Speaker 1: Get in touch with technology with tech Stuff from how
Speaker 1: stuff works dot com. Hey there, and welcome to tech Stuff.
Speaker 1: I'm your host, Jonathan Strickland. I'm an executive producer with
Speaker 1: How Stuff Works, and I love all things tech. Well,
Speaker 1: I say a love all things tech. But today I'm
Speaker 1: going to talk about three different disasters involving nuclear power facilities,
Speaker 1: and I don't really love that. It's a very serious subject. Also,
Speaker 1: I am coming down with a cold or a sinus
Speaker 1: infection or something, and I mentioned this in the last episode.
Speaker 1: It is even more true as I sit here now
Speaker 1: one hour after I recorded that last episode, and I
Speaker 1: can feel my body falling apart. So I apologize if
Speaker 1: I sound particularly uh wonky, but I don't want to
Speaker 1: suggest that I'm covering these topics in order to scare
Speaker 1: people will away from the possibilities of using nuclear power
Speaker 1: to generate electricity. I think if you implement nuclear power
Speaker 1: correctly and responsibly, which includes securing a long term storage
Speaker 1: facility for spent nuclear fuel, it can be a viable
Speaker 1: method to generate electricity. But it would be dishonest to
Speaker 1: suggest there are not significant risks involved. And the three
Speaker 1: stories I'm going to cover today illustrate that fact. So
Speaker 1: we're going to start with the Three Mile Island accident.
Speaker 1: We're gonna go in chronological order of when they happened.
Speaker 1: So Three Mile Island is the earliest. It is also
Speaker 1: the worst nuclear power accident to happen in the United States.
Speaker 1: But there's an interesting side to that, and we'll get
Speaker 1: to that. So Three Mile Island is a nuclear power facility.
Speaker 1: It's located near Middleton, Pennsylvania, and at the time of
Speaker 1: the accident it had to water reactors. I mean, it
Speaker 1: was using light water as the coolant. T m I
Speaker 1: one t m I stands for three Mile Island, not
Speaker 1: too much information, and t m I two now t
Speaker 1: m I one had been in operation since nineteen seventy four.
Speaker 1: T m I two came online a couple of years later,
Speaker 1: and then on March ninety nine, that t m I
Speaker 1: two nuclear reactor experienced a partial meltdown. Now, a meltdown
Speaker 1: happens when the heat inside a reactor core builds beyond
Speaker 1: the melting point of the nuclear fuel that's arranged in
Speaker 1: rods inside the nuclear core. Reactors use a combination of
Speaker 1: things like coolant and moderators and control rods to maintain
Speaker 1: the rate of nuclear reactions. And by controlling the rate
Speaker 1: of nuclear reactions, you then by extension, control the reactor
Speaker 1: core temperature. The more reactions there are, the higher the
Speaker 1: temperature goes. The slower the reactions are, the lower you
Speaker 1: can make the temperature. And if you actually insert control
Speaker 1: rods all the way through your bundles, the bundles being
Speaker 1: that where the fuel rods are, then you will absorb
Speaker 1: enough neutrons to stop the reaction overall. Keep in mind
Speaker 1: these are sustained nuclear reactions where a heavy atom splits apart,
Speaker 1: and one of the things that shoots off are high
Speaker 1: speed neutrons, and if another heavy atom of that same type,
Speaker 1: like uranium two thirty five, for example, absorbs that incoming neutron,
Speaker 1: it too will split. And so once you start the reaction,
Speaker 1: it can sustain itself if you have enough uranium two
Speaker 1: five in the mixture the critical mass. So if this happens,
Speaker 1: if these reactions keep on happening and they increase in
Speaker 1: rate to the point where the temperature has grown beyond
Speaker 1: the melting point of the fuel, the fuel starts to
Speaker 1: melt down. This is a big problem. At four am
Speaker 1: on March something went wrong at Three Mile Island. Now
Speaker 1: to understand what happened, it helps to get a general
Speaker 1: understanding of that reactor's design. So you've got the nuclear
Speaker 1: side of the system and the non nuclear side. The
Speaker 1: nuclear side consists of the nuclear reactor which has the fuel,
Speaker 1: which was uranium, and it has the control rods, has
Speaker 1: the coolant in it. The coolant is water, but the
Speaker 1: coolant is water under pressure, so it's a pressurized system.
Speaker 1: The water can circulate through the core, through the rest
Speaker 1: of the system to a heat exchanger more on that
Speaker 1: in a second. And then after it goes through the
Speaker 1: heat exchanger, some of the heat has been pulled away
Speaker 1: from the coolant, it continues to circulate, goes back into
Speaker 1: the core, heats up again, and it's kept under pressure
Speaker 1: so that way the coolant doesn't boil off, because if
Speaker 1: you don't have you know, if you don't keep it
Speaker 1: under pressure, then some of that water would boil off
Speaker 1: into steam, and that would make your whole system less
Speaker 1: efficient and also would create problems when you're trying to
Speaker 1: pump the water through that side, that's the nuclear side.
Speaker 1: Then uh you have the non nuclear section that's a
Speaker 1: secondary water system. Secondary loop of water. The water flows
Speaker 1: into a steam generator essentially a boiler, and that is
Speaker 1: on the other side that heat exchange that's on the
Speaker 1: nuclear side. So the coolant from the nuclear side, which
Speaker 1: is superheated water that's under pressure, transfers heat through the
Speaker 1: heat exchanger. The heat exchanger transfers heat to the steam generator,
Speaker 1: which boils water off from this second closed loop, So
Speaker 1: the two loops are not connected. And then that steam
Speaker 1: goes on to drive a a steam turbine which generates
Speaker 1: electricity and then goes through some cooling process to condense
Speaker 1: back into water and go back through the system again.
