When containers rust

In 2011 an important discovery was made by the HZDR scientists Dr. Regina Kirsch and Dr. Andreas Scheinost. They were able to demonstrate that the ferrous minerals that form as corrosion products on rusting containers bind plutonium, which is a particularly problematic element due to its longevity and radiotoxicity. In order to simulate the conditions pertaining in radioactive waste repositories, the researchers put a great deal of time and effort into producing samples in the laboratory and measuring them on the Rossendorf Beamline at the European Synchrotron (ESRF) in Grenoble. A particularly significant feature of such repositories is the absence of oxygen, with the result that all chemical processes take place in an “anoxic” environment. In the past, other research groups had studied the reactions of these highly radioactive wastes at atmospheric oxygen concentrations because it was technically easier to do so. Scheinost and Kirsch showed that under anoxic conditions plutonium is more strongly reduced than was previously thought. Although trivalent plutonium is easily soluble in water and should therefore be extremely mobile, it is firmly bound and immobilised on the surface of the rusting minerals. “Our results suggest that even rusting steel storage units can contain the plutonium. But they also make clear that further studies are needed under realistic final storage conditions in order to assess the safety of future radioactive waste repositories,” says Scheinost.

HZDR/Red.