Another significant decommissioning milestone has been achieved at Sellafield within the legacy Primary Separation Plant. A four year programme to decommission one of the highly radioactive process cells known as the HASO (High Active South Outer) cell has been completed.
The Primary Separation Plant was constructed in the early 1950s and is one of the many historic nuclear plants undergoing decommissioning at Sellafield. Decommissioning involves the safe reduction of the radiological hazards by removing nuclear materials and treating them, decontaminating process plant and equipment, and the eventual demolition of the building itself.
The plant originally carried out the first stage of reprocessing fuel from the Windscale pile reactors, which were developed to produce materials for the UK’s defence programme.
The HASO cell was one of the four highly active process cells associated with the site’s original uranium metal reprocessing operations. It was later modified as part of a process line to treat uranium oxide fuel, which was shut down in 1973.
Decommissioning work on HASO included the removal of 35 tonnes of process vessels, pipe-work, support steelwork and circa 1970s scaffold materials.
The decommissioning team had to overcome a number of challenges to decommission this highly radioactive process cell. The historic operations, plant modifications and incomplete plant records meant the job was far from straightforward.
Project Manager Mark Nealy said: “Whilst some elements of the work progressed faster than expected, we encountered other complications which impacted on the schedule. One of which was the elevated levels of loose radioactive contamination, which meant additional safety measures had to be put in place to ensure the safety of our workforce.”
“The high levels of airborne contamination meant that workers had to wear personal breathing apparatus during plasma cutting operations which dramatically reduced the amount of time they could spend in-cell.
“Despite these problems however, the team delivered the project safely.”
Completion of this decommissioning project has also provided good learning for future decommissioning projects. The project successfully trialled the N-Visage Dose Modelling and Fogging systems, together with other applications such as Rad-Ball dose modelling and radiation detection paints.