Chernobyl fallout particles keep their internal structure after 40 years, study finds

Analysis of six radioactive particles suggests some nuclear fuel debris is more stable than expected, but researchers warn the contamination is far from harmless

By LineZotpaper

Published23 October 2026

Read Time3 min

Four decades after the Chernobyl disaster, scientists examining microscopic radioactive particles still scattered in the surrounding soil have found that some have preserved much of their original crystal structure. The finding, from a team led by Leibniz University Hannover and the Helmholtz-Zentrum Dresden-Rossendorf, suggests at least some of the reactor debris is more chemically stable than previously believed, though researchers stress it does not mean the contamination is becoming safe.

Forty years after the reactor explosion at Chernobyl, now commonly referred to as Chornobyl, tiny radioactive particles between 8 and 50 micrometers across remain in the environment. Entering affected areas still requires protective clothing, and the long-term behaviour of these particles has been difficult to predict.

Using synchrotron X-ray diffraction at the Rossendorf Beamline in Grenoble, physicist Tobias Weissenborn of Leibniz University Hannover and crystallographer Dr. Christoph Hennig of the Helmholtz-Zentrum Dresden-Rossendorf analysed six particles recovered from Ukrainian soil samples. Each particle was rotated in an X-ray beam focused to about 100 micrometers and measured from 2,000 different angles.

The researchers identified three classes of particles. Some remain chemically and physically similar to the nuclear fuel uranium dioxide. A second group formed when melted fuel combined with zirconium, the metal used in the fuel's protective cladding, leaving particles partially or fully encased in or fused with the zirconium layer. The third type formed when the reactor's graphite moderator caught fire and burned for ten days, oxidising the fuel into fragile uranium oxides such as U3O8 that can readily break apart into microscopic fragments and be carried by wind.

A surprising result was that, despite four decades of exposure to the environment, the nuclear fuel inside the six particles had retained much of its original crystal structure. That stability could slow the release of radioactive substances, allowing particles to hold fission products in place rather than quickly leaking contaminants into soil and water.

The authors caution against broader conclusions. "Every single particle has a different structure," Weissenborn warned, noting that only six particles from two locations were studied. Even with more data, he said, universal statements about health risks would remain impossible, because persistent outlier particles could release radionuclides long after others have broken down.

The findings therefore do not suggest the Chernobyl Exclusion Zone restrictions can be lifted any time soon. Weissenborn and Hennig are continuing experiments on highly radioactive transuranic phases in the debris to better understand how the materials change over time.

Analysis

Why This Matters

The finding changes assumptions about how quickly Chernobyl's radioactive debris breaks down and releases contaminants into the environment.
If many particles remain stable, the movement of radioactive material into soil and groundwater could be slower than expected, but unpredictable particles still pose long-term risks.
The research informs how long the Exclusion Zone may need to remain restricted and how nuclear fallout behaves decades after a major accident.

Background

Chernobyl was the site of one of the worst nuclear accidents in history, when a reactor exploded during a test in April 1986, releasing enormous quantities of radioactive debris. Since then, scientists have studied the microscopic particles left in the soil around the plant to understand how radioactive material weathers into different uranium oxides over time. The new analysis is among the first to examine the crystalline structure of individual particles in detail, using a technique that reveals the arrangement of atoms inside solid materials.

Key Perspectives

Researchers (Weissenborn and Hennig): The six particles show that some nuclear fuel has stayed structurally intact for 40 years, which could help hold fission products inside the debris. They stress, however, that each particle is different and that no universal claims can be made from such a small sample. Health and environmental authorities: The stability of some particles does not mean the contamination is harmless. Persistent outlier particles could release radionuclides much later, so restrictions on the Exclusion Zone cannot be relaxed on the basis of this study. Scientific community: The results are promising but preliminary. Understanding how the wider region's contamination behaves would require studying many more particles from a far broader range of locations.

What to Watch

The ongoing experiments by Weissenborn and Hennig on highly radioactive transuranic phases in the debris.
Whether follow-up research examines many more particles from additional locations across the contaminated region.
How the findings influence future assessments of health risks and the long-term management of the Chernobyl Exclusion Zone.

Sources

40 years later, Chernobyl's nuclear fallout is not what scientists expected · Latest Science News -- ScienceDaily

Checked

8 claims in this story checked against 1 source: 6 supported.

Show each claim

Partly supportedChernobyl fallout particles kept their internal structure after 40 years.Latest Science News -- ScienceDaily: “Despite spending four decades in the environment, the nuclear fuel inside the six examined particles had retained much of its original crystal structure.”
SupportedThe analysis suggests some nuclear fuel debris is more stable than expected, but the contamination is not thereby harmless.Latest Science News -- ScienceDaily: “This suggests that at least some of the radioactive debris produced by the Chornobyl disaster is more chemically stable than researchers previously believed. ... the researchers emphasize that their findings should not be interpreted as evidence that Chornobyl's radioactive contamination is becoming harmless.”
Not in the sourcesThe research team was led by Leibniz University Hannover and the Helmholtz-Zentrum Dresden-Rossendorf.
SupportedMicroscopic radioactive particles remain scattered in soil around Chernobyl four decades after the disaster.Latest Science News -- ScienceDaily: “Four decades after the Chernobyl (known today as Chornobyl) nuclear disaster, microscopic radioactive particles remain scattered throughout the surrounding soil.”
SupportedThe researchers analyzed six particles recovered from Ukrainian soil samples using synchrotron X-ray diffraction at the Rossendorf Beamline in Grenoble.Latest Science News -- ScienceDaily: “Dr. Christoph Hennig, a crystallographer at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), has now completed the first successful structural analysis of radioactive fragments of this kind at the Rossendorf Beamline in Grenoble. Working with Weissenborn, Hennig analyzed six particles recovered from the Chornobyl region.”
SupportedEach particle was rotated in an X-ray beam focused to about 100 micrometers and measured from 2,000 different angles.Latest Science News -- ScienceDaily: “Ultimately, we fully rotated the particles in an X-ray beam focused down to 100 micrometers - about the thickness of a human hair. We measured each particle from 2,000 different angles to seamlessly capture all the reflections.”
SupportedWeissenborn said, “Every single particle has a different structure.”Latest Science News -- ScienceDaily: “However, every single particle has a different structure,” warns Weissenborn, “and our experiment only studied six such particles from two different locations.”
SupportedWeissenborn said universal statements about health risks would remain impossible because persistent outlier particles could release radionuclides later than others.Latest Science News -- ScienceDaily: ““And even if we obtained some averages at some point, we still wouldn't be able to make universal statements about health risks in the region,” Weissenborn cautions. “Because even if the particles decay in a largely uniform patten, there will always be outliers, more persistent particles, that will release radionuclides at a later point in time.””