A decommissioning team is well on its way to emptying the water-filled ponds used historically to store spent fuel from the Dounreay Fast Reactor.
This reduces one of DFR’s major hazards as the two six metre deep concrete chambers are drained in preparation for removing the concrete and bitumen liner as the former reactor is pulled apart.
The pond is a concrete vault similar to a swimming pool and the water provided shielding for workers from the radiation emitted by spent fuel placed in racks on the bottom.
One pond has been almost totally drained of its 500m3 of water and only four inches of the thick brown sludge remains. A cocktail of corrosion and remnants of historical pond storage material, this is now being removed by pressure washing into the contaminated radioactive mud-like substance through a dirt buster nozzle.
This agitation blends the sludge into a ‘soup like’ consistency which is then passed through a large filter containing twenty-seven cartridges. This captures the diluted brown matter which is then ready to be encapsulated in grout and stored in 200L waste drums.
The second pond will be half emptied in the near future so work is underway to erect further shielding as radiation levels increase as the water is reduced.
Project manager Mark Aitken explained: “Sludge retrieval and packaging is the most challenging part of the project. Removing the final remnants which remain following years of storage is a tricky process involving specialised filters and we are delighted with how efficiently this is working and safely removing the final dregs left inside the pond storage facility.”
The team is on course to meet a performance delivery target of removing all the water and its remains from the base of the two ponds by the end of March next year.