Posiva files construction permit application for research facility with Municipality of Eurajoki

Posiva Oy, which is responsible for the final disposal of spent nuclear fuel in Finland, today filed the construction permit application for the underground research facility ONKALO with the Municipality of Eurajoki. The research facility will be constructed to verify the results so far obtained by drillings from above ground on the suitability of the bedrock in Olkiluoto for final disposal. The construction of ONKALO will facilitate the planning of the final repository and the research activities carried out in ONKALO will produce information required for filing the building permit application for the final repository with the Finnish Government.

ONKALO will be built in the central part of the island of Olkiluoto, where investigations on the suitability of the location for final disposal have been carried out since the late 1980s. 23 deep research bore holes have been drilled in this area, located some 2 km east of the Olkiluoto nuclear power plants and drilling of yet another bore hole is under way.

ONKALO consists of a spiral access tunnel that is 5.5 km long, a ventilation shaft and research levels at a depth of 420 m (main research level) and 520 m. The total volume of the ONKALO facility is 330.000 m3.

According to current plans, excavations will commence in the summer of 2004 but preparations on the site will start already this year. In 2004-2010, the ONKALO project will employ a crew of 40 – 50 underground construction workers every year. The access route will be excavated using a drill and blast method. The ventilation shaft will be drilled first with raise boring technique and it will later be slashed to final dimensions by drill and blast method.

The construction of ONKALO is estimated to be completed by the year 2010 but research activities will be started already at the construction stage of the access route. Exploration niches will be excavated in the access route and on the research levels for the performance of geological, rock mechanical, geophysical and geochemical investigations and measurements. When completed, ONKALO can be used to test and simulate final disposal technology in authentic circumstances.

The cost estimate of the construction project of ONKALO is in the order of EUR 50 million.

Technical data on ONKALO:
  • Total volume 330,000 m3
  • Total tunnel length 8,300 m
  • Ventilation shaft length 530 m
  • Ventilation shaft diameter 6.0 m
  • Access route width x height 5.5 x 6.3 m
  • Access route inclination 1:10

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