Speaker 1: So the important thing to remember is that these are
Speaker 1: two closed systems that do not overlap. So the the
Speaker 1: the water that's being used to turn into steam and
Speaker 1: turn the steam turbines, never has any contact with the
Speaker 1: nuclear fuel. It is just heated by this heat exchange,
Speaker 1: and the other water, the coolant water, that's the one
Speaker 1: that's circulating through the nuclear reactor core. Well, that Monday
Speaker 1: in March, there was a malfunction in that secondary non
Speaker 1: nuclear water system, and that prevented the water from circulating properly. Now,
Speaker 1: the reactions in the reactor core continued, but there was
Speaker 1: no way for the coolant to pass heat to that
Speaker 1: secondary system, right. It could not pass heat through the
Speaker 1: heat exchanger to the secondary system. There was nothing to
Speaker 1: carry that heat away. And without anything to carry the
Speaker 1: heat away, it meant the temperature of the reactor's coolant
Speaker 1: began to rise. So the reactor cores temperature began to rise.
Speaker 1: The actual plant automatically shut down the reactor because it
Speaker 1: detected that this was happening. It saw that the temperature
Speaker 1: was rising, so as a safety measure, it shut down.
Speaker 1: That's a good thing. Then a pressure relief valve on
Speaker 1: the pressure riser on the nuclear side, so where the
Speaker 1: coolant gets pressurized so that it doesn't boil off. There's
Speaker 1: a safety valve there that opens up in the case
Speaker 1: of UH, temperatures rising too high in order to let
Speaker 1: out a little pressure, and it's supposed to open for
Speaker 1: about ten seconds and then close, so that way it
Speaker 1: releases some pressure. It closes, everything is fine, UH, and
Speaker 1: the steam it releases, because you know, you're talking about
Speaker 1: water that's been in contact with the nuclear reactor core,
Speaker 1: all of that is still contained within the facility. It's
Speaker 1: not like it's being vented out into the wilderness and
Speaker 1: suddenly you've got Bambi with eight heads or something. That
Speaker 1: doesn't happen. But what it's supposed to do is have
Speaker 1: that valve shut after about ten seconds, and the valve
Speaker 1: didn't shut, it stayed open, But the instrumentation in the
Speaker 1: control room indicated that the valve had shut, so the
Speaker 1: workers at three Mile Island were working under incorrect information.
Speaker 1: They saw that everything on the nuclear side appeared to
Speaker 1: be fine once this venting process was over, and then
Speaker 1: the valve had shut and everything should be good to go,
Speaker 1: But that valve was open, so the reactor coolant continued
Speaker 1: to escape the reactor. It continued to boil off into steam,
Speaker 1: and that began to drain the reactor coolant uh and
Speaker 1: that meant that the reactor core was losing coolant and
Speaker 1: residual to a heat was starting to build up, and
Speaker 1: the core would be damaged by this because once the
Speaker 1: coolant drains enough, then the reactor is able to the
Speaker 1: uranium inside the reactor is able to have these reactions
Speaker 1: with more regularity, and the temperature will grow very very
Speaker 1: quickly because of that. To make matters worse, the employees
Speaker 1: assumed that the coolant in the core was remaining at
Speaker 1: the right levels. They did not have an easy way
Speaker 1: to monitor how much water was actually in the reactor core.
Speaker 1: Now the plant it had a better idea of what
Speaker 1: was going on. The automated systems had detected this problem,
Speaker 1: and so the automated systems spring into action and began
Speaker 1: to inject water at high pressure into the reactor in
Speaker 1: order to replace the coolant that was being lost with
Speaker 1: the open valve. Now, at this point, the employees still
Speaker 1: thought the valve was closed. Cooling water entered the pressure
Speaker 1: riser in the nuclear reactor coolant system, so the employees
Speaker 1: couldn't see how much water was going into the reactor core.
Speaker 1: They didn't have the instrumentation to detect that. But they
Speaker 1: did see they had instrumentation to detect how much water
Speaker 1: was in the pressurizer, because if the pressurizer had too
Speaker 1: much water in it and attempted to add more pressure
Speaker 1: to the system, it could cause a rupture, which would
Speaker 1: be a really bad thing. Right, So the employees are
Speaker 1: looking at this figure and they're seeing it go up
Speaker 1: and up and up, and they start to think, oh, no,
Speaker 1: something's gone wrong. For some reason, the automated systems are
Speaker 1: pouring more water into the reactor and the pressurizer is
Speaker 1: getting over overloaded with water, so we need to shut
Speaker 1: down that water. They did not realize that that valve
Speaker 1: was still open and that coolant was still boiling off,
Speaker 1: so they were working under incorrect information. Now that allowed
Speaker 1: steam to form inside the reactor system in general, So
Speaker 1: the mixture of water and steam in the system, which
Speaker 1: was supposed to be just high pressure, high temperature water,
Speaker 1: was giving the coolant pumps problems when they were trying
Speaker 1: to pump the liquid through the system. That steam was
Speaker 1: causing issues. It was making the pumps start to vibrate,
Speaker 1: and that could have caused massive damage to the plant.
Speaker 1: So the employees shut down the pumps. The reactor court
Speaker 1: no longer had sufficient coolant. The level was too low
Speaker 1: and it was no longer circulating, so the fuel rods
Speaker 1: got hotter and hotter without sufficient coolant and partially melted.
