A novel radon reference chamber with radon-gas buffer storage: Design, control strategy, and performance

Conventional radon chambers vent radon produced by the radium source during non-replenishment periods, raising environmental concerns, while slow replenishment limits operational efficiency. To overcome both limitations, this study proposes a novel three-stage "source-storage-chamber" configuration with a dedicated activity concentration control strategy. By storing and reusing the radon gas that would otherwise be vented, the system achieves near-zero intentional radioactive discharge under normal operation while significantly improving the replenishment efficiency. Experiments were performed at four target concentration levels (700, 1500, 3000 and 10000 Bq/m³) using a custom-developed control system. The stabilized concentrations were measured as (732 ± 11), (1574 ± 14), (3082 ± 21) and (10434 ± 38) Bq/m³, with relative deviations of 4.6%, 4.9%, 2.7% and 4.3%, respectively. The replenishment time is reduced from hours to minutes-approximately one order of magnitude-compared with conventional designs. Theoretical calculations indicate that the equivalent radium source activity could be reduced by nearly 90% assuming 100% emanation efficiency. A continuous stepwise transition experiment (background→700 → 1500→3000 Bq/m³) further confirms the system's capability for sequential multi-level concentration changes. The proposed design fully utilizes the radon generated by the source, substantially reduces environmental discharge, accelerates replenishment, lowers the required activity, and maintains satisfactory concentration stability. It is particularly suited for laboratories that require frequent and rapid transitions among multiple concentration levels.