Development of a multiparametric system based on solid-state microsensors for monitoring a nuclear waste repository

Nuclear waste repositories are being installed in deep excavated rock formations in some places in Europe to isolate and store radioactive waste. Containers with radioactive waste are also protected with barriers made from porous materials such as bentonite. The objective of this work is to study the transport of radioactive compounds thorough bentonite models to obtain a database of the bentonite–water interaction processes. Among the chemical parameters tested in these barriers, the most significant are pH, conductivity and redox potential. For that purpose, solid-state microsensors fabricated with silicon semiconductor technology such as ion sensitive field effect transistors (ISFETs) for measuring pH and interdigitated structures (IDS) for measuring conductivity and redox potential were used. Response characteristics of these sensors were tested in aqueous samples with compositions similar to those present inside a bentonite barrier and results were compared with those obtained with commercial electrodes obtaining a good agreement between commercial and our sensors.