Preliminary design of the repository, stage 2

Timo Saanio, Timo Kirkkomäki, Paula Keto, Tapani Kukkola, Heikki Raiko

Research output: Book/ReportReport

Abstract

Spent nuclear fuel from Finnish nuclear power plants will be disposed of in deep bedrock in Olkiluoto, Eurajoki. The repository is planned to be excavated at a depth of 400 - 500 metres. Access routes to the repository include a 1:10 inclined access tunnel, and vertical shafts. The fuel is encapsulated in the encapsulation plant above ground and transferred to the repository in the canister lift. Deposition tunnels, central tunnels and technical rooms are excavated at the disposal level. The canisters are deposited in deposition holes that are covered with bentonite blocks. The deposition holes are bored in the floors of the deposition tunnels. The central tunnel system consists of two parallel central tunnels that are inter-connected at certain distances. Two parallel central tunnels improve the fire safety of the rooms and also allow flexible backfilling and closing of the deposition tunnels in stages at the operational phase of the repository.

An underground rock characterization facility, ONKALO, is excavated at the disposal level to support and confirm investigations carried out from above ground. ONKALO is designed so that it can later serve as part of the repository. ONKALO excavations were started in 2004. The repository will be excavated in the 2010s and operation will start in 2020. The fifth nuclear power unit makes the operational phase of the repository very long. Parts of the repository will be excavated and closed over the long operational period.

The repository can be constructed at one or several levels. The one-storey alternative is the so-called reference alternative in this preliminary design report. The two-storey alternative is also taken into account in the ONKALO designs. The preliminary designs of the repository are presented as located in Olkiluoto. The location of the repository will be revised when more information on the bedrock has been gained. More detailed data of the circumstances will be obtained from above ground investigations, investigations in ONKALO and investigations during the excavation and operation of the repository. The repository is planned so that technical development can be flexibly utilized. The total volume of the repository is approximately 1.3 million m3. The maximum open volume at any one time is around 0.6 million m3, because the repository is excavated and backfilled in stages.

The repository is divided into the controlled area and the uncontrolled area. Canisters are always handled and lowered to the deposition hole in the controlled area. The excavation and construction of new tunnels and the backfilling of the tunnels is carried out in the uncontrolled area. Extensive material transfers, such as transfers of broken rock and backfilling materials are conducted in the access tunnel. Separate ventilation systems are provided for the controlled and the uncontrolled area.
Original languageEnglish
PublisherPosiva
Number of pages130
Publication statusPublished - 2006
MoE publication typeD4 Published development or research report or study

Publication series

SeriesPosiva Working Report
Number2006-94

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Saanio, T., Kirkkomäki, T., Keto, P., Kukkola, T., & Raiko, H. (2006). Preliminary design of the repository, stage 2. Posiva. Posiva Working Report, No. 2006-94