Investigation of Multi-parameter Synchronous Detection Technology for Radioactive Aerosols in Spent Fuel Dissolution Process.

Abstract

Spent-fuel dissolution produces multi-nuclide, high-activity aerosols. Gross α/β CAMs are prone to interference and slow response, limiting timely dose assessment and alarms. We developed an integrated multiparameter synchronous detection system to simultaneously measure activity concentration, spectra, and particle size. The instrument integrates sampling and optical sizing (0.1-10 μm) with a silicon barrier (α), thin-window proportional (β), and 2 × 2 NaI (Tl) (γ) detectors. Signals are digitized (14-bit/100 MS s -1 ) for pulse-shape discrimination and 8,192-channel spectrometry. Performance followed ISO 11929/Currie. Standard sources and mixed-nuclide aerosols were used for calibration, linearity, response, and misclassification tests; stability was assessed over 720 h (50 L min -1 , 60 s integration). Detection efficiencies were 26.3% ( 241 Am α), 42.5% ( 90 Sr/ 90 Y β), and 31.2% ( 137 Cs γ). Minimum detectable activities were 8.5 × 10 -7 Bq cm -3 ( 241 Am), 9.2 × 10 -7 Bq cm -3 ( 239 Pu), and 3.1 × 10 -6 Bq cm -1 ( 90 Sr/ 90 Y). Dynamic tests gave T 90 = 17.5 s and T 95 = 22.3 s; α/β misclassification < 5%; linearity across five orders (R 2 = 0.9987). Compared with a representative CAM, spectral resolving power improved ≈5-fold and response time shortened 10-20 times. Energy and efficiency drift over 720 h were ≤±2% and ≤±3%. Multi-parameter acquisition reduces dose-assessment bias from nuclide misidentification and size assumptions and shortens alarm latency to < 30 s in high-background, multi-nuclide environments, supporting ALARA and process control during spent-fuel dissolution.