Studies of Ancient Glass and Their Application to Nuclear-Waste Management
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Studies of Ancient Glass and Their Application to Nuclear-Waste Management Hannelore Römich Abstract During several hundred years of burial in the soil, glass objects, especially those with the high potassium content of medieval compositions, develop heavily corroded surfaces, showing phenomena such as local pitting, laminated layers, and browning effects. The long-term behavior of glass in the soil or in contact with groundwater is not only of interest to glass scientists with a background in archaeology, but also for those with a special interest in nuclear-waste management. Several attempts have been made to propose the decomposition of ancient glasses as an indicator for the performance of buried nuclear-waste glasses. In spite of differences in glass composition and exposure conditions, the development of alteration or corrosion layers with time is a common concern, as shown in this article. Laboratory experiments, representing a simplified model for real conditions, offer the possibility for systematic investigations. Keywords: archaeology, corrosion, glasses, nuclear-waste management.
Introduction The interacting medium plays a dominant role in any corrosion process. For glass, reactions in aqueous solutions have been well investigated. For weathering of glass in the atmosphere, the experimental data are more difficult to interpret and do not always correlate with theoretical models. The reaction of glass in contact with soil is even more complex. Compared with corrosion in liquids or in humid air, corrosion of glass in the soil creates more severe degradation, leading to thicker alteration layers and a broader variety of alteration phenomena.1–4 Archaeological glasses were studied by different authors with emphasis on the structure of the alteration or corrosion layers, the distribution of trace elements, the original glass composition, and the environmental conditions.5–10 Archaeometric studies and questions related to conservation procedures are the major driving force
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for research on the degradation of archaeological glass. In nuclear-waste management, vitrification is the most frequently used method for the disposal of highly radioactive waste fluxes. Studies of the long-term safety of the concept have to evaluate the behavior of the nuclear-waste glasses in their anticipated disposal environment. Various research and development programs during recent years have dealt with research on glass dissolution mechanisms, with performance assessments based on experimental data and simulation models (an overview can be found in Reference 11).
The Concept of Time Among archaeologists, the question has been raised of whether it is safer for the glass objects to be excavated or to be left buried underground. This problem has to be discussed seriously, especially since the
resources for adequate restoration and controlled storage are limited. The concept is based on the assumption that archaeological materials eventually reach an equilibrium in their disposal environment, which implies that the rate of deg
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