Sunken nuclear submarine is leaking radioactive material intermittently

In April 1989, the Soviet Navy’s nuclear submarine Komsomolets caught fire while cruising 335 m beneath the surface of the Norwegian Sea. It was able to surface and 27 of 69 crew members survived the ordeal. The vessel then sank and now lies in 1680 m of water about 180 km off the coast of Norway’s Bear Island.

As well as being powered by a nuclear reactor, the Komsomolets is believed to contain two torpedo-mounted nuclear warheads. Not surprisingly, people are very concerned about the wreck and the possibility of radioactive materials leaking from the vessel.

Indeed, a Russian expedition in 1994 revealed that plutonium was leaking from one of the warheads. The following year, fractures in the hull and the torpedo tubes was sealed. Since then measurements taken near the Komsomolets suggest that any radioactive leakage is rapidly diluted by the surrounding water.

Now, scientists in Norway led by Justin Gwynn and Hilde Elise Heldal, have completed a comprehensive analysis of data taken by a 2019 survey of Komsomolets. The wreck’s marine environment was explored using Ægir 6000, which is a remote-controlled vehicle that is equipped with an array of cameras and other instruments and is capable of diving to 6000 m.

Writing in the Proceedings of the National Academy of Sciences, the team says analysis of seawater and sediment samples collected near the torpedo compartment reveals no evidence of plutonium being released from the warheads. However, analysis of samples from near a ventilation pipe show that radioactive material is being released intermittently from the nuclear reactor. By measuring the ratio of plutonium to uranium in the region, the team concluded that the fuel in the reactor is corroding.

Despite releases over the past three decades, Ægir 6000 found little evidence that radionuclides were accumulating in the region of the wreck – most likely because of the diluting effect of seawater.

The research is described in PNAS, where the team concludes, “Considering the global increase in military activities and geopolitical tensions, the fate of Komsomolets and the nuclear material within it can provide us with important insights as to impacts of any future accident involving nuclear powered vessels and nuclear weapons at sea”.

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