A decommissioning team is getting ready to begin breaking up the former research reactor fuel reprocessing plant at Dounreay.
They have spent the last three years stripping away redundant equipment and controls from the exterior of the concrete-walled chemical plant.
Now they are preparing for the next stage – dismantling the labyrinth of pipes and vessels inside the plant where highly radioactive spent fuel was dissolved in acid and underwent chemical separation.
The plant was built in1956/57 to recycle highly-enriched uranium from fuel irradiated in research reactors in the UK abroad.
More than 12,000 used elements were dissolved in acid inside the facility. The liquor went through a chemical process to separate the re-usable uranium from the radioactive waste in the irradiated fuel.
Workers were shielded from the high radiation levels in the vessels and pipes by a wall made of lead and concrete and four feet thick.
Reprocessing of spent fuel ceased in 1996 and the process of decommissioning started in 2000.
The chemical plant has been washed out using aggressive cleaning fluid and control systems dismantled in the main working area of the building. A pond where spent fuel was stored before being dissolved is being cleaned out in preparation for dismantling.
The next stage involves breaking open the containment wall around the chemical plant to begin dismantling the vessels and pipes.
Radiation levels are still too high to allow workers into this area, so the work will be done using remotely-operated cutting equipment.
Workers will be allowed inside to finish decontaminating the facility only when radiation levels have reduced to a safe level.
Demolition of the facility is scheduled for 2010. The total cost of decommissioning is £15 million.