Evolution of corrosion parameters in a buried pilot nuclear waste container in el Cabril

Modern concrete has a record of good performance of around 120 years although there are structures in perfect conservation made with roman concrete (mixture of lime and natural pozzolans). El Cabril repository has a design life of 300-500 years and therefore, it should keep its integrity much longer than the back experience we have on reinforced concrete structures, which makes necessary a closer monitoring with time on the aging of concrete in real conditions. With this purpose, Enresa has designed in collaboration with IETcc and Geocisa the installation of permanent sensors in a pilot nuclear waste container in buried conditions. The sensors were installed in 1995 for monitoring corrosion parameters and have been working until present. The non-destructive tests (NDT) applied are based in electrochemical measurements (corrosion rate, corrosion potential, electrical resistivity, concrete strains, oxygen availability). Relations between the climatic influence, the buried depth and the corrosion parameters are also presented. The results indicate that temperature is a very relevant variable influencing the measurements. All the other parameters evolve according to seasonal changes. Values of activation energies of the resistivity changes are given although it seems more adequate to model the evolution with time by simply plotting the values registered at 20 ± 2 °C.