Dangerous contaminated sites in the North Sea and Baltic Sea
Millions of tons of contaminated waste can be found in our oceans. Among them are munitions and poison gas grenades on the bottom of the North and Baltic Seas - dangerous legacies, according to the Fraunhofer Institute's "Forschung Kompakt" communication. One of many environmental hazards: The old ordnance rusts and releases its toxic contents. Removal is dangerous, time-consuming and expensive.
Around 1.6 million tons of conventional and 220,000 tons of chemical warfare agents, according to current estimates of contaminated sites, are stored at the bottom of the North and Baltic Seas and have been rotting away for decades - an enormous potential hazard for flora and fauna as well as for salvage personnel. For this reason, Fraunhofer researchers are working with salvage companies to develop a robotic system that enables semi-automatic disposal.
Explosive samples from the anchor mine
Increasingly, these explosive legacies of war are becoming a problem. Construction sites at sea are increasing, new shipping lanes have to be cleared, pipelines built, and submarine cables laid to connect wind farms to land. The arsenal of weapons that the explosive ordnance disposal services detect ranges from pistol cartridges and bazookas to sea mines, explosive bombs, incendiary bombs, torpedoes and poison gas grenades.
Most of the explosive cargo was dumped in the sea at the end of World War II. Fishermen were ordered by the Allies to dump the ordnance in designated areas far out at sea. But apparently some dumped the cargo much earlier into the sea to save fuel. As a result, there is a lot of ordnance outside the marked munitions areas as well. In addition, old mines, torpedoes, and bombs are being relocated by strong currents and bottom trawling.
Mines in shipping channels
Thus, the divers of the Explosive Ordnance Disposal Service repeatedly have to clear ammunition from fairways that were thought to be free of mines. Thanks to sensitive sonar technology and magnetic probes, it is now easier to detect war debris - and all the more bombs, shells and mines are discovered. However, clearance has so far only been possible with dangerous manual labor by divers from the explosive ordnance disposal services or specialized companies. Large bombs cannot be recovered: Often the change in pressure is enough for them to explode.
Therefore, they are relocated to the known munitions areas or blown up on site. In the process, however, some of the toxic explosives are dispersed over a wide area in the water. In addition, marine life such as porpoises or fish can be fatally injured by an explosion.
A "salvage and disposal" procedure
New environmentally friendly, non-hazardous and economical solutions are needed to dispose of the quantities of explosive war heritage. For example, with funding from the German Federal Ministry for Economic Affairs and Energy, researchers at the Fraunhofer Institute for Chemical Technology ICT in Pfinztal, together with the University of Leipzig and several industrial partners, are developing a "Robotic Underwater Salvage and Disposal Method including Technology for the Delaboration of Munitions in the Sea", or RoBEMM for short. The project is coordinated by the explosive ordnance disposal company Heinrich Hirdes EOD Services GmbH. "The long-term goal of the project," explains Paul Müller of the Fraunhofer ICT, "is to render the ammunition harmless directly at the site of discovery underwater in a partially automated process and to dispose of it in an environmentally friendly manner." Automatic Klein GmbH is responsible for the automation and connection of the subcomponents.
Fraunhofer ICT contributes its core competence in the safety-related analysis and characterization of hazardous substances. The task was to design the handling of explosives in all process steps in such a way that the unavoidable residual risk of a spontaneous explosion is minimized. This ranges from ammunition handling and dismantling to explosives destruction and residue handling. An important element is reducing the sensitivity of the explosive by adding water and then crushing it. Then the metal casings are cleaned and the explosives are incinerated so that only metal scrap is brought ashore.
Each bomb is different
Even after more than 70 years, the warfare agents are dangerous. The explosives can still explode, and the degradation substances are highly toxic. The researchers at the Fraunhofer ICT have found, for example, that the impact sensitivity of the explosives can even be increased. To avoid spontaneous detonation, the utmost care must be taken during handling. One problem is the extremely varied ammunition formats.
At the end of the war, all materials still available were used for the production of ammunition. Therefore, you never really know what ingredients are present and how they might suddenly react with each other. "From the safety studies of the explosive mixtures actually used at that time, we were able to deduce what had to be taken into account during handling," says safety expert Paul Müller.
Initial tests are now being undertaken with the new RoBEMM salvage and disposal system to replace the currently dangerous diving operations and the often alternative-less blasting of munitions.
