TWI’s laser experts have been recognised by the UK Nuclear Decommissioning Authority with a prestigious award for the successful introduction of a new technology to decommission radioactive metal storage containers. The team developed a remote cutting system – utilising TWI’s laser cutting technology – over a two-year period, culminating in full trials at Hinkley Point A. The new approach is expected to bring savings to the UK of hundreds of millions of pounds.
Magnox Ltd has a large number of radioactive metal storage containers which have been used over many years for storing and moving fuel elements for the UK’s Magnox reactors. Currently, the cost of storing low- and intermediate-level nuclear waste is related to the volume of the parts. The estimated cost of storing one such container for its lifetime is £0.5 million. There are around 300 such containers at Hinkley Point and upwards of 2000 at Sellafield.
Although laser cutting is a well-established method for precision cutting of metals, it has only recently been applied to decommissioning. Magnox Ltd wanted to investigate an approach for breaking down metal storage containers – also known as nuclear skips – which would result in a significant reduction in the amount of active material needing storage. Notably, radioactivity in these skips is restricted to within 1.5mm of the material surface.
TWI was able to demonstrate that by using robotics to address positioning tolerances; its remote one-pass laser cutting technology can be used to quickly and safely divide a Magnox nuclear skip into five pieces. From here the pieces pass into a five-axis milling machine, their geometries are scanned and 1.5mm cut away from exposed surfaces.
The resulting active material forms a mass of just over 50kg, compared to the 450kg weight of an empty contaminated skip. The newly cut mass also has a high packing density, so the volume remaining in storage is significantly reduced. Remaining (non-active) steel can be melted and recycled.
The facility has been designed such that it can be remobilised on another nuclear site.
TWI Chief Executive Christoph Wiesner said: ‘We are delighted that the NDA has recognised the hard work of the teams at TWI, Magnox and Fanuc Robotics. Remote laser cutting is an innovative solution making a real difference to decommissioning procedures in the UK at the same time as substantially reducing costs.’