Thirty-seven years after it sank, the Soviet nuclear submarine K-278 Komsomolets continues to release radioactive elements into the Norwegian Sea. In July 2019, a Norwegian robot found up to 791,700 becquerels of cesium-137 per cubic meter in one of the submarine's ventilation ducts, which is up to 800,000 times higher than the normal level for the region, which is around 1 Bq/m³. The robot’s cameras recorded a plume escaping from the wreck. The submarine lies at a depth of 1,680 meters in the Norwegian Sea, where it sank on April 7, 1989, after catching fire and sinking approximately 180 kilometers southwest of the Island of Bears. Of the 69 men on board, 42 died and 27 survived. Five years before the sinking, in 1984, this titanium-hulled submarine set a diving record, becoming one of the deepest vessels of its time. According to a recent study, a left-side ballast supply pipe may have ruptured, allowing high-pressure air to enter compartment 7 and cause the fire to become an explosive blaze. The submarine now rests at a depth of 1,680 meters, containing its reactor and two nuclear-tipped torpedoes. Initial inspections showed a cracked hull and seawater in contact with the torpedoes, and intermittent discharges have been monitored since the 1990s. The hull breaches were sealed between 1994 and 1996. In July 2019, the remotely operated vehicle Ægir 6000 was deployed to investigate the wreck. It collected water, sediments, and organisms around the submarine while filming the condition of the vessel. The highest measurement was recorded in the ventilation duct: 791,700 Bq/m³ of cesium-137, compared to about 1 Bq/m³ in ordinary seawater in the Norwegian Sea. Strontium-90 showed a similar trend, peaking 400,000 times higher than usual levels. Plutonium was 66 times more concentrated than the average found in seawater samples collected by surface ships between 1993 and 2018 and again between 2020 and 2022. Uranium was also higher in the same area. The study, published in March 2026 in the Proceedings of the National Academy of Sciences, was led by Justin Gwynn, a radiologist at the Norwegian Radiation Protection Authority based at the Fram Centre. The isotope ratios of plutonium (240 over 239) and uranium (236 over plutonium 239) indicate that the reactor fuel is corroding. The discharges are intermittent and originate from the reactor, not the warheads: the torpedoes remain sealed. The plumes visible in the robot's footage correspond to these episodes. Despite over 30 years of discharges, researchers see few signs of accumulation around the wreck. The radionuclides dilute quickly in seawater, and levels drop sharply a few meters from the hull. The sediments do not show high radioactivity, and the organisms collected on and around the submarine, including sponges and corals, only show minimal traces. The authors consider it likely that the reactor’s discharges continue and call for new investigations into the mechanisms of these discharges, the corrosion inside the core, and the fate of the remaining nuclear material. The warheads of the two torpedoes remain a long-term concern, even though nothing has leaked so far. The Komsomolets is among the nine known sunken nuclear submarines, but it is the only one of the series to have been filmed leaking.