Speaker 1: That introduced radioactive material into the water itself. Before the
Speaker 1: radioactive material was more or less contained and the water
Speaker 1: would go past it, but not you know, it's not
Speaker 1: like the water was soaking up radioactive isotopes or something,
Speaker 1: But now you had fuel melting off and falling into
Speaker 1: the water itself. Now the water actually is carrying radioactive material.
Speaker 1: At six two in the morning, keep in mind this
Speaker 1: started at four am. Employees were able to finally close
Speaker 1: a blocked valve that was between the pressurizer and that
Speaker 1: open relief valve, so they were able to take care
Speaker 1: of that. They found that problem and so that managed
Speaker 1: to stop the loss of coolant, But the coolant system
Speaker 1: inside the reactor was now partly filled with steam and
Speaker 1: steam from water that had contact with radioactive material, so
Speaker 1: this was very concerning. Eventually, the operators were able to
Speaker 1: condense that steam into water and they were able to
Speaker 1: inject more water into the system and restore the core
Speaker 1: to proper temperatures. They also captured several of the radioactive
Speaker 1: gases that were coming from the reactor. They would vent
Speaker 1: these gases from the reactor, but they vented it into
Speaker 1: trapping systems. It was all meant to go from the
Speaker 1: reactor into compressors that would then send this radioactive gas
Speaker 1: into uh a tank called the makeup tank. Then from
Speaker 1: the makeup tank it would be compressed to move into
Speaker 1: gas decay tanks. These are special containers designed to hold
Speaker 1: radioactive gases. If all of that had worked, yes, there
Speaker 1: still would have been a disaster in the sense that
Speaker 1: things had gone wrong, but radiation would have been contained.
Speaker 1: In the process of sending it along this chain, some
Speaker 1: of the compressors leaked and some of that gas got
Speaker 1: released into the environment. That gas also had to pass
Speaker 1: through several HEPPA filters, which removed most of the radio newclides,
Speaker 1: so most of the heavier radioactive materials. In fact, all
Speaker 1: the heavy radioactive materials were all caught, but some radioactive
Speaker 1: noble gases passed through those filters. Those gases had radio
Speaker 1: nuclides with a very short half life, and the gases
Speaker 1: themselves were biologically inert, so it wasn't like organisms were
Speaker 1: going to soak up those gases. They didn't interact with them,
Speaker 1: so it wasn't an environmental catastrophe. It's still not great
Speaker 1: to say radioactive gas escaped are our facility, but at
Speaker 1: least you could say, but this radioactive gas does not
Speaker 1: interact with the environment in any way, so we should
Speaker 1: be fine. So in fact, numerous independent health studies and
Speaker 1: environmental studies showed no real evidence of ill effects from
Speaker 1: this incident. So it was a bad accident. It should
Speaker 1: not have happened, but the safety measures that were in
Speaker 1: place in the event of catastrophic failure appeared to hold
Speaker 1: up pretty well. The accident revealed enormous gaps in technology
Speaker 1: and training, but the safety measures managed to hold in place.
Speaker 1: But the communication of the event caused a great deal
Speaker 1: of distress and panic, understandably so, so they clean up
Speaker 1: process for t m I too, because this radiation got
Speaker 1: leaked inside the facility. It took more than a decade
Speaker 1: and cost nearly a billion dollars. While the impact to
Speaker 1: the region around the plant was minimal, inside the plant
Speaker 1: was a different story. You had a lot of services
Speaker 1: that had to be decontaminated. The water in the cyste
Speaker 1: them had to be thoroughly processed and decontaminated. The damaged
Speaker 1: fuel in the reactor had to be retrieved and then stored.
Speaker 1: T m I one, the other reactor, was actually offline
Speaker 1: during this accident. It was shut down. It was undergoing refueling.
Speaker 1: It would end up remaining offline during an investigation led
Speaker 1: by the Nuclear Regulatory Commission and would come back online
Speaker 1: in October. So t m I two was offline but
Speaker 1: t m I one did come back into service, and
Speaker 1: the Exelon Corp Corporation, which then owned Three Mile Island,
Speaker 1: said that without action from the State of Pennsylvania, operations
Speaker 1: at t m I one would end in twenty nineteen,
Speaker 1: So next year, t m I one is licensed to
Speaker 1: operate until twenty four but it is not economically feasible
Speaker 1: to do so under the current climate. According to Exelon Corporation,
Speaker 1: Three Mile Island was the worst nuclear power disaster or
Speaker 1: in US history, but no one died as a result
Speaker 1: of Three Mile Island and there were no harmful effects
Speaker 1: that could be pointed to Three Mile Islands. So while
Speaker 1: it was bad and never should have happened, it could
Speaker 1: have been much worse, and it pales in comparison to
Speaker 1: some of the other disasters. So we're going to look
Speaker 1: at one of those in just a second, But first
Speaker 1: let's take a quick break to thank our sponsor from
Speaker 1: Pennsylvania in nineteen seventy nine. We now travel to the Ukraine.
Speaker 1: In nineteen eighties six, near the border between Ukraine and
Speaker 1: Belarus is Chernobyl, the site of a terrible nuclear disaster.
Speaker 1: The name Chernobyl has become synonymous with concepts like radiation
Speaker 1: and nuclear meltdowns. So what exactly happened at Chernobyl. Well,
Speaker 1: the short answer is that a trained staff working at
Speaker 1: a poorly designed Soviet nuclear power plant caused a massive
Speaker 1: catastrophe in one of the four reactors that directly resulted
Speaker 1: in the deaths of at least thirty people over the
Speaker 1: course of a few weeks. Initially, two thirty seven people
Speaker 1: received a diagnosis of acute radiation syndrome or a r S.
