TPi January 2011

The potential of high power lasers for tube and pipe cutting in nuclear decommissioning By PA Hilton, AH Khan and C Walters, TWI Ltd

Introduction This article describes the results of a recently completed project to demonstrate the potential of high power lasers in aspects of nuclear decommissioning. In March 2009, the UK’s Nuclear Decommissioning Authority awarded TWI a contract to develop prototype equipment, in order to effectively demonstrate the twin processes of tube cutting and concrete scabbling and how these technologies might be implemented for remote use in nuclear decommissioning environments. Contaminated concrete and pipework present major decommissioning challenges in terms of the total volumes of material to be treated, the radiation levels present and the number of facilities affected. This article describes the work performed on pipe cutting using a 5kW fibre laser. Although pipe cutting has been performed on numerous occasions, most of the techniques employed are slow to operate or are not suitable for remote deployment in highly active cells. Laser cutting is well suited to remote deployment due to the availability of light and compact process heads, the lack of reaction force between such heads and the tube and limited fume generation. However, for single sided cutting of pipe and tube, the process needs to be adequately demonstrated before active deployment will be seriously considered. Chosen laser source A key parameter in most laser processes is the power density in the beam applied to the surface of the material in question. The two processes of concern in this project were unusual in that laser cutting requires a very high power density in the beam, whereas laser scabbling requires a relatively modest power density. For this work, because of the former requirement, the need for an efficient, robust and compact laser source and the need, in remote applications, for optical fibre delivery of the laser beam power, an industrial fibre laser was chosen. This laser has an output power of 5kW, adequate to demonstrate both processes, but the same type of laser is commercially available with powers up to 50kW. The performance of the laser was monitored using a laptop computer, which also provided detailed information about the operating status of the laser. Control of the laser was routed to the controller of the deployment system in use, in this case an articulated arm robot.

Figure 1: The cutting head

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Tube Products International January 2011

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