There are about 150 nuclear  submarines operating today.

They spend a lot of time underwater, but surface when they need to. …Or at least they’re supposed to. Sometimes subs end up permanently submerged.

After all, accidents can happen. And this presents a bit of an issue. A nuclear reactor isn’t a great thing to just leave out in the wild.

So there have been some efforts to recover these wrecks before they become a bigger problem. But getting a nuclear reactor off the ocean floor turns out to be kind of hard! Here’s how scientists and engineers rescue nuclear subs when things go very, very wrong. [♪INTRO] While there are a lot of nuclear submarines in the world, the number of known nuclear submarine wrecks is, thankfully, much lower.

The US currently has two lost nuclear subs, the Soviet Union lost four,  and the Russian Navy two, for a grand total of eight. So you can count them on your hands. But still, it’s a lot when you consider  all the nuclear waste on board.

A sub’s nuclear reactor is  essentially a miniaturized version of the reactors at big power plants. It uses heat from radioactive  fuel to boil water into steam. That steam spins a turbine,  which is how the propellers move.

It’s also how they get electricity. And this isn’t the only nuclear thing on board. In addition to the reactor, a submarine may be carrying some spent nuclear  waste as well as nuclear weapons in the form of missiles or torpedoes.

Now, normally these are all sealed up nicely. You can stand right next  to all of them and be fine. But, normally, the sub is not a  wreck at the bottom of the ocean.

Whatever happened to sink the sub like a fire or explosion or something can crack open the reactor or the other equipment. Even if the reactor does  survive the incident intact, the slow corrosion of salt water  can open up that metal shell. In any of these cases, it can  result in radioactive atoms, also known as radionuclides,  being released into the water, spreading and contaminating whatever’s nearby.

This is something we don’t really want to happen, so different countries have been monitoring these wrecked nuclear submarines for years. The US monitors their two wrecks, the Thresher and Scorpion, for example. And Russia and nearby countries like Norway have been monitoring the ones near them.

They send boats out to take  samples of the seawater or sediment around the wrecks to see how  much radioactivity there is. So far, the data that we  have access to suggests that, while some radionuclides are getting out from at least a handful of these  wrecks, it’s not a lot. At least as of 2012, the Soviet submarine known as K-27’s radiation leakage was negligible.

According to Russian research,  levels of radionuclides around another Soviet sub, K-159, are elevated, but not enough to be of real concern right now. And a third, K-278, leaked. But not enough to be of huge  concern to the Norwegians.

So that’s something to be thankful for. …For now. I guess, at least. It could still become a  problem in the future, though.

Further corrosion can create new leaks. And something could jostle the remaining nuclear material in such a way to throw it out of control. See, a working nuclear reactor  depends on its fuel rods being arranged in a certain shape to keep  the reaction hot but not too hot.

But if, say, some part of the sub  were to collapse, the fuel could get jumbled together, start to react  way too fast and get way too hot. However unlikely, this could lead to a meltdown. Which is bad, we don’t want one of those.

But even without a big explosion, a new crack in the shell releasing previously  radioactive stuff into the ocean could still have significant effects. A 2017 paper, for example, examined what would happen if there was a big leak with the K-27. They predicted how far currents  might carry the radioactivity, based on computer models  of water and ice movement.

They also predicted how much this would affect the environment and people living near the wreck, based on models of the food chain and estimates of how much seafood people eat. Their results suggest that  it could contaminate fish in the area to the point where people who rely on subsistence fishing may not  be able to catch and eat them. But pretty much only that population, and it might not even be a problem for them.

But if it is, it’s thanks to phenomena known as bioaccumulation and biomagnification. Even though the amount of radioactive material in the water would end up relatively small, if little critters like fish or plankton ate it, those radionuclides would  stick around in their tissue. That’s bioaccumulation.

Then, as creatures higher up the  food chain ate those critters, they would become radioactive, and on and on. And because you need a lot of  little fish to feed one big fish, the higher up the food chain you  go, the greater the dose ends up. That’s biomagnification.

Even if some of the fish would  technically be safe to eat, the scare of radioactivity could still be a disaster for fishermen in the area. Like, if you were at the  grocery store, would you eat the fish that were caught next  to the radioactive submarine? Or would you maybe go ahead and  buy the another different fish?

This isn’t a hypothetical question. After the Fukushima nuclear disaster, Japan suspended fishing in nearby waters over contamination concerns. And eventually, when they started  discharging treated wastewater, China straight-up banned fish from the area.

