WEBVTT - Japan's Nuclear Problem

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<v Speaker 1>Welcome to brain Stuff from house stuff works dot com,

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<v Speaker 1>where smart happens. Hi am ourshall brain with today's question,

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<v Speaker 1>what the heck happened with Japan's nuclear power plants this weekend?

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<v Speaker 1>As you'll recall, Japan had its giant earthquake and tsunami

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<v Speaker 1>last Friday, and right after the earthquake, everything looked pretty

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<v Speaker 1>much fine as far as the nuclear power plants were concerned.

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<v Speaker 1>The New York Times ran a story about how everything

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<v Speaker 1>looked good. There were no major problems. The reactor hadn't

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<v Speaker 1>cracked or you know, fallen over anything because of the earthquake,

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<v Speaker 1>and it looked really good. But then by Saturday, things

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<v Speaker 1>had taken a turn for the worst, so there were

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<v Speaker 1>reactor buildings exploding. There was all kinds of talk about

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<v Speaker 1>meltdowns and China syndrome and all this other stuff. So

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<v Speaker 1>when you think about it, a nuclear power plant is

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<v Speaker 1>supposed us to be one of the most amazingly engineered,

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<v Speaker 1>super wonderful things in the world. With umpteen levels of redundancy,

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<v Speaker 1>and every single contingency thought about and poured over and

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<v Speaker 1>inspected both nationally and internationally, there should have been nothing

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<v Speaker 1>that could go wrong in Japan's nuclear power plants, and

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<v Speaker 1>yet it did. So what happened and how did things

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<v Speaker 1>go from being really quite stable to completely unstable and

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<v Speaker 1>leading to some of the worst nuclear accidents ever to

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<v Speaker 1>occur on the planet. So let's take a look at

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<v Speaker 1>what happened step by step, because it really is an

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<v Speaker 1>interesting story and it shows how even when something is

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<v Speaker 1>engineered to the highest levels and given multiple layers of

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<v Speaker 1>redundancy and so on, things can still go sour. In

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<v Speaker 1>step one, the earthquake happened, and this was fine. The

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<v Speaker 1>four reactors that were nearest the epicenter of the earthquake

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<v Speaker 1>detected the earthquake and they shut down automatic, just like

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<v Speaker 1>they were supposed to. So what does shut down mean?

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<v Speaker 1>If you were to look inside these nuclear reactors, you

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<v Speaker 1>would see fuel rods filled with nuclear fuel little pellets

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<v Speaker 1>about the size of your little finger that are arranged

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<v Speaker 1>in these rods and collected together in bundles, and the

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<v Speaker 1>control rods moved down between the rods to absorb neutrons

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<v Speaker 1>that are coming out of the uranium atoms in the fuel.

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<v Speaker 1>And once you absorb the neutrons, you basically quench or

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<v Speaker 1>stop the nuclear reaction. That's creating the heat that's creating

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<v Speaker 1>the steam that's creating the electricity for the power plant.

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<v Speaker 1>So they automatically shut down the control rods moved into

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<v Speaker 1>the reactor core, absorbed all the neutrons quen the reaction.

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<v Speaker 1>Now there's still some, well not some, a lot of

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<v Speaker 1>residual heat in that reactor core, both from other radioactive

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<v Speaker 1>elements of short life that are in the core before

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<v Speaker 1>it's quenched, and also just the heat that had accumulated.

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<v Speaker 1>You can't have a gigawatt power plant with you know,

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<v Speaker 1>a light bulb as that. Here, you have a giant

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<v Speaker 1>mass of something that's hot and it's it's itself is

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<v Speaker 1>going to take time to cool down. So the earthquake happened,

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<v Speaker 1>nothing happened to the buildings. They were engineered properly and

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<v Speaker 1>and sustained no damage in the earthquake. The reactors shut

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<v Speaker 1>down and everything was fine. So now you have these

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<v Speaker 1>big nuclear reactors which are in the process of cooling down,

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<v Speaker 1>which is gonna take some time. And during that cooling

