Study of The Leachability and Solubility of Some Radionuclides in The Waste Repository

Abstract

The safety of radioactive wastes in the repository depends on its capacity to confine radioactivity from being released to the biosphere. The process that most likely process can lead to the release of radionuclides from a repository is the transport by groundwater. The release rate of radionuclides from the solidified blocks is controlled by the solubility limits and leaching rate of radionuclides. The present work aims at investigating the solubility and leaching processes and their effect on the safety assessment of a radioactive waste in the repository. This work studies both processes with different concentrations of elements. The experimental study focused on the elements; strontium (Sr), cobalt (Co) and iron (Fe). To simulate the effect of radiation emitted from the radionuclides of these elements, the cement blocks that confine the elements are irradiated by Gamma (ɣ) Rays of doses; 40, 120, and 240 kGy. The results of non-irradiated and irradiated blocks are compared. The results indicate that ɣ radiation has a significant effect on the pH of the leachate. The relation between leaching rate and solubility is illustrated.

Effect of Gamma Radaition on the Morphology of Concrete in Radioactive Waste Disposal Site 2

“…Additionally, the decrease of pH reduces metal mobility for some elements was briefly discussed by R.S. Zaky et al [22]. Carbonation of waste seems to be a best process for immobilization of elements in cement blocks.…”

“…Although carbon dioxide diffusivity is considerably higher in gas filled cement blocks pores, compared to cement blocks water filled pores, the presence of moisture is essential for the reaction of carbon dioxide with calcium hydroxide [28]. In the limiting step of the carbonation process the changes result as the rate of calcium hydroxide carbonation decreases due to the formation of calcium carbonate thin layer on the surface of CH crystals [25,27,22,[29][30][31]. (Ca (CO 3 ) 2 ) crystals form at the calcium hydroxide surface random on Figure (1, a-d).…”