Highly sensitive hydrogen analysis employing low pressure laser induced breakdown spectroscopy in helium surrounding gas under electric field

Abstract

Abstract We conduct an experimental study to search for the urgently needed method for routine, no sample pretreatment, in-situ, and less-destructive analysis of Hydrogen (H) content in Zircaloy-4 tube used as radioactive fuel container in light water nuclear power plant. For this purpose, we implemented laser-induced breakdown spectroscopy (LIBS) in Helium (He) surrounding gas at a relatively low pressure of around 3 kPa and low laser energy of 17 mJ. In addition, we designed a new compact and portable sample chamber accommodating an open end so the chamber can tightly fit the Zircaloy-4 tube surface. Inside the chamber we put electrodes to apply an additional electric field. We found that applying an electric field in the plasma expansion region increases the H emission intensity by a factor of 6. Consequently, the H I 656.2 nm emission line obtained from the Zircaloy-4 sample containing H of 11 ppm impurity featuring a sharp linewidth (0.1 nm) with high signal-to-noise ratio (S/N = 120). Thus, it offers potential applications to non-destructive H analysis in Zircaloy-4 tubes used in light water nuclear power plant. The detection limit of H was estimated less than 0.26 ppm, well below the sensitivity limit of around 600 ppm required for the regular inspection of Zircaloy-4 tubes in light water nuclear power plant.