Three Nuclear Disasters

and I don't really love that. It's a very serious subject. Also, I am coming down with a cold or a sinus infection or something, and I mentioned this in the last episode. It is even more true as I sit here now one hour after I recorded that last episode, and I can feel my body falling apart. So I apologize if I sound particularly uh wonky, but I don't want to suggest that I'm covering these topics in order to scare people will away from the possibilities of using nuclear power

to generate electricity. I think if you implement nuclear power correctly and responsibly, which includes securing a long term storage facility for spent nuclear fuel, it can be a viable method to generate electricity. But it would be dishonest to suggest there are not significant risks involved. And the three stories I'm going to cover today illustrate that fact. So we're going to start with the Three Mile Island accident. We're gonna go in chronological order of when they happened.

So Three Mile Island is the earliest. It is also the worst nuclear power accident to happen in the United States. But there's an interesting side to that, and we'll get to that. So Three Mile Island is a nuclear power facility. It's located near Middleton, Pennsylvania, and at the time of the accident it had to water reactors. I mean, it

was using light water as the coolant. T m I one t m I stands for three Mile Island, not too much information, and t m I two now t m I one had been in operation since nineteen seventy four. T m I two came online a couple of years later, and then on March ninety nine, that t m I two nuclear reactor experienced a partial meltdown. Now, a meltdown happens when the heat inside a reactor core builds beyond the melting point of the nuclear fuel that's arranged in

rods inside the nuclear core. Reactors use a combination of things like coolant and moderators and control rods to maintain the rate of nuclear reactions. And by controlling the rate of nuclear reactions, you then by extension, control the reactor core temperature. The more reactions there are, the higher the temperature goes. The slower the reactions are, the lower you

can make the temperature. And if you actually insert control rods all the way through your bundles, the bundles being that where the fuel rods are, then you will absorb enough neutrons to stop the reaction overall. Keep in mind these are sustained nuclear reactions where a heavy atom splits apart, and one of the things that shoots off are high speed neutrons, and if another heavy atom of that same type, like uranium two thirty five, for example, absorbs that incoming neutron,

it too will split. And so once you start the reaction, it can sustain itself if you have enough uranium two five in the mixture the critical mass. So if this happens, if these reactions keep on happening and they increase in rate to the point where the temperature has grown beyond the melting point of the fuel, the fuel starts to melt down. This is a big problem. At four am on March something went wrong at Three Mile Island. Now to understand what happened, it helps to get a general

understanding of that reactor's design. So you've got the nuclear side of the system and the non nuclear side. The nuclear side consists of the nuclear reactor which has the fuel, which was uranium, and it has the control rods, has the coolant in it. The coolant is water, but the coolant is water under pressure, so it's a pressurized system. The water can circulate through the core, through the rest of the system to a heat exchanger more on that

in a second. And then after it goes through the heat exchanger, some of the heat has been pulled away from the coolant, it continues to circulate, goes back into the core, heats up again, and it's kept under pressure so that way the coolant doesn't boil off, because if you don't have you know, if you don't keep it under pressure, then some of that water would boil off into steam, and that would make your whole system less efficient and also would create problems when you're trying to

pump the water through that side, that's the nuclear side. Then uh you have the non nuclear section that's a secondary water system. Secondary loop of water. The water flows into a steam generator essentially a boiler, and that is on the other side that heat exchange that's on the nuclear side. So the coolant from the nuclear side, which is superheated water that's under pressure, transfers heat through the

heat exchanger. The heat exchanger transfers heat to the steam generator, which boils water off from this second closed loop, So the two loops are not connected. And then that steam goes on to drive a a steam turbine which generates electricity and then goes through some cooling process to condense back into water and go back through the system again. So the important thing to remember is that these are

two closed systems that do not overlap. So the the the water that's being used to turn into steam and turn the steam turbines, never has any contact with the nuclear fuel. It is just heated by this heat exchange, and the other water, the coolant water, that's the one that's circulating through the nuclear reactor core. Well, that Monday in March, there was a malfunction in that secondary non

nuclear water system, and that prevented the water from circulating properly. Now, the reactions in the reactor core continued, but there was no way for the coolant to pass heat to that secondary system, right. It could not pass heat through the heat exchanger to the secondary system. There was nothing to carry that heat away. And without anything to carry the heat away, it meant the temperature of the reactor's coolant began to rise. So the reactor cores temperature began to rise.

