Traces of plutonium from the damaged Fukushima reactors have been found throughout Japan
Scientists from six countries using advanced analytical techniques found that the plutonium contained in nuclear fuel plant Fukushima-1, destroyed in March 2011, still contained in the environment in the composition of micro-particles ejected during an accident. The study is published in the journal Science of the Total Environment.
Environmentalists and chemists previously noted that the materials released into the atmosphere, soil and seawater after the accident, contained traces of plutonium, but its physical, chemical and isotopic forms remained unknown.
A new study conducted by scientists from Japan, Finland, France, Switzerland, UK and USA, has shown that nanoscale inclusions of oxides of plutonium are contained in cesium-rich microparticles (CsMP).
Nuclear fuel burning inside the reactor interacts with the structural concrete of the reactor. The destruction of the material disintegrated into microscopic radioactive particles that the wind blew across Japan.
Studies have shown that the CsMP is highly radioactive and consist mainly of siliceous glass of concrete and radioactive cesium — volatile fission product generated in the reactor by the combustion of fuel.
The authors have studied the chemical composition of micro-particles using a combination of advanced analytical techniques — synchrotron option micro x-ray analysis, secondary ion mass spectrometry and transmission electron microscopy of high resolution.
Initially, the researchers found inside the smallest CsMP inclusion of dioxide of uranium — uraninite — diameter less than ten nanometers. This pointed to the possible location of nuclear fuel inside the particles. Detailed analysis showed that the oxides of plutonium are associated with these inclusions, and isotopic composition of uranium and plutonium corresponds to the nuclear fuel.
"The results convincingly demonstrate that nanoscale heterogeneity, which is characteristic of normal nuclear fuel is still present in the remnants of fuel that remain inside the damaged reactor site — presented in the press release of the University of Helsinki, the head of research Dr. Satoshi Utsunomiya (Utsunomiya Satoshi) from the Japanese University of Kyushu. — This is important information because it tells us about the degree of melting facilities. This understanding is necessary for the eventual decommissioning of the damaged reactors and long term management of their waste".
"It is now clear that cesium-rich microparticles is an important factor of radioactive contamination in nuclear accidents," emphasizes another author, Professor Gareth Lowe (Gareth Law) from the University of Helsinki.
The authors note that they continue the study of microparticles CsMP to better understand their long-term behavior and the impact on the environment.
"It's been almost ten years since the nuclear disaster at Fukushima, but a study of the impact of the accident on the environment is still far from complete, continues to Utsunomiya. — It took a long time to deal with solid particles of plutonium. This is a great scientific achievement made possible by international cooperation."
Scientists now are absolutely certain that the inclusion of radioactive nuclear fuel is still contained in the walls of the stopped nuclear reactors, and the need for special security measures during their decommissioning.