The Fate of a Soviet Nuclear Sub Decades After It Sank
On April 7, 1989, the Soviet nuclear-powered submarine K-278 Komsomolets carrying two nuclear warheads was moving silently beneath the frigid waters off the Norwegian coast of Bear Island when disaster struck. A short circuit in the technical compartment triggers a fire which spreads through the partitions, feeding as the cables pass through.
As the submarine’s electrical systems failed, the nuclear reaction powering the ship was shut down and its crew abandoned ship. The submarine came to rest on the ocean floor, 5,500 feet underwater, where it remains today. Today, new research published in the Proceedings of the National Academy of Sciences reveals his fate.
In 2019, Justin Gwynn of the Norwegian Radiological and Nuclear Safety Authority and researchers from the Institute of Marine Research conducted a study of the Komsomolets wreck using a remote-controlled deep-sea submersible. They took video of the wreck, sampling the surrounding water, marine life and sediment to measure radioactivity. Gwynn’s recently published analysis of data collected during the investigation shows the extent of the damage.
The researchers discovered that the forward section of the submarine had been destroyed, exposing the torpedo compartment containing the nuclear weapons to seawater. Fortunately, their analysis showed no signs of a plutonium leak. Titanium plates installed by the Russian government more than 30 years ago to prevent seawater from passing through the torpedo compartment remained in place.
The nuclear reactor is another story. Readings from samples taken around one of the ventilation pipes detected the continued release of radioactive isotopes, albeit intermittently. Levels of radioactive strontium and cesium (two isotopes generated by nuclear fission) were 400,000 and 800,000 times higher, respectively, than normal seawater. Samples of sponges, corals and anemones also showed high concentrations of radioactive cesium.
According to the researchers, the levels of plutonium and uranium isotopes detected indicate that the nuclear fuel in the reactor is corroding. Fortunately, radiation does not accumulate. Instead, radiation levels show a sharp drop within a few meters of the submarine wreckage, indicating that it is diluted by seawater. Sediment samples also showed no signs of elevated radioactivity.
Overall, this may seem like the best-case scenario for a sunken nuclear submarine (one of nine we know of), but it’s unclear what the future holds for the Komsomolets. Researchers say radioactive material will continue to seep from the submarine into the ocean as reactor corrosion progresses, and continued research will be needed to monitor it. 
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Main image: Marine Research Institute / Ægir6000
