Radioactivity distribution measurement of various natural material surfaces with imaging plate

Distribution images of natural radioactivity in natural materials such as vegetables were obtained by using Imaging Plate. In such cases, it is necessary to reduce background radiation intensity by one order or more. Graded shielding is very important. Especially, the innermost surface of a shielding box should he covered with acrylic resin plate. We obtained natural radioactivity distribution images of vegetables, sea food, meat etc. Mostly beta-rays emitted from K-40 print the radioactivity distribution image. Comparison between gamma-ray intensity of KCl solution measured with HPGe detector and that of natural material specimen gave the radioactivity around 0.06 similar to 0.4 Bq/g depending on the kind and the part of specimens.