Radioactive drums at sea: 70 years later, is there a risk for the marine environment?

Our oceans are filled with human-made waste. If one immediately thinks of pollution plastic, unfortunately clearly visible, there is another, hidden away from view, on the ocean floor. It is Radioactive wastepackaged in watertight metal drums, which were thrown into the sea between the 1950s and 1990s.

Armaments, energy, medicine, industry: the vast use of nuclear technology

The post-war period saw the rapid expansion of nuclear technology in many sectors. Armament and energy of course, with the construction of the first nuclear reactors, but not only. Medicine as well as industry have also greatly benefited from the progress of knowledge in this field. The medical x-rays or the use of radioactive tracers have also led to significant progress in medicine. On the industry side, the uses are also very numerous. Nuclear technology is used, for example, to sterilize certain foods, for irradiation.

All of these uses require the use of varying amounts of radioactive material and produce waste. Although the majority of this waste comes from the nuclear industry for the generation of energy, any object that has been in contact with a radioactive source is also considered, at the end of its use, as radioactive waste, because of its contamination. Nuclear technology therefore produces very varied types of waste, ash from the combustible of very high radioactive activity, to the gloves used by doctors during scintigraphswhich are of very low activity.

200,000 barrels of radioactive waste thrown into the sea

At the beginning of the 1950s, the various countries were quickly confronted to the problem of waste management which kept piling up. Some waste containing radionuclides long-lived also require management over the very long term, in a secure environment to prevent any radioactive leakage. Faced with this problem, the deep marine environment quickly appeared as a solution to get rid of this bulky waste. Especially since this environment, located more than 4,000 meters deep, was then considered desert and lifeless.

For 40 years, the United States and several European countries thus threw into the North Atlantic 200-litre metal drums containing various Radioactive waste. In total, around 200,000 drums, or several thousand tons of radioactive waste, now lie at the bottom of the ocean. France alone immersed more than 46,000 drums during two campaigns, in 1967 and 1969. No jurisdiction then regulated this type of dropping in international waters. It was not until 1975 that the London Convention established a moratorium on this practice, then a total ban in the early 1990s.

Although we can rejoice at the end of these discharges, it does not prevent certain barrels from sleeping at the bottom of the ocean for more than 70 years now, while their duration life was estimated at 20-25 years. According to the available data, the drums dumped at sea did not contain any high-level or long-lived waste. Most of this waste is classified as very low, low and intermediate level. But they would however contain different types of radionuclides, with behaviors, a toxicity and a very variable lifespan. A minimum of monitoring therefore seems necessary. However, apart from two scientific campaigns organized in the 1980s, no long-term action has been implemented.

Two oceanographic missions planned to take stock of the situation

During these two campaigns, only six barrels had been found, apparently in good condition. But what about thousands more? It must be noted that currently there is no data concerning the condition of the drums and any radioactive pollution. However, we now know that the abyssal plains represent fragile ecosystemsand that life is well established there.

Two oceanographic campaigns aimed at acquiring data on the condition of the drums and detecting any pollution are therefore planned. The first should take place in 2023 or 2024 and will focus on seabed mapping and on the location of the drums. Because one of the major problems that scientists will have to face is the lack of information concerning the location of the barrels.

Two zones of 6,000 km² will thus be screened. On the program: detailed mapping of the bottom, but also sampling of seawater near the drums found, in order to find out if there have been leaks of radionuclides and if so, in what form.

Indeed, it is not currently known how the radionuclides would behave in the event of damage to the drums. The question of their mobility is particularly crucial because, while some radionuclides can attach themselves to sediments and thus pose little danger, others could very well migrate into the water column. These could represent a risk for animals, although it is not yet known what their toxicity is or whether they are capable of being assimilated by living organisms.

These more specific questions will be the subject of the second mission to be held one year after the first. The complexity of the study will reside in the fact of succeeding in isolating the potential radioactive activity linked to the drums from the ambient activity resulting mainly from nuclear tests and discharges authorized by the power stations. Shells, sediments, Pisces will be sampled near the barrels in order to establish whether there has been contamination and if so, observe the effects.

Data that will be made available to the public

In total, about forty scientists will embark for each campaign. Ifremer’s UlyX autonomous submarineable to dive to 6,000 meters deep, will also be on the trip and in charge of taking photographs of the metal drums.

These two large-scale oceanographic missions are of vital scientific and public interest. They should make it possible to make a precise inventory of the location of the drums and the radioactive footprint of the seabed. In the event that leaks of radioactivity would be detected, new actions could be envisaged, or at least the establishment of more regular monitoring.

All the results and data of the two missions will be made available to the public, in complete transparencyassures the two heads of mission, Javier Escartin, of the Laboratory of geology from the École Normale Supérieure, and Patrick Chardon, from the Laboratory of Physical of Clermont-Ferrand.

The researchers estimate that the accumulation of submerged waste represents approximately 36 petabecquerels, which represents a radioactivity 300 times lower than that emitted by theaccident of Chernobyl. A quantity which, without being catastrophic, is far from negligible.