Development of a 3D-printed two-stage virtual impactor for radioactive aerosol size classification and direct analysis

Laffolley, H.; Tsubota, Yoichi   ; Kuroe, Ayame; Kato, Tomoaki 

Radioactive aerosol size classification is crucial for exposure assessment during nuclear decommissioning. This study presents SPLIT, a two-stage 3D-printed virtual impactor separating aerosols into three aerodynamic classes (10 m, 110 m, and 1 m) while enabling direct analysis on integrated filters. This low-cost, disposable device eliminates hazardous cleaning and metallic waste by allowing incineration after use. Flow paths were optimized via computational fluid dynamics, and prototypes were fabricated by stereolithography. Simulations predicted sharp separation with cutoff diameters of 9.0 m and 1.3 m, despite minor cross-flow particle contamination. Prototype measurements revealed shrinkage and corner rounding, necessitating fabrication compensation. Experiments with incense smoke confirmed submicrometric particles collected mostly in the 1 m class. Tests using Rn-progeny-bearing NaCl particles (1.70 m mean diameter) showed the highest activity on the 110 m filter, confirming the expected classification. These results validate this lightweight, low-cost impactor for simultaneous size classification and direct radioactive particle analysis.