Russian scientists have completed a project to predict the properties of corium at the Fukushima Daiichi NPP
TENEX in a consortium with specialists of V. G. Khlopin Radium Institute JSC, SSC NIIAR (part of the scientific division of the ROSATOM), FSUE A. P. Alexandrov NITI, as well as the St. Petersburg branch of the Institute of Geoecology of the Russian Academy of Sciences successfully completed work on a two-year project to study the impact of storage conditions on the characteristics of simulant fuel-containing materials (corium) which were developed based on the characteristics of fuel debris formed after the accident at the Fukushima Daiichi NPS. The project administrator is Mitsubishi Research Institute, Inc., Japan).
The scientists produced simulants of silicate-containing fuel fragments and studied their properties in the aging process in three conditions. The resulting mathematical model makes it possible to predict the behavior of materials during extraction, transportation and storage with discrete steps of 10, 20, 30 and 50 years.
«The program on experimental handling of fuel-containing materials, which is significant in terms of volume and duration, has been completed. The results of the project are important both from the point of view of significant research value and from the point of view of practical applicability,» said the Deputy Director General of TENEX for back-end Elena Artemova.
The experiments have shown that long-term storage of corium under water leads to its partial leaching, as well as to secondary phase formation in the surface layer. In the future, during extraction and drying, the surface of such a material may turn into dust. The conclusions obtained as a result of the project will allow to make experimentally based decisions when choosing a technology for safe extraction of corium from the post severe accident power station.
"The results of our research will help our Japanese colleagues to take into account the possible risks associated with the formation of radioactive dust and the occurrence of any uncontrolled situations leading to secondary contamination of the territory during the decommissioning of the power station. These results can also help minimize the possibility of personnel exposure and reduce the financial costs of eliminating the consequences of accident. According to the comments of Albert Aloy, Chief Researcher of the Department of Applied Radiochemistry of V. G. Khlopin Radium Institute JSC, the presence of a silicate component in solidified corium expands the possibility of applying the results obtained and allows us to predict the stability of vitrified highly active waste during its long-term storage before final disposal.
Corium (fuel-containing material) is a lava-like material formed in the core of a nuclear reactor during severe accidents with the melting of the core. In 2011, during the accident at the Fukushima Daiichi nuclear power plant, the temperature inside the reactor rose above 2000°C, causing the melting of uranium fuel and its further reaction with the zirconium cladding oxidized by steam, which, in turn, led to the formation of corium.
The project of “Decommissioning and contaminated water management (development of analysis and estimation technology for characterization of fuel debris (development of estimation technology of aging properties of fuel debris)” was performed by the funds from Japanese government as The Subsidy Program and managed by Mitsubishi Research Institute, Inc., Japan.