![]() This research contributes to the case for CS’s use in nuclear decommissioning by characterising the behaviour of the grout, working with industry to identify applications for it in decommissioning, and identifying ways of modifying and improving its properties to best fit these and to reduce its cost. These advantages give CS potential to make aspects of nuclear decommissioning cheaper, faster, and safer, but its application has thus far been limited. CS may also be suitable for other decommissioning applications, such as encapsulating radioactive waste canisters, or as a spray coating for contaminated dust. Unlike standard cementitious grouts, CS is non-toxic and environmentally-friendly, has nano-scale particle size, allowing superior penetration, has precisely controllable gelation time, and presents no risk of ground disturbance. CS gel’s very low hydraulic conductivity facilitates its use as a hydraulic barrier, but CS also strengthens weak soils and has potential as a chemical barrier, being able to trap radioactive ions of Cs-137 and Sr-90 via chemical sorption. Colloidal silica (CS) is a novel grouting material with water-like viscosity, which allows it to be injected into soil at minimal pressure to fill free porosity, where it eventually transitions into a rigid hydrogel without change in volume. Disturbances from surface-level decommissioning operations exacerbate the risk of contaminant release into the environment via groundwater and airborne particulate. Legacy nuclear sites often feature regions of contaminated soil, and containment structures which have deteriorated over time. These findings may allow, for example, stronger, more durable, and potentially cheaper barriers to be produced for nuclear decommissioning. This has been done using different additives, by adjusting the properties of the grout itself, or those of its surroundings. Through experimental investigation, various ways have been identified to improve the mechanical performance of colloidal silica, and potentially reduce its cost. At nuclear sites, it has been injected into soil to act as a barrier to trap underground contaminants, but it may have other decommissioning applications. Colloidal silica is a water-like liquid which, after a desired period, will transition into a rigid gel. The focus of this project is to make the case for colloidal silica in decommissioning by modifying and enhancing its properties, aiming to reduce the risk, cost, and complexity of operations. Colloidal silica is a novel, environmentally friendly grout with advantages over standard materials, but it isn’t yet widely used in decommissioning. The risks and high complexity of nuclear decommissioning operations makes them expensive and time consuming with current techniques. In Collaboration with: National Nuclear Lab
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