The concept of geological storage is to isolate waste from the biosphere (radioactive waste), the atmosphere and the hydrosphere (carbon dioxide) over periods of time that may last for several centuries, millennia or even millions of years.
The objective is to delay, for as long as possible, the release and dispersal of radioactive elements or CO2. This makes it possible to prevent the toxic effects of ionising radiation from nuclear substances or even the greenhouse effect and acidification of the oceans by CO2.
This type of storage is based on the principle of multiplication of barriers, the most important being the geological structure itself. Other artificial barriers, as well as monitoring measures, are used to complete the storage system.
The main problems of deep geological storage are water seepage, undetected leaks and geological events (earthquake, volcanic eruption). The human element is also to be taken into consideration, in the event of inauspicious drilling or a war, for example.
The different risks of geological storage of nuclear waste in Yucca Mountain (United States). © DOE, public domain