The actual plant automatically shut down the reactor because it detected that this was happening. It saw that the temperature was rising, so as a safety measure, it shut down. That's a good thing. Then a pressure relief valve on the pressure riser on the nuclear side, so where the

coolant gets pressurized so that it doesn't boil off. There's a safety valve there that opens up in the case of UH, temperatures rising too high in order to let out a little pressure, and it's supposed to open for about ten seconds and then close, so that way it releases some pressure. It closes, everything is fine, UH, and the steam it releases, because you know, you're talking about water that's been in contact with the nuclear reactor core,

all of that is still contained within the facility. It's not like it's being vented out into the wilderness and suddenly you've got Bambi with eight heads or something. That doesn't happen. But what it's supposed to do is have that valve shut after about ten seconds, and the valve didn't shut, it stayed open, But the instrumentation in the control room indicated that the valve had shut, so the workers at three Mile Island were working under incorrect information.

They saw that everything on the nuclear side appeared to be fine once this venting process was over, and then the valve had shut and everything should be good to go, But that valve was open, so the reactor coolant continued

to escape the reactor. It continued to boil off into steam, and that began to drain the reactor coolant uh and that meant that the reactor core was losing coolant and residual to a heat was starting to build up, and the core would be damaged by this because once the coolant drains enough, then the reactor is able to the uranium inside the reactor is able to have these reactions with more regularity, and the temperature will grow very very

quickly because of that. To make matters worse, the employees assumed that the coolant in the core was remaining at the right levels. They did not have an easy way to monitor how much water was actually in the reactor core. Now the plant it had a better idea of what was going on. The automated systems had detected this problem, and so the automated systems spring into action and began to inject water at high pressure into the reactor in order to replace the coolant that was being lost with

the open valve. Now, at this point, the employees still thought the valve was closed. Cooling water entered the pressure riser in the nuclear reactor coolant system, so the employees couldn't see how much water was going into the reactor core.

They didn't have the instrumentation to detect that. But they did see they had instrumentation to detect how much water was in the pressurizer, because if the pressurizer had too much water in it and attempted to add more pressure to the system, it could cause a rupture, which would be a really bad thing. Right, So the employees are looking at this figure and they're seeing it go up and up and up, and they start to think, oh, no,

something's gone wrong. For some reason, the automated systems are pouring more water into the reactor and the pressurizer is getting over overloaded with water, so we need to shut down that water. They did not realize that that valve was still open and that coolant was still boiling off,

so they were working under incorrect information. Now that allowed steam to form inside the reactor system in general, So the mixture of water and steam in the system, which was supposed to be just high pressure, high temperature water, was giving the coolant pumps problems when they were trying to pump the liquid through the system. That steam was causing issues. It was making the pumps start to vibrate, and that could have caused massive damage to the plant.

So the employees shut down the pumps. The reactor court no longer had sufficient coolant. The level was too low and it was no longer circulating, so the fuel rods got hotter and hotter without sufficient coolant and partially melted.

That introduced radioactive material into the water itself. Before the radioactive material was more or less contained and the water would go past it, but not you know, it's not like the water was soaking up radioactive isotopes or something, But now you had fuel melting off and falling into the water itself. Now the water actually is carrying radioactive material. At six two in the morning, keep in mind this

started at four am. Employees were able to finally close a blocked valve that was between the pressurizer and that open relief valve, so they were able to take care of that. They found that problem and so that managed to stop the loss of coolant, But the coolant system inside the reactor was now partly filled with steam and steam from water that had contact with radioactive material, so

this was very concerning. Eventually, the operators were able to condense that steam into water and they were able to inject more water into the system and restore the core to proper temperatures. They also captured several of the radioactive gases that were coming from the reactor. They would vent these gases from the reactor, but they vented it into trapping systems. It was all meant to go from the reactor into compressors that would then send this radioactive gas

into uh a tank called the makeup tank. Then from the makeup tank it would be compressed to move into gas decay tanks. These are special containers designed to hold radioactive gases. If all of that had worked, yes, there still would have been a disaster in the sense that things had gone wrong, but radiation would have been contained. In the process of sending it along this chain, some of the compressors leaked and some of that gas got

released into the environment. That gas also had to pass through several HEPPA filters, which removed most of the radio newclides, so most of the heavier radioactive materials. In fact, all the heavy radioactive materials were all caught, but some radioactive noble gases passed through those filters. Those gases had radio nuclides with a very short half life, and the gases themselves were biologically inert, so it wasn't like organisms were

