Prediction of Long Term Corrosion Behaviour in Nuclear Waste Systems
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Prediction of Long Term Corrosion Behaviour in Nuclear Waste Systems Damien Féron1 and Digby D. Macdonald2 1 Service de la Corrosion et du Comportement de Matériaux dans leur Environnement, Département de Physico-Chimie, CEA-Saclay, Bât. 548, 91 191 Gif-sur-Yvette, France 2 Center for Electrochemical Science and Technology, Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, U.S.A.
ABSTRACT The corrosion resistance of container materials in underground repositories is an important issue for the safe disposal of High Level Nuclear Waste (HLNW). The reliable prediction of container degradation rate and engineering barrier integrity over extended periods, up to several thousands years or even several hundreds of thousands of years, represents one of the greatest scientific and technical challenges. The first and the second International Workshops on Prediction of Long Term Corrosion Behaviour in Nuclear Waste Systems, which were held in 2001 (Cadarache) and 2004 (Nice), sought to compare the scientific and experimental approaches that are being developed in various organisations worldwide for predicting long term corrosion phenomena, including corrosion strategies for interim storage and geological disposal. The lessons learned during these Workshops, include the necessity of developing two approaches based on semi-empiricism and determinism in a complementary manner for effective prediction. The use of archaeological artefacts to demonstrate the feasibility of long term storage and to provide a database for testing and validating modelling work was also emphasized.
INTRODUCTION Worldwide, industrial development requires the ever-increasing production of energy. Currently, almost one fifth of the world’s total electricity production arises from nuclear power plants. However, besides producing electricity for the benefit of society, nuclear power leaves dangerous radioactive residues for which a safe, long-term solution has to be found to protect the many generations to come. The generally accepted strategy for dealing with long-lived High Level Nuclear Waste (HLNW) is deep underground burial in stable geological formations, after a period of interim storage to allow for the decay of both the temperature and the most active, short-lived isotopes (transmutation of long term radioactive elements is the other main approach). In geological disposal, or in long term interim storage, isolation of the waste is achieved by applying the multibarrier concept, which involves the use of several natural and/or engineered barriers to retard and/or to prevent the transport of radio-nuclides into the biosphere. The metallic container constitutes one of the most important engineered barriers, with the main threat to metal or alloy integrity being corrosion. Clearly, the reliability and the viability of integrity predictions are of paramount importance in assuring the public that safe storage and disposal can be achieved. The prediction of accumulated corrosion damage with regard t
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