Soviet submarine leak and Pacific nuclear dome raise contamination concerns
Scientists are raising fresh concerns over two Cold War-era nuclear sites that continue to release radioactive materials into the world’s oceans. A new study has confirmed ongoing leaks from a sunken Soviet submarine in the Norwegian Sea, while structural weaknesses in a US-built nuclear waste dome in the Marshall Islands are drawing renewed scrutiny as sea levels rise.
Research published on March 23 in the Proceedings of the National Academy of Sciences found that the Soviet nuclear submarine K 278 Komsomolets is actively leaking radioactive substances as its reactor continues to corrode on the seabed. The submarine sank in 1989 following a fire that killed 42 crew members and now rests at a depth of 1,680 meters. It carried two nuclear torpedoes containing a total of 12 kilograms of plutonium in addition to its onboard nuclear reactor.
The study, led by marine radioecologist Justin Gwynn of the Norwegian Radiation and Nuclear Safety Authority, analyzed data collected during a 2019 expedition using a remotely operated vehicle. Researchers detected intermittent plumes of radioactive strontium, cesium, uranium, and plutonium escaping from the hull. Measurements showed strontium levels up to 400,000 times higher and cesium levels up to 800,000 times higher than typical background concentrations in the Norwegian Sea.
Despite these readings, the contamination appears to decline sharply within a short distance from the wreck. Previous efforts in the 1990s to seal the torpedo compartment remain intact, limiting immediate spread. Marine organisms living on the hull showed slightly elevated cesium levels but no visible signs of damage. However, scientists warned that the reactor fuel is still degrading and the submarine’s structure will continue to weaken over time, increasing the risk of further leakage.
Thousands of kilometers away, a separate nuclear concern is unfolding in the Pacific. The Runit Dome in the Marshall Islands, built to contain radioactive debris from US nuclear tests, is showing visible cracks as rising sea levels threaten its stability. The concrete structure, about 115 meters wide, was constructed between 1977 and 1980 as a temporary containment solution. It covers more than 120,000 tonnes of radioactive waste, including plutonium 239, which remains hazardous for over 24,000 years.
The dome sits on a porous coral base, allowing groundwater to seep through. Ivana Nikolic Hughes of Columbia University, who examined the site during soil sampling, reported elevated radiation levels outside the structure. She warned that increasing storm intensity and rising sea levels could compromise the dome’s integrity, raising the risk of contamination spreading across the atoll.
A 2024 assessment by the Pacific Northwest National Laboratory, part of the US Department of Energy, identified storm surges and gradual sea level rise as the main threats to the containment system. Much of Runit Island lies only about two meters above sea level, making it highly vulnerable to climate-driven changes. Scientists project that sea levels around the Marshall Islands could rise by up to one meter by 2100.
Researchers studying the Komsomolets emphasized the importance of continued monitoring, noting that the wreck provides critical insight into long term risks from submerged nuclear reactors in Arctic waters. For residents of the Marshall Islands, the risks are more immediate. Local communities face growing uncertainty as environmental pressures increase and containment systems show signs of strain.
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