Application of the Deconvolution Method to Alpha-Ray Energy Spectrum to Improve the Performance of a Radiation Airborne Particulate Monitor

Background: At nuclear facilities and decommissioning sites, monitoring radioactivity concentrations in airborne particulates is crucial to prevent worker exposure. To avoid internal exposure, alpha-decay radionuclides must be detected. When monitoring alpha-decay radionuclides in airborne dust, we want to measure the concentration of only artificial radionuclides (e.g. , 238Pu, 239Pu, 240Pu, 235U, 238U, 241Am, and 244Cm). The radioactivity concentration must be measured separately for artificial (4.3–5.8 MeV) and natural radionuclides (212Bi, 214Po, and 212Po at 6.0, 7.7, and 8.8 MeV, respectively).Materials and Methods: We created response functions for various alpha-ray energies using a radiation simulation toolkit. Utilizing these response functions, we deconvolved the alpha-ray energy spectra measured while collecting dust on filter paper. To ensure the precision of the response function, we prepared a model including the distance between the filter and the detector and the structure of the light shield in detail.Results and Discussion: The deconvolved spectra had three clear peaks at 6.0, 7.7, and 8.8 MeV. These energies were consistent with those of 212Bi, 214Po, and 212Po. The deconvolved energy spectra showed that only a few measurements (4.0–5.8 MeV) were included in the energy range due to artificial radionuclides. From these measurements, the decision threshold for artificial radionuclides was determined to be about 1.5×10−7 Bq/cm3.Conclusion: Our findings demonstrated that we could measure artificial and natural radionuclides separately with the deconvolved alpha-ray energy spectra. Specifically, we were able to monitor artificial radionuclides down to low radioactivity concentrations in 10-minute measurements.