WASTE MANAGEMENT | GEOPOLYMER ENCAPSULATION
Scaling up on geopolymers
The challenge of managing problematic radioactive waste in a more scaling up its MIDAR®
sustainable way has prompted research into geopolymer encapsulants as an alternative to Portland cement. Lucideon has been working on technology to deliver a low-carbon low-cost approach
By Stuart Maclachlan, Keir Joynson, and Tim Abbott, Lucideon
AS NUCLEAR ENERGY CONTINUES TO scale into the future as part of the global energy mix, the continuing challenge of how to deal with problematic radioactive waste becomes only more pressing. Nuclear waste immobilisation is part of the process of safely transporting and storing these nuclear materials. This process transforms radioactive waste into a compact form through solidification and encapsulation, reducing the potential for migration or spreading of radionuclides into the environment during transportation and disposal.
Immobilisation of waste is attained by its chemical absorption into the structure of a suitable matrix, such as cement, glass, or a polymeric composite, preventing leachate escape from the matrix. The use of cement- base slurries the favoured method in some countries to encapsulate and immobilise a wide range of hazardous compounds, but the most common, Portland cement (PC), exhibits some limitations when aiming to encapsulate some key types of wastes. For instance, Portland cement
may not be the most suitable candidate to encapsulate radioactive wastes since its hydration process is highly exothermic and this can exacerbate the activity of radionuclides rather than assisting to immobilise them. In addition, Portland cement pastes cured at
high temperatures tend to develop a more porous microstructure which limits their long-term quality as an immobilisation agent. Likewise, Portland cement does not perform very well when encapsulating organic wastes, but the lack of compatibility is of a different nature. Most organic compounds will inhibit the hydration of Portland cement leading to a very inhomogeneous and not chemically bonded product. Although these limitations can be to some extent
addressed through the addition of other materials such as inert fillers, the economic and supply chain implications arising from this solution bring about problems of their own. A clear demand is therefore present for an appropriate alternative to existing cements for nuclear waste encapsulation.
Above: Geopolymer technology can use a low-temperature chemical reaction to consolidate aluminosilicates with high strength and chemical stability
30 | September 2024 |
www.neimagazine.com
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