Divers remove radioactive waste

Scuba divers have begun work to decommission a spent nuclear fuel storage tank located at the UK’s Sizewell A nuclear power station. They are using experience learned from underwater work carried out to remove radioactive waste at the Dungeness A plant.

A team of 12 divers from the US Underwater Construction Corporation (UCC), made the first dive in the Sizewell A power plant basin. The main purpose of this dive was to check the bottom of the basin, transfer the silt to a purpose-built tank, set up cutting equipment and downsize the first of 35 containers that were used to store spent nuclear fuel.

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The treatment of such tanks is usually carried out using remotely operated equipment that lifts the containers from the water to the surface where they are cut before decontamination, storage and eventual disposal. This process is quite slow and generates a risk of irradiation to workers.

Working underwater, divers have easier access to difficult areas, making the whole process of dismantling tanks safer, faster and more productive. In addition, the water acts as a shield, reducing the radiation doses to which the diving teams are exposed, who are in any case protected by protective suits.

This way of working was tested and approved by Magnox, the operator of 12 extinguished UK nuclear power stations, working on behalf of the Nuclear Decommissioning Authority, during work at Dungeness A power station. UCC carried out a total of 265 dives in two pools there from late 2016 to 2017. During this time, the dive team cut empty fuel tanks and extracted other submerged components.

A number of innovations have emerged during the work at Dungeness A, including the use of lightweight plastic platforms that divers can use when exploring unexplored areas of the seabed. The lessons learned at Dungeness A are being implemented at Sizewell A as part of a decommissioning project that is likely to take around ten months.

Two 210 MW gas-cooled Magnox Sizewell A reactors operated from 1966 until 2006. In 2009, the clean-up of the plant began with the fuel, which, once removed from the reactors, was stored in special containers in dedicated pools. These were then transported to the Sellafield complex for reprocessing. The last shipment was sent to Sellafield in August 2014. Sizewell A was declared completely fuel-free in February 2015.

Sizewell A Site Ponds programme manager Steve Franks said: “The scale of work to be carried out by divers is huge. Although we only have one pool to decommission, the scope of work is greater than at Dungeness A, but we will still want to speed up the work while maintaining safety measures.”

Geoff Suitor, Magnox programme manager for the NDA, added: “Magnox’s use of innovative solutions, such as the use of divers to decommission radioactive waste, is making real progress in reducing risks during work. We are successfully cleaning up and securing the UK’s oldest nuclear power stations on behalf of communities and the environment.”

Source: world-nuclear-news.org

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