Chernobyl Four Decades Later: What a New Analysis Reveals About Radioactive Particles in the Soil

Four decades after the Chernobyl nuclear disaster, microscopic radioactive particles are still present in the soil around the former power plant. New research by scientists in Germany has shown that some of these particles have retained much of their original crystal structure, indicating that they undergo chemical degradation and dissolution more slowly than expected, and consequently release radionuclides into the environment at a slower rate.

Experts from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the University of Hanover analyzed six radioactive particles collected at two locations in the Chernobyl area. The results revealed the unexpected persistence of certain particles, even after 40 years of exposure to environmental conditions.

The reactor explosion on 26 April 1986 released large quantities of radioactive material, which spread throughout the surrounding area. The radioactive debris includes particles measuring between eight and 50 micrometers, whose behavior depends on their chemical composition and how they were formed, according to an HZDR statement.

Scientists distinguish between three main groups of these particles. The first consists of particles similar to nuclear fuel, namely uranium dioxide. The second includes particles in which the fuel is partially or completely mixed with, or chemically bonded to, zirconium from the protective cladding of the fuel elements. The third group comprises particles formed during the fire involving the reactor’s graphite moderator, a material used to slow down neutrons in the reactor.

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High temperatures and exposure to air during the fire caused the fuel to oxidize, forming various uranium oxides. Some of these are mechanically unstable and can break down into smaller fragments that wind can carry through the environment.

Because of differences in composition and structure, scientists still find it difficult to reliably predict how quickly individual particles will dissolve and release radionuclides.

What did the X-ray scans reveal?

The researchers extracted six particles from soil samples. Due to their high radioactivity, the samples had to be placed in multiple protective layers before being transported to a research facility in Grenoble.

Each particle was scanned from approximately 2,000 different angles using a focused X-ray beam. This made it possible to identify different crystalline phases of uranium oxides and examine the internal structure of the material in greater detail.

The results show that the nuclear fuel in the analyzed particles has retained much of its original crystal structure. This indicates that these particles are more chemically stable than previously assumed. Such stability could slow the release of radionuclides, or radioactive isotopes, into the surrounding soil and water.

However, this does not mean that the contamination has disappeared or that the particles are harmless. The findings apply only to the six particles analyzed from two locations and cannot be extrapolated to the entire area affected by the disaster.

The new findings contribute to a better understanding of the disaster’s long-term consequences, but they do not provide grounds for concluding that the danger has passed. Radioactive material in the area surrounding the power plant still requires careful monitoring, and its long-term fate remains a subject of scientific research.

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