The ventilation building of ONKALO at rooftop height – underground work also progressing
The ONKALO ventilation building project located in Olkiluoto is now at rooftop height. In the future, the approximately 20-metre-high building will be the place for taking care of ONKALO’s ventilation in a centralised and effective way so that the capacity of the building’s ventilation systems will also cater to the needs of the final disposal facilities. The systems of the building will be gradually introduced during this year: air will be conducted through the intake air shaft to the level of ONKALO’s technical facilities at the depth of 437 metres. Rakennustyöt Ville Kauppi Oy is in charge of the ventilation building project.“The ventilation building will be the most visible landmark of the ONKALO site in the future. A lifting equipment building is being constructed in conjunction with the ventilation building. In addition to the driving tunnel, a personnel hoist installed in the hoist building will enable personnel access to the underground facilities,” said Erkki Palonen, Design Manager (Construction Director as of 1 February 2011) at the ventilation building topping-out ceremony in Olkiluoto.
“However, the driving tunnel will in practice be the only access to ONKALO for a long time because the hoist will be introduced around the middle of this decade,” says Palonen.
The underground work for ONKALO is also in progress. The driving tunnel will be excavated to the level of the technical facilities, 437 metres, in the next few weeks. After this, the ventilation shafts and the personnel shaft of ONKALO will be raise-bored to their full length at the depth of the technical facilities, and the ventilation of ONKALO will gradually start using separate air intake and exhaust shafts.
In addition to excavating the driving tunnel, ONKALO will prepare for the construction of testing and demonstration facilities during the spring. The task is to excavate two test tunnels at the final disposal depth (420 m) according to the actual dimensions and requirements of the final disposal tunnels.
“Excavating the test tunnels is an important part of the construction license process of the final disposal facility because the purpose of the underground work is to show in practice that Posiva is capable of specifying suitable rock volumes for the final disposal tunnels and canisters with respect to long-term safety and to excavate the tunnels according to the applicable requirements,” says Reijo Sundell, President of Posiva.