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<v Speaker 1>down process you need to circulate cooling water through the cores. Unfortunately,

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<v Speaker 1>the power grid wasn't in such great shape and so

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<v Speaker 1>power failed to the nuclear power plants, and you would

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<v Speaker 1>think this wouldn't be the big problem, since they are

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<v Speaker 1>power plants after all, but they had been shut down automatically,

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<v Speaker 1>so they aren't producing electricity. So in this situation where

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<v Speaker 1>your nuclear power plant is shut down and you have

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<v Speaker 1>lost the connection to the power grid, what they've got

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<v Speaker 1>is on site backup diesel generators. So these diesel generators

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<v Speaker 1>fired up to provide power that would run the pumps

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<v Speaker 1>that would keep these cores cool. That system worked properly

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<v Speaker 1>and everything was fine until the tsunami hit. And normally

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<v Speaker 1>a tsunami hitting a nuclear power plant wouldn't be a

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<v Speaker 1>big deal because they know about tsunamis and had designed

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<v Speaker 1>against them. But they had not expected this big of

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<v Speaker 1>a tsunami, so when it hit, it basically inundated the

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<v Speaker 1>diesel generators, all of them, and took them out of service.

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<v Speaker 1>Now you could argue that the engineers should have put

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<v Speaker 1>the diesel generators up higher so they couldn't have gotten

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<v Speaker 1>hit by a tsunami, or they should have made the

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<v Speaker 1>diesel generators submersible so even if the tsunami came, they

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<v Speaker 1>could run submerged and keep power going. But neither of

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<v Speaker 1>those things happened, so the diesel generators failed. Now, in

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<v Speaker 1>a nuclear power plant, there's another backup system which involve

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<v Speaker 1>alves batteries, and batteries are there in case the diesel

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<v Speaker 1>generators fail so that you have time to get some

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<v Speaker 1>kind of additional backup plan in place. But these are batteries.

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<v Speaker 1>Think about how batteries are in your life. They're always

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<v Speaker 1>going dead, they never last long enough. If they're fully charged,

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<v Speaker 1>you're you're still subconsciously thinking about them going dead. And

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<v Speaker 1>batteries at a nuclear power plant are no different. These

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<v Speaker 1>were designed to have a lifespan of about eight hours.

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<v Speaker 1>So the batteries are circulating cooling water through the cores

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<v Speaker 1>and everything's fine, And meanwhile the engineers are trucking in

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<v Speaker 1>backup backup diesel generators to puck into the nuclear power

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<v Speaker 1>plants and fire them up. But when these when these

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<v Speaker 1>backup backup generators arrived, apparently they had the wrong plugs

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<v Speaker 1>on them. They weren't quite compatible with the nuclear power plant,

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<v Speaker 1>according to some reports, and they couldn't just be hooked

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<v Speaker 1>in instantly, which meant that the batteries went dead. And

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<v Speaker 1>this is where things started to come unraveled without cooling

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<v Speaker 1>water circulating through the core, the reactor core starts to

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<v Speaker 1>heat up and it starts to boil the cooling water,

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<v Speaker 1>and as that water boils off, it starts to lower

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<v Speaker 1>the level of water in the reactor core, causing some

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<v Speaker 1>of the clear fuel rods to not be submerged in

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<v Speaker 1>water anymore. At this point, the fuel rods overheated and cracked,

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<v Speaker 1>allowing water to get into the very very hot nuclear

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<v Speaker 1>pellets and you get dissociation of the water molecules and

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<v Speaker 1>the production of hydrogen. It builds up in pressure and

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<v Speaker 1>it has to be vented off, and that normally wouldn't

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<v Speaker 1>be a problem. Factories vent gases all the time, but

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<v Speaker 1>for some reason, when they vented off a large quantity

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<v Speaker 1>of hydrogen gas, it ignited and exploded, and this caused

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<v Speaker 1>the building around the reactor vessel to disintegrate. Basically, the

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<v Speaker 1>whole top of it was blown off by the hydrogen explosion.

