Excavation of joint functional test final disposal tunnel started at Posiva’s ONKALO
If it were placed above ground, the 460-metre steel frame built for the personnel shaft would be the tallest human-made steel structure in the Nordic countries. The construction and installation work at ONKALO and the encapsulation plant are proceeding rapidly as part of the EKA project. Posiva will be the first company in the world to start the geological final disposal of spent nuclear fuel in the mid-2020s.
Excavation work has started at the underground research and final disposal facility ONKALO, located at Olkiluoto in Eurajoki, for a final disposal tunnel for the joint functional test (YTK) that will take place in the near future. A tunnel with an approximate length of 80 metres will be excavated during the winter and spring, and four deposition holes will be drilled into it during the joint functional test.
The excavation has been preceded by careful preparation and planning in cooperation with the Radiation and Nuclear Safety Authority, since the YTK tunnel simulates a real final disposal tunnel. The central tunnel related to the test was already excavated earlier.
- In February, we will reach 48 metres, after which the excavation will be interrupted, the base of the tunnel will be levelled out and the required compaction work will be done, says worksite manager Kimmo Lehtola from Posiva Oy, the company responsible for the final disposal of spent nuclear fuel.
Lehtola emphasises that the excavation is a method test that pays special attention to the block between 19 and 48 metres.
- Surveys and subsurface imaging measurements will be performed in the region of this block. They are used to confirm that the bedrock has no water flow paths or discontinuities caused by the excavation. The method test is used to demonstrate that we can perform the work according to the plans and requirements.
The excavation of the tunnel will continue after the investigation, and 80 metres will be reached around April–May. The YTK tunnel is shorter than the actual final disposal tunnels that will typically be some 350 metres in length.
The joint functional test that will take place in 2023 will test final disposal using the technology designed for it. However, the canisters placed in the bedrock during the test will not contain spent nuclear fuel, as the intention is to ensure that the methods designed for final disposal operate as planned. The joint functional test will also be monitored by the authorities who will be examining the processes of the joint functional test with a view to the operating licence.
- Once the tunnel for the joint functional test is complete, excavation of the first five final disposal tunnels will begin. Actual final disposal activities will begin in one of the tunnels around 2025, says construction manager Juha Riihimäki from Posiva.
“Posiva Solutions is right now preparing a model where waste management organizations (WMOs) from all over the world will be able to participate to closely follow this test. Should you be interested to hear more about this opportunity, please contact Posiva Solutions through this linkPosiva Solutions contact detailsOpen link in a new tab”
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