Scientists from six countries found that particles of plutonium contained in nuclear fuel was destroyed in the 2011 nuclear power plant “Fukushima-1”, still remain in the environment. 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.
It turned out that 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,” said study leader, Dr. Satoshi Utsunomiya Japanese Kyushu University.
According to the scientist, this information is an indication of the degree of melting of the damaged reactor. Realizing this, energy will be able to remove them from service and properly handle waste.
“It is now clear that cesium-rich microparticles is an important factor of radioactive contamination in nuclear accidents”, — stressed the co-author of the scientific work of Professor Gareth Lowe from the University of Helsinki.
The researchers will continue the study of microparticles CsMP to better understand their long-term behavior and the impact on the environment.