Posiva’s ONKALO at the final disposal depth
ONKALO, the underground rockcharacterisation facility excavated in the Olkiluoto bedrock, will reach its final disposal depth in June.
Started in 2004, the tunnel excavation and research performed during the work have strengthened the understanding provided by aboveground drilling and measurements of the suitability of the Olkiluoto bedrock for the final disposal of spent nuclear fuel. In addition to underground research, bedrock investigations will also be continued above the ground. Currently, the 54th deep research hole is being drilled in Olkiluoto.
“The first deep research hole was drilled in Olkiluoto as early as 1989, after which we have collected more than 30 kilometres of rock samples. In recent years, the emphasis of drilling has been placed on the eastern parts of the island where we are investigating the suitability of the bedrock for the spent fuel produced by potential new plant units of our owners,” says Reijo Sundell, President of Posiva.
The excavation of ONKALO has proceeded to a depth where the properties of the bedrock represent those of the final repository. The properties will be studied in greater detail in the ONKALO research niches. A total of five research niches are used for studying bedrock stress, hydrochemistry, and water conductivity. “We have launched an experiment at a depth of 350 metres, studying the impact of bedrock stress. We will drill three holes of 1.5 metres in diameter and 7 meters deep,” says Timo Äikäs, Executive Vice President of Posiva.
Two test and demonstration tunnels will be excavated at the final disposal depth so that their design and implementation correspond with those of the final disposal tunnels. The primary objective is to indicate the readiness to localise a suitable bedrock volume for the final disposal tunnels and canister holes, and to excavate the tunnels according to the requirements. In addition to the test and demonstration tunnels, we will excavate equipment and maintenance facilities deep into the bedrock. The planned excavation will be completed by the end of 2011.
Currently, the aboveground construction of ONKALO is focused on the foundations of the ventilation and hoist building. The objective is that the ONKALO facility will be ventilated through the ventilation building in 2011.
In honour of reaching the final disposal depth of 420 metres, Posiva organised a topping-out ceremony in ONKALO on 17 June 2010. The festivities were led by Erkki Virtanen, Permanent Secretary of the Ministry of Employment and the Economy.
Pictures of the topping-out ceremony will be available on the Posiva website at Image gallery after the festivities starting from 6:00 p.m.
For more information, please contact:
Reijo Sundell, President, tel +358 2 8372 3700
Timo Äikäs, Executive Vice President, tel. +358 2 8372 3730Timo Seppälä, Senior Manager, Communications, tel. +358 50 351 1193