WASTE MANAGEMENT | ENCAPSULATION TECHNOLOGY


Above: Homogeneous sample section of an oil matrix with a 40% volume of oil incorporated


challenges, most significantly low percentage waste


loading rates, or in some instances providing a solution where no viable route for disposal presently exists. The Lucideon/NUVIA collaboration has provided evidence to demonstrate MALLET™


● Has controlled porosity, voids, and homogeneity. ● Low viscosity allows the product to be pumped very


easily directly into containers and enables application of pour-on/infiltration techniques.


as a superior method of managing


intermediate and low-level waste streams, including oils, graphite, zeolites, sludges, and ashes. The raw materials used 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. MALLET™


increases loading rates through geopolymer


formulations that fully encapsulate waste homogenously throughout the matrix, as shown in the images below: 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: ● Is fully set and free from cracking. The casting and curing procedures were done at room temperature (RT).


● Is dimensionally and physically stable at RT before and after leaching in various solutions including deionised water, buffer solution with high pH, and organic solvent.


● Is leach resistant (no release of strontium and caesium ions).


● Has strong compressive strength (>0.4 MPa, in many cases much greater) before and after leaching procedures.


● Generates a minimal exothermal reaction during the mixing, curing, and setting.


Irradiation testing was undertaken on a range of samples, demonstrating end-product integrity after 1 MGy total absorbed dose of gamma radiation from Cobolt 60. This technical innovation is delivered by the geopolymer


formulations and encapsulation methods. With existing encapsulation methods, relatively low levels of difficult-to- treat waste materials are encapsulated, usually at levels between 2% and 30% (the loading rate). This new approach has allowed the loading rate to increase to up to 70%. The potential savings from such an increase in loading are considerable. The new encapsulation technique enables nuclear waste


owners to process oils, graphite, zeolites, and sludges into a passive waste matrix that maximises waste loading and reduces overall waste disposal volumes, providing a simple batch process with little process variability and a significantly lower carbon footprint. The encapsulation system has demonstrated how


collaborative innovators can quickly develop solutions to complex challenges, supported by physical trials and proof of concept. As a replacement to PC for nuclear waste encapsulation, -Augmented Lower-cost Lower-carbon


the MIDAR®


Encapsulation Technique has the potential to reduce the carbon impact of cementation processes, considerably reduce storage costs and provide security of supply. The flexibility of the developed formulations also allow the material to be adapted for broader nuclear applications such as stable, corrosion and fire-resistant structural materials for long-term storage. Given the scale of the expected impact on nuclear


Right: Homogeneous sample section of AW500 Zeolite at 70 wt.%, encapsulated via MALLET™


‘pour on’


that eliminates the need for mechanical mixing procedure


42 | November 2023 | www.neimagazine.com


decommissioning, it is not a question of whether this technology will be deployed – but who will prioritise the scale-up first and thus become the world leaders in advancing how we treat legacy and future wastes. ■


Foot note:


Some of the activities described in this article were facilitated by Innovate UK Knowledge Transfer Network and were partially funded via the UK Research and Innovation (UKRI) Challenge Fund (through Innovate UK).


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