Using clay materials for developing safety barrier of decommissioning ad reactor

The relevance of the research is caused by the necessity of developing the additional safety barriers providing implementation of radiation safety requirements in the time of reactor decommissioning by the method of burial site. The aim of the research is to evaluate the impact of clay materials properties on barrier durability and to determine the optimum type of material for applying as a barrier; to show that the effect of the vertical diffusion and convective transport of radionuclides in the soil moistened layer with water, filtered through a bed of solid wastes, play a decisive role in distribution of radionuclides. The results of mathematical modeling of diffusion and filtration of radiocarbon in the generated clay barrier are the subject of the paper. Methods: unsteady-state diffusion math equation by finite difference method in MatLab software package. Results. The authors have developed the mathematical model for estimating radiocarbon migration in the decommissioning reactor AD safety barrier and defined the most reliable clay type as well as the radionuclide specific activity distribution in clay safety barrier thickness. It is shown that in a long time interval the clay layers will maintain their waterproofing and barrier properties, and the burial site of radioactive wastes, built outside the influence of tectonic faults, won't be destroyed and filled with water during its operation and conservation. It was determined that the placement of a radioactive waste in geological formations with a multi-barrier geotechnological protection system is the optimum security option of scientifically sound and commercially available solution to the problem of radioactive waste disposal.