Speaker 1: That number would be reduced to one four once those
Speaker 1: cases were confirmed, But that really doesn't tell us much
Speaker 1: about what actually happened, right, So to understand what happened
Speaker 1: at Chernobyl helps to understand the difference in the design
Speaker 1: of that power plant compared to say, the three Mile
Speaker 1: Island designed. So this design was called the r b
Speaker 1: m K one thousand, and I am not about to
Speaker 1: attempt to pronounce the words that r B m K
Speaker 1: stands for, because my Russian is just as bad as
Speaker 1: all my other pronunciations, which you guys know is uniformly terrible.
Speaker 1: But the meaning in English, if you were to translate
Speaker 1: those Russian words is high power channel reactor and the
Speaker 1: r B M K design used water as a coolant
Speaker 1: and graphite as a moderator, although water was also a moderator,
Speaker 1: so that is the moderators, they help absorb neutrons and
Speaker 1: that controls the rate of nuclear reactions. As I mentioned
Speaker 1: in the previous section, the R and B m K
Speaker 1: also had boron carbide control rods that would do that
Speaker 1: as well. So if you were to insert the boron
Speaker 1: carbide control rods all the way into the UH, into
Speaker 1: the reactor core, you would shut down reactions because you
Speaker 1: would be absorbing all the neutrons that were being given
Speaker 1: off and the reaction would not be able to sustain itself,
Speaker 1: so you would no longer have nuclear power that way.
Speaker 1: But one thing the R B M K design did
Speaker 1: not have was a heat exchanger. It did not have
Speaker 1: these two closed loops like three Mile Island did, so
Speaker 1: instead it used one loop for water. The water that
Speaker 1: was the coolant for the actual reactor core was the
Speaker 1: same water that we get turned into steam, go through
Speaker 1: a steam turbine, go through a cooling process, condensed back
Speaker 1: into water, and go back into the system. So it
Speaker 1: was a very different approach from Three Mile Island UH.
Speaker 1: The water would boil within that reactor design. So you
Speaker 1: remember Three Mile Island that was bad when the cool
Speaker 1: it was boiling off and steam was introduced into the
Speaker 1: system because the cooling pumps had trouble pumping the water
Speaker 1: with steam in it. The Soviet version depended upon having
Speaker 1: steam inside the system, so uh, you needed it to
Speaker 1: work this way to generate power the way the Soviets
Speaker 1: had intended. But it did introduce another problem with the
Speaker 1: r b M K one thousand, which is that you
Speaker 1: have an issue called positive voy coefficient. So water like graphite,
Speaker 1: can absorb neutrons, so it can act as a bit
Speaker 1: of a moderator, not just a coolant. So water it
Speaker 1: can help cool core, but it can also absorb some
Speaker 1: of those neutrons that are being given off and thus
Speaker 1: help with the rate of nuclear reaction. Liquid water does
Speaker 1: this much better than steam does. So the more steam
Speaker 1: you have in your mixture, the less capable the water
Speaker 1: is to absorb those neutrons. And we call the little
Speaker 1: steam bubbles in the water supply voids in the nuclear
Speaker 1: power biz. So as the number of steam bubbles grows,
Speaker 1: the neutron absorbing capability of the water decreases. And since
Speaker 1: sustain nuclear reactions depend upon nuclear fuel absorbing neutrons. That
Speaker 1: means you get more reactions as the positive void coefficient increases.
Speaker 1: So the more steam bubbles are in the water, the
Speaker 1: more neutrons are going to get absorbed by other atoms
Speaker 1: of uranium, and the more reactions you're gonna get as
Speaker 1: a result, and the more heat you get. The Soviet
Speaker 1: design depended upon that process. The control rods could be
Speaker 1: inserted into the pressurized tubes that contain the nuclear fuel
Speaker 1: rods and shut down a reaction if things got out
Speaker 1: of hand, Now it's your noble. The process got out
Speaker 1: of hand big time. So first it became a cycle
Speaker 1: that fed upon itself. The nuclear reactions would heat up
Speaker 1: the coolant water and start to convert some of that
Speaker 1: water into steam. Steam bubbles or voids began to form.
Speaker 1: That reduced the capability of the water in the system
Speaker 1: to absorb neutrons, and that increase the rate of nuclear
Speaker 1: reactions within the core, which meant the core got hotter,
Speaker 1: which meant heated up the water even more, which meant
Speaker 1: it increased the number of voids, which meant that even
Speaker 1: fewer neutrons were absorbed. So you see how this very
Speaker 1: quickly becomes a problem. On a reactor four at the
Speaker 1: Chernobyl facility was beginning to shut down. It was getting
Speaker 1: ready for a scheduled maintenance and refueling. This was totally routine,
Speaker 1: but before it was to shut down, it was going
Speaker 1: to go through a testing procedure on the following day,
Speaker 1: on April uh and that test was to see how
Speaker 1: long the reactor would be able to generate steam and
Speaker 1: thus spin turbines in the event of a main electrical
Speaker 1: power supply loss. So they were going to simulate losing
Speaker 1: power at this facility and they were going to see
Speaker 1: how long can this reactor continue to generate steam and
Speaker 1: turn this turbine even if the power is lost to
Speaker 1: the reactor itself. So to conduct that test on the
Speaker 1: back on the operators started to disable automatic shutdown features.
