IAEA's ALMERA network: Supporting the quality of environmental radioactivity measurements.

The International Atomic Energy Agency coordinates and provides methodological and analytical quality support to the network of Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA), comprising 150 laboratories in 84 countries. Annual proficiency tests (PTs) are organized for the network laboratories using sets of different samples typically encountered in environmental and food monitoring laboratories. The PT system is designed to respond to the needs of the network for rapid response and reliable measurement results, and to metrological principles and international standards and guides. Comparison of performance of ALMERA and non-ALMERA laboratories in PTs indicates that the "PT - method development - training - PT" strategy adopted for capability building is beneficial to the network.

Assessment of measurement result uncertainty in determination of (210)Pb with the focus on matrix composition effect in gamma-ray spectrometry.

Reference materials were used to assess measurement result uncertainty in determination of (210)Pb by gamma-ray spectrometry, liquid scintillation counting, or indirectly by alpha-particle spectrometry, using its daughter (210)Po in radioactive equilibrium. Combined standard uncertainties of (210)Pb massic activities obtained by liquid scintillation counting are in the range 2-12%, depending on matrices and massic activity values. They are in the range 1-3% for the measurement of its daughter (210)Po using alpha-particle spectrometry. Three approaches (direct computation of counting efficiency and efficiency transfer approaches based on the computation and, respectively, experimental determination of the efficiency transfer factors) were applied for the evaluation of (210)Pb using gamma-ray spectrometry. Combined standard uncertainties of gamma-ray spectrometry results were found in the range 2-17%. The effect of matrix composition on self-attenuation was investigated and a detailed assessment of uncertainty components was performed.

Measurement of ²²6Ra in soil from oil field: advantages of γ-ray spectrometry and application to the IAEA-448 CRM.

The analytical performance of gamma-ray spectrometry for the measurement of (226)Ra in TENORM (Technically Enhanced Naturally Occurring Radioactive Material) soil was investigated by the IAEA. Fast results were obtained for characterization and certification of a new TENORM Certified Reference Material (CRM), identified as IAEA-448 (soil from oil field). The combined standard uncertainty of the gamma-ray spectrometry results is of the order of 2-3% for massic activity measurement values ranging from 16500 Bq kg(-1) to 21500 Bq kg(-1). Methodologies used for the production and certification of the IAEA-448 CRM are presented. Analytical results were confirmed by alpha spectrometry. The "t" test showed agreement between alpha and gamma results at 95% confidence level.