WASTE MANAGEMENT | GEOPOLYMER ENCAPSULATION
Above: FISC’s first project, ‘Economic Materials Innovation for the Sustainable and Efficient Use of Resources’ (EconoMISER) is building a new level of scalability and consistency to geopolymer development
MALLET™ MALLET™ was developed in response to several nuclear
industry waste disposal challenges, most significantly low percentage waste loading rates, or in some instances providing a solution where no viable route for disposal presently exists. The geopolymer increases loading rates through formulations that fully encapsulate waste homogenously throughout the matrix. The properties of aluminosilicate sources and the mix
formulation in developing geopolymers are among the key factors that greatly affect the resulting immobilisation and encapsulation efficiency. The passing criteria of the immobilisation technology depends on the following factors:
● Type, amount and chemical composition of waste: the waste loading needs to contain a significant amount (20-50%) for minimising the volume and reduce the cost
● Storage and disposal facility of waste: compatibility with the disposal environment conditions, stored container, etc.
● Durability and stability during leachability conditions ● Chemical stability between the cement and radioactive waste without formation of another phase or compound
● Reduction in risk of releasing radionuclides from damaged containers due to corrosion, accidents, natural disasters, or human interference for example.
Among other factors, leachability resistance plays an important role when the geopolymer-encapsulated radioactive waste matrix is exposed to various conditions such as alkaline buffer solution, sulphate and phosphate solutions, acid attacks, and various forms of water such as groundwater and sea water. Wastes encapsulated within a geopolymer matrix have shown good resistance to leaching. The raw materials used with MALLET™
are not reliant on
scarce source materials such as Ground Granulated Blast- furnace Slag (GGBS) or Pulverised Fuel Ash (PFA), which are becoming more difficult to source to produce traditional nuclear waste cementation products. Ultimately, the objective is to enable nuclear waste
owners to process oils, graphite, zeolites, and sludges into a passive matrix that maximises waste loading and reduces overall waste disposal volumes, therefore providing a simple batch process with little process variability and a significantly lower carbon footprint.
Above: Establishment of a dedicated geopolymer facility is a core output of the geopolymer scale-up programme
32 | September 2024 |
www.neimagazine.com
Performance and characterisation Considering waste acceptance criteria for existing waste disposal routes, the resulting product was monitored and characterised to provide qualitative evidence of performance. The results evidenced a final product which:
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