Speaker 1: And when you hear about shutting down ematic shutdown features,
Speaker 1: that should raise some pretty big alarm flags in your
Speaker 1: in your head, you should be thinking that doesn't sound
Speaker 1: like a good idea, and in fact it wasn't. So
Speaker 1: the operator went to shut down the reactor by instarting
Speaker 1: the control rods into the core, and for some reason
Speaker 1: or another, that action, telling the the control arms too
Speaker 1: insert those control rods caused a power surge, and the
Speaker 1: hot fuel in the reactor began to fragment. Water began
Speaker 1: converting into steam at an accelerated rate, and as I mentioned,
Speaker 1: that meant the water was less efficient at absorbing neutrons.
Speaker 1: So the reaction began to accelerate. The production of steam
Speaker 1: began to increase, and that increased the pressure inside the
Speaker 1: system so much that the pressure actually partially detached the
Speaker 1: steel cover plate on top of the reactor. That steel
Speaker 1: cover plate weighed one thousand tons. That's how much pressure
Speaker 1: was inside this react term enough pressure to displace at
Speaker 1: least partially one thousand tons of steel. Worse, when this
Speaker 1: cover plate became partially dislodged, it it wedged the control
Speaker 1: rods in such a way that they could not insert
Speaker 1: completely into the pressure tubes. So the control rods were stuck.
Speaker 1: They couldn't go all the way in and thus shut
Speaker 1: down the nuclear reaction. They had only reached about the
Speaker 1: halfway mark, so the nuclear reaction was continuing because there
Speaker 1: was the control rods couldn't absorb those extra neutrons. The
Speaker 1: build up of steam reached catastrophic levels, and there was
Speaker 1: an explosive rupture which released nuclear material into the atmosphere.
Speaker 1: Seconds later, another explosion followed, and this one flung out
Speaker 1: superheated graphite and nuclear fuel flying out from the facility.
Speaker 1: The general consensus is that the second explosion happened after
Speaker 1: hydrogen gas, which had been generated from the reactions in
Speaker 1: the core, ignited from those high temperatures. The explosion killed
Speaker 1: two of the workers at Chernobyl outright. The hot material
Speaker 1: started numerous fires in the area because chernobyls in the
Speaker 1: middle of a forest, and so the four started catching fire,
Speaker 1: and that helped distribute radioactive material further into the atmosphere
Speaker 1: and the general environment. And some of the radioactive elements
Speaker 1: included iodine one and ses M one thirty seven. Both
Speaker 1: of those post significant dangers to the public in the region.
Speaker 1: Iodine one one has a relatively short half life of
Speaker 1: just a few days. Caesium one thirty seven is like
Speaker 1: a decade our thirty years rather, so you've got thirty
Speaker 1: years half life or case one thirty seven a few
Speaker 1: days for iodine one nine. So it became a very
Speaker 1: dangerous mixture, and winds were carrying radioactive materials pretty far away,
Speaker 1: like little radioactive particles flying way up in the atmosphere.
Speaker 1: It started to go as far as across Ukraine, Belarus, Russia,
Speaker 1: even into Scandinavia. Many people at the site were exposed
Speaker 1: to massive amounts of radiation in a short amount of time,
Speaker 1: and within three weeks, twenty eight people died from radiation poisoning.
Speaker 1: Around one six thousand people in a thirty kilometer UH
Speaker 1: radius around the facility were relocated by May four, but
Speaker 1: around a thousand of them would secretly kind of return
Speaker 1: to the area on the QT in order to go
Speaker 1: back home. Another two d twenty thousand people would eventually
Speaker 1: be relocated over the course of the next few years. Now,
Speaker 1: independent studies found that the populations around Chernobyl do not
Speaker 1: appear to have had abnormally high incidents of cancer, with
Speaker 1: the exception of thyroid cancer. Thyroid cancer numbers shot up.
Speaker 1: Thyroid cancer, fortunately, if caught early, is very treatable, but
Speaker 1: it's still obviously is a big concern. The thyroid cancer
Speaker 1: was an outlier, but they did not see a rise
Speaker 1: in incidents and stuff like leukemia, And some people say
Speaker 1: perhaps some of those cases of thyroid cancer they might
Speaker 1: have already been an issue before the Chernobyl disaster, but
Speaker 1: because you suddenly had all these doctors in the area
Speaker 1: specifically looking for problems, they were finding them more frequently.
Speaker 1: So not that the Chernobyl disaster didn't cause some of that.
Speaker 1: It more than likely had to have because the numbers
Speaker 1: shot up so much. But because our focus turned to this,
Speaker 1: we discovered stuff that we otherwise would have overlooked. Sometimes
Speaker 1: when you know what you're looking for, you find it
Speaker 1: um whereas before you would have overlooked it. So Uh,
Speaker 1: it's hard to say exactly how much it contributed, but
Speaker 1: it probably contributed at least to thyroid cancer rates in
Speaker 1: the area. But otherwise the harm to humans seemed to
Speaker 1: be fairly limited. Uh. The immediate area around the plant
Speaker 1: suffered a quick die off, like within you know, ten
Speaker 1: kilometers of the plant. There was a quick die off
Speaker 1: around there, but it recovered very quickly. Within the next year,
Speaker 1: it was starting to recover. This I'm talking about like
Speaker 1: things like plants and trees, and the incidents didn't seem
Speaker 1: to you know, contribute to long lasting health effects in
Speaker 1: that area, at least not at a level that is
Speaker 1: easy to point out and say This is evidence that
Speaker 1: this disaster directly led to these results. There did happened
Speaker 1: to be a very powerful psychological impact on the region,
Speaker 1: largely fueled by the public perception of the effects of radiation. Essentially,
Speaker 1: if you're told over and over again that you're going
Speaker 1: to get sick and you're going to suffer, then you're
Speaker 1: gonna believe that and you will get sick and you
Speaker 1: will suffer because it becomes sort of a self fulfilling prophecy.