So we have to clean up these wrecks. Maybe we put the EPA on the job, or the International Atomic Energy Agency. …Or the CIA. We went with the CIA.

In 1968, the Soviet sub K-129 sank  in the Northern Pacific Ocean. By 1970, the CIA’s engineers  had a plan to retrieve it through a scheme called Project Azorian. This secret six-year mission  was really an effort to gain intel on Soviet military  capabilities during the Cold War, not the US cleaning up an accident  out of the goodness of their hearts.

Which is why the CIA took the helm. Though, as a bonus, it would clear the water of dangerous nuclear waste… if done right. The thing is, there was no  protocol for the right way to steal your enemy’s sunken nuclear submarine.

So CIA engineers determined that the best way to remove this nuclear waste was to play the world’s riskiest claw machine game, building what was essentially a giant grabber on a ship. And if anyone asked why this boat needed a giant grabber out in the middle of the ocean, the cover story was that it was a  vessel for deep sea marine research. This is going to be great for science.

Nobody ever thinks scientists  are secretly CIA agents because of stuff like this. Unfortunately, the claw device  they built for the job was just about as effective as the claw  machines that you’re familiar with. It brought the sub about halfway up before the sub broke apart and most of it, including the engine room  and presumably the reactor, fell back into the depths.

The CIA retained the portion that didn’t fall. And while they didn’t get  the intelligence they wanted, they still called it a success. Which I disagree with.

Not the resounding success they were hoping for, but they did also reportedly  get two nuclear torpedoes, so I guess it cleaned up some of the waste, and also gave them some intel. That might be the most dramatic  example of a sub retrieval, but there have been others. In 2001, most of one Russian submarine, the Kursk, was retrieved.

This time, they wouldn’t let it slip  through their giant metal claw fingers. They drilled holes through the hull  and put grippers through the holes. And I said most of it was  retrieved because they basically opted to avoid some of the  Project Azorian troubles entirely by not even trying to retrieve  the forward section of the sub.

They had legitimate reason to be  worried that it would break off and destabilize things as they  were lifting up the sub. So they left it behind. Sometimes it's just better to leave your mistakes in the past.

In another rescue, an American  sub called the USS Guitarro had the “good fortune” to sink in a  shipyard as it was being built. Which is nice because probably  not as many people died. The water was shallow enough that the top bit still stuck out of the water next to the pier.

So they could just temporarily dam the area, then pump all the water around it out, which let them go fix the problem and refloat it. And right now, Russia is constructing  their own specially made vessel to recover K-27 from the Kara Sea  and K-159 from the Barents Sea. The Kara Sea is part of the Arctic Ocean, and has already been used as a  dumping ground for nuclear waste.

So the Soviets figured it was the perfect place for a known radiation threat: K-27. K-27 had an on-board nuclear reactor leak, which killed nine crew members  from radiation poisoning. Thankfully, since the Russian Navy  knew it was a nuclear problem, they had the foresight to fill the reactor with tar before sinking it so  that it would be more stable.

However, that fix is only  designed to last until 2032, which is shockingly soon so, so they're going to have to do something about it. Researchers considered entombing  the sub where it was in concrete, but decided that the additional  pressure on the reactor from all that weight might actually  raise the risk of an explosion. So, yes, please bring that  up and do something about it.

Meanwhile, the K-159 wasn’t originally supposed to be sunk like the K-27. But it got so rusted between  decommissioning and attempted deconstruction that it fell  apart when they tried to move it. It sank along with 800 kg of nuclear fuel.

Whoops! Just... little woopsie K-159’s hull is too fragile to just lift it up. And a hole in the hull rules out pumping in air or balloons to raise it to the surface.

So the rescue team plans to have  a pair of barges lower down giant, curved grippers that get a hold  of the whole thing at once. Then they’ll lift it up  enough to slide a submersible platform underneath it for  further support before bringing the whole kit and kaboodle up to the surface. Hopefully, they’ll be more successful than many of our previous attempts to do this kind of thing.

Sunken nuclear submarines can’t stay  on the ocean floor indefinitely. I mean they can, but shouldn’t. But it’s quite a challenge to remove them.

While few seem to be immediate dangers, lost subs are still liabilities  to the local environment and the people around them. And that’s not even considering  new nuclear weapons that could also leave nuclear reactors  sitting at the bottom of the ocean. So maybe our best scientists  and engineers need to log some hours at the local  arcade with the claw machine.

This video was made possible  by the Outrider Foundation, an organization that supports  multimedia storytelling about nuclear threats and climate change. To learn more, head to outrider.org [♪OUTRO]