In September 2016, CERAD scientists have performed a comprehensive fieldwork within the exclusion zone around the Fukushima reactors. Water, fish, sediments and soils, plants and earthworm were collected in order to study transfer of radioactive contamination in the environment and its effects on the organisms.
Iodine in ponds
Hans Christian Teien is leading the research on the dynamic transfer of contaminants in nature. He has finalized the measurements of Cesium-137 and Iodine-129 in the water of the ponds in the Fukushima region. Two ponds were chosen for their geographic location: Inkyozaka is situated close to the Fukushima nuclear power plant (ca 1.3 km), while Suzuuchi is further away (ca 4.6 km).
The results of analysis showed that concentrations of cesium-137 are lower in Inkyozaka pond near to the reactor than in Suzuuchi pond, while for Iodine-129 the picture is completely opposite. The differences in concentration of radionuclides can be explained by 3 different source term and releases from the power plant, with plumes of contaminants transported in different directions. These results are important as they show that by measuring only one radionuclide – cesium, one would underestimate the levels of other contaminants such as radioactive iodine.
Earlier, CERAD researchers have confirmed the presence of condensation particles from the Fukushima accident in the contaminated areas (see picture below). Condensation particles are those formed when volatile nuclides like cesium are released from damaged spent nuclear fuel due to the heat, and deposited on non-nuclear particles in air (e.g. ash, soot or soil) during transport.
Particles are important to consider when studying the environmental impact of releases from a nuclear accident. Particles can carry substantial amount of radioactivity and represent a radiological hazard due to potential skin burns, inhalation and uptake with food. Particles are unevenly distributed in the environment (hot spots) and representative sampling can be difficult to obtain. Particles can be difficult to dissolve prior to analysis, and analytical results may underestimate the activity concentrations, and thereby the inventory of the contaminated area. Particles can be retained in filtering organisms (e.g., blue mussels) or in grazing animals, thus the “standard” transfer factors (Kd, CR, TF) assuming equilibrium conditions cannot be applied.
Characterization of particles and their properties is an important field of science internationally. The Isotope laboratory at NMBU has a unique particle archive, and has access to a series of advanced analytical platforms (synchrotrons in Germany, France, Australia; and AMS in Spain and Australia) due to close international collaboration, especially with University of Antwerp. The combination of particle characterization techniques developed for nanometer-micrometer sized entities represent state-of-the-art. The particle characterization work is performed within CERAD sub-projects (lead by Ole Christian Lind), EC funded projects as well as within the IAEA Coordinated research program (CRP) on particles, chaired by Brit Salbu.
The analyses of other samples are still ongoing. We will keep you updated on our progress and on the exciting discoveries!
Salbu, B., Lind, O.C., 2016. Radioactive Particles Released to the Environment from the Fukushima Reactors-Confirmation Is Still Needed. Integr. Environ. Assess. Manag. 12, 687-689.