Comparison of different approaches of soil sampling uncertainty determination

Method and equipment for estimation activity nuclides in samples of finite dimensions

This study presents a method of measuring the activity of a specific radionuclide 234mPa in samples placed in bulk transport containers under changing background conditions. The method makes it possible to measure specific activity of 234 mPa in objects without the need for sampling. The change in the effective sample volume limited by the surfaces of the containers is considered depending on the density of the measured material and the energy of gamma radiation of the radionuclide. The high sensitivity of scintillation detector, supplemented by adequate Monte Carlo simulation, allows spectrum measurements to be taken in a short time (less than an hour) with subsequent determination of specific activity. A comparison of measurement results and calculation of 234mPa activity in samples with different densities and compositions using the proposed algorithm, and those obtained by an HPGe spectrometer, demonstrated the high efficiency of the proposed solution.

Uncertainty due to primary sampling of 222Rn in analyses of water

Measurement uncertainty is an important variable, to be accounted for when decisions have to be made based on measurement results. Measurement uncertainty is composed of two main components; one is related to the primary sampling, the other to the sample preparation and the subsequent analysis of the sample. The component related to the sample preparation and the analysis is commonly well evaluated in proficiency testing while there is generally no straightforward similar approach to evaluate sampling uncertainty. ISO 17025:2017 explicitly requires that testing laboratories performing sampling and analyses determine the uncertainty related to the primary sampling. In order to determine uncertainty arising in the primary sampling of ²²²Rn in water destined for human consumption, three laboratories IRE (BE), DiSa (LU) and SCK CEN (BE) initiated a joined sampling and measurement campaign. The dual split sample method in combination with ANOVA was used to evaluate the primary sampling uncertainty (precision) of the different methods. The tests showed that sampling bias is very probably, but that with good laboratory practice the sampling uncertainty precision and respectively bias can be kept below 5%.