Thoron Gas Measurement Using Airflow-Through Scintillation Cell with Consideration of Progeny Deposition

Accurate measurement of low-level thoron gas and high-accuracy calibration of thoron measurement devices are essential for assessing and preventing thoron radiological risks. This study aimed to develop a thoron gas measurement technique using an airflow-through scintillation cell for both low-level measurement and high-accuracy calibration. To achieve this, a compartment model was developed to estimate the influence of progeny deposition and accumulation on the wall of the scintillation cell to prevent an overestimation of thoron. A self-developed scintillation cell was utilised to implement and validate this technique. The lower detection limit and measurement uncertainty were then evaluated to assess the feasibility of the technique for low-level measurement and high-accuracy calibration. The results showed that the compartment model effectively addressed the influence of progeny deposition. The measurement technique achieved a lower detection limit below 100 Bq m(-3) even with the coexistence of that of 100 Bq m(-3) of radon and attained a measurement uncertainty (k = 2) below 10% when the concentration of thoron exceeded 1000 Bq m(-3). In summary, this study developed a reliable and practical thoron gas measurement technique using an airflow-through scintillation cell with a consideration of progeny deposition, and is expected to contribute to the assessment and prevention of thoron radiological risk.