Measurement of uranium in a glass matrix based on spatial confinement using fiber-optic laser-induced breakdown spectroscopy

The storage and management of nuclear waste materials require the detection of uranium, but traditional analytical methods are unsuitable for radioactive environments. The enhancement methods of uranium in glass matrices using fiber-optic laser-induced breakdown spectroscopy are still underdeveloped. Using an optical diagnostic system coupled with fast photography, shadowgraphy, and optical emission spectroscopy, the evolution of laser-induced plasma generated from a glass matrix under spatial confinement is studied. The plasma evolution image illustrates the temporal consistency between the compression of plasma width and the enhancement of luminescence intensity. Two enhancements were observed when the plate spacing was smaller than the plasma, which might be due to the high density of the core plasma or a synergistic effect of plasma expansion and shockwave confinement. Under spatial confinement, there is a 3–4-times enhancement in the intensity of uranium spectral lines and a 2–4 times enhancement in the signal-to-noise ratio. Several calibration curves are established under spatial confinement based on U II 409.01 nm, U II 367.01 nm and U I 358.48 nm. The lowest limit of detection (LOD) of uranium reaches 95 ppm, which supports the application of FO-LIBS in the detection of uranium-containing nuclear waste materials.