Natural radioactivities in iron and nickel ores imported into Japan and the dose assessmentfor workers handling them

Abstract

Japan imports Fe and Ni ores from abroad for use as industrial raw materials inthe manufacture of industrial products like stainless steel. Some of these oresmight contain high levels of radioactivity, and then workers handling them wouldbe exposed to radiation without being aware of it. Activity concentrations inthese ores should be measured to evaluate the radiation exposure of workers.In this study, Fe and Ni ores used as industrial raw materials were collectedfrom iron and steel companies, and the activity concentrations of the 238U series, the 232Th seriesand 40K in these ores were determined using inductively coupled plasma mass spectrometry(ICP-MS) and gamma ray spectrometry. The activity concentrations of the 238U series, the 232Th seriesand 40K in these ores samples were lower than the International Atomic Energy Agency (IAEA)values. The doses to workers handling these ores were estimated using methods for doseassessment given in a report by the European Commission. In each scenario, amaximum value of the annual effective dose to workers was estimated to be about6.8 × 10−6 Sv, which was lower than intervention exemption levels (annual dose1.0 × 10−3 Sv) given in International Commission on Radiological Protection (ICRP) Publication82.