Scientists Inspect 200,000 Barrels of Radioactive Waste Dumped on Atlantic Seafloor

The site holds the legacy of a disposal practice that ran for more than three decades. The International Atomic Energy Agency now recommends that low-level waste be placed in robust containment and kept isolated for at least a few hundred years, but mid-20th-century guidelines were different: containers were required only to reach the seafloor intact and remain sealed long enough for short-lived radionuclides to decay. After that, the remaining material was expected to escape slowly and disperse through the surrounding ocean, so the corrosion observed on the seabed is not necessarily a departure from the original plan.

Not everything in the barrels would decay away on that timetable. They held a radioactive mixture that included cesium-137, plutonium isotopes and tritium, some of which can persist for thousands of years.

The investigation grew out of a question posed by nuclear engineer Patrick Chardon and marine geologist Javier Escartin of the French National Center for Scientific Research, who wondered what had become of the dumped material. That question became NODSSUM, the Nuclear Ocean Dump Site Survey Monitoring project, which brings together nuclear physics, geology, oceanography, biology and marine chemistry to locate the barrels and determine what effect, if any, they are having on the surrounding environment.

On the otherwise sparsely populated sandy seafloor, the barrels appeared to function as small oases. Anemones had attached themselves to the containers, and sponges, sea cucumbers, fish and crustaceans lived around them, with crabs apparently particularly drawn to the artificial shelters.

Instruments aboard the research ship detected significant signals of cobalt-60 and niobium-94 that the researchers could link specifically to the dumped waste. Samples collected at the site are now being analyzed.

There is precedent suggesting that even striking radioactivity around a source does not necessarily travel far. A recent study of the sunken Soviet submarine Komsomolets found radionuclide levels hundreds of thousands of times above background immediately around its leaking reactor, but those levels fell sharply within just a few meters as the material dispersed through seawater. The NODSSUM team likewise found that, despite the significant radioactive signals around the barrels, activity levels were not high enough to pose major radiation-protection problems for the scientists handling the samples. The three-person submersible Nautile and the instruments it carried showed no signs of contamination.

The team's central achievement, according to the account, was mapping the exact location of the barrels. The article concluded that none of this means the waste is harmless, but that it also does not mean the ocean is about to be overrun by radioactive crabs.