Long-term safety
The goal of the disposal of radioactive waste in deep geological formations is to prevent harmful effects of the waste on humans and the environment in the long term. Therefore, demonstrating long-term safety is a central element of the disposal of radioactive waste.
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The aim of a final disposal for radioactive waste in deep geological formations is to prevent any long-term damage to people and the environment caused by the waste. The hazardous nature of the waste declines over time as a result of radioactive decay. However, some of the waste with long-lived radionuclides can still radiate even after 100,000 years, which means that the waste still needs to be isolated from the biosphere beyond this time frame. Time periods of up to 1 million years are therefore taken into consideration in the long-term safety analysis.
1 million years is a very long time period when seen in the context of mankind. We are just as incapable today of predicting how mankind will develop over this period of time, as the early human beings existing 1 million years ago − in other words, long before Neanderthals or Cro-Magnon man − could foresee how we live today. However, 1 million years is a very short period of time in terms of the history of the earth, and in geologically stable regions where the development of the geology can be traced back over several tens or hundreds of millions of years, it is possible to reliably predict how these will develop geologically over the next 1 million years. This is why final disposal in geological formations has been selected as the way forward: where the long-term safety of the geologic repository depends on the stability of the geological barriers, and does not require any subsequent human attention.
A long-term safety analysis is carried out to determine whether a geologic repository could give rise to any radiological impact on the biosphere during the course of the next 1 million years. This involves creating scenarios combining all of the feasible future features, events and processes – such as the thermal expansion of the host rock due to the disposal of heat-generating waste, gas formation in the repository due to corrosion processes, or the occurrence of an ice age with potential glaciation and significant impacts on the underground. The consequences for the geological barriers of these scenarios are determined on the basis of numerical simulations.