More than 200,000 barrels of low-level radioactive waste were stored on the floor of the Atlantic Ocean between 1949 and 1982, [1]reports ScienceAlert .

Whatever happened to those barrels?

> Scientists have descended to the wreckage in a crewed submersible to investigate — and found many of the barrels [2]corroded and degraded, their contents spilling across the seafloor. Surprisingly, this isn't necessarily a subversion of the original plan... The International Atomic Energy Agency [3]recommends that low-level waste be disposed of in robust containment in isolation for at least a few hundred years — but back in the mid-20th century, the recommendations were a little different. The contemporaneous guidelines recommended that containers needed to reach the seafloor intact and remain sealed only long enough for the short-lived radionuclides to decay. After that, the remaining waste was expected to slowly escape and disperse through the surrounding ocean. Not everything in the barrels would conveniently decay away, however. They contained a radioactive hodgepodge, including cesium-137, plutonium isotopes, and tritium, some of which can persist for thousands of years...

>

> [A] few years ago, nuclear engineer Patrick Chardon and marine geologist Javier Escartín of the French National Center for Scientific Research started to wonder what had become of the dumped waste. That question eventually became [4]NODSSUM — Nuclear Ocean Dump Site Survey Monitoring — an interdisciplinary project bringing together nuclear physics, geology, oceanography, biology, and marine chemistry to find the barrels and investigate what, if anything, they were doing to the surrounding environment.... [T]he barrels also appeared to function as tiny oases on the otherwise sparsely populated sandy seafloor. Anemones had attached themselves to the barrels. Sponges, sea cucumbers, fish, and crustaceans lived around them, with [5]crabs apparently particularly fond of the artificial shelters ...

>

> Instruments aboard the ship [6]detected significant signals of cobalt-60 and niobium-94, which the researchers could specifically link to the dumped waste... [Samples are now being analyzed] There is precedent, however, to suggest that even striking levels of radioactivity around a source don't necessarily spread very far. A [7]recent study of the sunken Soviet submarine Komsomolets found radionuclide levels hundreds of thousands of times above background immediately around the leaking reactor — but those levels dropped sharply within just a few meters as the material dispersed through the seawater. The NODSSUM team similarly found that, despite the significant radioactive signals around the barrels, activity levels weren't high enough to pose major radiation-protection problems for the scientists handling the samples. [Their three-person submersible] Nautile and the instruments it carried showed no signs of contamination.

The real achievement was mapping the exact location of the barrels. "None of this means the waste is harmless," the article concludes — but it also doesn't mean we're about to be overrun by radioactive crabs."



[1] https://www.sciencealert.com/150000-tons-of-radioactive-waste-were-dumped-in-the-atlantic-decades-later-its-visibly-oozing

[2] https://bsky.app/profile/did:plc:ofafcv55i5fdtv7o6nnoklkn/post/3mpnpwiaiq22x

[3] https://vocabulary.iaea.org/iaea-safety-glossary/211.html

[4] https://miti.cnrs.fr/radiocean/

[5] https://www.lemonde.fr/planete/article/2026/07/02/futs-de-dechets-radioactifs-au-fond-de-l-ocean-atlantique-ce-que-les-scientifiques-ont-vu-par-pres-de-5-000-metres-de-fond_6717801_3244.html

[6] https://www.ens.psl.eu/en/node/9080

[7] https://www.sciencealert.com/sunken-soviet-submarine-is-leaking-radioactive-material-in-the-ocean