Final disposal

Research and Development for more than 40 years

Posiva investigates the bedrock on the final disposal site and develops technical release barriers for the final disposal of spent fuel. The purpose of the R&D efforts is to ensure compliance with the requirements set forth for the long-term safety of final disposal. The Final Disposal Research has started in Finland over 40 years ago in the end of 1970's.

Site Characterisation Above Ground

Above-ground site investigations include

  • drilling of drillholes for research purposes
  • excavating investigation trenches 
  • groundwater and environmental studies.

Site characterisation investigations related to the final disposal of spent nuclear fuel have been carried out in Olkiluoto since 1980s. The investigations have focused on above-ground conditions, but along with the construction of research facility ONKALO the investigations have proceeded underground.


The excavation of the underground rock characterisation facility ONKALO is part of the site investigations carried out in Olkiluoto. ONKALO reaches the depth of 450 m and is being excavated by a drilling-blasting method. Shafts are built using the raise-drilling method.

The investigations carried out in ONKALO focus on the bedrock and groundwater conditions prevailing on the final disposal site and how construction work affects them. They also serve the purposes of construction and design activities at the construction stage as well as the general design of the final disposal facility.


The investigations carried out in Olkiluoto both above ground and in ONKALO and the results of the investigations are utilised in modelling. Models can be used to assess the performance of final disposal and the effects it has on the rock environment in terms of long-term safety.

Development of Release Barriers

Technical R&D efforts focus on the release barriers used in final disposal. The technical release barriers – the copper canisters, the bentonite clay in which the canisters are enclosed as well as the back-filling material of the tunnels – play an essential role in safe final disposal.

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