Classification of ores used for the radiation source in NORM as consumer products by PGAA

Abstract

Abstract NORM means Naturally Occurring Radioactive Material. Our object in this study is only consumer products in several kinds of NORM. The existence of NORM in our living-environment raises the radiation exposure dose of the users. This has become a world-wide issue. The sources of NORMs are mainly radionuclides in the thorium (Th) and uranium (U) series. However, we have little published information about the kinds of ores added to NORMs and there are little indications on the NORMs' labels. It is well-known that Th and U usually exist with rare earth elements. So we sought a classification method for identifying the kinds of ores added to the consumer products from the correlation of the concentration ratios of the Th/U and the Gd/Sm in NORM and ores. The conventional γ-ray spectrometry by a Ge detector for analysis of Th and U and the prompt gamma-ray activation analysis for the determination of Sm and Gd were employed. It was found that the radiation sources of NORM in the consumer products in recent markets were mainly monazite. This classification method is found to be useful to identify the ores used for the radiation sources in consumer products of NORMs.