Speaker 1: So that was a real issue. Today, Chernobyl as a
Speaker 1: tourist site, you can actually go there. The wildlife in
Speaker 1: the area has not only made a comeback, it's actually
Speaker 1: gotten better than it was from before the accident. There's
Speaker 1: greater biological diversity in the region than there was prior
Speaker 1: to the accident. Now that's not because of radiation. It's
Speaker 1: not that radiation is suddenly magically helped animals get better.
Speaker 1: It's largely because people have stayed the hell away from Chernobyl.
Speaker 1: So if you take human beings out of an environment,
Speaker 1: it tends to do better. I'm just gonna leave that
Speaker 1: idea there. But since two ten, the Ukraine has led
Speaker 1: the way in resettling the area. Though with some restrictions
Speaker 1: in place to protect settlers. So for Examp Bowl, you're
Speaker 1: not supposed to use wood from the area in case
Speaker 1: it has uh any radioactive material in that would and
Speaker 1: you're also supposed to check soil very thoroughly for contamination
Speaker 1: levels before you try and farm there. But we're starting
Speaker 1: to see some reclamation of the land around Chernobyl, and
Speaker 1: that disaster is the greatest for at least an immediate
Speaker 1: effect on people of all time for for nuclear power plants.
Speaker 1: Our next one is an ongoing story, so it's impossible
Speaker 1: to say right now what the full effect of that
Speaker 1: disaster is because it's still playing out as I speak.
Speaker 1: But before I get to that, let's take another quick
Speaker 1: break to thank our sponsor. All Right, this brings us
Speaker 1: to Fukushima in Japan. On March eleventh, two eleven, at PM,
Speaker 1: there was a massive earthquake off the coast of Japan.
Speaker 1: It measured nine on the Richter scale, which makes it
Speaker 1: the fourth largest earthquake ever recorded. The earthquake created a
Speaker 1: tsunami that was fifteen meters tall at the point of Fukushima.
Speaker 1: That's just under fifty feet tall. Imagine not a wave,
Speaker 1: but a wall of water fifty feet tall that hit
Speaker 1: the Fukushima Daichi Nuclear Facility, and that natural disaster led
Speaker 1: to a terrible man made disaster. The tsunami disabled the
Speaker 1: power supply and thus the cooling systems for three of
Speaker 1: the reactors at that facility, Reactors one, two, and three.
Speaker 1: In fact, the facility actually withstood the initial shock of
Speaker 1: the earthquake pretty well. The uh the various inspections that
Speaker 1: have happened since this disaster have suggested that the earthquake
Speaker 1: did not really damage the facilities in any meaningful way,
Speaker 1: so that's kind of impressive. There were six reactors at Fukushima,
Speaker 1: but reactors four or five and six were not in
Speaker 1: operation at the time of the earthquake. Um at least
Speaker 1: reactor four did have a lot of nuclear material as
Speaker 1: part of that building because they have waste fuel pools
Speaker 1: storage pools where you take the fuel you've used in
Speaker 1: the reactor that no longer has enough feasible material in
Speaker 1: it for it to be useful. It's no longer going
Speaker 1: to produce efficient nuclear reactions. You have to put that somewhere,
Speaker 1: so generally speaking, right now, most nuclear facilities store nuclear
Speaker 1: waste on site, so they were to go into cooling
Speaker 1: pools for a few years before being moved to a
Speaker 1: different facility, and so reactor four, while it was not active,
Speaker 1: did have uh spent nuclear fuel inside these cooling pools. Anyway,
Speaker 1: when that's soon Nummi hit, it's shut down twelve of
Speaker 1: the thirteen backup generators on site designed to run the
Speaker 1: residual heat removal system cooling pumps, and it also disabled
Speaker 1: the heat exchangers that would take heat from the reactor
Speaker 1: and transfer it to the ocean. To make matters worse,
Speaker 1: the seawater pumps on site that were designed to pump
Speaker 1: seawater off the system. They were there expressly in case
Speaker 1: there was a tsunami. We're located at too low an
Speaker 1: elevation to be of any help. So when they designed
Speaker 1: the Fukushima Daiichi facility, they estimated a tsunami of three
Speaker 1: point one meters in height, so they positioned the seawater
Speaker 1: pumps at four meters above sea level because they said, oh,
Speaker 1: three point one meters that's how high the tsunami would
Speaker 1: likely be, will go about a meter above that. The
Speaker 1: facility itself was at ten ms above sea level, but
Speaker 1: because it was a fifteen m tsunami. It meant that
Speaker 1: those pumps were actually eleven meters below the water's surface
Speaker 1: when that tsunami hit, and they were all overwhelmed. Reactors one, two,
Speaker 1: and three could not moderate reactor core temperatures, and the
Speaker 1: cooling systems that could transfer excess heat were not operational.
Speaker 1: So the reactors had been shut down automatically after the earthquake,
Speaker 1: which is good, so they weren't in operation at that moment,
Speaker 1: but even in shutdown mode there's still some residual fission
Speaker 1: reactions taking place. The reactor cores were producing about one
Speaker 1: point five pc of their nominal thermal power, but that
Speaker 1: heat was building up and it was beginning to convert
Speaker 1: water into steam, and there was no way to transfer
Speaker 1: the heat away from the reactor cores, so they were
Speaker 1: just getting hotter and hotter. The steam vented out through
Speaker 1: safety valves into a primary containment vessel, so again not
Speaker 1: just venting out into the general region. The steam included
Speaker 1: some hydrogen gas as well, which was generated from reactor
Speaker 1: reactions between the superheated zirconium cladding in the reactor core
Speaker 1: and the steam, and so you get this hydrogen gas
Speaker 1: as a byproduct and As I mentioned before, hydrogen gas
Speaker 1: can be very dangerous. It's extremely you know, flammable or explosive.
