Immobilisation of Fe floc: Part 1, pre-treatment of floc with slaked lime

The suitability of a supersulfated cement for nuclear waste immobilisation

“…The historical composite cement formulations developed have proved suitable for immobilising ILW arising from fuel reprocessing and large numbers of drums are currently curing in storage awaiting ultimate disposal [10][11][12][13][14]. These systems have advantageous properties such as a high pH pore water which is reported to provide an environment in which the solubility of many heavy metal oxides, carbonates and hydroxides is reduced, limiting their migration through the porous microstructure of the hardened cement paste [15].…”

Immobilisation of Fe floc: Part 2, encapsulation of floc in composite cement

“…The interaction of the floc with Ca(OH) 2 during pre-treatment has been reported [2] and initial results investigating the subsequent cement encapsulation process have previously been reported [1]. However, this paper provides a more in-depth analysis of the chemical and physical interactions between the cement and an inactive floc of the same composition as one of the active flocs produced at Sellafield.…”

“…The simulant floc was supplied by Nexia Solutions and initial characterisation has previously been reported [1]. The method of floc preparation is described in part 1 of this paper [2]. To summarise, the floc was a brown viscous aqueous colloidal suspension which had no odour, exhibited thixotropic characteristics and the solids were largely X-ray amorphous.…”

“…the C-S-H during hydration of the composite cement due to the more highly alkaline environment created by the slaked lime during pre-treatment. Additionally, the main reaction product of pre-treatment (an X-ray amorphous calcium ferrite phase [2]) may be more reactive and lead to more incorporation of iron into the C-S-H.…”