Safety - precondition for final disposal
The assessment of the safety of final disposal covers the operation of final disposal facility and the performance of the repository after its closure. Long-term safety assessment refers to the post closure period of the final disposal facility.
Multiple Barriers Prevent the Release of Any Radioactive Substance to the Biosphere
Long-term safety is based on the multibarrier
principle. Radioactive substances are contained in several barriers that
support each other, yet are as independent from each other as possible, so that
the failure of one barrier will not endanger the overall functioning of the
The technical barriers of final disposal include
- the ceramic state of the fuel
- the canister made of copper and cast iron
- the bentonite buffer and the tunnel back-filling
The bedrock function as a natural barrier.
The safety is appraised in several stages
Long-term safety of the solution is essential when it
comes to final disposal of spent nuclear fuel. The performance of the engineered barrier system in the Olkiluoto bedrock conditions during thousands of years is under scrutiny in the long-term safety assessment. When assessing the safety of final disposal, also unlikely scenarios like failures in the performance of the engineered barrier system, are considered.
Long-term safety of final disposal is assessed at several licensing stages, including the the Decision-in-Principle, construction license and operation license. The Radiation and Nuclear Safety Authority, STUK, issued the preliminary safety assessment report in 2000 before the Government made the favorable Decision-in-Principle on the selection of Olkiluoto as the final disposal site for spent nuclear fuel.
Posiva submitted the construction license application to the authorities in December 2012. Substantial part of the application deals with the safety case for final disposal. It comprises of the report portfolio, which sums up arguments and conclusions of the long-term safety of final disposal. The safety case demonstrates how the engineered barrier system consisting of final disposal canister, bentonite buffer and tunnel back-fill will perform in Olkiluoto bedrock conditions over the course of thousands of years and also assesses radiation doses to environment if the isolation of the engineered barrier system was deteriorated.
Construction licence for final disposal facility of spent nuclear fuel was granted in November 2015. In February 2015, Finnish safety authority STUK issued a statement to the Ministry of Employment and the Economy stating that Posiva's encapsulation plant and final repository for spent nuclear fuel can be built to be safe. Posiva can now proceed to construction of the final disposal facility in Olkiluoto according to the concept it has developed.