going to soak up those gases. They didn't interact with them, so it wasn't an environmental catastrophe. It's still not great to say radioactive gas escaped are our facility, but at least you could say, but this radioactive gas does not interact with the environment in any way, so we should be fine. So in fact, numerous independent health studies and environmental studies showed no real evidence of ill effects from

this incident. So it was a bad accident. It should not have happened, but the safety measures that were in place in the event of catastrophic failure appeared to hold up pretty well. The accident revealed enormous gaps in technology and training, but the safety measures managed to hold in place. But the communication of the event caused a great deal of distress and panic, understandably so, so they clean up process for t m I too, because this radiation got

leaked inside the facility. It took more than a decade and cost nearly a billion dollars. While the impact to the region around the plant was minimal, inside the plant was a different story. You had a lot of services that had to be decontaminated. The water in the cyste them had to be thoroughly processed and decontaminated. The damaged fuel in the reactor had to be retrieved and then stored. T m I one, the other reactor, was actually offline

during this accident. It was shut down. It was undergoing refueling. It would end up remaining offline during an investigation led by the Nuclear Regulatory Commission and would come back online

in October. So t m I two was offline but t m I one did come back into service, and the Exelon Corp Corporation, which then owned Three Mile Island, said that without action from the State of Pennsylvania, operations at t m I one would end in twenty nineteen, So next year, t m I one is licensed to operate until twenty four but it is not economically feasible

to do so under the current climate. According to Exelon Corporation, Three Mile Island was the worst nuclear power disaster or in US history, but no one died as a result of Three Mile Island and there were no harmful effects that could be pointed to Three Mile Islands. So while it was bad and never should have happened, it could have been much worse, and it pales in comparison to

some of the other disasters. So we're going to look at one of those in just a second, But first let's take a quick break to thank our sponsor from Pennsylvania in nineteen seventy nine. We now travel to the Ukraine. In nineteen eighties six, near the border between Ukraine and Belarus is Chernobyl, the site of a terrible nuclear disaster. The name Chernobyl has become synonymous with concepts like radiation

and nuclear meltdowns. So what exactly happened at Chernobyl. Well, the short answer is that a trained staff working at a poorly designed Soviet nuclear power plant caused a massive catastrophe in one of the four reactors that directly resulted in the deaths of at least thirty people over the

course of a few weeks. Initially, two thirty seven people received a diagnosis of acute radiation syndrome or a r S. That number would be reduced to one four once those cases were confirmed, But that really doesn't tell us much about what actually happened, right, So to understand what happened at Chernobyl helps to understand the difference in the design of that power plant compared to say, the three Mile

Island designed. So this design was called the r b m K one thousand, and I am not about to attempt to pronounce the words that r B m K stands for, because my Russian is just as bad as all my other pronunciations, which you guys know is uniformly terrible.

But the meaning in English, if you were to translate those Russian words is high power channel reactor and the r B M K design used water as a coolant and graphite as a moderator, although water was also a moderator, so that is the moderators, they help absorb neutrons and that controls the rate of nuclear reactions. As I mentioned in the previous section, the R and B m K also had boron carbide control rods that would do that

as well. So if you were to insert the boron carbide control rods all the way into the UH, into the reactor core, you would shut down reactions because you would be absorbing all the neutrons that were being given off and the reaction would not be able to sustain itself, so you would no longer have nuclear power that way. But one thing the R B M K design did not have was a heat exchanger. It did not have these two closed loops like three Mile Island did, so

instead it used one loop for water. The water that was the coolant for the actual reactor core was the same water that we get turned into steam, go through a steam turbine, go through a cooling process, condensed back into water, and go back into the system. So it was a very different approach from Three Mile Island UH.

The water would boil within that reactor design. So you remember Three Mile Island that was bad when the cool it was boiling off and steam was introduced into the system because the cooling pumps had trouble pumping the water with steam in it. The Soviet version depended upon having steam inside the system, so uh, you needed it to work this way to generate power the way the Soviets had intended. But it did introduce another problem with the r b M K one thousand, which is that you

have an issue called positive voy coefficient. So water like graphite, can absorb neutrons, so it can act as a bit of a moderator, not just a coolant. So water it can help cool core, but it can also absorb some of those neutrons that are being given off and thus help with the rate of nuclear reaction. Liquid water does this much better than steam does. So the more steam you have in your mixture, the less capable the water

is to absorb those neutrons. And we call the little steam bubbles in the water supply voids in the nuclear power biz. So as the number of steam bubbles grows, the neutron absorbing capability of the water decreases. And since sustain nuclear reactions depend upon nuclear fuel absorbing neutrons. That means you get more reactions as the positive void coefficient increases.

