Chernobyl Particles Reveal Unexpectedly Stable Nuclear Fuel After 40 Years

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Researchers analyzed six radioactive particles from two locations near Chernobyl and found that the nuclear fuel’s crystal structure had remained largely intact. The result suggests the particles may retain radioactive fission products, but the small sample cannot establish how stable particles are across the region or determine health risks.

Researchers from Leibniz University Hannover and the Helmholtz-Zentrum Dresden-Rossendorf found that the crystal structure of nuclear fuel in six radioactive particles from the 1986 Chernobyl disaster has remained largely intact. The study, published in the Journal of Hazardous Materials, suggests the particles may retain radioactive fission products, but its small sample does not establish how stable such fragments are across the affected region or what risks they pose to people.

The fragments, known as hot particles, measure about 8 to 50 micrometers and remain highly radioactive. The team analyzed particles isolated from Ukrainian soil samples collected at two locations. Researchers secured each fragment to a tungsten electrode and transported it under several layers of containment to the Rossendorf Beamline in Grenoble for examination.

Using synchrotron X-ray diffraction, the researchers identified different uranium oxide phases inside the samples. They rotated each particle in an X-ray beam and measured it from 2,000 angles to capture reflections from its internal structure. The authors describe the work as the first successful structural investigation of this kind on these highly radioactive fragments.

The finding that the fuel’s crystal structure remained largely intact was unexpected, according to the researchers. They said this points to greater chemical stability in the tested particles than previously assumed and could help estimate how quickly they release radioactive substances. It does not mean the particles are harmless: the study did not measure exposure or health effects.

What Fuel Stability Could Mean

If some fuel fragments retain their internal structure, they may also keep fission products contained rather than releasing them quickly into surrounding soil or water. Better information about particle composition and weathering could support more precise assessments of environmental contamination and help researchers refine estimates of radionuclide release.

The finding is a piece of evidence about the behavior of particular particles, not a reassessment of safety across the Chernobyl Exclusion Zone. The researchers caution that particles differ from one another and that a small laboratory study cannot establish overall human health risks. The report says access restrictions will not be lifted on the basis of these results.

How the Chernobyl Particles Formed

The particles were released after the 1986 reactor accident, when explosions scattered debris from the destroyed reactor. The researchers describe three broad types: particles still resembling uranium dioxide fuel; particles partly or fully encased in, or fused with, a zirconium layer; and particles formed after the graphite moderator caught fire. The graphite burned for 10 days, and the fuel oxidized into compounds including U₃O₈.

These different origins matter because a particle’s composition and structure affect how it weathers. The report says some uranium oxide compounds can form mechanically unstable microscopic particles that are easily carried by wind, and inhaling radioactive dust can pose serious health risks. Until this analysis, the rate at which different Chernobyl particles weathered remained poorly understood. The new study examines structure in just six fragments; it does not represent every particle or location.

“Every single particle has a different structure.”

— Tobias Weissenborn, physicist and doctoral candidate at Leibniz University Hannover

Limits of the Six-Particle Sample

The study examined just six particles from two locations, and the report says each has a different structure. Researchers therefore cannot draw broad conclusions about how all Chernobyl particles age, how quickly radionuclides are released across the region, or the health risks to people who might encounter them. The findings do not establish whether other particles are less stable or more persistent.

The report also does not provide a region-wide measurement of radioactive contamination or a new risk estimate. It remains unclear how representative the analyzed fragments are of particles in other soils and locations. The observed intact crystal structures are a finding about these samples, not proof that radioactive material is permanently contained.

Further Sampling and Phase Research

The researchers say that more particles from a wider range of locations must be analyzed before they can draw stronger conclusions about stability. Even then, they caution that averages would not describe every particle, including fragments that could release radionuclides later.

Weissenborn and Hennig are conducting follow-up experiments on transuranic phases in the reactor remnants. The report does not give a publication date or findings for that work. For now, the new results add structural evidence about a very small set of particles; they do not change the stated access restrictions for the Exclusion Zone.

Key Questions

What did the researchers find?

They found that the crystal structure of the nuclear fuel in six tested Chernobyl particles remained largely intact. The particles also contained different uranium oxide phases.

Does this mean Chernobyl particles are safe?

No. The study did not measure exposure or health effects, and the researchers say its results cannot establish regional health risks. The particles remain radioactive.

How many particles were examined?

The team analyzed six particles collected from two locations. Researchers say many more samples from a wider range of places are needed for broader conclusions.

How were the particles studied?

The team used synchrotron X-ray diffraction to investigate internal crystal structures, measuring each particle at 2,000 angles.

Will the findings change access to the Exclusion Zone?

The report says the findings will not lead to restrictions being lifted. The study is too limited to support a general safety assessment of the region.

Source: hn