On-line Measurement of Hydrogen Gas using Raman Spectroscopy for Process Gas Systems

Advanced reprocessing schemes such as the Zircex process are important for continued development of the nuclear fuel cycle. The hydrochlorination reaction of the Zircex process flow sheet for metallic fuels has a known off-gas stream of H₂(g) and HCl. The flow sheet can be simplified through HCl recycling, which requires detection and quantification of any residual H₂(g) for safety and purity. In this work, commercially available Raman spectroscopy was applied for low-level, on-line detection of H₂(g) in process gas streams, and parameters were adjusted to optimize the H₂(g) Raman signal. Increasing the number of scans and exposure time in the spectrometer increased the signal-to-noise ratio of the H₂(g) Raman signal, while the gas flow rate was optimized at 2.3 L/min. The limit of detection for H₂(g) was estimated to be 2,100 ppm H₂(g) in an N₂(g) background. This scoping study for the application of Raman spectroscopy for on-line measurements of H₂(g) shows that H₂(g) can be detected at low levels (approximately 5% of the lower explosive limit (LEL)) in flowing gas streams.