Durability of Concrete Vaults for Radioactive Waste Disposal

The development of a program for the design and construction of a facility for the final disposal of intermediate-level radioactive wastes in the Argentine Republic is the responsibility of the Atomic Energy Commission (CNEA). The proposed model is the near-surface monolithic repository similar to that in operation in El Cabril, Spain. The design of this type of repository is based on the use of multiple, independent, and redundant barriers. Since the vault and cover are made of reinforced concrete and they are major components of the engineered barriers, the durability of these concrete structures is an important aspect for the facilities’ integrity. This paper presents a laboratory and field investigation performed during the last 6 years on reinforced concrete specimens made with high-performance concrete, in order to predict the service life of the intermediate-level radioactive waste disposal vaults from data obtained from electrochemical techniques. The development of corrosion sensors that allow on-line measurements of reinforcing steel corrosion potential and corrosion current density, incoming oxygen flow that reaches the metal surface, concrete electrical resistivity, chloride concentration, and internal concrete temperature is shown. These sensors, properly embedded in a prototype of the vault, allow the monitoring of the corrosion process of the reinforcing steel embedded in the structure. All the information obtained from the sensors is being used for the final design of the container to achieve a service life greater than the foreseen durability for this type of facilities (more than 300 years).