So the more steam bubbles are in the water, the more neutrons are going to get absorbed by other atoms of uranium, and the more reactions you're gonna get as a result, and the more heat you get. The Soviet design depended upon that process. The control rods could be inserted into the pressurized tubes that contain the nuclear fuel rods and shut down a reaction if things got out of hand, Now it's your noble. The process got out of hand big time. So first it became a cycle

that fed upon itself. The nuclear reactions would heat up the coolant water and start to convert some of that water into steam. Steam bubbles or voids began to form. That reduced the capability of the water in the system to absorb neutrons, and that increase the rate of nuclear reactions within the core, which meant the core got hotter, which meant heated up the water even more, which meant it increased the number of voids, which meant that even

fewer neutrons were absorbed. So you see how this very quickly becomes a problem. On a reactor four at the Chernobyl facility was beginning to shut down. It was getting ready for a scheduled maintenance and refueling. This was totally routine, but before it was to shut down, it was going to go through a testing procedure on the following day, on April uh and that test was to see how long the reactor would be able to generate steam and thus spin turbines in the event of a main electrical

power supply loss. So they were going to simulate losing power at this facility and they were going to see how long can this reactor continue to generate steam and turn this turbine even if the power is lost to the reactor itself. So to conduct that test on the back on the operators started to disable automatic shutdown features.

And when you hear about shutting down ematic shutdown features, that should raise some pretty big alarm flags in your in your head, you should be thinking that doesn't sound like a good idea, and in fact it wasn't. So the operator went to shut down the reactor by instarting the control rods into the core, and for some reason or another, that action, telling the the control arms too insert those control rods caused a power surge, and the

hot fuel in the reactor began to fragment. Water began converting into steam at an accelerated rate, and as I mentioned, that meant the water was less efficient at absorbing neutrons. So the reaction began to accelerate. The production of steam began to increase, and that increased the pressure inside the system so much that the pressure actually partially detached the steel cover plate on top of the reactor. That steel

cover plate weighed one thousand tons. That's how much pressure was inside this react term enough pressure to displace at least partially one thousand tons of steel. Worse, when this cover plate became partially dislodged, it it wedged the control rods in such a way that they could not insert completely into the pressure tubes. So the control rods were stuck. They couldn't go all the way in and thus shut

down the nuclear reaction. They had only reached about the halfway mark, so the nuclear reaction was continuing because there was the control rods couldn't absorb those extra neutrons. The build up of steam reached catastrophic levels, and there was an explosive rupture which released nuclear material into the atmosphere. Seconds later, another explosion followed, and this one flung out superheated graphite and nuclear fuel flying out from the facility.

The general consensus is that the second explosion happened after hydrogen gas, which had been generated from the reactions in the core, ignited from those high temperatures. The explosion killed two of the workers at Chernobyl outright. The hot material started numerous fires in the area because chernobyls in the middle of a forest, and so the four started catching fire, and that helped distribute radioactive material further into the atmosphere

and the general environment. And some of the radioactive elements included iodine one and ses M one thirty seven. Both of those post significant dangers to the public in the region. Iodine one one has a relatively short half life of just a few days. Caesium one thirty seven is like a decade our thirty years rather, so you've got thirty years half life or case one thirty seven a few

days for iodine one nine. So it became a very dangerous mixture, and winds were carrying radioactive materials pretty far away, like little radioactive particles flying way up in the atmosphere. It started to go as far as across Ukraine, Belarus, Russia, even into Scandinavia. Many people at the site were exposed to massive amounts of radiation in a short amount of time, and within three weeks, twenty eight people died from radiation poisoning.

