Assessment of Laser-Induced Breakdown Spectroscopy as a Method to Pre-Screen Environmental Swipe Samples

Among the recent technical developments in Safeguards applications, Laser-Induced Breakdown Spectroscopy (LIBS) provides a promising approach for characterization, analysis and detection of nuclear material. The LIBS method is capable of detecting isotopic signals from U-235 and U-238, therefore allowing enrichment determination of detected uranium. The advantage of the LIBS methodology is that it does not require any sophisticated sample preparation and promises a quick evaluation of uranium isotope ratios. In this context the International Atomic Energy Agency (IAEA) has identified LIBS as a potential pre-screening method for swipe samples which have been obtained in environmental sampling as part of the Safeguards activities undertaken by the IAEA. Determination of isotopic content in a pre-screening step permits an efficient use of analytical procedures in the analysis of swipe samples and, therefore, quicker analysis results and an increase of sample throughput. As part of the German Support Programme to the IAEA, the Fraunhofer-Institute for Laser Technology is exploring the feasibility of scanning microanalysis LIBS to screen swipe samples. Studies have been carried out to identify feasible ways of improving the methods towards a better separation of isotopic signals and sensitivity for trace detection on swipe substrates. Experiments on samples carrying a small amount of uranium show that isotopic signals can be separated in the recorded optical line emissions such that samples of different levels of enrichment can be distinguished. At the same time, the used approach is sensitive enough to detect contaminations in the order of a few µg/cm². The potential of scanning microanalysis LIBS as a pre-screening method for Safeguards applications has been evaluated by analysing swipe samples prepared with uranium and artificial dust simulating typical background contributions.