[France24] For nearly five decades, more than 200,000 barrels of radioactive waste were dumped in the icy depths of the northeast Atlantic. Today, no one knows precisely where these barrels are located, or what kind of state they are in. On June 15, a French-led team of scientists will set sail from Brittany in a bid to map the barrels and assess their impacts on surrounding marine ecosystems.
It had long been considered a safe way to dispose of radioactive waste. For nearly five decades, tens of thousands of tonnes of waste – sealed in watertight barrels of asphalt and cement – were dumped in international waters.
Although the practice is now banned, between 1946 and 1993, 14 European countries – including France and the UK – carried out dumping operations at more than 80 locations in the Arctic, Atlantic and Pacific.
In the northeast Atlantic, home to the most concentrated stretch of this radioactive marine waste, some 200,000 barrels lie at a depth of 4,000 metres. On June 15, a team of scientists from the CNRS (France’s National Centre for Scientific Research), Ifremer (the French national institute for ocean science and technology) and the French oceanographic fleet, will set sail from the Brittany port of Brest in a bid to locate the barrels.
The team of nuclear physicists, geologists, oceanographers, biologists and marine chemists will be joined by UlyX, a 4.5 metre autonomous underwater robot that will be their eyes and ears during the 26-day expedition.
"The robot can dive to a depth of 6,000 metres,” explained geophysicist Javier Escartin, who will co-lead the mission. “It will be able to use sonar-type systems to map large areas and detect where barrels are located. It will also be able to get close to the seabed and take photographs, enabling us to assess the barrels’ condition, establish where they are scattered, and to plan further studies at a later date."
A STABLE ENVIRONMENT
The submerged barrels, which have a lifespan of between 20 and 26 years, are now long past their expiry date.
In 2000, the environmental NGO Greenpeace filmed barrels of waste at the site closest to the French coast, the Casquets trench in the English Channel, used to dump waste by Belgium and the UK. Their footage showed the rusting barrels were badly degraded and corroded.
However, the barrels dumped at sea do not contain the most hazardous waste. Most of the waste is classified as very low-, low- and medium-level radioactive waste, according to the available data.
In addition, the radioactivity emitted by radioactive waste gradually diminishes over time. The time it takes for a radioactive substance to decrease by half is called the half-life. However, this half-life period varies greatly – depending on the type of atom or radionuclide. For instance, it is approximately two years for caesium 134, approximately 13 years for plutonium 241, approximately 30 years for caesium 137 and some 4.5 billion years for uranium 238.
The radioactive waste comes in two forms: either solid or liquid. Solid waste is surrounded by a concrete or bitumen matrix before being sealed in a watertight barrel. Only the former USSR and the United States have dumped other types of waste, such as nuclear reactor tanks, some of which still contain fuel, reported the French National Agency for Nuclear Waste Management (Andra).
The total radiological activity of the submerged waste was around 85,000 terabecquerels when it was released into the ocean, Andra added.
In the postwar period, as nuclear technology spread to many sectors of activity, developed countries viewed dumping waste in deep waters as a safe option. The deep ocean is one of the most stable environments on Earth and scientists mistakenly believed it to be deserted and devoid of life.
On their return to dry land, the scientists will spend several months studying the samples taken near the radioactive barrels. A second mission to refine the results will then be scheduled. All the data from both missions will be made available to the public in the interests of transparency.
“This is not a mission to assess whether the releases were well or badly done,” warned Escartin. "It's an opportunity to look at what was done in the past, without passing judgment, to carry out scientific studies. Afterwards, of course, we'll have to conduct a complete inventory, because we need one."
However, during the mission, the scientists will only be able to assess the condition of a small fraction of the 200,000 barrels in the northeast Atlantic. And on each dive, the UlyX autonomous robot will only be able to focus on an area of around 20 square kilometres – a drop in the ocean given that the two research areas where the submerged barrels lie covers more than 6,000 km2. 
|