Speaker 1: You can look at things like the Hindenburg disaster, which
Speaker 1: happened because of a hydrogen disaster. Will pressure inside these
Speaker 1: units continued to increase. Steam was directed into special suppression
Speaker 1: chambers that were located under these reactors. So you have
Speaker 1: these special chambers underneath that were meant to hold this
Speaker 1: kind of stuff in the case of an emergency um
Speaker 1: Water injection followed. That's where you you know, obviously, you
Speaker 1: introduce water into the system along with the initiation of
Speaker 1: the emergency core cooling system. So all measures were being
Speaker 1: put into place to try and get this reactor horror
Speaker 1: temperature under control. But the water injection systems began to
Speaker 1: fail for each of those first three units, and so
Speaker 1: responders began to use fire pumps to inject more water
Speaker 1: into the reactors using fire trucks and fire hoses, and
Speaker 1: then they started using seawater, pumping seawater in to help
Speaker 1: inject into the reactors and cool them down. And this
Speaker 1: was all to keep the fuel submerged in water. But
Speaker 1: in Unit one, that water level fell enough to expose
Speaker 1: the top of the fuel rods to air, and the
Speaker 1: reactions began to speed up. The water was not there
Speaker 1: to moderate those reactions. An hour and a half later,
Speaker 1: all of the fuel and Unit one had become uncovered
Speaker 1: because as a heat up, it obviously turned more of
Speaker 1: the water into steam, and while there was still water
Speaker 1: inside the vessel that contains the reactor core, all the
Speaker 1: fuel was open to the air. At that point, the
Speaker 1: water was still in the base of the vessel, but
Speaker 1: the fuel is suspended above of the base, so the
Speaker 1: temperature of the fuel inside Unit one climbed to around
Speaker 1: two thousand, eight hundred degrees celsius. It began to melt,
Speaker 1: it fell apart. The falling fuel landed into the water
Speaker 1: that was still pooled at the bottom of the reactor
Speaker 1: pressure vessel, and that helped actually bring temperatures down. The
Speaker 1: temperatures began to decrease once the melted fuel hit water again.
Speaker 1: Gases and steam were building up inside the reactor building,
Speaker 1: so attempts were made to vent the gases through an
Speaker 1: external system that would contain the gases so you wouldn't
Speaker 1: have radiated material released into the environment, But there was
Speaker 1: a backflow problem and gases began to accumulate inside the
Speaker 1: reactor building itself, not just the reactor core, and one
Speaker 1: of those gases was hydrogen, and on March twelve, that
Speaker 1: hydrogen exploded on the service floor above the Unit one reactor.
Speaker 1: This destroyed the roof of the facility and the fuel
Speaker 1: inside the reactor pressure vessel was later found to have
Speaker 1: melted through the vessel and had melted about sixty down
Speaker 1: into the concrete below the vessel. Now that concrete was
Speaker 1: two point six meters thick, so it held firm and
Speaker 1: the mass eventually cooled down enough to solidify. Units two
Speaker 1: and three had also had some nuclear fuel melt, but
Speaker 1: they appeared to be less affected than Unit one at
Speaker 1: that point. But then Unit two's water injection systems failed,
Speaker 1: just as Unit one had, and the responders attempted to
Speaker 1: inject water from fire pumps and from seawater. This time,
Speaker 1: they ventilated the building. They used a blowout panel near
Speaker 1: the top of the building to help avoid another hydrogen
Speaker 1: build up like in Unit one. On March fifteen, the
Speaker 1: pressure inside one of the containment systems beneath the reactor
Speaker 1: dropped after what was believed to be a hydrogen gas explosion.
Speaker 1: And the initial thought was that some sort of rupture
Speaker 1: must have happened, but investigations haven't really been able to
Speaker 1: turn up signs of a rupture, so there's a lot
Speaker 1: of questions about what actually happened that day. But somewhere
Speaker 1: pressure was released and some radioactive material was released into
Speaker 1: the environment on that day from Unit two. Unit three
Speaker 1: seemed initially to have fared better, with responders able to
Speaker 1: inject water and ventilate the building. But on March fourteen,
Speaker 1: there was an explosion inside Unit four. Now, remember Unit
Speaker 1: four was de fueled. There was no nuclear fuel inside
Speaker 1: the core of Unit four, so why did it explode. Well,
Speaker 1: the hypothesis is that hydrogen forming from Unit three had
Speaker 1: reached Unit four by backflow because the two buildings, the
Speaker 1: one for Unit three and the one for Unit four,
Speaker 1: shared a common duct system. So they thought is that
Speaker 1: the hydrogen gas must have passed through this duct system
Speaker 1: it got into Unit four, and while Unit four didn't
Speaker 1: have any nuclear fuel in the reactor, it did have
Speaker 1: all this hydrogen gas build up, and then there was
Speaker 1: an explosion. That explosion also for they're damaged the building
Speaker 1: that housed Unit three. Now, out of all these events,
Speaker 1: the one that seemed to release the most radioactive material
Speaker 1: into the environment happened on March fifteenth from the issues
Speaker 1: with Unit two, but the actual mechanism that led to
Speaker 1: that release still remains a mystery. The three units now
Speaker 1: receive cooling water from a special water plant supplying recycled
Speaker 1: water to the units. They have cooling circuits UH to
Speaker 1: help do this. They are all being held at around
Speaker 1: atmospheric temperatures, so the temperature of the core is about
Speaker 1: the same as what it is outside. The government has
Speaker 1: also injected nitrogen into those units, and that was an
Speaker 1: attempt to capture hydrogen and prevent hydrogen gas from building up.
