The ability of microbial biofilms to modify the surface properties of nuclear cements

Initial work will focus on the establishment and characterization of the cement test pieces. These test pieces with simulated cracks, will be cast in flow through biocells and the exposed cement surfaces will be initially characterized through SEM, EDX and CLSM. Background data on the ability of these surfaces to retard the transport of Ni, U and Th plus the complexing agent Iso-saccharinic acid will be determined under strict anaerobic conditions using simulated groundwaters. This work is enabled by the fact that SAS now have the ability to work with these radioelements. To increase the academic impact, the STFC Diamond XRD and XAFS facility will be used to characterize the speciation of the radioelements associated with these surfaces. Collaborators at the University of Leeds will assist in accessing the facility and the analysis of the resulting data.

Once the background data has been acquired, replicate cement biocells will be established which will be exposed to the alkaliphilic, biofilm forming communities that have been under investigation by the environmental microbiology team in recent years. These cells will be run until biofilms have been established and then exposed to the radioelements under investigation. The impact of the biofilms on radioelement retention will be determined initially through mass balancing, followed by more detailed surface characterization via SEM/EDX potentially followed by XRD and XAFS if sufficient retention of radioelements has occurred. CLSM will be used to characterize the structural aspects of the biofilm allowing the 3D structure to be determined and the relative positioning of key components such as proteins, lipids, carbohydrates and extracellular DNA identified. Comparison between flow cells with and without biofilms will allow a retention adjustment factor to be calculated which can then be factored into environmental transport calculation. Once the flow cells are fully characterized the associated microbial populations will be characterized. In order to optimize the impact of the research metagenomics/metatranscriptomic approaches will be applied to identify the key active metabolic pathways within these unique microbial systems.