Around one six thousand people in a thirty kilometer UH radius around the facility were relocated by May four, but around a thousand of them would secretly kind of return to the area on the QT in order to go back home. Another two d twenty thousand people would eventually be relocated over the course of the next few years. Now, independent studies found that the populations around Chernobyl do not appear to have had abnormally high incidents of cancer, with

the exception of thyroid cancer. Thyroid cancer numbers shot up. Thyroid cancer, fortunately, if caught early, is very treatable, but

it's still obviously is a big concern. The thyroid cancer was an outlier, but they did not see a rise in incidents and stuff like leukemia, And some people say perhaps some of those cases of thyroid cancer they might have already been an issue before the Chernobyl disaster, but because you suddenly had all these doctors in the area specifically looking for problems, they were finding them more frequently. So not that the Chernobyl disaster didn't cause some of that.

It more than likely had to have because the numbers shot up so much. But because our focus turned to this, we discovered stuff that we otherwise would have overlooked. Sometimes when you know what you're looking for, you find it um whereas before you would have overlooked it. So Uh, it's hard to say exactly how much it contributed, but it probably contributed at least to thyroid cancer rates in the area. But otherwise the harm to humans seemed to

be fairly limited. Uh. The immediate area around the plant suffered a quick die off, like within you know, ten kilometers of the plant. There was a quick die off around there, but it recovered very quickly. Within the next year, it was starting to recover. This I'm talking about like things like plants and trees, and the incidents didn't seem to you know, contribute to long lasting health effects in that area, at least not at a level that is easy to point out and say This is evidence that

this disaster directly led to these results. There did happened to be a very powerful psychological impact on the region, largely fueled by the public perception of the effects of radiation. Essentially, if you're told over and over again that you're going to get sick and you're going to suffer, then you're gonna believe that and you will get sick and you will suffer because it becomes sort of a self fulfilling prophecy. So that was a real issue. Today, Chernobyl as a

tourist site, you can actually go there. The wildlife in the area has not only made a comeback, it's actually gotten better than it was from before the accident. There's greater biological diversity in the region than there was prior to the accident. Now that's not because of radiation. It's not that radiation is suddenly magically helped animals get better. It's largely because people have stayed the hell away from Chernobyl. So if you take human beings out of an environment,

it tends to do better. I'm just gonna leave that idea there. But since two ten, the Ukraine has led the way in resettling the area. Though with some restrictions in place to protect settlers. So for Examp Bowl, you're not supposed to use wood from the area in case it has uh any radioactive material in that would and you're also supposed to check soil very thoroughly for contamination

levels before you try and farm there. But we're starting to see some reclamation of the land around Chernobyl, and that disaster is the greatest for at least an immediate effect on people of all time for for nuclear power plants. Our next one is an ongoing story, so it's impossible to say right now what the full effect of that disaster is because it's still playing out as I speak. But before I get to that, let's take another quick break to thank our sponsor. All Right, this brings us

to Fukushima in Japan. On March eleventh, two eleven, at PM, there was a massive earthquake off the coast of Japan. It measured nine on the Richter scale, which makes it the fourth largest earthquake ever recorded. The earthquake created a tsunami that was fifteen meters tall at the point of Fukushima. That's just under fifty feet tall. Imagine not a wave, but a wall of water fifty feet tall that hit the Fukushima Daichi Nuclear Facility, and that natural disaster led

to a terrible man made disaster. The tsunami disabled the power supply and thus the cooling systems for three of the reactors at that facility, Reactors one, two, and three. In fact, the facility actually withstood the initial shock of the earthquake pretty well. The uh the various inspections that have happened since this disaster have suggested that the earthquake did not really damage the facilities in any meaningful way,

so that's kind of impressive. There were six reactors at Fukushima, but reactors four or five and six were not in operation at the time of the earthquake. Um at least reactor four did have a lot of nuclear material as part of that building because they have waste fuel pools storage pools where you take the fuel you've used in the reactor that no longer has enough feasible material in it for it to be useful. It's no longer going

to produce efficient nuclear reactions. You have to put that somewhere, so generally speaking, right now, most nuclear facilities store nuclear waste on site, so they were to go into cooling pools for a few years before being moved to a different facility, and so reactor four, while it was not active,

did have uh spent nuclear fuel inside these cooling pools. Anyway, when that's soon Nummi hit, it's shut down twelve of the thirteen backup generators on site designed to run the residual heat removal system cooling pumps, and it also disabled the heat exchangers that would take heat from the reactor and transfer it to the ocean. To make matters worse, the seawater pumps on site that were designed to pump seawater off the system. They were there expressly in case

there was a tsunami. We're located at too low an elevation to be of any help. So when they designed the Fukushima Daiichi facility, they estimated a tsunami of three point one meters in height, so they positioned the seawater pumps at four meters above sea level because they said, oh, three point one meters that's how high the tsunami would likely be, will go about a meter above that. The facility itself was at ten ms above sea level, but

because it was a fifteen m tsunami. It meant that those pumps were actually eleven meters below the water's surface when that tsunami hit, and they were all overwhelmed. Reactors one, two, and three could not moderate reactor core temperatures, and the cooling systems that could transfer excess heat were not operational.

