Disposable device enables easy measurement of airborne particles

Senior Principal Researcher Youichi Tsubota, Postdoctoral Researcher Hugo Laffolley, and Researcher Tomoaki Kato of the Collaborative Laboratories for Advanced Decommissioning Science at the Fukushima Research and Engineering Institute, Japan Atomic Energy Agency (JAEA), together with Team Leader Ayame Kuroe of the Nuclear Cycle Engineering Laboratories, have developed µSPLIT (micro-SPLIT), a disposable classification and measurement device that separates airborne fine particles by size and collects them on filters.

Tsubota said: "During decommissioning work at Fukushima Daiichi Nuclear Power Station (F1), radioactive materials may become airborne during dismantling and other operations. Existing measurement devices are expensive, so we developed one that can be easily discarded after use. We hope to accelerate its social implementation and encourage widespread adoption." The results were published in ACS Omega.

At sites where harmful fine particles are generated, such as factories, mines, and nuclear facilities, understanding the size and concentration of airborne particles is essential for protecting workers' health. Particle size determines how deeply particles penetrate the respiratory tract and the extent of their health effects. Particles larger than 10 microns tend to deposit in the nasal cavity and pharynx, particles between 1 and 10 microns can reach the trachea and bronchi, and particles smaller than 0.1 microns may reach the alveoli. In the case of radioactive materials, particle size must be evaluated because it directly affects internal radiation exposure.

However, conventional measurement instruments, which are typically made of precision-machined metal, cost several million to tens of millions of yen per unit. The interior must be thoroughly cleaned after each measurement before the device can be used again. This cleaning process itself poses a risk of secondary radiation exposure to workers, making it difficult to deploy multiple measurement devices simultaneously across a site.

The research team designed the device as a single-use disposable system fabricated from transparent resin using a 3D printer. Measuring approximately 12 × 3 × 3 cm, the device can be produced at significantly lower cost than conventional instruments. Because devices contaminated during monitoring can simply be discarded, the need for decontamination work and secondary contamination control measures can be greatly reduced, lowering worker exposure risks.

The internal flow path was designed using numerical simulations and utilizes airflow to separate particles into three size categories. By integrating particle separation and collection on a HEPA filter within a single module, the device eliminates the risk of sample loss and contamination during transfer. The flow-path design exploits differences in particle inertia to separate fine particles into three size ranges: greater than 10 microns, 1 to 10 microns, and less than 1 micron.

In demonstration tests using radioactive aerosol particles, the device successfully separated particles by size on filters directly connected to radiation measurement instruments, and direct alpha-radiation measurements were successfully conducted. The team also developed a software application that allows the device to be redesigned for different particle-size ranges.

In addition to monitoring radioactive aerosols in work areas during future F1 decommissioning operations, the technology is expected to find applications in environmental monitoring and occupational health, including the measurement of PM2.5, dust, and airborne microplastics. To achieve early social implementation, the team plans to carry out demonstration tests at sites in Japan and overseas, expand technology licensing to private companies, and pursue the establishment of startup ventures.

Journal Information
Publication: ACS Omega
Title: Development of a 3D-Printed Two-Stage Virtual Impactor for Radioactive Aerosol Size Classification and Direct Analysis
DOI: 10.1021/acsomega.6c04521