Characterization of NORM-type scales from the oil industry through spectrometry techniques and multivariate analysis

The oil industries have as main problem in their activities of formation of scales containing material of the naturally occurring radioactive material (NORM) type on the internal walls of pipes and in some equipment that make up the process lines plant. This NORM can contribute to the exposure of workers during routine activities, either through external exposure, or internal, through inhalation or ingestion. Considering the concern with occupational exposure, environmental impacts and the plant's production capacity, resulting from the formation of the scales, this work characterized samples of scale by means of techniques of x-ray fluorescence (XRF), x-ray diffraction (XRD) and high-resolution gamma spectrometry. The XRF showed concentrations of P, S, Cl, Ca, Mn, Fe, Sr, and Ba as the main elements of the sample; the XRD showed calcite and barite as predominant composition; in the gamma analysis, the concentrations of the activities varied from 104.6 to 1112.6 Bq kg(-1) for Ra-226 and from 16.4 to 385.2 Bq kg(-1) for Ra-228, within the limits set by the International Atomic Energy Agency. The indices radium equivalent activity, absorbed dose rate and annual effective dose indices varied from 128.4 to 1665.9 Bq kg(1); 58.4 to 748.0 nGy h(-1) and 0.072 to 0.918 mSv y(-1), respectively. Only the effective dose values were within the limits established by United Nations Scientific Committee on the Effects of Atomic Radiation, reinforcing the need for continuous monitoring on the platforms and the importance of keeping the radiological protection plan up to date, since the mobilization of NORM increases proportionally with the useful life of the production wells, thus increasing exposure indices.