The slow strength gain and low exothermic properties of ggbs have led to its use in the decommissioning of Britain’s older nuclear power plants.
Sellafield Ltd acts as a contractor to the Nuclear Decommissioning Authority, whose objective is to ensure that the 20 civil nuclear sites under its ownership are decommissioned and cleaned up safely. Sellafield first used ggbs for the encapsulation of medium-level radioactive waste in the 1980s.
Since then, with the £3.2 billion nuclear decommissioning programme gathering pace, it has been using up to 2,000 tonnes of ggbs a year for the encapsulation of waste streams from its thermal oxide reprocessing plant.
A 90 per cent ggbs to 10 per cent Portland cement ratio is used in the grout for the encapsulation process. This high ratio controls the strength gain, reduces the heat generated, minimises the risk of thermal cracking and restricts diffusion.
The precisely controlled particle size distribution of the specially produced ggbs produces a grout with high flow and extended working life without the use of chemical admixtures. In this challenging application, encapsulation with ggbs grout provides long term durability, stability and peace of mind.