Corrosion of Nuclear Waste Glass in Complex Natural Environments—A Natural Analogue Approach

Borosilicate glass is commonly used to immobilise high activity waste liquors and is increasingly considered for low and intermediate activity waste streams¹. Radioactive elements, chemically incorporated in the glass structure, will be released at the same rate as the glass itself dissolves. Understanding the long-term behaviour of glass is therefore important in constructing the safety case for its storage and eventual subsurface disposal. The majority of studies aimed at understanding glass dissolution rates and mechanisms have been conducted at elevated temperatures and under, static, sterile conditions, taking no account of changing geochemistry, adjacent mineralogy or geomicrobiology². Here, a combination of field and laboratory tests are used to explore the behaviour of glasses in complex natural environments.<br/><br/>Alteration observed on glasses from long-term studies, in neutral - high pH, iron rich environments relevant to the subsurface disposal of radioactive waste, is compared to alteration observed in short-term laboratory based tests. In addition to observing the mineralogy of the glass alteration layers, field experiments also aim to identify and characterise the unique microbial communities that colonise the interface between nuclear waste type glasses and their environment. Under laboratory conditions, inactive surrogate nuclear waste glasses, containing the essential nutrients, had a controlling effect on the microbial community that were able to utilized nutrients dissolved from the glass where they were absent in solution. The influence of microbial respiration on the dissolution rate of the glass was found to be complex with some conditions inducing a pacifying effect due to biomineral precipitation whilst other conditions appeared to enhance glass corrosion.<br/><br/><i>References:</i><br/>[1] Thorpe CL et al. NPJ Mat Degrad. 2021, 5, 61.<br/>[2] Weaver JL et al. NPJ Mat Degrad. 2021, 5, 11.