Study On The Leaching Behavior Of Glass Wasteforms By Monte Carlo Simulation

The disposal of high level radioactive waste(HLW) relates to human health and environment safety, thus, it has been aroused a great attention in the world.At present, geological disposal is considered to be the most ideal scheme.However, during the long process of geologic disposal, the glassy waste form will suffer groundwater erosion, chemical reaction and dissolution, leading to leaching of nuclides, which threatens the safety of the biosphere. Therefore, the studies of interactions between the vitrified HLW form and the water are very significant for safe assessment of geological disposal. The researches on the dissolution behaviors of waste vitrification in the water have great significant for deep disposal of HLW.This paper summarizes the research status of the modeling techniques of glass dissolution. From the basic principle of these models, we describe the details of their applications and evaluate their advantages and disadvantages, analyze applicable object of the different models and their development prospect. In the experiments, we have studied the long term dissolution behavior of vitrified HLW glass in deionized water by the MCC-1 static leaching experiment. In addition, the measurements of XRD, FTIR, ICP, and other testing techniques are used. The experiments show that the concentrations of silicon, boron and aluminum in solution reach a certain balance at different times. After soaking in deionized water for 150 days, 180 days and 210 days, respectively, the concentrations of silicon, boron and aluminum reach a balance, which are 21.5ug/m L, 2.5 ug/m L and 6.5 ug/m L, respectively. During the leaching process,there is no crystallization phenomenon, the structure of the surface is amorphous.The main structural unit of the glass does not change significantly. At the same time, a Monte-carlo model for the dissolution of waste vitrification is primarily developed. The simulation shows that the silicon concentration in solution reaches a balance which is controlled by the dissolution and condensation probability. The silicon dissolution and condensation dynamics lead to form altered layer in the reaction surface of glass and water which causes a corrosion blocking and limits the release of boron and aluminum. Simulation results fitwell with experimental results. Besides, on the basis of the three component model, we add aluminum atoms. We use the new reaction parameters to describe the characteristics of the aluminum atoms, which further verify the reliability of the model.