Earthquakes and radwaste repository in deep geological formations

The safety of the site of a radwaste repository in deep geological formations depends on the containment afforded by various barriers. For France, these barriers, three in number, are respectively: (a) the packaging of the waste, (b) the engineered barrier, and (c) the geological barrier. Among the range of events liable to have an impact on the site of an underground waste repository, earthquakes seem to be particularly of concern in that they are capable of affecting all three barriers simultaneously. The integrity of the repository site can be endangered, when the earthquake is nearby, by the fault rupture and the associated deformations, and when it is more distant, by the seismic motion generated by the rupture. In either case, the safety of the repository will be guaranteed, in the last analysis, by the geological barrier: its behavior, essentially from a hydromechanical standpoint, must remain stable in order to prevent the migration of fluids towards the biosphere. Since 1989, the Institute of Protection and Nuclear Safety (IPSN) has developed a research program for the purpose of taking into account the specificities of a deep waste repository in terms of depth and life-expectancy in the seismic risk assessment. This program calls upon a wide assortment of disciplines in earth science (geology, tectonics, geophysics, seismology, engineering seismology, hydromechanics, etc.). (authors). 5 figs., 24 refs