Plutonium dioxide particle imaging using a high-resolution alpha imager for radiation protection

Akihiro Yamaji,Shunsuke Kurosawa,Taisuke Makita,Yuki Morishita,Masateru Hayashi,Tetsushi Azuma,Makoto Sasano

doi:10.1038/s41598-021-84515-z

Abstract

The internal exposure of workers who inhale plutonium dioxide particles in nuclear facilities is a crucial matter for human protection from radiation. To determine the activity median aerodynamic diameter values at the working sites of nuclear facilities in real time, we developed a high-resolution alpha imager using a ZnS(Ag) scintillator sheet, an optical microscope, and an electron-multiplying charge-coupled device camera. Then, we designed and applied a setup to measure a plutonium dioxide particle and identify the locations of the individual alpha particles in real time. Employing a Gaussian fitting, we evaluated the average spatial resolution of the multiple alpha particles was evaluated to be 16.2 ± 2.2 μmFWHM with a zoom range of 5 ×. Also, the spatial resolution for the plutonium dioxide particle was 302.7 ± 4.6 µmFWHM due to the distance between the plutonium dioxide particle and the ZnS(Ag) scintillator. The influence of beta particles was negligible, and alpha particles were discernible in the alpha–beta particle contamination. The equivalent volume diameter of the plutonium dioxide particle was calculated from the measured count rate. These results indicate that the developed alpha imager is effective in the plutonium dioxide particle measurements at the working sites of nuclear facilities for internal exposure dose evaluation.

Highlights

The internal exposure of workers who inhale plutonium dioxide particles in nuclear facilities is a crucial matter for human protection from radiation
We develop a high-resolution alpha imager using a charged-coupled device (CCD) camera and an optical microscope based on previous studies and applies the technique to measure an actual P uO2 particle
The electron-multiplying charged-coupled device (EMCCD) camera is capable of changing the exposure time intervals from 13.9 ms to 2 h

Summary

Introduction

The internal exposure of workers who inhale plutonium dioxide particles in nuclear facilities is a crucial matter for human protection from radiation. To determine the activity median aerodynamic diameter values at the working sites of nuclear facilities in real time, we developed a high-resolution alpha imager using a ZnS(Ag) scintillator sheet, an optical microscope, and an electron-multiplying charge-coupled device camera. The equivalent volume diameter of the plutonium dioxide particle was calculated from the measured count rate These results indicate that the developed alpha imager is effective in the plutonium dioxide particle measurements at the working sites of nuclear facilities for internal exposure dose evaluation. Alpha particle imaging detectors using position sensitive photomultiplier tubes (PSPMTs) and silicon photomultipliers (SiPMs) have been developed in the past[12,13,14,15] They can obtain alpha particle counts in real-time and are used to estimate P uO2 particle diameters. Miller et al developed an alpha camera named iQID camera, and the spatial resolution of ∼ 20 μm FWHM was a chieved[17]

Methods

Results

Discussion

Conclusion