Laser induced breakdown spectroscopy tandem with laser ablation

The government is committed to deliver sustainable, low-carbon energy and this strategic goal requires a cross-disciplinary effort to advance the current understanding of the interaction of radionuclides with earth materials, including minerals, soils and rocks. The data generated will be employed to monitor and minimise the environmental impact from the leaching of radioactive materials, and to predict their migration rate. This could be built into the safety case for storage and geological disposal of radioactive waste.
Current research at the University of Surrey focuses on the safety of radioactive waste disposal. In particular; (1) characterisation of natural uranium-bearing minerals to investigate the evolution of radioactive wastes; (2) mechanisms of interaction of radionuclides with rocks and soils; and (3) effect of natural organic matter and concomitant pollutants on the retardation of radionuclides. One of the biggest challenges encountered by this investigation is the determination of the migration profiles of key elements and radionuclides and their association to specific mineral phases. For this purpose, the tandem LIBS-LA (laser-induced breakdown spectroscopy with laser ablation) would offer the elemental range, sensitivity and spatial resolution necessary to support this research.
Many conventional techniques of analysis only provide average concentration of the elements present in the bulk material and require intensive sample preparation, while others can obtain information on the distribution and specific interactions of some elements (elemental mapping), for example XRF (X-ray fluorescence) or EDX (energy-dispersive X-ray). However, due to their low sensitivity they can only be applied to a limited range of elements. Both laser-induced breakdown spectroscopy (LIBS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) are techniques that enable elemental mapping for solid sample and can provided isotopic information, with minimum sample preparation requirements, and they are well-established analytical techniques with their own unique advantages and disadvantages. The combination of the two analytical methods in one unique instrumentation, as proposed here, is a very promising way to overcome the challenges faced by each method individually.

Despite the advances in sensitivity and resolution of LA-ICP-MS, there are certain elements and isotopes that still cannot be measured. These include among others F, O, H and N. This is due to interferences, saturation of the detector (for major elements) and problems with the ionisation potential (either too high or too low). On the other hand, while LIBS can successfully provide quantitative and distribution information of these light and bulk components, it suffers from precision limitations due to temporal and spatial variations generated by the physical and chemical heterogeneity of the solid samples (matrix effects). LIBS and LA can be combined, as the same laser pulse used to ablate small particles from the solid samples to be carried into the ICP-MS can also generate a laser- induced plasma that can be detected and analysed spectroscopically. Thus, the combination of LIBS and LA-ICP-MS not only expands the coverage of elements that can be measured simultaneously, but also it will lead to improved precision and reduction of spectral interferences by using the signals from both the MS and spectroscopy detectors applying a multivariate approach to calibration and signal processing.

This proposed unique analytical facility in the UK will have the capability to determine simultaneously the distribution and association of radionuclides with mineral and other major components in soils, rocks and structural materials contaminated by accidental leaks. This will provide knowledge of the pathways of radioisotopes into the environment and mechanisms of interaction with the natural media, to evaluate and minimise the impact of human activities.

Nuclear is a vital part of the UK energy mix, providing low carbon power to achieve the government targets to reduce emissions in alignment with the Clean Growth Grand Challenge set out in the Industrial Strategy. The low-carbon infrastructure needed to support industrial decarbonisation will attract new investment and innovation.

The safe and efficient decommissioning of our nuclear legacy is an area of world-leading expertise as highlighted in the UK's Industrial Strategy document. It presents an opportunity to improve our industrial productivity, while still delivering affordable and reliable nuclear power through research and innovation that will contribute to the reduction in decommissioning costs to the taxpayer.

We believe that this new state of the art LIBS-LA-ICPMS facility will serve the wide research community working on radioactive decommissioning, including industrial and governmental laboratories. This will also contribute significantly to "the commitment of NERC to address the impact of radioactive waste and contaminates sites". This new asset will support research applications in multiple areas of radiochemistry, surface chemistry, mineralogy, geophysics and environmental sciences, in particular through the work carried out by the applicant group and their research partners in TRANSCEND as well as National Physical Laboratory (NPL), National Nuclear Laboratory (NNL) and Nuclear Decommissioning Authority (NDA) it will underpin the generation of knowledge and strategical technical training in analytical and radiochemistry, including geochemistry and ecotoxicology.

The LIBS-LA system will provide a comprehensive and high-throughput characterisation of solid samples (minerals, rocks, soils and structures contaminated by discharge leaks). The data obtained (along with the other characterisation techniques) will be shared with the other universities and industrial partners. Cloud storage and secure data transfer among collaborating institutions will allow timely and easy access to the data. This is especially important for those exploring the large and complex mechanism of radionuclide migration. If a particular set of conditions can be found which minimises the spread of radionuclei (i.e. reduce solubility and mobility), this could provide an economical and environmental benefit to the problem of how to safely dispose of radioactive waste. The results will also be presented at international conferences, annual project meetings and in peer-reviewed journals.

It is envisaged that the society and UK economy will benefit from the research carried out with this asset. Nuclear energy appears as a reliable and low carbon footprint alternative, but in order to achieve this objective it is necessary to provide robust scientific evidence of the safety of waste disposal and generate knowledge that will increase the confidence of the British public on nuclear energy. Thus, public interaction is key to realising the full impact of the research enabled by this asset as it will increase awareness of the challenges and progress in environmental radiochemistry.

The Nuclear Industry Council has reported approx. 40,000 highly skilled professionals in the nuclear sector and the government is committed to benefit from this expertise, by promoting the number of nuclear-related PhDs and Research & Innovation programs. The addition of the LIBS-LA to the other unique facilities already existing at the University of Surrey will increase collaboration with third parties for the generation of excellence in research. In addition to the academic impact, this will have a societal impact by providing an unique equipment for the training of a new generation of radiochemistry graduate, postgraduate students and early career researchers.