Non-destructive analysis by gamma ray spectrometry of archaeological ceramics

Full text: The method of gamma ray spectrometry has proved its efficiency in the radioactivity determination of samples for several purposes (geochemical characterization, dating techniques, radiogenic heat calculations, radiological impact of geological materials used in buildings, etc...). For all these applications, it is important to establish good calibration curves for specific sample-detector geometries. In laboratory measurements, generally, it is necessary to mill the sample to adapt the geometry, permitting absolute determinations of samples activities. The necessity of crushing the samples makes the gamma spectrometric methods impractical for the analysis of archaeological artifacts, where to preserve the integrity of the sample is essential. The objective of this work is to develop an experimental method that allows, without any destruction of the sample, the measurement of the absolute activity ratios between the natural radioelements, eTh (ppm) / eU (ppm) and eTh (ppm)/ K (%). The method is based in the comparison among counts obtained for distinct gamma lines of the radionuclides belonging to the U-238 and Th-232 natural series (Pb-212, Pb-214, Tl-208, Bi-214, Bi-212 and Ac-228) . The measurements must be accomplished with a high resolution gamma spectrometric system. Preliminary results show that the method can estimate the ratios with relative errors lower than 15 %. (author)