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531 ST 6.3 – Protección radiológica del público y el ambiente
SHORT-TERM STABILITY TEST FOR URANIUM
IN SOIL REFERENCE MATERIAL
Clain, Almir*; Fonseca, Adelaide;
Dantas, Vanessa; Bragança, Maura
IRD/CNEN. Brazil.
* Responsible author, email: almir@ird.gov.br
Brazil has large deposits of uranium and the radiochemical procedures to determine uranium
concentration in natural matrices is critical to an accurate assessment of the content of this
element in the various minerals of interest. The environmental control of the radionuclide
concentration in the vicinity of uranium mines is another area which also requires reliable
measurements and standards. Radiochemical analysis requires not only standards for
instrument calibration but also for evaluation of the analysis yield performance. Therefore the
production of uranium in soil reference material is extremely important for the chemical analysis
of this element. The objective of this work is to produce a soil reference material to be used for
chemical analysis of uranium with metrological traceability for environmental analysis,
equipment calibration, validation methods and quality control. The short-term stability of the soil
is an essential property to be determined. The slopes and their uncertainties (-0.0004 ±
0.001174 at 20oC and 0.0008 ± 0.000681 at 60oC) were obtained from the regression lines at
temperatures of 20oC and 60oC and a statistical t-test was applied. At 20 oC the t-value
obtained was 0.34 and the critical value was 2.78. At 60oC the t-value was 1.19 and the critical
value was 3.18. As the calculated t-value is lower than the critical value we can conclude with
95% confidence level, that no significant changes during the study period concerning the
uranium concentration in soil at temperatures of 20oC and 60oC, showing stability at these
temperatures.