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More than a decade after the Fukushima Daiichi nuclear power plant disaster, its operators are dumping once-contaminated water into the Pacific Ocean. Is that OK?

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This SciShow video is supported by Ground News, a website and app that lets  you compare how major events are being covered so you can  see more sides of more stories.

You can go to  or click the link in the description to get 30% off  the Vantage level subscription. In 2011, a catastrophic earthquake hit Japan and damaged the Fukushima  Daiichi nuclear power plant.

Not to the point that it stopped working. Just enough that they needed to  get a backup power supply involved. The backup power kept things  running smoothly for a hot minute.

But less than an hour later, a tsunami triggered by the earthquake came in and  broke the backup generators. At that point, the plant couldn’t  keep its nuclear fuel cool, and three of its reactors melted. It was the end for those reactors, but just the beginning of a  monumental nuclear waste disaster that was rated right up there with Chernobyl as one of the worst the world has ever seen.

And we’re still dealing with  the radioactive material that resulted from the event.  More than a decade later, responders continue to roll out new interventions to minimize global contamination. Like, this year they started dumping some of the nuclear wastewater into the ocean on purpose. Which begs the question: Is that okay? [♪ INTRO] When a tsunami hits a power  plant after an earthquake has already weakened its defenses, there are a few emergencies to deal with.

But one of the biggest is water overflow. Water from the giant wave ran  into Fukushima’s nuclear reactors, into the plant buildings, and  into the trenches where pipes run. It was just kind of everywhere.

Nuclear power plants also run  cold water through the reactors during normal operation to  keep them from overheating and to absorb energy in the event of an accident. Those reactors are the part of the  power plant that generate electricity using rods of uranium oxide to  boil water and turn steam turbines. They’re also where the radioactivity comes from.

When the reactors melted, all of the water in that area became radioactive. The plant had storage tanks where water that was supposed to be there was treated. But the tsunami basically flooded the plant, which meant it didn’t have enough space to store all of the extra contaminated water.

That meant that one way or another,  some of it needed to leave. Authorities decided to release  the water that they knew was less contaminated first to make room  to store the more dangerous stuff, so ultimately dumping 10,000  tons of wastewater into the sea. I know it doesn’t sound great,  but reports from the Nuclear and Industrial Safety Agency  suggested that radioactivity levels in the ocean didn’t significantly  change after the dump.

So, all things considered, it wasn’t the worst choice they could have made. But that wasn’t the only contaminated  water coming from this plant. It was also leaking.

And I’m  not talking about a tiny crack you can put a piece of duct tape over. The plant leaked about 60% of  its contents into the ground, which then mixed with nearby groundwater. Within a few months, the company  that operates the power plant built underground walls around the entire property to keep the seepage contained.

Then, a freezing underground wall was constructed around the plant buildings to prevent water from flowing back into the reactors. Water expands when it’s frozen, so  by freezing the water in the soil, the ground became more solid and less passable. Once responders stopped the worst of the leakage, they needed to remove the worst  of the toxins in the water.

By “toxins,” here, I mean the  isotopes of elements that decayed from the original uranium  oxide fuel, like caesium-134. Those isotopes can release energy in the form of radioactivity for years. They’re also referred to as radionuclides.

If those radionuclides have enough energy, they can break the bonds between molecules in your body, including your DNA. That’s the kind of thing that makes radiation harmful to us and a potential source of cancer. So, to get rid of those radionuclides, Japan started treating the  wastewater with a method called the Advanced Liquid Processing System.

Basically, the radionuclides  were captured in a filter so that only water and tritium could pass through. Now, we want the water to  clear through the system, but that other stuff? Tritium?

It sounds like the kind of thing  that could take down Superman. Well the good news is tritium  isn’t as scary as it sounds. It’s a naturally occurring form  of hydrogen with two neutrons.

It comes from the clash of  cosmic rays hitting air molecules in our atmosphere. So it’s all over the place. And, really, it’s only a radiation  hazard in very large quantities.

