Persistent radioactive particles found in Chornobyl soil — ScienceDaily
Scientists examined six microscopic radioactive particles collected in Ukraine’s Chornobyl region and found that some of them retained a significant part of the original crystal structure of nuclear fuel four decades after the Chornobyl Nuclear Power Plant accident. ScienceDaily reports on the study’s results.
The particles, ranging in size from 8 to 50 micrometers, remain highly active. They formed as a result of the release of debris from the reactor, and entering contaminated areas, according to the researchers, still requires protective clothing.
Three types of particles
Physicist and doctoral researcher at Leibniz University Hannover Tobias Weissenborn described three classes of such particles. The first includes those that are close to uranium dioxide — nuclear fuel — in their chemical and physical properties. The second class formed at extreme temperatures inside the reactor, when molten fuel mixed with zirconium used in fuel element cladding.
The third type emerged during the fire in the graphite moderator, which lasted ten days. During the process, the fuel oxidized and formed various uranium oxides, including U3O8. This material is mechanically fragile and can therefore break down into microscopic fragments that can be carried by the wind. Inhaling such particles poses a health hazard.
More current news is available on the UA.News Telegram channel Telegram.
Analysis at a synchrotron
Crystallographer Christoph Hennig of Helmholtz-Zentrum Dresden-Rossendorf, together with Weissenborn, conducted a structural analysis of the samples at the Rossendorf Beamline in Grenoble. The particles were separated from Ukrainian soil samples, mounted on tungsten electrodes, and transported in several protective casings due to their high radioactivity.
To study the internal structure, the scientists used synchrotron X-ray diffraction. Each particle was fully rotated in a 100-micrometer-wide X-ray beam and measured from 2,000 angles. This made it possible to distinguish crystalline phases of uranium oxides.
The results indicate that some particles may retain fission products in their structure for longer and therefore may not necessarily release radioactive substances rapidly into soil and water. At the same time, the researchers stress that the sample was small and included particles from only two locations. Their structure, composition, and resistance to environmental effects differ, so it is not yet possible to draw general conclusions about risks across the entire contaminated area.
