A choice between two locations for the site of the proposed underground storage vault for nuclear waste in Sweden is expected to be made by mid-2009.

Bedrock drilling at both sites – Forsmark, near Osthammar, and Laxemar, near Oskarshamn – that were completed at the end of last year. The Swedish Nuclear Fuel and Waste Management Co (SKB) said that both locations look favourable according to analyses performed so far.

SKB said it expects to choose the site in May or June next year and then submit an application around mid-2010 to develop the tunnels and cavern waste storage system. The towns and SKB hope that a decision on the application would be made around 2012-13.

Based on an approval of the project to the schedule envisaged, SKB said it would take approximately five years to excavate and complete the vaults – almost a decade after site is elected and application submitted.

The final repository vaults will be at depths of 400m-700m, and the spent fuel will be held in copper canisters that are welded shut and embedded in bentonite clay within deposit holes in the caverns.

At Forsmark, SKB is considering having the repository slightly deeper – approximately 450m-500m below the surface compared to early plans of 400m depth as rock stresses do not increase as rapidly as assumed. Deeper vaults are also better in terms of minimising the proximity of fracture zones. The preliminary site investigation data at Laxemar indicated that vaults could be located at a depth of approximately 500m.

SKB said in its interim research report of September 2007 that one of the construction challenges will be to develop grouts and equipment to manage inflows that may occur in the final repository. It added that a particular challenge would be learning to seal small fractures with high water pressures, especially as the grout must not produce a high alkaline leachate that would affect the storage capability.

Excavation research for the final repository project has been underway in co-operation with a number of countries on various aspects of general tunnelling, and also specific bores for deposition holes, at the Hard Rock Laboratory on Aspo, near Oskarshamn, on the south east coast.

Nuclear waste is presently stored at an interim repository near Oskarshamn, and a repository at the Forsmark power plant.

Site investigation for Sweden’s nuclear waste final repository Tests at the Hard Rock Laboratory in Aspo