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<v Speaker 1>And this occurred multiple times, apparently at multiple plants. Now,

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<v Speaker 1>if this process had been allowed to continue, the process

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<v Speaker 1>of boiling the cooling water off and exposing more and

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<v Speaker 1>more of the core, things would have gone from bad

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<v Speaker 1>to worse because eventually the nuclear fuel pellets would get

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<v Speaker 1>so hot that they would melt. And this is where

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<v Speaker 1>the word meltdown comes from. The idea that the nuclear

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<v Speaker 1>fuel heats up, melts and becomes what one article termed

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<v Speaker 1>radioactive lava that flows to the bottom of the reactor

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<v Speaker 1>vessel and potentially each through it and ends up in

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<v Speaker 1>the floor of the reactor containment building. To prevent that

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<v Speaker 1>from happening. To prevent a meltdown, the technicians in Japan

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<v Speaker 1>decided to start pumping seawater into the reactors. And this

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<v Speaker 1>is largely a desperation measure because the seawater ruins the

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<v Speaker 1>reactor and you're not ever going to be able to

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<v Speaker 1>to fix it. You're gonna have to scrap the whole

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<v Speaker 1>thing and start over. So they start pumping seawater in

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<v Speaker 1>and that prevents a meltdown. Long term, that's going to

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<v Speaker 1>have some serious consequences for the whole nuclear industry in

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<v Speaker 1>Japan and for the Japanese Power Group, because nuclear power

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<v Speaker 1>is an important part of the power system in Japan.

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<v Speaker 1>It makes up you know, these failed reactors make up

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<v Speaker 1>something like fifteen percent of the whole electricity generating capacity

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<v Speaker 1>of the country and that's a big loss for a

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<v Speaker 1>country to sustain and will have to be replaced both

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<v Speaker 1>short term and long term. So what does this whole

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<v Speaker 1>episode mean in real terms? That depends on how you

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<v Speaker 1>want to spin it. So if you don't like nuclear power,

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<v Speaker 1>the way you spin this is you say, look, these

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<v Speaker 1>terrible things happened. These were supposed to be well engineered systems,

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<v Speaker 1>but clearly they were not. There was radiation that was

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<v Speaker 1>released into the environment, there were explosions, there could have

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<v Speaker 1>been a meltdown. Things just did not go as we

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<v Speaker 1>were are told they were go. Would go in an

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<v Speaker 1>engineer system like this, Nuclear power should not be allowed

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<v Speaker 1>anywhere on the planet. If you're pro nuclear, you'd spin

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<v Speaker 1>it the other way. You'd say, well, these reactors were

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<v Speaker 1>designed and engineered with redundant systems and with procedures to

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<v Speaker 1>handle just about any possible scenarios. So a lot of

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<v Speaker 1>stuff went wrong, and yet in the big picture, nothing

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<v Speaker 1>seriously dangerous happened as a result of the problems that occurred. So, yes,

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<v Speaker 1>a little bit of radiation was leaked into the atmosphere,

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<v Speaker 1>but most of it is harmless, very short lived, and

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<v Speaker 1>that which wasn't completely harmless happened to blow out to see,

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<v Speaker 1>so it wasn't affecting any major population areas or anything

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<v Speaker 1>like that. And there were no meltdowns and there were

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<v Speaker 1>no you know, radioactive explosions like we had at Chernobyl,

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<v Speaker 1>So nothing really bad happened. And even if the meltdown

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<v Speaker 1>had occurred, it would have been okay because it would

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<v Speaker 1>have been contained within the containment build thing and it

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<v Speaker 1>wouldn't have been any big deal. You can kind of

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<v Speaker 1>pick how you want to personally spend this event, whether

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<v Speaker 1>you want to be pro nuclear or anti nuclear, or

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<v Speaker 1>somewhere in between. Be sure to check out our new

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<v Speaker 1>video podcast, Stuff from the Future. Join how Stuffwork staff

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<v Speaker 1>as we explore the most promising and perplexing possibilities of tomorrow.

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