The final disposal solution is the result of decades of research
and development work aimed at developing a safe solution for permanent
isolation of nuclear waste.
The Olkiluoto island was chosen as the site of the repository from among many survey sites on the basis of location surveys and safety assessments carried out between 1987 and 2000. The underground research tunnel that has been under construction since 2004 in the Olkiluoto bedrock has enabled research at the actual disposal depth. The aim has been to preserve the good characteristics of the bedrock as far as possible at the construction phase of the underground research facility.
The research carried out during the construction has confirmed earlier assumptions about the bedrock properties. Based on the research, it is now known that
There are only few cracks in the bedrock at the disposal depth
The bedrock is stable
At a depth of hundreds of meters, the groundwater is oxygen-free
Groundwater flows are minimal
The safety of final disposal is supported with information obtained through research. The bedrock, the materials used in the disposal process, and the functionality of the technical solutions are subjected to safety studies.
An extensive body of assessment documentation, known as the safety case, is prepared to prove the safety of final disposal. The most central part of the safety case is scenario analysis whereby the behavior of the final disposal system installed deep in bedrock is assessed on the basis of postulated event sequences. The temporal scopes of the analyses stretch far into the future, and they consider factors such as climate change and the formation of a thick glacier as well as associated bedrock movements.