So the reactors had been shut down automatically after the earthquake, which is good, so they weren't in operation at that moment, but even in shutdown mode there's still some residual fission reactions taking place. The reactor cores were producing about one point five pc of their nominal thermal power, but that heat was building up and it was beginning to convert water into steam, and there was no way to transfer the heat away from the reactor cores, so they were

just getting hotter and hotter. The steam vented out through safety valves into a primary containment vessel, so again not just venting out into the general region. The steam included some hydrogen gas as well, which was generated from reactor reactions between the superheated zirconium cladding in the reactor core and the steam, and so you get this hydrogen gas as a byproduct and As I mentioned before, hydrogen gas can be very dangerous. It's extremely you know, flammable or explosive.

You can look at things like the Hindenburg disaster, which happened because of a hydrogen disaster. Will pressure inside these units continued to increase. Steam was directed into special suppression chambers that were located under these reactors. So you have these special chambers underneath that were meant to hold this kind of stuff in the case of an emergency um Water injection followed. That's where you you know, obviously, you introduce water into the system along with the initiation of

the emergency core cooling system. So all measures were being put into place to try and get this reactor horror temperature under control. But the water injection systems began to fail for each of those first three units, and so responders began to use fire pumps to inject more water into the reactors using fire trucks and fire hoses, and then they started using seawater, pumping seawater in to help inject into the reactors and cool them down. And this

was all to keep the fuel submerged in water. But in Unit one, that water level fell enough to expose the top of the fuel rods to air, and the reactions began to speed up. The water was not there to moderate those reactions. An hour and a half later, all of the fuel and Unit one had become uncovered because as a heat up, it obviously turned more of the water into steam, and while there was still water inside the vessel that contains the reactor core, all the

fuel was open to the air. At that point, the water was still in the base of the vessel, but the fuel is suspended above of the base, so the temperature of the fuel inside Unit one climbed to around two thousand, eight hundred degrees celsius. It began to melt, it fell apart. The falling fuel landed into the water that was still pooled at the bottom of the reactor

pressure vessel, and that helped actually bring temperatures down. The temperatures began to decrease once the melted fuel hit water again.

Gases and steam were building up inside the reactor building, so attempts were made to vent the gases through an external system that would contain the gases so you wouldn't have radiated material released into the environment, But there was a backflow problem and gases began to accumulate inside the reactor building itself, not just the reactor core, and one of those gases was hydrogen, and on March twelve, that hydrogen exploded on the service floor above the Unit one reactor.

This destroyed the roof of the facility and the fuel inside the reactor pressure vessel was later found to have melted through the vessel and had melted about sixty down into the concrete below the vessel. Now that concrete was two point six meters thick, so it held firm and the mass eventually cooled down enough to solidify. Units two and three had also had some nuclear fuel melt, but they appeared to be less affected than Unit one at

that point. But then Unit two's water injection systems failed, just as Unit one had, and the responders attempted to inject water from fire pumps and from seawater. This time, they ventilated the building. They used a blowout panel near the top of the building to help avoid another hydrogen build up like in Unit one. On March fifteen, the pressure inside one of the containment systems beneath the reactor dropped after what was believed to be a hydrogen gas explosion.

And the initial thought was that some sort of rupture must have happened, but investigations haven't really been able to turn up signs of a rupture, so there's a lot of questions about what actually happened that day. But somewhere pressure was released and some radioactive material was released into the environment on that day from Unit two. Unit three seemed initially to have fared better, with responders able to inject water and ventilate the building. But on March fourteen,

there was an explosion inside Unit four. Now, remember Unit four was de fueled. There was no nuclear fuel inside the core of Unit four, so why did it explode. Well, the hypothesis is that hydrogen forming from Unit three had reached Unit four by backflow because the two buildings, the one for Unit three and the one for Unit four,

shared a common duct system. So they thought is that the hydrogen gas must have passed through this duct system it got into Unit four, and while Unit four didn't have any nuclear fuel in the reactor, it did have all this hydrogen gas build up, and then there was an explosion. That explosion also for they're damaged the building

