Laser assisted removal of fixed radioactive contamination from metallic substrate

Metallic waste contaminated with radioactive materials accounts for a large proportion of the nuclear wastes generated in nuclear facilities. Storage of these highly contaminated wastes is known to attract high cost. Reduction of activity of these wastes can significantly bring down the cost of their storage. Further, for recycling of the precious metal, it's mandatory that it's surface contamination is first brought down to the accepted level. We report here a practical method of significant reduction of volumes of contaminated wastes to be stored by way of employing coherent radiation emanating from a laser to ablate fixed radioactive contamination alone from the surface of metallic wastes. A single mode pulsed fiber laser was used to remove fixed contamination from stainless steel substrate by ablation. Optimisation of the removal process was effected with respect to the laser power, repetition rate, laser beam scanning speed and number of passes. Ablation depths ranging from few microns to few hundreds of microns could be readily achieved as per the requirement simply by suitably varying the above processing parameters. Samples simulated with U-232 contamination as well as samples from the pipe line of a Boiling Water Reactor (BWR) were found to be decontaminated containing only marginal residual activity using this technique.