While there are things we can do  to reduce the amount of tritium, it’s the least dangerous of the  contaminants in Fukushima’s water. So once responders figured out how  to treat the contaminated water, they had pretty much solved all  of the plant’s problems, right? Well… You know how there wasn’t enough  space to store all of the water after the tsunami hit and they  needed to dump a bunch of it?

Well, the tanks kind of refilled. See, when the disaster hit, an  explosion literally blew the roof off. And the debris from that  explosion was radioactive.

So any rain that fell in the  area and came into contact with that debris became contaminated as well. Not to mention, before the frozen  underground walls were erected, groundwater flowed into containment  tanks sitting near the reactors. So water had been building up  inside the plant for years.

And all that time, water was getting pumped into the system to keep it cool. Eventually, there wasn’t anywhere left to put it. Estimates suggested that if the  plant’s operators did nothing, the tanks would be full by 2024.

Faced with another tough decision, they began to release treated water into  the Pacific Ocean in 2023. If this sounds awful, you should  know that it’s the same thing other nuclear power plants  do with their wastewater once it has been treated, as well. And the world wasn’t just taking it for granted that the water was safe to dump.

Switzerland, France, the US, South Korea, Austria, and Monaco conducted an international study. They gathered samples of the treated water at the plant and the seawater  near the release site. Using those samples and machines  like gamma-ray spectrometers, each lab tallied up the amount of radionuclides they could find to see how  dangerous the water was.

A gamma-ray spectrometer is  a tool that shows scientists the spectrum of gamma ray energy coming off of whatever material they feed into the machine. Since different elements give off different amounts of gamma ray energy, scientists can figure out which ones they’re looking at from the readouts. After measuring the amount of  each radionuclide independently, the labs found less than  1% of the regulatory limit for any of these dangerous molecules.

And they’re going to continue sampling and testing the wastewater as it’s released. So if the amount of detectable radionuclides starts to rise to concerning  levels, they’ll need a new approach. Some nearby countries,  including China and South Korea, still aren’t sure that enough is being done to protect the animals that live in those waters.

They’ve even gone so far as to  ban seafood imports from Japan. And I get the concern. Just  after the 2011 disaster, 53% of fish caught near the plant were high in radionuclides like caesium-134.

But by 2014, that number dropped to 0.6%. Which is more than nothing,  but a huge improvement. So if we’re at a point where  the fish are less contaminated and the water is less toxic based  on international assessments, it’s time to start thinking about the future of the Fukushima Daiichi plant.

Right now, the plan is to  seal off the damaged units for another decade or two to let  more of the radionuclides decay away, and then demolish the remains. And we’re left with water that’s  being released into the ocean that isn’t completely free  of toxins, but way below accepted limits of contamination. So dumping water that spent years  mingling with radioactive debris might seem like a scary prospect.  But scientists across the world say that, thanks to treatment,  it probably is okay.

Thank you to Ground News for  supporting this SciShow video! When it comes to following  Fukushima’s nuclear waste news, various sources may present different narratives, sometimes leaving out specific details. That’s where Ground News comes in.

Ground News is a startup founded in 2018 by former NASA engineer Harleen Kaur. This platform compiles news  from around the world into one place so curious people like you and me can get a comprehensive view of current events. For example, there are over 120 articles covering Japan’s release of Fukushima plant water.

There is a majority of left-leaning  sources with 63% of all sources that have a high factuality rating, which means they’re probably not as sensationalized. Both local and international  sources cover the same story but might emphasize different aspects providing you with a range of  perspectives to help you stay informed. And Ground News also has a  feature called My News Bias, which helps you track your habits.

This feature provides a breakdown  of your top news sources and assesses whether you’re  exposed to diverse views that can challenge your own beliefs. To get started with 30% off unlimited access to reliable information with the vantage plan, You can go to  or click the link in the description down below. And thank you for watching SciShow! [♪ OUTRO]