Decades ago, several countries dumped barrels of nuclear waste in the middle of the Atlantic.

Dumping nuclear waste into the ocean seems absurd from today's perspective. Yet that's exactly what happened on a large scale between the 1950s and 1980s. At least 200,000 barrels are believed to be in the Northeast Atlantic alone. A team of European researchers is now searching for the barrels and is traveling to the area where probably half of the waste ended up. Also on board is a scientist from the Thünen Institute of Fisheries Ecology in Bremerhaven.

With the advent of nuclear power in Europe, many countries also faced the question of nuclear waste disposal. The depths of the ocean, far from shore and human activity, appeared to be a cheap and easy solution for disposing of the waste produced in laboratories during industrial development—at least where the ocean was considered geologically stable. At that time, little was known about life in the world's oceans. It wasn't until 1993 that the disposal of nuclear waste in the ocean was finally banned.

Patrick Chardon, head of the NODSSUM (Nuclear Ocean Dump Site Survey Monitoring) project, assumes that the radioactivity of the vast majority of nuclear waste that landed in the North Atlantic will be virtually gone after about 300 to 400 years. Only about two percent of the waste has a significantly longer radiation duration, said the nuclear physicist, who works at the Clermont Auvergne Laboratory in Clermont-Ferrand.

According to Chardon, the barrels were designed to withstand the pressure at depth, but not to actually contain the radioactivity. The physicist suspects that radioactivity may have been escaping from the containers for some time.

In the project, 21 scientists plan to spend a month tracking down the barrels, which are believed to be located at a depth of 3,000 to 5,000 meters. The search area is located more than 1,000 kilometers west of La Rochelle in the Western European Basin of the Atlantic.

The goal is to reassess the consequences of marine waste disposal and examine the state of the ecosystem. The experts plan to create a map of nuclear waste barrel finds and take numerous samples of water, soil, and animals. They also plan to examine a reference area for later comparison.

The team is supported by an autonomous diving robot. The Ulyx robot can descend to depths of up to 6,000 meters. In addition to physical and chemical sensors, it is equipped with a camera for 3D images and a sonar system for locating objects using sound. Using the robot's images, the experts hope to track the individual barrels and their condition, as well as record their position. The exact location of the containers, whether they are lying individually or in groups, and whether they are still intact are currently unknown.

Co-project leader Javier Escartin of the ENS University in Paris estimated that it would take the team years to search the entire area of ​​their study. They aim to cover approximately 200 square kilometers in various zones over the four weeks. Based on the robot images, the scientists will then decide exactly where to sample water or animals.

In addition to the amount of radioactivity, researchers are also interested in the environment of the waste - for example, whether the radiation is blocked by sediments or what influence deep currents have.

What consequences the barrels could have? "That's really unknown," said Escartin. "We don't even know the basic ecosystem in the area very well." This is because the deep-sea plain is largely unexplored. From the marine geologist's perspective, exploring the area will therefore be of interest beyond the nuclear issue. "Every piece of information will be useful for better understanding the system."

After the four-week mission, the collected samples will be sent to various laboratories in Europe. The scientists then plan to set sail again to collect even more targeted samples. An exact date for the second mission has not yet been set. Escartin hopes it will be next year.