Microbial activity in Cementitious Matrices for the Storage of Radioactive Waste from the Decommissioning of Nuclear Power Plants 

The most used materials in civil engineering is concrete and steel. Their unique properties made them candidate materials for components of engineered barrier system for high- and intermediate-level radioactive waste (ILW and HLW) deposition including material from decommissioning of nuclear power plants. Activated materials include mainly stainless steel of nuclear reactor structural elements or carbon steel and shielding concrete of the reactor shaft construction materials. This study is focused on standard and alternative cementitious matrices for deposition of such activated materials mainly in terms of its long-term sustainability in the presence of microorganisms.Four different matrices including cement paste based on Ordinary Portland Cement (OPC), cement paste enriched with bentonite or nano-iron, and finally geopolymer, are exposed to conditions that simulate real repository (anaerobic groundwater). One of the objectives is to describe the growth of microorganisms on/in these matrices as a potential risk for the long-term sustainability of such disposal. After a defined time, changes in microbial activity of the matrices, water leachate and interface between matrix and metal coupons simulating activated waste are monitored using cultivation-dependent and independent approach. Here we will demonstrate results of first samplings after 6, 12 and 24 months of incubation in anaerobic conditions. The results will shed more light on evolution of microbial activity in such extreme conditions in time and bring more information on processing and detection of microbial activity in alkaline materials.