Abstract
Initial leaching characteristics of simulated nuclear waste immobilized in three alkali- borosilicate glasses (ABS-waste) were studied. The effects of matrix composition on the containment performance and degradation resistance measures were evaluated. Normalized release rates are in conformance with data reported in the literature. High Li and Mg loadings lead to the highest initial de-polymerization of sample ABS-waste (17) and contributed to its thermodynamic instability. Ca stabilizes non-bridging oxygen (NBO) and reduces the thermodynamic instability of the modified matrix. An exponential temporal change in the alteration thickness was noted for samples ABS-waste (17) and Modified Alkali-Borosilicate (MABS)-waste (20), whereas a linear temporal change was noted for sample ABS-waste (25). Leaching processes that contribute to the fractional release of all studied elements within the initial stage of glass corrosion were quantified and the main controlling leach process for each element was identified. As the waste loading increases, the contribution of the dissolution process to the overall fractional release of structural elements decreases by 43.44, 5.05, 38.07, and 52.99% for Si, B, Na, and Li respectively, and the presence of modifiers reduces this contribution for all the studied metalloids. The dissolution process plays an important role in controlling the release of Li and Cs, and this role is reduced by increasing the waste loading.
Highlights
Radioactive waste disposal is considered to be the last step in radioactive waste management systems [1,2,3]
The release of alkaline earth metals from Modified Alkali-Borosilicate (MABS)-Waste (20) and alkali-borosilicate waste glass (ABS)-Waste (25) is characterized by very slow rates (Figure 1e,f) and their normalized release rates are in conformance with published data for different ABS-waste matrices [30]
Leaching characteristics of different structural elements, modifiers, and waste components were investigated for three alkali-borosilicate-mixed oxide glasses that represent different waste loadings
Summary
Radioactive waste disposal is considered to be the last step (end point) in radioactive waste management systems [1,2,3]. To ensure safe performance of these facilities throughout their life cycles, assessment studies have to be conducted to support the decision-making process In these assessments, temporal evolution of engineering barriers and the dynamic nature of hydrological and biological subsystems in the host environment are considered by applying a modular approach [3,5,6]. The main safety function of glass waste matrices is to slow down radionuclide releases from a geological disposal facility [15] In this respect, two performance indicators are used to assess the quality, reliability, and efficiency of the waste matrices, namely the glass–water reaction rate and the radionuclide leach rate that ensure the degradation resistance and containment ability of the matrices, respectively. These indicators are evaluated by conducting leaching experiments that simulate leaching conditions under conservative disposal conditions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
