Fukushima: SCK CEN on site

2011: Early response

Our contribution in the first hours and days after the accident was threefold:

• Contamination monitoring: Belgian nationals were repatriated. Once they landed in Brussels, they were received at the military hospital in Neder-Over-Heembeek. This was carried out in cooperation with several organisations, including Defence, FANC, and SCK CEN. SCK CEN checked the travellers for external and internal radioactive contamination. Their luggage was also closely screened. No contamination was detected.
• Atmospheric models: In late March/early April, traces of radioactive iodine and caesium released during the nuclear accident were detected in Belgium. By then, the cloud had diluted enough to pose no threat to public health. SCK CEN closely monitored the situation using its atmospheric models.
• Marine investigation: SCK CEN was immediately contacted by the United Nations Safety Committee on the Effects of Atomic Radiation (UNSCEAR) to shed its expert light on the impact of radiation on marine life as a result of the accident. We conducted a radiological impact assessment on the accidental discharges to the seawater, modelling the transfer and radiation doses to populations of marine wildlife. This has led to an ongoing effort ever since 2011 to Improve the study as more data became available, leading to 15 peer-reviewed scientific publications on the subject, which you can find in our research portal.
• Advisory role to importers: There was a surge in requests for advice from companies importing from Japan. SCK CEN provided clear information, straightforward guidelines, and practical training on how to properly monitor contamination.

In response to Fukushima, several European projects were launched to develop more accurate atmospheric models. Attention was focused, among other things, on deposition parameters. How do radionuclides reach the Earth's surface under dry and wet weather conditions? Through deposition, radionuclides enter the biosphere and, subsequently, the food chain. These insights help improve emergency planning.

2012-2016: Soil Research

The subsoil in Japan differs from that in Belgium. Japan is located in a volcanic area and therefore has typical 'andosol' soil: dark, volcanic soil composed of ash, tuff and pumice. A different soil composition can mean that radionuclides, including caesium, will move and bind differently compared with sandy, loamy, or clay soils like those we are familiar with. Between 2012 and 2016, SCK CEN examined this behaviour. We took contaminated soil samples on site and grew rice plants on them in our laboratories. That study showed that the amount of caesium that sticks to the soil (clay particles) in Japanese soil is significantly lower than in European soil. In other words, caesium in Japanese soils is more readily taken up by the vegetation growing there. These ‘soil-to-plant transfer’ figures form the basis of models used to calculate the eventual impact on humans and the environment. The research was able to make recommendations on how to refine the model parameters so that they also take into account the other characteristics typical of Japanese andosol soils.

2016-2019-2022 – Pines

SCK CEN researchers travelled to Japan three times to collect samples from pine trees. Previous research in Chernobyl had taught us that these trees are just as sensitive to radiation as humans, and therefore more sensitive to radiation than other vegetation. We observed the same effect in Fukushima, where the doses were much lower. The aim was to unravel the underlying mechanisms behind this vulnerability. This knowledge is essential for quickly identifying the most vulnerable plant species during site remediation. And if the same mechanisms also apply to humans, they could offer new insights for cancer treatments. This is ongoing research; the code behind the radiation sensitivity of pine trees has not yet been cracked, but some clues have already been uncovered.

2025 – Analysis of purified sea water

In August 2023, TEPCO began discharging contaminated water from the Fukushima Daiichi power plant into the Pacific Ocean. The water was treated with the ALPS procedure mentioned above. The discharge was done under supervision from the IAEA. To ensure compliance with international safety standards, the IAEA and the Japanese government decided to introduce additional controls and analyse the treated water. As part of this, the IAEA organised a (fourth) international mission to Fukushima Daiichi. SCK CEN also participated in this mission. The assignment was divided internally between two specialised groups: ISR (Impact & Site Remediation) took care of the sampling on site, while LRM (Low-level Radioactivity Measurements) analysed the water samples in Belgium.