Over 30 years after it sank, a Soviet nuclear submarine is still leaking radioactive material in the deep sea. Scientists have now confirmed that these releases can even be observed as plumes, although their impact so far remains surprisingly limited.
The K-278 Komsomolets sank in April 1989 after a fire broke out on board. It was carrying a nuclear reactor and two nuclear torpedoes when it went down to a depth of 1,680 meters. Since then, the site has been closely monitored due to the potential risks involved.
Early inspections revealed significant damage, including a cracked hull that allowed seawater to enter parts of the submarine. A repair operation carried out in 1994 sealed the torpedo compartment. According to Norwegian monitoring efforts, there has been no evidence of weapons-grade plutonium leaking from those torpedoes since.
Visible Radioactive Plumes Caught On Camera
In 2019, researchers sent down the remotely operated vehicle Ægir 6000to take a closer look. Results later published in PNAS showed that the submarine does not leak constantly but in irregular bursts from specific points on the hull.
The footage shows actual plumes drifting out into the water, especially near a ventilation pipe and around the reactor section. Samples taken from these plumes contained radioactive elements such as strontium, cesium, uranium, and plutonium.
The scientists stated the levels of cesium and strontium right next to the wreck were up to 800,000 and 400,000 times higher than normal in the Norwegian Sea. The mix of uranium and plutonium also suggests that the reactor fuel itself is slowly breaking down.
Contamination Drops Off Just Meters Away
In the study, the research team explained that the radiation levels fall sharply just a few meters from the submarine as the seawater rapidly dilutes the released material. Creatures living on the submarine, including sponges, corals, and anemones, do show slightly higher levels of radioactive cesium.
Still, researchers did not observe deformities or clear signs of damage. Sediment samples from the surrounding seabed also show very little contamination. This suggests that even after decades of leakage, the impact remains very localized.
A Submarine Wreck That Will Keep Changing Over Time
The torpedo section appears stable for now, but the reactor is another story. The authors of the study reported that the leaks come in bursts because of ongoing corrosion processes inside the damaged reactor.
The submarine’s structure will keep weakening as it sits in the deep sea. Scientists see the Komsomolets as a rare case that can help understand what happens to nuclear material left underwater for long periods.
“Komsomolets provides a unique opportunity to understand the risks and consequences of releases from other sunken or dumped reactors in the Arctic as well as risks from any further accidents involving nuclear powered vessels and any other type of nuclear technologies used at sea,” the authors wrote.
They stress that continued monitoring is needed to track how the situation evolves and to better understand what might happen next.
“Further investigations should be carried out to determine the mechanisms behind the observed releases, the corrosion processes that are occurring within the reactor, and the implications of these for further releases and the fate of the remaining nuclear material in the reactor,” they added.
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