ИСТИНА

Chernobyl exclusion zone remains one of the most dangerous radiation-contaminated areas worldwide even through 37 years after the Chernobyl accident. Fuel “hot” particles are still the most unpredictable dose-forming components in the soils of this region. Over time in the environment, they undergo gradual dissolution with the release of uranium as well as fission and neutron-activation products trapped inside the uranium-oxide fuel matrix. “Hot” particles could be found and extracted from soil samples using highly sensitive method of digital radiography with Imaging Plate (IP). The non-destructive tool using Imaging Plate has been developed for rapid assessment of the fraction of radioactivity stored in “hot” particles (HPfr). Individual particles found in the near-Chernobyl soil are uranium-oxygen. Two subgroups could be distinguished: relatively stable stoichiometric particles of uranium dioxide and UO2+x and the second subgroup which has high burnup values, the particles have undergone significant destruction as a result of environmental impact. The correlation between fuel burnup and uranium oxidation state within the western trace of the Chernobyl fallout is justified for the reason that the particles were in the environment for the same time – 30 years, and were in the same area – while they were exposed to similar environmental conditions: temperature, humidity, etc. In the course of this study, we have gone from determining the proportion of “hot” particles in the soil sample in general to a fine analysis of individual “hot” particles (fig. 1). It was found that with increasing distance from the 4th unit of Chernobyl NPP, the fraction of radioactivity of the sample stored in “hot” particles decreases, as does the activity ratio A(241Am)/A(137Cs). It was found that for the particles of the western trace, the following pattern occurs: particles with low fuel burnup retain the oxidation state of uranium (+4) and they are morphologically less susceptible to environmental conditions, while particles with higher fuel burnup consist of more oxidized uranium (+6) and they are morphologically more destroyed. A different pattern is observed for the “hot” particles of the northern trace. The particles were located in peat soil, in anaerobic slightly acidic conditions, which led to the preservation of the oxidation state of uranium (+4) even in particles with high burnup. Individual particles are unique objects, the structure of which is very different from each other.