Imaging of plutonium particles using a CCD-camera-based alpha-particle imaging system

摘要： Measuring individual activities of Plutonium dioxide (PuO2) particles is extremely important for the internal exposure of a worker to these particles. For this purpose, a film-based autoradiographic camera, Imaging Plates, and a SiPM-based alpha particle imaging detector have been used in a site of nuclear facilities. However, there is a room for improvement regarding a spatial resolution or a quantification of activity. Recently, an alpha imaging system using a cooled CCD camera has been developed and used for detecting Pu contamination in a glove box. In this study, actual PuO2 particles were measured using the CCD-camera-based alpha-particle imaging system, and the system’s effectiveness was proven by comparing to conventional systems. An electron multiplying (EM) CCD Camera (ImagEM X2 C9100-23B, Hamamatsu, Japan) was used for alpha particle imaging in this study. A Pu sample was placed on top of the ZnS(Ag) scintillator, and produced scintillation light was captured using the CCD camera. The number of alpha particles on a 2-dimensional distribution image was measured to convert into activity. The frame rate for obtaining the image was set to 33.3 frames/s (at 30 ms intervals). This study showed that the CCD camera-based alpha-particle imaging system has some advantages compared to the conventional alpha particle imaging systems; 1) High spatial resolution, 2) Counting capability of individual alpha particles, 3) Real-time imaging.