at that thing that happened over here make sure it doesn't happen to you whole lot of little things in there safer just this aircraft r+ advances in materials and computers and controls and also all that stuff so sure they're better are they perfect no way can an accident like this happen again you bet is it likely no could it happen tomorrow yes what's the probability way less than we thought way unless they used to be is this higher than we thought I don't know who would have thought that they would have put reactors at a place where it's onami this big was going to come along every few hundred years we didn't understand that I'm sure they didn't okay what would a fine so we're pretty humble I got to tell you it's really tough about thank you for a great talk

Channel: CITRIS

Views: 76,887

Rating: 4.647059 out of 5

Keywords: fukushima, nuclear, reactor, i4energy, citris, budnitz, technology, accident, earthquake, japan, tsunami

Id: LS6kqo9qZnM

Length: 67min 9sec (4029 seconds)

Published: Mon Sep 26 2011