Excavation of world's first final deposition tunnels starts in Posiva's ONKALO facility


As the operator responsible for the final disposal of spent nuclear fuel, Posiva Oy has started the excavation of the actual final disposal tunnels in Olkiluoto, located in the Eurajoki municipality. The start of the excavation is a significant milestone for Posiva, as it comes after years of development activities on research and methodology for rock construction. The Radiation and Nuclear Safety Authority of Finland (STUK) verified before the excavation started that the pre-conditions specified for starting the work had been fulfilled.

- The years of research and development of rock construction that have produced procedures for construction of a nuclear facility suited for the Finnish bedrock culminate in this moment. The development of the methodology started with the construction of the ONKALO® facility already in 2004, says Posiva's Construction Manager Juha Riihimäki.

The first five tunnels to be excavated during the next 18 months mark the beginning of an extensive building effort. It is estimated that one hundred deposition tunnels will be excavated during the 100-year operational period of the final disposal facility, totalling a length of about 35 kilometres. The maximum length of one tunnel is 350 metres. The tunnels are about 4.5 metres high and about 3.5 metres wide.

The excavation of the first five tunnels is part of Posiva's approximately 500 million-euro EKA project that covers all the final disposal facilities needed, including both their construction and the equipment, as well as the start of the final disposal operation in the first deposition tunnel. To pin down the EKA project, it means that Posiva is the first operator in the world to start geological final disposal of spent nuclear fuel.

- About 30 canisters will be placed in one tunnel. Their number depends on how many deposition holes there are in the tunnel and that is determined by the volume of suitable rock based on the rock fractures. The thirty canisters placed in one tunnel can accommodate about 65 tons of spent nuclear fuel, Mr. Riihimäki explains.

The encapsulation of spent nuclear fuel and the emplacement of the canisters in the deposition holes will start once the Finnish Government grants the operating licence for the final disposal facility.

- The current estimate is that the final disposal operation will start in the mid-2020s, says Posiva's Programme Manager Kimmo Kemppainen.

- The excavation and reinforcement of the tunnels, which have now been started according to tight regulatory requirements, signify for Posiva a transfer to the execution of the most complex and exacting rock structure system in ONKALO, Mr. Kemppainen says.

Approximately dozens of subcontractors and 300 persons are currently working in the ONKALO area.

For more information, please contact:
Janne Mokka, President and CEO, Posiva Oy

Interview requests:
Pasi Tuohimaa, Communications Manager, Posiva Oy, tel. +358 40 5445001

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Posiva's commercial subsidiary Posiva Solutions provides tailored expert services based on all of Posiva’s know-how. We can add value to your nuclear waste management programme by turning our experience into your benefit. Our expertise is based on Posiva's decades-long experience in research & development, design, and construction of final disposal of spent nuclear fuel in Finland.