CONCRETE BEHAVIOUR IN ENGINEERING BARRIERS FOR LOW AND MEDIUM RADIOACTIVE WASTE REPOSITORY: EXAMPLE OF El CABRIL, CORDOBA, SPAIN

Prestressed and reinforced concrete are the most usual material used as engineering barriers in nuclear disposal facilities. The record of modern concrete is however no longer than about 100 years. During this time, it has been noticed that the material gives a good performance in many environments, however several chemical aggressive species in water, soil or the atmosphere may react with the cement mineralogical phases and perturbate its integrity. The challenge of concrete as an engineering barrier is therefore its long term stability. Concrete to be used in engineering barriers has to be properly designed. The cements have to be traditional and able enable low transport rate. They have to be of low C3A and alkali contents. The concrete proportioning has to be so, to result in low porosity. The El Cabril repository has a design life of 300–500 years and therefore, these structures should remain until this target service life. The possible aggressive conditions that the cement based materials can suffer have been identified to be: carbonation, water permeation (leaching) and reinforcement corrosion. More unlikely may be the biological attack. Chlorides are not in the environment but they are inside the drums as part of analytical wastes. The main cement based materials used as engineer barrier in the repository of El Cabril for low and medium radioactive wastes are the Cells, the Containers and the mortar filling the gaps between the drums introduced in the containers. Cells and containers are made of the same concrete composition while the mortar was specifically designed to be pumpable and with high impermeability. In this paper results of concrete chararcteristies are given as well as the monitoring of the behaviour of reinforcement corrosion parameters from 1995. This monitoring has been made in a buried structure with embedded sensors. The effect of temperature is commented.

• INTRODUCTION

• TYPES OF STRUCTURES WITH CBM IN EL CABRIL

• SERVICE LIFE PREDICTION OF CBM IN EL CABRIL

• ENVIRONMENTAL CONDITIONS AT EL CABRIL

• TESTS CARRIED OUT TO DEVELOP A LIFE MODEL

• BASIS FOR MODELLING CORROSION OF REINFORCEMENTS

• FINAL COMMENTS

• ACKNOWLEDGEMENTS

• REFERENCES