The Nuclear Decommissioning Authority

Dounreay shaft project ahead of schedule

20 August 2008

The first phase of decommissioning Dounreay’s waste shaft is nearing completion. A final set of boreholes in the toe section of the grout curtain and additional groundwater monitoring boreholes will see the project move a step closer towards isolation of the shaft from the groundwater.

Subject to the weather remaining favourable, an underground grout curtain is expected to be totally complete by end of August, ahead of programme and budget, with all works at the raised working platform to be fully complete by the end of August 2008, ahead of programme and under budget, with all works at the raised working platform to be fully complete by the summer.

Retrieving waste from the 65 metre deep shaft is a major decommissioning and clean-up project. The barrier is needed to isolate the waste material inside the shaft and to minimise the amount of water leaking into it during waste retrieval, and becoming contaminated.

Independent Swiss hydrotest experts are validating the hydro testing of the completed section of the grout curtain. The preliminary results have been positive and the second phase of hydro testing will take place in the spring.

Since the project started in January, more than 200 boreholes, with a combined total depth of over 15 kilometres, have been drilled and filled with grout.

Scotland’s Environmental Protection Agency (SEPA) has requested that extra boreholes are drilled so they can monitor groundwater outside of the shaft. These will be completed this year. In addition two more boreholes are being drilled inside the grout curtain to help the waste retrieval project team.

Randall Bargelt, the NDA’s programme director for Dounreay, said: “We are pleased that the grouting solution for isolation of the shaft from the environment appears to be working properly -resulting in good progress on the work needed to decommission the shaft. Of course there is much more to do, but these are positive steps forward.”

Work is continuing on the concept designs developed for the shaft and silo waste retrieval and treatment facilities. This includes evaluating what techniques can be used and the equipment needed to successfully retrieve the waste.

Other work recently finished on this project include: building a cover over the top to reduce rain water getting into the shaft and installing a permanent electric supply for the grouting equipment.

Work to empty the shaft is scheduled to begin in 2019.