Characterization of Ce:La-GPS scintillator for tritiated water detection

Tritium in water is difficult to monitor because the low-energy beta particles emitted by tritium are strongly self-absorbed. Although liquid scintillation counting provides high sensitivity, it requires sample preparation and generates radioactive organic liquid waste, limiting its suitability for on-site continuous monitoring. In this study, we investigated the inorganic single-crystal scintillator (La,Gd) 2 Si 2 O 7 :Ce (Ce:La-GPS) for tritiated water measurements. The as-grown sample showed long-term afterglow that increased the count rate in the region of interest for tritium detection, but air annealing at 1200 °C suppressed the afterglow to the background level. The annealed sample exhibited a light output of approximately 35,000 photons/MeV and an energy resolution of 5.5% at 662 keV under 137 Cs gamma-ray excitation. Immersion measurements in tritiated water showed a linear counting response, with a minimum detectable activity of 3.85 MBq/L for a 600 s measurement. These results indicate that Ce:La-GPS is a promising solid scintillator for high-activity tritiated water monitoring, while application to low-level monitoring will require increasing the effective scintillator surface area.