Speaker 1: Another challenge that had to be overcome was dealing with
Speaker 1: spent fuel, because, as I said, each of the units
Speaker 1: has a waste fuel pond and that provides cooling and
Speaker 1: moderation of spent fuel. Since the accident, there is now
Speaker 1: a new set of heat exchangers and cooling circuits attached
Speaker 1: to each unit to help keep those those cooling ponds
Speaker 1: cool enough, and arrangements have been made to remove and
Speaker 1: transport the spent fuel rods to a more permanent facility. UH.
Speaker 1: Typically you keep them in the pool for a few years,
Speaker 1: and then you move them to air cooled facilities once
Speaker 1: they've reached a certain level of non activity and uh,
Speaker 1: and so you kind of have to wait for things
Speaker 1: to cool down enough for you to be able to
Speaker 1: move them, and that started to happen. So there's some
Speaker 1: good news and there's some bad news. And the good
Speaker 1: news is that the effects of radiation from the disaster
Speaker 1: appear to have had no real impact on human health
Speaker 1: in the area. Based upon the various research projects that
Speaker 1: have gone on since then, it doesn't like there's been
Speaker 1: widespread negative impact on human health. The general region had
Speaker 1: been evacuated, but since two thousand and twelve, the government
Speaker 1: has allowed people in small groups to come back um
Speaker 1: one at a time, like small groups at a time.
Speaker 1: But the bad news is that the radiation levels inside
Speaker 1: the facilities themselves are still really really high, like deadly
Speaker 1: high in those facilities, and that contaminated water around the
Speaker 1: units is starting to seep into the ground in that
Speaker 1: area now that it happens to be an area that's
Speaker 1: next to the ocean. So I guess the media bright
Speaker 1: side is that the any water that seeps into the
Speaker 1: ground isn't going into the water table that serves up
Speaker 1: the water for the people there, because the water is
Speaker 1: coming from further inland and it's flowing out to the ocean.
Speaker 1: But without containing that contaminated water properly, that could end
Speaker 1: up leaking into the ocean and contaminating ocean water and
Speaker 1: spread radiation quite far. Uh. There's still a lot of
Speaker 1: efforts going on in Japan to contain all of that,
Speaker 1: but I've read some pretty disturbing reports about the way
Speaker 1: it's all being handled, and that it's suggests that that
Speaker 1: way is not the most effective. Uh. So, the plant
Speaker 1: decommissioning process is going on in Fukushima, and there's gonna
Speaker 1: be a lot of different steps. It's probably gonna take
Speaker 1: more than a decade of work to be able to
Speaker 1: bring those those uh those buildings to a point where
Speaker 1: we can truly decommission them. So that's it. That's the
Speaker 1: look at three of the biggest nuclear powered disasters. They're
Speaker 1: all bad and and people tragically lost their lives in
Speaker 1: the Chernobyl one in particular. Um, and they you never
Speaker 1: want to have any of these sort of incidents happen. Uh.
Speaker 1: They do suggest perhaps that in the event of a
Speaker 1: nuclear disaster like this, the impact might not be as dramatic,
Speaker 1: at least at first as we tend to think. I
Speaker 1: mean again, are thoughts are often shaped by stuff like
Speaker 1: pop culture, and in the fifties, you know, all the
Speaker 1: different science fiction films were all about how how radiation
Speaker 1: was going to mutate people in weird and unpredictable ways.
Speaker 1: Reality is that doesn't actually happen that way in the
Speaker 1: long term. Who knows, we may see long term effects
Speaker 1: that are much more troubling than what we're seeing in
Speaker 1: the short term. So I'm not suggesting, like I'm not
Speaker 1: suggesting that people have overreacted to these disasters. Maybe three
Speaker 1: Mile Island out of all of them, the result of
Speaker 1: three Mile Island was still should never have happened. But
Speaker 1: at least it appears that in the grand scheme of things,
Speaker 1: it was not that dangerous to people because these safety
Speaker 1: systems worked properly. Still shouldn't have happened, And it's still
Speaker 1: kind of scary, more than more than kind of scary.
Speaker 1: But I wanted to look into them because you hear
Speaker 1: about these stories all the time, and without really understanding
Speaker 1: what happened, then all you really feel is anxiety. I
Speaker 1: think the only way to really greet that is through education,
Speaker 1: and that education means well, now I feel like I'm
Speaker 1: more informed with what can happen, what can go wrong
Speaker 1: with nuclear power. Maybe that guides my decision about whether
Speaker 1: or not I support it. That's totally legitimate, uh, and
Speaker 1: I am no longer just imagining worst case scenarios. That
Speaker 1: wraps up this episode. If you have any ideas for
Speaker 1: future episodes, we will be going to something totally different
Speaker 1: from nuclear power in next week. I'm not sure what
Speaker 1: that is because I don't have my schedule opened up,
Speaker 1: but it will be something different, so look forward to that.
Speaker 1: If you have suggestions for future episodes, let me know.
Speaker 1: Send me an email. The addresses tech Stuff at how
Speaker 1: stuff works dot com or drop me a line on
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