New electrolytic enrichment system for tritium determination in water research institute in Bratislava and IT'S first results of tritium activity in precipitation.

The method of tritium activity measurements by electrolytic enrichment in combination with liquid scintillation counting is well known for many years. In the Water Research Institute in Bratislava was this system employed since the 60-ties of the 20th century. In 2018 the laboratory of radiochemistry of Water Research Institute obtained a new electrolytic enrichment system with higher enrichment factor (varying from 9 to 22, depending on the total ampere-hours used). The enrichment factor of the previous system was about 6. Complementary to the new system, also the new LCS counter Quantulus GCT 6220 was added. This spectrometer has active background suppression function (Guard Compensation Technology - GCT) and for the tritium measurement the background counts decreased from cca. 9 cpm (for Tricarb 2900 TR) to approximately 1 cpm. To demonstrate the capabilities of this system, we present results of the tritium concentration in precipitations during the period from May 2016 to May 2019. The seasonal variations of tritium activities in precipitation are observed, with maximum values in spring season and minimum in winter. Additionally, selected tritium activities from the extensive monitoring of river waters in Slovakia are presented.

Results of an EC laboratory comparison on 4°K, 9°Sr and ¹³7Cs in dried bilberry powder.

The evaluation is presented of a laboratory comparison (LC) on (90)Sr, (40)K and (137)Cs in dried bilberries organised in 2011 by the IRMM. The activity concentrations reported by 88 participant laboratories are compared to the reference values of the new reference material IRMM-426 Wild Berries. Nine per cent and 17% of activity concentration results for (137)Cs and (40)K, respectively, deviate more than 20% from the reference values, a result worse than that obtained in previous LCs. For (90)Sr, about 88% of results lie within 30% of the reference value, better than observed in previous LCs. But only 58% of (90)Sr results are satisfactory in terms of the En criterion, indicating difficulties with a complete uncertainty estimation.

Critical remarks on gross alpha/beta activity analysis in drinking waters: conclusions from a European interlaboratory comparison.

The most common gross alpha/beta standard methods used for drinking water analysis are discussed, and sources of interferences are reviewed from a metrological point of view. Our study reveals serious drawbacks of gross methods on the basis of an interlaboratory comparison analyzing commercial mineral water samples with the participation of 71 laboratories. A proposal is made to obtain comparable measurement results using true standardized methods.

Determination of natural and anthropogenic radionuclides in soil--results of an European Union comparison.

A comparison was organised by the Institute for Reference Materials and Measurements (IRMM) among 73 environmental radioactivity monitoring laboratories for the determination of 15 radionuclides in soil. The reference material IAEA-375 soil was reprocessed to provide the comparison material and reference values traceable to SI units and SIR were established at IRMM. The analytical procedures used by participants laboratories are discussed and performances evaluted using relative deviations and E(n) numbers. This paper focuses on the results for (40)K, (90)Sr, (137)Cs, (226)Ra, (234)U, (235)U and (238)U. Worst performance was found for (90)Sr and (235)U, where 65% and 78% of the results, respectively, deviate more than 20% from the reference values. The use of the E(n) criterion revealed that the uncertainty estimation of many participants is poor.

Inter-laboratory comparison measurements of radiochemical laboratories in Slovakia.

The first inter-laboratory comparison organized by the radiochemistry laboratory of Water Research Institute (WRI) in Bratislava was carried out in 1993 and since then is it realized on an annual basis and about 10 radiochemical laboratories from all over Slovakia are participating. The gross alpha and gross beta activities, and the activity concentrations of (222)Rn, tritium, and (226)Ra, and U(nat) concentration in synthetic water samples are compared. The distributed samples are covering the concentration range prevailing in potable and surface waters and are prepared by dilution of certified reference materials. Over the course of the years 1993-2008, we observed the improvement in the quality of results for most of the laboratories. However, the success rate of the gross alpha determination activity is not improving as much as the other parameters.