Development of a method of evaluating PuO₂ particle diameters using an alpha-particle imaging detector

It is very important to evaluate the diameters (activity median aerodynamic diameter) of plutonium dioxide (PuO₂) particles for internal exposure dose evaluation. In this study, a method of evaluating PuO₂ particle diameters using an alpha-particle imaging detector was developed. PuO₂ particles with different diameters were modeled by Monte Carlo simulation, and the change in the shape of the energy spectrum for each particle diameter was evaluated. Two different patterns were modeled, namely, the case of ²³⁹PuO₂ and the case of PuO₂ (including isotopic composition of Pu). Multiple regression analysis was performed to determine the PuO₂ particle diameter from the obtained parameters. The simulated diameters and the diameters obtained with the regression model were in good agreement. The advantage of using the alpha-particle imaging detector is to measure the alpha energy spectrum for individual particle, and this allows accurate measurement of particle diameter distribution. (authors)