Fifty years ago Dounreay was a cornerstone of British research with highly-enriched uranium. Today, the array of vessels, gloveboxes, evaporators and ovens that made up Britain’s uranium recovery effort is coming apart.
Tonnes of fissile material passed through the chemical plant at Dounreay and into the hands of Britain’s top atomic scientists at sites across the country.
Today, the array of vessels, gloveboxes, evaporators and ovens that made up Britain’s uranium recovery effort is coming apart.
A six-minute film produced by DSRL has been published on-line, showing the latest section of the chemical complex to come down – the uranium trioxide line.
It filled almost 70 containers with radioactive waste and took 10 workers, wearing full protective clothing and breathing apparatus, two months to complete.
Highly-enriched uranium in the form of ammonium diuranate was baked in platinum trays inside ovens at temperatures up 300 degrees Celsius in this section of the plant.
The process created uranium trioxide that was crushed, sieved, mixed with hydrogen and reheated to 700 degrees Celsius, creating uranium dioxide that would be used to make metal billets.
Decommissioning this latest section of the chemical plant saw it shrouded in a giant plastic tent to contain any toxic residue.
Workers dressed in whole-body airline suits entered the sealed tent at the end of August to begin dismantling the chemical equipment.
Over the next two months they systematically stripped down and cut up the series of ovens, vessels, pipes and boxes.
Their exposure to any residual radioactivity was monitored constantly throughout the painstaking work.
The uranium trioxide line filled 75 drums and containers and will now be processed as low-level radioactive waste.
The containers will be stored with other waste from decommissioning Dounreay until a new disposal site for low-level waste is ready in 2013.
The dismantling and demolition of the rest of the recovery plant will take until 2019 to complete.
“The main radiological hazard involved in work like this comes from the risk of internal exposure, which occurs if there is inhalation or ingestion of any airborne residues from the vessels and pipework as they are cut up,” explained Gordon Tait, senior project manager at Dounreay Site Restoration Ltd.
“That’s why we take the precaution of erecting a containment barrier around the whole area and stipulating the use of airline suits to protect the health of workers.
“The team carrying out this work is a good example of how operators of plant can make the transition to decommissioning, taking they skills they’ve learned and adding to them to get the job done safely and slickly.”
The decommissioning team is made up of workers from three companies – Dounreay Site Restoration Ltd, Nuvia and NDSL. The work is funded by the Nuclear Decommissioning Authority, which owns the site.