Development of online measurement technology for total alpha activity in radioactive solution based on liquid film

Accurate and rapid online measurement of alpha radioactivity in radioactive solutions poses significant challenges in the nuclear industry. Conventional methods are often limited by susceptibility to detector contamination, operational complexity, and difficulties in real-time monitoring and calibration. This study presents an innovative online device and methodology based on a rotating-wheel liquid-film technique. A precision wheel generates a stable, uniform ∼100-micron-thick liquid film on its polished surface, enabling direct alpha detection. Optimization of wheel surface finish and rotation speed ensured reproducible film thickness. An integrated compressed air purge system effectively shields the detector from aerosols, preventing background accumulation during extended operation. Crucially, a built-in calibration disk facilitates online measurement calibration. A specially designed high-efficiency ZnS(Ag) scintillation detector enhances detection efficiency while ensuring stability. The performance of the online measurement device was evaluated using a plutonium-containing organic phase solution as the test material. It demonstrated excellent linearity (R² = 0.9996) across a wide activity range of 1.16 × 10⁶ to 1.16 × 10⁹ Bq·L^-1. Precision (relative standard deviation, RSD) was ≤2.61 %, with a detection limit of 1.45 × 10⁴ Bq·L^-1. The device maintained good stability (RSD = 1.91 %) during a 10-day continuous operation test. This device exhibits superior detection efficiency, contamination resistance, online calibration capability, and long-term stability, meeting the stringent demands for high-precision, real-time α monitoring in complex radiochemical streams.