Norway Surveys Sunken Soviet Submarine

Norwegian researchers have completed a survey of a sunken Soviet-era nuclear submarine that went down 30 years ago. The research team found that the sub is leaking a small amount of radiation from its reactors, but that it poses no threat to the surrounding environment.

The vessel, known as Komsomolets, was a one-of-a-kind attack submarine. Its hull was made of titanium, allowing it to operate at depths of more than 3,000 feet — far below what U.S. submarines could achieve at the time. It was powered by two reactors and carried both nuclear and conventional weapons.

On April 7, 1989, a high-pressure air line connected to the sub's main ballast tanks burst. The failure sparked a fire aft that slowly worked its way forward through the submarine. Of the 69 crew, only 27 survived the incident, and the submarine sank to the ocean floor in the Norwegian Sea.

Norwegian authorities monitor conditions around the wreck on an annual basis, says to Hilde Elise Heldal, who led the latest expedition by the Institute of Marine Research in Bergen. "But this year we got the unique opportunity to do sampling with a remote operated vehicle."

Undersea video of the wreckage. IMR YouTube

The robotic mini-sub allowed them to take samples from the submarine itself. When the researchers sampled water from a ventilation pipe leading to the sub's reactor, they measured elevated levels of cesium-137. The radioactive cesium is leaking from one of the nuclear cores, Heldal says.

The radiation level in the pipe was far above what's found in the surrounding seawater; however, Heldal says it's not particularly worrying.

"I don't think it poses any threat to either fish or humans," she says. The radioactive cesium is quickly diluted: measurements just a few feet above the opening showed no elevated radiation levels.

Enlarge this image toggle caption STF/AFP/Getty Images STF/AFP/Getty Images

The Komsomolets wreck also has two nuclear-tipped torpedoes on board. Heldal says that the robotic submersible took samples near the torpedo compartment to see if the material in the weapons had contaminated the local environment, but that analysis will be done in a laboratory in coming weeks.

The survey comes just a week after fire aboard a secret Russian nuclear-powered submersible killed 14 naval officers. Russian authorities maintain that the fire was contained and that the submersible's reactor was not affected. As of last Thursday, officials with the Norwegian Radiation and Nuclear Safety Authority said they had seen no indication of radioactive emissions from the most recent incident.