2 40 years after Chernobyl – how we measure and what we know

Radiological measurement methods have evolved considerably since 1986. Today, they are carried out within a well-defined framework, including through CELMES (Central Measurements and Sampling), the measurement unit of the federal nuclear emergency plan. CELMES ensures that there is a coordinated approach to radiological measurements in the event of nuclear or radiological incidents, and SCK CEN makes a significant substantive and operational contribution in this regard.

Measurement and modelling: an interaction

In addition to measurement, modelling also plays a crucial role. Modelling results are used to inform the measurement strategy: they help determine where, when and what should be measured. Conversely, we use measurement results to verify and refine models, including through techniques such as inverse modelling. Thanks to this continuous interaction between measurement and modelling, we gain an increasingly accurate picture of the distribution and impact of radioactivity on the population and ecosystems.

European exchange of radiation measurements

Following the Chernobyl disaster, it became clear that Europe needed a system for the rapid and coordinated exchange of radiological information. Consequently, Council Decision ‘87/600/Euratom’ was adopted, obliging Member States to share information in good time in the event of serious nuclear or radiological incidents.

This cooperation is based on two platforms: ECURIE, the 24/7 alert system for urgent notifications, and EURDEP, the European platform for near-real-time exchange of radiological measurement data between 39 countries. National monitoring networks continuously share their data via EURDEP. In emergency situations, data is shared at least every hour. The data is compiled into public maps showing gamma radiation measurements from around 5,000 monitoring stations across Europe, going back up to 35 days.

Forty years after the Chernobyl nuclear disaster, the stricken region is still a unique, but stark, reminder of the long-term effects of radioactive contamination. For SCK CEN, the exclusion zone has been an important area of research for decades. Through field campaigns, laboratory research and modelling, our researchers have provided – and continue to provide – crucial insights for the protection of people and the environment.

SCK CEN quickly at the scene: the first field campaigns (1990s)

SCK CEN was active in the exclusion zone around Chernobyl shortly after the accident. In the early 1990s, several field campaigns were launched, with three clear objectives:

• Mapping the radioactive contamination in the soil and the surroundings
• Gaining insight into the behaviour of caesium-137 (Cs-137) and strontium-90 (Sr-90) in soil and food chains
• Collecting data to better assess human exposure

The measurements and samples from this period, supplemented by targeted experiments at a now-decommissioned SCK CEN farm in Mol, subsequently formed the scientific basis for the biosphere model approved by the FANC. This model is still used today for impact assessments of human radiation exposure from existing and new nuclear facilities.

In addition, SCK CEN researchers have also investigated alternative remediation options for contaminated timber, including in the heavily contaminated Red Forest. These early campaigns demonstrate how SCK CEN combined measurement, experimentation and modelling from the very outset to tackle complex environmental issues.

1. New questions, new insights: COMET field campaigns (2016)

In 2016, we organised new field campaigns as part of the European COMET project, which was coordinated by SCK CEN. The aim of COMET was to bolster the scientific basis of radioecology by better coordinating field measurements, laboratory experiments and modelling, thereby reducing uncertainties in risk assessments for humans and the environment.

A comparative approach was consciously taken for COMET. Consequently, the field campaigns in Chernobyl ran in parallel with similar research in Fukushima, where, since the nuclear disaster in 2011, there has also been long-term, chronic exposure of organisms to elevated radiation levels. By combining data from two different but heavily contaminated environments, researchers were able to ascertain what the general impacts are in cases of chronic exposure, and which are more context- or ecosystem-dependent.

In Chernobyl, samples were taken from soil, plants and animals, including earthworms and frogs. These samples were used both for the analysis of long-lived radionuclides (such as Cs-137, Sr-90, plutonium isotopes and Am-241) and for biological analyses of potential impacts across multiple generations. At the same time, specific laboratory experiments were carried out within COMET, so that field and laboratory results could mutually reinforce and clarify each another. 

The combined results of the field campaigns in Chernobyl and Fukushima were compiled in this peer-reviewed scientific publication.

The data from the COMET project helped to improve existing models and therefore to estimate the long-term effects of radiation on the environment more accurately. The results clearly showed that prolonged (chronic) exposure has different impacts from short, high (acute) exposure, and that this difference is important for an accurate risk assessment.

In addition, the data made it possible to determine more effectively how much radiation organisms actually absorb and to further improve environmental models. As such, it was confirmed that the impacts of chronic exposure must be looked at separately when assessing the effects of radiation on ecosystems.

Read the COMET final report.

Together with our international partners, including UK-CEH, SCK CEN developed a population model for rodents in the Red Forest. This model makes it possible to extrapolate the effects of radiation on individual animals to entire populations, based on realistic field data. 

You can find the paper here.

Will we go back?

The exclusion zone around Chernobyl is still one of the most radioactively contaminated areas in the world and is therefore of particular scientific interest as a kind of outdoor laboratory for long-term research.

There were concrete plans to carry out further field campaigns as part of the European CHRONIC-ITN project. However, due to the war in Ukraine since February 2022, this was no longer possible. Shortly after the war broke out, the exclusion zone was temporarily occupied by Russian troops, and access is still difficult even today, partly due to the presence of landmines. Discussions have been held via the European radiological protection platform ALLIANCE to restart cooperation with Ukrainian researchers, but fieldwork on-site is not feasible for the time being.

For SCK CEN, the CHRONIC project was ultimately successfully completed on the basis of alternative data and tests. In the meantime, we are exploring new possibilities for future field campaigns in the hope that peace and stability will eventually return to the region.