Acknowledgements

reference materials, BCR-320R, Channel Sediment, NIST SRM 1572, Citrus Leaves, and reference material, NIES no 7, Tea Leaves, respectively. Tables 7 and 8 show examples of samples analysed at the Laboratory for Neutron Activation Analysis, as small and large samples.

The Laboratory for Neutron Activation Analysis at CDTN, Brazil, needs to be prepared to meet customer analysis requirements. In order to answer this requirement, it was necessary to establish a methodology to analyse large samples, from 0.5 to 5 g sample, applying the k0 standardised method keeping the current infrastructure for irradiation and gamma measurements. Another objective was to overcome technical limitations while analysing samples smaller than 0.5 g, as, for instance, inhomogeneity of the sample and lower thermal neutron

To carry out the establishment, it was necessary to calculate several relevant parameters that would point out the feasibility to analyse large samples: detector efficiency over the volume source, neutron self-shielding during neutron irradiation and gamma-ray attenuation within

The results [16, 36, 37] pointed out that all parameters may be negligible for the large sample. At least, within the uncertainty range, once the elemental concentration results are in good agreement with the recommended values of the reference material IAEA-SOIL-7. All results obtained during the development using the reference material were evaluated by the statistical test, En-score, which pointed out that the k0-method applied using KayWin software presented an overall satisfactory performance. Few exceptions are already being investigated using other reference materials. It means that the KayWin software proved to be a robust programme to

calculate the elemental concentration of large samples producing reliable results.

7. Conclusions

Element Soil sample

Small sample (0.1133 g) (mg kg�<sup>1</sup>

)

104 Advanced Technologies and Applications of Neutron Activation Analysis

Experimental values are given as combined standard uncertainty.

Table 8. Mass fractions obtained for soil, analysed as small and large samples.

Large sample (0.6313 g) (mg kg�<sup>1</sup>

)

Fe 23,070 � 952 22,100 � 1235 Ta 2.31 � 0.09 2.26 � 0.12 Ga 37.2 � 1.3 33.9 � 1.2 Tb 0.503 � 0.032 0.515 � 0.019 Hf 32.8 � 1.5 30.4 � 2.0 Th 31.0 � 1.3 29.9 � 1.5 K 347 � 30 367 � 25 U 3.71 � 0.14 3.49 � 0.15 La 70.3 � 2.7 70.0 � 2.5 W 13.4 � 0.5 13.7 � 0.5 Sb 0.471 � 0.046 0.430 � 0.038 Yb 5.61 � 0.36 5.21 � 0.15 Sc 10.4 � 0.4 9.7 � 0.5 Zn 15.2 � 1.9 16.0 � 2.1

Element Small sample

(0.1133 g) (mg kg�<sup>1</sup>

)

Large sample (0.6313 g) (mg kg�<sup>1</sup>

)

flux of the reactor.

the sample during counting.

This work was partially supported by the International Atomic Energy Agency under grant BRA-14798, by the Brazilian Foundation for Research Support of Minas Gerais, FAPEMIG, under grant APQ-01259-09, and by financial support from the Slovenian Research Agency (ARRS) through programme P1-0143. Thanks to Brazilian National Council for Scientific and Technological Development, CNPq, and to Coordination for the Improvement of Higher Education Personnel, CAPES. Thanks to the TRIGA MARK I IPR-R1 reactor staff for making the use of the reactor for the experiments possible. Last but not least thanks to Dr Tibor G. Kocsor (Journal of Radioanalytical and Nuclear Chemistry) for allowing the use of tables and figures previously published.
