A Compact Optical Sensor for Environmental Monitoring of Lithium

There is a growing need to detect lithium and its build-up in the environment, given its widespread use in lithium-ion batteries and potential use in thermonuclear weapons. Improper disposal of lithium-ion batteries may lead to difficult-to-contain fires and contamination of soil and groundwater. Lithium-6 isotope may also be used in thermonuclear weapons as it can be used to produce tritium. However, lithium has to be enriched to 40-95% from its natural abundance of 4.85-7.59%. Significant increases in the Li-6 isotope in the environment will be a good indicator that clandestine enrichment of lithium has taken place. At present, soil samples are collected and then sent to laboratories for analysis using large and expensive equipment, such as inductively coupled plasma mass spectrometers (ICP-MS) or secondary-ion mass spectrometers (SIMS). This can take weeks to obtain results, and utmost care must be taken to ensure the integrity of the sample. Optical techniques, such as laser-induced breakdown spectroscopy (LIBS) and tunable diode laser absorption (TDLAS), show potential as viable field detectors for nuclear materials. However, field LIBS instruments suffer from poor spectral resolution to detect isotopic shifts of nuclear materials. To overcome these limitations, we propose a compact optical spectroscopy instrument for the environmental detection and isotopic ratio analysis of lithium. In recent work we have demonstrated the feasibility of this LA-TDLAS approach by identifying and resolving isotopic and ground state hyperfine splitting in rubidium as well as in uranium. In this Phase II effort, we will extend this capability to detect lithium and its isotopes and demonstrate its feasibility for portable system. This will lead to the development of a prototype instrument at the end of Phase II. The proposed technology uses an innovative atomic absorption spectroscopy for the environmental detection and isotopic ratio analysis of lithium. Our technology will also be much more compact than mass spectrometer and higher resolving power than currently available optical spectroscopy systems, allowing our technology to be more suitable for field applications and in challenging environments. The proposed technology will also benefit the analytical chemistry community and nuclear energy community.