Published on 02 March 2012
A million pound contract to demonstrate the efficiency of using lasers in the decommissioning of nuclear facilities was won by TWI.
The task was to procure the latest in fibre lasers and set up realistic demonstrations to show how a one centimetre deep skin of concrete can be removed from pre-cast specimens; a process known as scabbling. The idea is to simulate firing a diffused laser beam, about 100mm in diameter, at the contaminated concrete region of a nuclear facility. The beam rapidly heats the material and causes differential expansion between the coarse aggregate and the fine cementitious matrix.
When decommissioning a nuclear facility most of the concrete is 'clean' so if this can be separated from the contaminated fraction, the costs in terms of nuclear waste disposal can be greatly reduced. The laser technique can treat approximately one square metre per hour.
Removal by high pressure water jet is a competing process, however this creates significant quantities of secondary waste because the used water becomes contaminated and has to be disposed of separately.
Although laser scabbling was first demonstrated almost twenty years ago, lasers at that time were too unreliable. However the recent advent of the fibre laser now offers a robust, easily deployable, tool suitable for use in nuclear decommissioning environments. The laser is ideal for remote operations. It uses a small head on a lightweight manipulator.
A bonus of laser scabbling is that by adding a simple lens in the beam's path the laser is capable of being focused for cutting steel reinforcement or steel process vessels and associated pipework.