GOVERNMENT APPROVAL of a complex 500M operation to clearradioactive waste from a vast underground shaft at Scotlands Dounreay nuclear facility is expected in the next few weeks.
The 10 year scheme is expected to use either ground freezing or diaphragm wall containment around the full 65m depth of the water filled shaft.
The 4.6m diameter shaft was built 40 years ago to remove muck during excavation of a long sea effluent outfall from the nuclear plant. A thick concrete plug now seals the shaft from the outfall and for years it has been used as a vast bin for radioactive rubbish.
The UK Atomic Energy Authority, Dounreays operator, submitted confidential proposals to the Department of Trade & Industry last December. Favoured option is to seal a 10m radius around the shaft with either grout, freezing or a deep cut-off wall before, several years later, its 700m3 of intermediate level nuclear waste is taken out and stored in surface bunkers.
Constant pumping from the shaft is known to induce groundwater inflow and although UKAEA claims there have been no known leaks, persistent environmental pressure has encouraged it to seek a solution.
Extensive ground facilities for separation, treatment and storage are needed before retrieval can start. It is possible that the shafts radioactive contents will also be frozen, allowing removal within large diameter cores drilled through the ice.
UKAEA head of waste storage and studies Dr Doug Graham said that whatever was chosen, 10M would be spent on hydrological surveys to confirm ground conditions. We must be confident that any solution could not risk a plume of (radio) activity being released from the shaft.