A Method of evaluating PuO
particle diameters by an alpha particle imaging detector
イメージング検出器によるPuO
粒子径評価法
森下 祐樹
; 佐川 直貴; 高田 千恵
; 百瀬 琢麿
; 高崎 浩司
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Morishita, Yuki; Sagawa, Naoki; Takada, Chie; Momose, Takumaro; Takasaki, Koji
Alpha emitting radionuclides such as plutonium (Pu) isotopes require special consideration in terms of internal exposure. The evaluation of the diameters (activity median aerodynamic diameter (AMAD)) of PuO
particles is very important for internal exposure dose evaluation. In this study, we propose a new method to determine the PuO
particle diameter from the energy spectrum obtained by the developed alpha particle imaging detector. PuO
particles with different diameters were modeled by Monte Carlo simulation. The change in the shape of the energy spectrum for each particle diameter was evaluated. Two different patterns were modeled: (1) the case of
PuO
, and (2) the case of PuO
(including isotopic composition of Pu). The value of the energy resolution of the simulation was based on the measured value of the detector energy resolution. Multiple regression analysis was performed to determine the PuO
particle diameter from the obtained parameters. The simulation results showed that the radioactivity (measured counts) was lower when the PuO
particle size was smaller. In addition, the energy spectrum was sharper due to the smaller effect of self-absorption of the PuO
particles themselves. On the other hand, when the PuO
diameter was large, the radioactivity (measured counts) was high. In addition, the energy spectrum became broad and the position of the peak shifted to the lower side. Using the obtained parameters (measured radioactivity, peak counts, peak position, and peak width), multiple regression analysis was performed to evaluate the PuO
diameter. The proposed method was compared with the conventional method and found to be in agreement.