避難退域時検査効率化に向けた車両用ゲートモニタの新たな測定手法の開発

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

平岡 大和 ; 川崎 晃平*; 木村 仁宣 ; 齊藤 将大 ; 江嵜 巌*; 亀田 周二*; 外川 織彦 

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

避難退域時検査における車両検査の効率化を図るため、可搬型ゲートモニタでタイヤ側面とワイパー部を同時検査する手法の開発を進めている。本研究では、タイヤとワイパー部のいずれが汚染しているかを判別する手法として、検出器を地面近くに水平・垂直に配置するL字型の測定構成を設計した。このL字測定法による判別手法をモンテカルロシミュレーションで評価した結果、点線源がタイヤ・ワイパー部のいずれにあるかにより、水平・垂直の検出器で得られる計数値の大小関係に差異が生じることが示された。この関係から汚染箇所を特定する判別手法を検討し、ゲートモニタ(千代田テクノル製「ガンマ・ポール」)による測定でL字測定法の有効性を検証した。その結果、タイヤ汚染を模擬した実験では30回全てでタイヤを正しく特定でき、ワイパー部汚染を模擬した実験では30回中29回でワイパー部を正しく特定できた。

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.