Two-dimensional measurement of natural radioactivity of granitic rocks by photostimulated luminescence technique

Two-dimensional measurement of radiation produced by natural irradiation of granitic rocks was performed by the use of an imaging plate, which is a storage film coated with photostimulated phosphor (BaFBr:Eu2+). Radiation images of small volume specimens, such as thin sections were obtained with the imaging plate. Irradiation images of granitic rocks are inhomogeneous and the intensity of photostimulated luminescence per unit area, which is principally converted into the integrated dose, increases with the increasing potassium content in the rocks. The results of the present study indicate that the disintegration of 40K is the dominant radiation source of granitic rocks. The imaging plate is a new research tool for the evaluation of the natural radioactive properties of geological materials and is applicable as a semi-quantitative two-dimensional dosimeter for natural radioactivity.