engleski

Interlaboratory comparison of tritium electrolytic enrichment systems at RBI (Zagreb) and JSI (Ljubljana)

Tritium (3H) activity of natural waters (precipitation, groundwater, surface waters) has recently become too low to be directly measured by low-level liquid scintillation (LSC) techniques. It is therefore necessary to perform electrolytical enrichment of tritium in such waters prior to LSC measurements. Electrolytical enrichment procedure has been implemented in the Laboratory for liquid scintillation counting at the Department of Low and Medium Energy Physics of the Jožef Stefan Institute (JSI) in Ljubljana, Slovenia, in 2007 and in the Radiocarbon and Tritium Laboratory at the Department of Experimental Physics of the Ruđer Bošković Institute (RBI) in Zagreb, Croatia, in 2008. Both electrolysis systems were obtained from the same producer (AGH University of Science and Technology, Krakow, Poland). Since establishment 21 electrolyses have been completed at RBI and more than 100 at JSI, where last66 were carried out under identical conditions. The mean enrichment factor E (a ratio between the final and initial 3H activities) after stabilisation of the system is ERBI = 22.8 ± 0.8, and the mean enrichment parameter (which describes the process of water mass reduction during electrolysis) is PRBI = 0.947 ± 0.003. The corresponding values at JSI (after 66 electrolyses) are EJSI = 18.9 ± 1.5, and PJSI = 0.896 ± 0.021. Both RBI and JSI laboratories have Ultra-low-level LSC Quantulus 1220 (Wallac, PerkinElmer) for measurement of 3H activity. A set of water samples having 3H activities in the range from 0 TU ("dead-water" samples) to 18 000 TU (1 TU = 0.118 Bq/L) were measured at both laboratories. Samples having 3H activity <200 TU were electrolytically enriched, while the others were measured directly in LSC. A very good agreement was obtained (correlation coefficient 0.991). Both laboratories participated in the IAEA TRIC2008 international intercomparison exercise. The analyses of reported 3H activity results in terms of z and u parameters showed that all results in both laboratories were acceptable.

tritium; intercomparison; enrichment

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