Assessing the physical suitability of different immobilisation grouts for LLW and ILW encapsulation.

The issue of legacy wastes from early civil nuclear operations is vast, complex and multifaceted. Variations in composition, radioactivity and state (liquid, solid or a combination) mean that a ‘toolbox’ of different systems is required to provide appropriate conditioning prior to final disposal. For Low level waste (LLW) and Intermediate level waste (ILW), the preferred method in the UK is encapsulation in a cementitious matrix. This study has been performed to assess the physical performance of one such grout in comparison to potential replacements in order to determine their potential suitability. This work aims to define a set of physical tests which may be applied as a precursor to more rigorous assessment of future grouting systems. Samples were prepared at varying cement:replacement and water:binder ratios, as shown in Table 1, in accordance with current practice in industry and to ensure suitable workability and setting time. Following curing at 20°C ±1°C and 98% RH for 28 days, UCS, permeability, sorptivity and Acid neutralising capacity (ANC) were measured with further characterisation via SEM-BSE and simultaneous thermal analysis (STA).