that housed Unit three. Now, out of all these events, the one that seemed to release the most radioactive material into the environment happened on March fifteenth from the issues with Unit two, but the actual mechanism that led to that release still remains a mystery. The three units now receive cooling water from a special water plant supplying recycled water to the units. They have cooling circuits UH to

help do this. They are all being held at around atmospheric temperatures, so the temperature of the core is about the same as what it is outside. The government has also injected nitrogen into those units, and that was an attempt to capture hydrogen and prevent hydrogen gas from building up. Another challenge that had to be overcome was dealing with spent fuel, because, as I said, each of the units has a waste fuel pond and that provides cooling and

moderation of spent fuel. Since the accident, there is now a new set of heat exchangers and cooling circuits attached to each unit to help keep those those cooling ponds cool enough, and arrangements have been made to remove and

transport the spent fuel rods to a more permanent facility. UH. Typically you keep them in the pool for a few years, and then you move them to air cooled facilities once they've reached a certain level of non activity and uh, and so you kind of have to wait for things to cool down enough for you to be able to move them, and that started to happen. So there's some

good news and there's some bad news. And the good news is that the effects of radiation from the disaster appear to have had no real impact on human health in the area. Based upon the various research projects that have gone on since then, it doesn't like there's been widespread negative impact on human health. The general region had been evacuated, but since two thousand and twelve, the government has allowed people in small groups to come back um one at a time, like small groups at a time.

But the bad news is that the radiation levels inside the facilities themselves are still really really high, like deadly high in those facilities, and that contaminated water around the units is starting to seep into the ground in that area now that it happens to be an area that's

next to the ocean. So I guess the media bright side is that the any water that seeps into the ground isn't going into the water table that serves up the water for the people there, because the water is coming from further inland and it's flowing out to the ocean. But without containing that contaminated water properly, that could end up leaking into the ocean and contaminating ocean water and

spread radiation quite far. Uh. There's still a lot of efforts going on in Japan to contain all of that, but I've read some pretty disturbing reports about the way it's all being handled, and that it's suggests that that way is not the most effective. Uh. So, the plant decommissioning process is going on in Fukushima, and there's gonna be a lot of different steps. It's probably gonna take more than a decade of work to be able to bring those those uh those buildings to a point where

we can truly decommission them. So that's it. That's the look at three of the biggest nuclear powered disasters. They're all bad and and people tragically lost their lives in the Chernobyl one in particular. Um, and they you never want to have any of these sort of incidents happen. Uh. They do suggest perhaps that in the event of a nuclear disaster like this, the impact might not be as dramatic,

at least at first as we tend to think. I mean again, are thoughts are often shaped by stuff like pop culture, and in the fifties, you know, all the different science fiction films were all about how how radiation was going to mutate people in weird and unpredictable ways. Reality is that doesn't actually happen that way in the long term. Who knows, we may see long term effects that are much more troubling than what we're seeing in the short term. So I'm not suggesting, like I'm not

suggesting that people have overreacted to these disasters. Maybe three Mile Island out of all of them, the result of three Mile Island was still should never have happened. But at least it appears that in the grand scheme of things, it was not that dangerous to people because these safety systems worked properly. Still shouldn't have happened, And it's still kind of scary, more than more than kind of scary.

But I wanted to look into them because you hear about these stories all the time, and without really understanding what happened, then all you really feel is anxiety. I think the only way to really greet that is through education, and that education means well, now I feel like I'm more informed with what can happen, what can go wrong with nuclear power. Maybe that guides my decision about whether or not I support it. That's totally legitimate, uh, and

I am no longer just imagining worst case scenarios. That wraps up this episode. If you have any ideas for future episodes, we will be going to something totally different from nuclear power in next week. I'm not sure what that is because I don't have my schedule opened up, but it will be something different, so look forward to that. If you have suggestions for future episodes, let me know. Send me an email. The addresses tech Stuff at how stuff works dot com or drop me a line on

Facebook or Twitter. The handle for both of those says tech Stuff hs W. Don't forget go by t public dot com slash tech stuff to take a look at our merchandise store. Everything you purchase ends up benefiting the show, which is awesome, and you get some cool stuff in return, So go check that out and don't forget to follow us on Instagram and I will talk to you again really soon for more on this and thousands of other topics because it how staff works dot com