Research helps accelerate Sellafield clean-up

The findings of a four-year study on the corrosion behaviours of magnesium and uranium may help to significantly reduce the timescale and costs of cleaning up the Magnox Swarf Storage Silo at Sellafield, one of the UK's most hazardous buildings.

The findings of a four-year study on the corrosion behaviours of magnesium and uranium may help to significantly reduce the timescale and costs of cleaning up the Magnox Swarf Storage Silo at Sellafield, one of the UK's most hazardous buildings.

The Magnox Swarf Storage Silo (Image: Sellafield Ltd)

The study was led by the Nuclear Decommissioning Authority (NDA), Sellafield Limited and the National Nuclear Laboratory, with academics from the universities of Bristol, Leeds and London South Bank.

The researchers looked at the chemical behaviours of intermediate-level waste (ILW) stored at the Magnox Swarf Storage Silo (MSSS), which has been prioritized for clean-up by the NDA. A 22-step mechanical treatment and encapsulation process had previously been thought necessary to manage and ultimately dispose of the ILW stored in the silos, built over 50 years ago.

However, the study concluded that a three-step solution could be employed in which "raw" waste with concrete grout is stored inside a shielded container. This waste package would be suitable for interim storage at Sellafield, the NDA said, and then for final disposal in the UK's proposed geological repository.

In addition, using the new technique will lead to a reduction in "secondary wastes" created during the treatment process, resulting in an estimated 10% fewer waste packages being produced during the decommissioning of MSSS.

According to the NDA, "Switching to this new method could speed up the decommissioning of the silo by several years and provide huge savings to the taxpayer. The technique could also be applied to other redundant nuclear facilities in the UK and around the world."

The MSSS project was built to accommodate the swarf waste produced by the decanning of Magnox fuel prior to reprocessing. The swarf was stored underwater, and the first facility of six silos began operations in 1964. By 1983 a total of 22 silos had been built, but by the early 1990s wet storage of Magnox swarf was superseded by dry storage.

Three silo emptying plants are currently being built, the first of which will be delivered to the site later this year. After undergoing testing, this should be available for solid waste retrievals in 2017.

NDA strategy and technology director Adrian Simper said the research could lead to a "paradigm shift" in the management of nuclear waste. He said, "To be able to deliver a technical solution to historic ILW at Sellafield, which not only offers a safe and secure route but also opens up the possibility of a quicker and cheaper alternative to current technology, is a genuinely exciting development."

Researched and written
by World Nuclear News