When optimising waste glass compositions, chemical durability is a key consideration along with melting rate to allow a fast waste throughput, waste loading, homogeneity, and processing ease (melting temperature, viscosity, etc.). However, sodium-aluminophosphate glass is used to immobilise HLW in Russia, while iron-phosphate glasses have been investigated for potential immobilisation of HLW and LAW in the USA (Table 1 refs. Most countries use alkali–borosilicate glass compositions to immobilise calcined or liquid feed reprocessing waste. Meanwhile, in the USA, a vitrification plant is shortly to begin to encapsulate low-activity waste (LAW) and, eventually, processed HLW at the Hanford Site in Washington State 14, 15. These programmes are considering vitrification technologies, including continuous feed joule-heated melters, and in-container vitrification using Kurion GeoMelt ®/Veolia Geomelt ® technology 9, 10, 11, 12, 13. Extensive research programmes are underway in European countries including the UK, France and Belgium, under the European H2020 research programmes, THERAMIN and PREDIS 7, 8. Vitrification has also been applied to the immobilisation of lower-activity waste streams with a range of glass compositions 4, 5, 6.
Vitrification is the most common treatment technology for the immobilisation of high-level radioactive wastes (HLW) arising from spent fuel reprocessing, being applied since the late 1970’s at facilities in Belgium, China, Germany, India, Japan, Pakistan, Russia, Slovakia, UK and USA (Table 1) 1, 2, 3. The methodology discussed is relevant across a wide range of nuclear and non-nuclear glass compositions including silicate, borosilicate, and phosphate glasses as well as glass ceramics. This review will focus on the laboratory testing methodology developed to predict the durability of nuclear waste glasses that are typically highly durable.
However, the main economic, technical, and regulatory, driver behind the need to estimate the corrosion behaviour of vitreous materials over very long timescales, 10 3–10 6 years, arises from planned isolation of vitrification of radioactive wastes in subsurface repositories. Understanding the behaviour of glasses in contact with water, or water vapour, is of interest across many disciplines including archaeology, geology, waste encapsulation, construction, fibre optics, semiconductors and art.
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