Elemental analysis of solid samples under water by fiber-coupled laser induced breakdown spectroscopy

Oba, Hironori  ; Saeki, Morihisa; Ito, Chikara   ; Takano, Masahide ; Akaoka, Katsuaki ; Thornton, B.*; Sakka, Tetsuo*; Wakaida, Ikuo  

To inspect the post-accident nuclear core reactor of the TEPCO Fukushima Daiichi Nuclear Power Plants, a transportable fiber-coupled laser-induced breakdown spectroscopy (LIBS) instrument has been employed. In the post-accident nuclear core reactor, melted fuel core, fuel cladding and construction material might drop in the lower part of the reactor, which filled with seawater that was injected for urgent cooling. The major components of the debris material are assumed to be uranium oxide (UO, fuel core), zirconium alloy (Zry, fuel cladding), stainless steel (Fe, construction material) and boron carbide (BC, critical control material). In this presentation, we report underwater analysis of simulated corium debris, (U,Zr)O, and BC by fiber-coupled LIBS instrument. The experiments were carried out using near-infrared wavelength region for pulsed-lasers and plasma emission measurements, which shows no attenuation in the optical transmittance of the fiber optic cable by intense radiation dose. We determined candidates of the emission lines of Zr, U, Fe and B (BO) that are applicable to analyses of the debris without mutual interference.