Grout curtain in place around shaft
April 10, 2008
Dounreay’s waste shaft is now surrounded on all sides by a 10-metre wide band of grouted-up rock.
The grout has been injected into the rock through approximately 400 boreholes drilled around the 65-metre deep vertical shaft.
This has filled up the fissures in a 10-metre wide band of rock around the shaft.
The volume of water that needs to be pumped daily from the shaft to maintain its water level below that of sea-level has reduced from 15 m3 at the start of grouting two years ago to 1.3m3 today.
Further boreholes will now be drilled for hydro testing to validate the performance of the grout curtain.
Some further grouting may be required, depending on the results of these tests, to strengthen the barrier or plug gaps.
The shaft – a licensed disposal site for intermediate-level waste used from 1958 until 1977 – is largely unlined.
Throughout its use, water has had to be pumped daily from the shaft to minimise the amount of water that passes through it, carrying radioactive contamination.
Isolating the waste from the groundwater greatly reduces the amount of contaminated liquid that will need to be managed when work begins in 2018 to recover the waste from the shaft.
