Uranium and other radioactive materials, including caesium and technetium, have been found in tiny particles released from Japan’s damaged Fukushima Daiichi nuclear plant, the UK’s University of Manchester announced on 28 February.
A new study by the team of international researchers said this may mean the environmental impact from the fallout will last much longer than previously expected. The team said that, for the first time, the fallout of Fukushima Daiichi nuclear fuel debris into the surrounding environment has been "explicitly revealed" by the study.
The scientists have been looking at tiny pieces of debris or micro-particles, which were released into the environment during the initial disaster in 2011. They discovered uranium from nuclear fuel embedded in or associated with caesium-rich microparticles that were emitted from the plant's reactors during the meltdowns. The particles found measure just five micrometres or less, which means they can be inhaled. The fuel debris fragments were found inside the exclusion zone, in paddy soils and at an abandoned aquaculture centre several kilometres from the Fukushima nuclear plant.
It was previously thought that only volatile, gaseous radionuclides, such as caesium and iodine, were released from the damaged reactors. However, it is now becoming clear that small, solid particles were also emitted, and that some of these particles contain very long-lived radionuclides.
Dr Gareth Law, Senior Lecturer in Analytical Radiochemistry at The University of Manchester and an author on the paper, said: "Our research strongly suggests there is a need for [a] further detailed investigation on Fukushima fuel debris, inside, and potentially outside the nuclear exclusion zone."
He added: "Whilst it is extremely difficult to get samples from such an inhospitable environment, further work will enhance our understanding of the long-term behaviour of the fuel debris nano-particles and their impact."
Dr Satoshi Utsunomiya, Associate Professor at Kyushu University (Japan), who led the study, noted that having better knowledge of the released microparticles is "vitally important" as it offers much-needed data on the status of the melted nuclear fuels in the damaged reactors, which will prove extremely useful for decommissioning. At present, chemical data on the fuel debris located within the damaged nuclear reactors is impossible to get due to the high levels of radiation. The microparticles found by the international team of researchers will provide vital clues on decommissioning challenges that lie ahead.