Measuring of surface potential of radiocaesium-bearing microparticles by Kelvin Probe Force Microscopy

Kurosawa, Keiichi*; Iwata, Ayumu*; Satou, Yukihiko   ; Abe, Yoshinari*; Igarashi, Yasuhito*; Okuda, Tomoaki*

The Fukushima Daiichi Nuclear Power Plant accident caused serious emission of radionuclides into the atmosphere. After several years, insoluble radiocaesium-bearing microparticles (CsMP) have been found in some regions in Japan. These insoluble solid particles remain as a particle in human airways and continue emitting radiation when they are inhaled. Therefore, these particles have a potentially significant adverse effect on human health. Because of the continuous emission of the -rays, which is energetic electron beam, previous studies reported that the radioactive particles would have specific electrostatic charging characteristics. Also, several laboratory experiments and numerical simulations have shown that the electrostatically charged particles are more deposited on the human respiratory airway. Therefore, the electrostatic charging characterization of the CsMP is important for the accurate evaluation of its health effects. In this study, we used Kelvin Probe Force Microscopy to measure the surface potential of CsMP. The obtained mapping image was shown that the radioactive particle has a certain distribution of surface potential ranged between +0.3 V and -0.3 V. This distribution of the surface potential within the particle may be associated with the distribution of radioactive Cs in the surface layer of the particle.