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Norwegian researchers descended almost 1,700 meters into the Norwegian Sea with a submarine robot and filmed plumes of radioactive material leaking from the hull of a Soviet submarine that has been carrying a nuclear reactor and two atomic torpedoes since 1989
Published in 2026 in the journal Proceedings of the National Academy of Sciences (PNAS), the study led by Justin P. Gwynn revealed that the Soviet submarine K-278 Komsomolets is intermittently leaking radioactive material on the bottom of the Norwegian Sea.
The K-278 sank on April 7, 1989, after an onboard fire that killed 42 of the 69 crew members.
Since then, it has rested at a depth of 1,680 meters with a nuclear reactor and two nuclear torpedoes.
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That’s 37 years on the ocean floor — and the reactor is degrading.
Radiation 800,000 times above normal detected near the hull
Researchers used the ROV Ægir 6000, a remotely operated submarine robot, to conduct four separate dives around the Komsomolets.
They collected samples of water, sediments, and living organisms from the region.
The numbers are alarming.
Near a metal grate on the submarine’s hull, the concentration of cesium-137 reached 800,000 times the typical background level of the Norwegian Sea.
Furthermore, strontium-90 was detected at 400,000 times above normal.
And plutonium — one of the most dangerous radioactive materials known — appeared in concentrations 66 times higher than the historical averages recorded between 1993 and 2022.
The ROV’s cameras filmed visible plumes of radioactive material leaking from the submarine during so-called intermittent “release events”.
However, the good news is that contamination drops drastically a few meters away from the hull.
How the Komsomolets sank: the 1989 fire that the Soviet Union tried to minimize
The K-278 Komsomolets was considered one of the most advanced submarines in the Soviet Navy.
Built with a titanium hull — a very rare material in submarines of that era — it could dive to depths that no other attack submarine in the world could reach.
On April 7, 1989, a fire broke out in the aft compartment during a patrol in the Norwegian Sea.
The flames spread rapidly through the compartments.
The submarine surfaced, but could not be saved.
Of the 69 crew members on board, 42 died — many from hypothermia in the icy Arctic waters while awaiting rescue.
The K-278 sank with its nuclear reactor still active and two torpedoes equipped with nuclear warheads.
The Soviet Union had already demonstrated extreme ambition by drilling 12,262 meters into the Earth’s crust in Kola — and the Komsomolets was another example of this engineering philosophy pushed to its limits.
The nuclear torpedoes are intact — but the reactor is degrading
One of the scientists’ biggest concerns was the state of the two nuclear torpedoes on board.
However, the study brought partial relief.
The nuclear warheads were found intact, with no detectable release of radioactive material.
Thus, the risk of plutonium contamination from the torpedoes remains controlled — for now.
Furthermore, the emergency sealing work carried out in 1994 by Russian and Norwegian teams is still functional.
However, the reactor is another story.
The intermittent releases of cesium-137 and strontium-90 indicate that the reactor’s containment is gradually failing.
On the other hand, the study concluded that “radionuclide releases from the Komsomolets reactor to date have not impacted the immediate or wider marine environment.”
Norwegian monitoring programs have not detected unusual concentrations in the Norwegian Sea or the Barents Sea.
The bigger problem: there are dozens of nuclear reactors on the ocean floor
The Komsomolets is not the only nuclear submarine on the seabed.
The Soviet Navy lost at least four nuclear submarines between the 1960s and 1980s.
The modern naval race for autonomous submarines and naval drones raises an inevitable question: what will happen to the reactors of these new vehicles if they sink?
In the United States, 123 retired submarine reactors are stored in concrete coffins in the Hanford desert, in Washington state.
However, the Soviet reactors on the ocean floor did not receive this treatment.
They are exposed to pressure, corrosion, and time — without anyone being able to intervene at 1,680 meters deep.
- K-278 Komsomolets: 1,680m, Norwegian Sea, 1 reactor + 2 nuclear torpedoes
- K-27: intentionally dumped in the Kara Sea in 1981, with reactors on board
- K-159: sank in 2003 while being towed for decommissioning, 800 kg of nuclear fuel
- K-219: sank in 1986 in the Atlantic with 16 nuclear missiles on board
The issue is that none of these reactors will last forever on the seabed.
Monitoring continues — and the risk increases over time
Norway maintains continuous environmental monitoring programs in the Norwegian Sea and the Barents Sea.
So far, no significant contamination has been detected outside the submarine’s immediate zone.
But time is against it.
The Komsomolets’ titanium hull resists corrosion better than conventional steel — but it is not eternal.
The pressure at 1,680 meters is brutal: more than 170 atmospheres continuously compressing the structure.
And the sealing materials installed in 1994 — over 30 years ago — have a limited lifespan.
If the reactor’s containment fails more broadly, the releases that are currently “intermittent” could become continuous.
Still, there’s a caveat: oceanic dilution at this depth is enormous, and researchers emphasize that the current risk to the human food chain remains insignificant.
The full study is available in the
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