Near-field/far-field interface of a near-surface low level radioactive waste site

Experimental and Modelling studies have been used to investigate the biogeochemical processes occurring at the interface zone between the near-field and far-field of the Drigg Low- Level radioactive Waste (LLW) trenches. These have led to a conceptual model of interface biogeochemistry, which has subsequently been modelled by the BNFL code known as the Generalised Repository Model (GRM). GRM simulations suggest that as organic rich leachate migrates into the far-field, iron III minerals such as iron hydroxide will dissolve, and reduced iron minerals such as siderite will precipitate due to microbial processes. Batch and column experimental studies have verified this conceptual understanding. Some unexpected processes, such as the presence of nitrate enhancing sulphate reduction, were also observed.