The 1986 Chernobyl disaster in Ukraine remains one of the worst nuclear incidents in history and highlighted the risks of generating power by splitting atoms. But it's not the only nuclear waste the Soviet Union left behind. Scattered across the ocean floor in the cold waters of the Arctic are nuclear submarines and reactors dumped by the Soviets up until the early 1990s.

Now, as energy companies are seeking to drill in those same waters, the Russian government has shown an interest in cleaning up its nuclear waste. But after decades of sitting on the ocean floor, some of the most dangerous pieces may be too unstable to remove, leaving the potential for radioactive material to leak, which could disrupt commercial fisheries and destroy aquatic ecosystems.

"Taking reactors and cutting out the bottom of your ships and letting them sink to the bottom is about as irresponsible as you can get when it comes to radioactive waste," Jim Riccio, a nuclear expert with Greenpeace, told VICE News. "We've had some weird [behavior] in this country where we haven't been all that great with it but nothing that rose to the level of what the Soviets had done."

Before the London Convention of 1972, an international agreement that prohibited marine dumping, countries were free to use the oceans as a trash heep for nuclear waste. Though the Soviets signed the treaty in the late 1980s, it wasn't until after the break up of the Soviet Union in 1991 that the Russians opened up to the international community about the extent of the Arctic dumping campaign.

'There could be environmental consequences if something goes wrong.'

Two years ago, the Russian government provided a tally: two submarines, 14 reactors — five of which contain spent nuclear fuel — 19 other vessels sunk with radioactive waste on board, and about 17,000 containers holding radioactive waste. The last known dumping occurred in 1993.

Of particular concern are the two submarines, the K-27, which was dumped into the Kara Sea in 1981, and the K-159, which sunk in 2003 into the Barents Sea, while being towed for dismantling. After an expedition to the K-159 last summer, Russian authorities concluded that there was no unusual radioactivity.

"There was no extra radiation from that submarine," Nils Bohmer, a nuclear expert at the Bellona Foundation, a Norwegian environmental nonprofit, told VICE News. "But later the Russian authorities said that within 10 to 15 years, a decision had to be made whether or not the sub should be lifted."

The Barents Sea borders both Norway and Russia and is vital to the Norwegian fishing industry. To the east is the Kara Sea, off the coast of Siberia.

The K-27 has highly enriched uranium on board, Bohmer said. Seawater could corrode the reactor and even kick-start a nuclear chain reaction. Ocean currents in those seas travel eastward and any contamination would move away from the active fisheries in the Barents Sea but could ultimately end up in US waters.

The K-159 is at risk of causing "environmental catastrophe," said Greenpeace Russia, because of deterioration of the reactor container. Any leak from the K-159 would affect fisheries for both the Russians and the Norwegians, Bohmer said.

But removing the subs carries their own risks, due to years of saltwater corrosion.

"If the Russians had the money, they would just start ahead with the lifting operation," Bohmer told VICE News. "But I think it's important that before they start the lifting, it is necessary to do this risk assessment. There could be environmental consequences if something goes wrong."

The Norwegian government has spent more than $126 million on Russian nuclear safety projects in the last two decades, according to the Norwegian Radiation Protection Authority.

The 17,000 dumped containers are also a potential disaster, creating a minefield for oil companies looking to drill in the area, particularly because the exact locations of most of the containers are unknown.

If the waste can't be removed, it could be protected with covers that would keep radioactive material contained in the event of a leak. But finding a material that can survive as long as nuclear waste is a big impediment.

"I doubt very much it's possible to build this on the bottom of the sea, which will last for as long as necessary," Bohmer told VICE News. "I hope that it's possible to lift those submarines. But it's quite a long process. You need to start to do the risk assessment already now."