Monitoring of natural radioactivity in working places

摘要

Radioactive materials are treated and transformed mainly in nuclear industries. However, non-nuclear industries use raw materials containing significant levels of natural radionuclides; the processing of these materials can expose workers and people living near such sites to radiation levels well above the natural background. This radioactivity is due to nuclides belonging to the U-238 and Th-232 decay chains and to K-40. Inductively coupled plasma mass spectrometry (ICP-MS) and gamma-ray spectrometry have been used together to determine uranium and thorium concentration and the conditions of secular equilibrium in their decay chains for samples from ceramic and phosphate-fertiliser plants. In fact, the knowledge of the secular equilibrium conditions is necessary in order to make correct assumptions for the dose assessment. The results indicate that the secular equilibrium is verified for the samples from ceramic plants, whereas a situation of disequilibrium between parents and daughters of the natural chains is detected in phosphate fertilisers. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 19]