Development of a new measurement method using a portable radiation portal monitor for vehicles to enhance contamination screening efficiency

Hiraoka, Hirokazu ; Kawasaki, Kohei*; Kimura, Masanori ; Saito, Shota ; Ezaki, Iwao*; Kameda, Shuji*; Togawa, Orihiko 

A method to enable the simultaneous inspection of tires and the wiper area using a portable radiation portal monitor is being developed to improve the efficiency of vehicle inspection during contamination screening. To achieve this, we devised an approach to identify whether contamination is located on the tires or in the wiper area. We designed an L-shaped measurement configuration, where detectors are positioned horizontally near the ground and vertically upright. An identification approach based on this L-shaped configuration was evaluated using Monte Carlo simulations. The results showed that the magnitude relation of counts measured by the horizontal and vertical detectors varies depending on whether the point source is located on the tires or in the wiper area. We examined an identification method that utilizes this relationship to determine the contaminated location. Next, we conducted measurements using a portal monitor (Gamma Pole, manufactured by Chiyoda Technol) and attempted to identify the contaminated location by the L-shaped measurement method. As a result, in the experiment simulating tire contamination, all 30 measurements correctly identified the tires as the contaminated location. In contrast, in the experiment simulating wiper contamination, 29 out of 30 measurements correctly identified the wiper area.