Research performed by Debabrata Ghosh.
The nuclear industry has used for decades cement‐based materials (CBM) to immobilize radioactive liquid waste originating from different nuclear applications. CBM show many advantages as an partial replacement to Ordinary Portland Cement (OPC) and the waste‐form generated by the immobilization process must be stable in long‐term. CBM can be degraded, among other processes, by alkali‐silica reaction (ASR) and leaching. These processes have the potential of cause cracking and loss of integrity of the waste‐form and their single effects have being study for long time. However, there is still lack of studies on their combined effects. This PhD project aims at performing a comprehensive study to assess the coupled effect of ASR and leaching on the development of microstructure, mineralogy, expansion and stability of the blended cement based matrix used for encapsulation of radioactive liquid waste containing high nitrate content. Simulated waste with a varied chemical composition (non‐active) will be produced and conditioned in a cementitious matrix based on OPC and CBM’s. A variety of characterization techniques will be used to assess the changes in microstructure, mineralogy, transport and mechanical properties caused by these processes. Besides an intensive experimental program, a modelling approach will be carried out to develop a conceptual model in order to assess the long‐term evolution of a cementitious matrix – waste stream system.
