Laser scabbling is a non-contact, defocused laser beam process for ablative removal of concrete surfaces. The major potential use is in the nuclear power industry where, over the life of a nuclear facility, concrete surfaces can become contaminated with radio-nuclides, typically to a depth of a few millimetres.
During decommissioning, remote separation of the contaminated surface from the bulk of the concrete will significantly reduce the volume of material required to be treated as low to intermediate level nuclear waste, as the remaining bulk then can be considered contamination free and removed using conventional means. In the UK alone, it is estimated that there are over 200,000 square metres of contaminated concrete requiring attention.
TWI has developed equipment and techniques to demonstrate the use of a high power fibre laser for the remote scabbling of concrete surfaces. For concrete containing limestone aggregate, at a speed of 200mm/min and using 5kW of laser power with a removal depth of >10mm, one square metre can be treated in 110 minutes. The TWI designed 'scabbling head' was attached to an articulated arm robot and included a vision system which automatically maintained the process head both perpendicular to and at a constant distance from, the surface of the concrete during traverses of the robot arm.
This work was undertaken as a result of TWI's successful bid in response to a competitive call from the NDA, to take potential new decommissioning techniques from the laboratory stage to something much closer to deployment in an active environment. The project also looked at the first use of high power fibre lasers for single sided tube cutting.
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