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Glass behavior in geological disposal

On January 27, the AFP news agency published a dispatch concerning an American study on the behavior of the glasses in which high-level radioactive waste is conditioned. According to this study, corrosion of the glass or ceramic used to confine this waste is "significantly accelerated" under certain conditions. This dispatch has been the subject of numerous press and social media reports. But the results of this study cannot be transposed to Cigeo: Decryption.

The published study deals with the American geological storage project, the Yucca Mountain project, the concept of which is different from Cigeo. Consequently, the conclusions on the behavior of the glasses in question in this study cannot be transposed to Cigeo. In fact, Cigeo's long-term safety relies on the clay layer of the Callovo-Oxfordian which has been selected for its properties favoring the confinement of radioactive elements (low permeability, thickness of the layer, physicochemical properties, etc.). Thus the geological environment limits and slows the movement of radioactive elements for hundreds of thousands of years.

The geological barrier is supplemented by several complementary barriers, such as glass serving as a matrix for high-level waste. In a prudent approach and to take into account the residual uncertainties on the behavior of the glasses, Andra conducts safety analyzes which take into account the disposal conditions and integrate all the storage components (clay, concrete, steel, glass…), as well as the possibility of a faster than expected dissolution of the glass.
 
Numerous studies involving Andra and the producers of radioactive waste have been performed, by CEA R&D, on the behavior of glass in disposal conditions, and are based in particular on experiments carried out at the underground laboratory. This work concerns in particular the temperature within the repository, the presence of Callovo-Oxfordian (host geology) water, the saturated and unsaturated water conditions, contact with the Callovo-Oxfordian, contact with steel and its corrosion products. and more recently the presence of water vapor, the presence of cement water at low pH, and the effect of radiation.

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