Calculation of the detection limits by explicit expressions.

A method for calculating the approximate value of the detection limit for measurements of ionizing radiation is presented. The method can be applied when the indication corresponding to the detection limit and its uncertainty are given as explicit functions. Then also the detection limit can be calculated explicitly, which means that the iteration procedure for its calculation can be avoided. The advantage of the method becomes apparent when the iteration process for calculating the detection limit is difficult to apply.

Slovenian-Romanian bilateral intercomparison on tritium samples.

A Slovenian laboratory from the Jozef Stefan Institute (JSI) and a Romanian laboratory from the National Research and Development Institute for Cryogenics and Isotopic Technologies (ICIT) performed bilateral intercomparisons of tritium determination in environmental samples. On the basis of the results, the measurement and analysis methods were compared. Comparability and traceability were confirmed with the results from international radioactivity proficiency test exercises organized by IAEA and NPL where both laboratories participated. New knowledge gained leads to harmonized, precise and traceable results of low level tritium environmental samples measurements.

Detection of Fukushima plume within regular Slovenian environmental radioactivity surveillance.

After the Fukushima accident aerosol and rain water samples collected within regular national monitoring programmes were carefully analysed. In rain water samples, aerosol and iodine filters collected in the second half of March and in April 2011 I-131, Cs-134 and Cs-137 were detected. In May 2011 the activities of I-131 and Cs-134 were close or below the detection limit and Cs-137 reached values from the period before the Fukushima accident. Additionally plutonium and americium activity concentrations in aerosol filters were analysed. These measured data were compared with measured data after the Chernobyl contamination in Slovenia in 1986. We can conclude that with adequate regular monitoring programmes influences of radioactivity contamination due to nuclear accidents worldwide can be properly assessed.

Traceability in gamma-ray spectrometry.

The new edition of the International vocabulary of metrology-basic and general concepts and associated terms (VIM) defines metrological traceability in a different way than was defined in the previous edition. The reference to an "unbroken chain of comparisons" is replaced by a "chain of calibrations." Calibrations, unlike comparisons, render possible an interpolation of the quantity values between indicated parameters where the calibration was performed. Calibrations of software may be performed using software-measurement standards as well. Furthermore, the traceability of quantities having a minor influence on the measurement result is not mandatory. As a consequence of these modifications, the traceability of gamma-ray spectrometric results can also be attained when gamma-ray spectrometry is implemented other than as a relative method.

Towards establishing traceability of results measured in specific counting conditions in gamma-ray spectrometry.

Due to biased potassium activity results in the proficiency test soil samples, measurements of a set of control samples containing potassium compounds with known concentrations of potassium were performed in order to establish the traceability of potassium activity results in to the unit of mass. The radius and the mass of the control samples were equal to the radius and the mass of the proficiency test samples. The density of samples in both cases varied between 1 and 2g/cm(3). No influence of sample density on the potassium activity results could be detected at the accuracy level achieved. The source of disagreement could not be found within the participating laboratory.

Quality assurance of automated gamma-ray spectrometric analysis

Fully automatic gamma-ray spectrometric analysis procedures perform complete processing of the spectrum without intervention of the operator. In order to maintain the reliability of the final results the analysis checks the intermediate results automatically. When a disagreement is identified by such a check the uncertainty of the intermediate results is increased in order to accommodate the disagreement. The increased uncertainty is propagated into the uncertainty of the final results in order to take into account the disagreement. This approach was implemented in Canberra's Genie ESP gamma-ray spectrometry package for examining the results of the peak analysis. In addition to this intermediate check also a-posteriori checks of the final results can be performed by statistical analysis. Such analysis shows whether the results are under statistical control and can discover sources of variability which are not taken into account in the uncertainty budget.

Quality control of gamma-ray spectrometry measurements

Specific techniques have been implemented to assess the quality of routine gamma-ray measurements and the associated analysis procedures. Appropriate steps monitor three factors influencing the quality of performance: the performance of the spectrometer, the quality of the measurement and the quality of the peak analysis. In order to illustrate the approach, time dependencies of parameters describing the performance of the spectrometer, the quality of the measurements and the sample activities are presented.

IAEA Internet database of natural matrix reference materials.

The International Atomic Energy Agency maintains a database on internationally available certified reference materials of natural origin. The database was updated in 1998 and prepared for an Internet implementation. A user-friendly structure was created, providing two main pathways for browsing, either according to the matrix classification or the producer's name. The database presently contains over 20,000 values for 480 measurands and 1085 reference materials from 43 different producers. Most of the materials entered contain values for trace and minor elements (66%).