A sunken Cold War-era nuclear submarine is quietly leaking radioactive material into the deep, dark waters at the bottom of the Norwegian Sea, a survey has determined. The Soviet K-278 Komsomolets sank after an on-board fire in April 1989, carrying not just the nuclear reactor that powered her, but two nuclear torpedoes. Now, the results of a dedicated survey led by marine radioecologist Justin Gwynn of the Fram Centre’s Norwegian Radiation and Nuclear Safety Authority reveal that the ongoing decay of the submarine hasn’t yet caused the devastation it’s capable of. While the torpedoes remain sealed, the reactor is degrading, periodically releasing visible plumes of radioactive material into the water, Gwynn and colleagues report in a new paper. “Releases from the reactor have occurred for over 30 years,” the researchers write, but “there is little evidence of any accumulation of radionuclides in the near environment around the submarine as the released radionuclides appear to be rapidly diluted in the surrounding seawater.”
The wreck of the Komsomolets was a tragic disaster that resulted in the deaths of most of the crew, and left a long-term radioactive hazard in the permanent darkness 1,680 meters (5,510 feet) below the surface of the Norwegian Sea. Ongoing monitoring of the wreck since the 1990s has indicated intermittent radioactive leakage. Early investigations showed that the submarine was significantly damaged, the hull was cracked open, and seawater was in contact with the nuclear torpedoes. Major work was undertaken to seal the damaged torpedo compartment in 1994, and there has been no evidence of weapons-grade plutonium leakage in the surrounding environment. However, ongoing annual investigations by the Norwegian government revealed radioactive cesium isotopes in the water around the submarine.
In 2019, scientists undertook a major survey, using a remotely-operated vehicle (ROV) called Ågir 6000 to sample the water and life around Komsomolets, and assess the damage to the vessel itself. At the time, it was clear that the submarine was leaking. Now, Gwynn and his colleagues have finished analyzing the data collected, and have quantified the leak, its source, and its effects on the seabed ecosystem. The team found that the leak is not constant but occurs in sporadic bursts from specific locations along the hull, including a ventilation pipe and the area around the reactor compartment. The ROV recorded video of visible plumes seeping out into the sea.
Samples of those plumes revealed levels of isotopes of strontium, cesium, uranium, and plutonium. Close to the vessel, the researchers report, the levels of strontium and cesium were “400,000 and 800,000 times higher, respectively, than typical levels of these radionuclides in the Norwegian Sea.” The elevated levels and ratios of uranium and plutonium…
