Relevant radionuclides in Estonian drinking and ground waters – measurement techniques and activity concentrations

First comprehensive studies of the radionuclides’ concentration and its composition in Estonian ground water began in 1990s. It was quickly realized that the activity concentration of 226Ra and 228Ra in Cambrian-Vendian (Cm-V) aquifer are the highest contributors to the total indicative dose (TID). About 22% of the population in Estonia uses Cm-V ground water for drinking water supply. In recent study [1], it was concluded, that about 91% of Cm-V aquifer consumers (20% of the Estonian population) obtain higher TID doses (TID exceeding 0.1 mSv/y) than set by European Commission and national regulations. Over the years, a good representation level by the number of measured samples for 226Ra and 228Ra from Cm-V aquifer has been obtained. However, for other widely used aquifers – Ordovician-Cambrian, Silurian-Ordovician and Devonian – only poor data is available. In several southern counties, only few percent of the water supplies have been surveyed. Data for other natural radionuclides (234,238U, 210Po and 210Pb) is also poor. Scarce data has been partly due to the lack of analysis techniques available in Estonian nuclear analysis laboratories. This has been the motivation in the development of gamma spectrometric and liquid scintillation (LSC) counting techniques for ground and drinking water applications

Applying gross alpha and beta measurements as an estimate to the total indicative dose of Cambrian-Vendian ground water in Estonia

Gross alpha and beta measurements are common procedures for screening water samples in order to estimate the level of total indicative dose (TID) from the radionuclides in water. However, it has been pointed out that gross alpha and beta measurements are not suitable for waters containing high concentrations of natural radionuclides, especially Ra-226 and Ra-228. Cambrian-Vendian aquifer system is the major source of public water supply in northern and north-eastern Estonia. The aquifer is known for its high radionuclide concentrations. The main sources of TID are Ra-226 and Ra-228, but the water also contains K-40. Other nuclides from uranium and thorium series may be present as well. A set of Ra-226, Ra-228 and K-40 activity concentrations measured by gammaspectrometry are studied to analyze the applicability of gross alpha and beta measurements in case of Cambrian-Vendian ground water. The calculations indicate that the levels suggested by WHO guidelines are not suitable for the Cambrian-Vendian ground water. Results on the applicability analysis are given

Development of a reference material for analysing naturally occurring radioactive material from the steel industry

Accurate measurement of naturally occurring radionuclides in blast furnace slag, a by-product of the steel industry, is required for compliance with building regulations where it is often used as an ingredient in cement. A matrix reference blast furnace slag material has been developed to support traceability in these measurements. Raw material provided by a commercial producer underwent stability and homogeneity testing, as well as characterisation of matrix constituents, to provide a final candidate reference material. The radionuclide content was then determined during a comparison exercise that included 23 laboratories from 14 countries. Participants determined the activity per unit mass for 226Ra, 232Th and 40K using a range of techniques. The consensus values obtained from the power-moderated mean of the reported participant results were used as indicative activity per unit mass values for the three radionuclides: A0(226Ra) = 106.3 (34) Bq·kg−1, A0(232Th) = 130.0 (48) Bq·kg−1 and A0(40K) = 161 (11) Bq·kg−1 (where the number in parentheses is the numerical value of the combined standard uncertainty referred to the corresponding last digits of the quoted result). This exercise helps to address the current shortage of NORM industry reference materials, putting in place infrastructure for production of further reference materials.[Display omitted]•Current availability of reference materials for naturally occurring radioactive material has been expanded upon.•A blast furnace slag reference material has been developed to support the steel industry and regulations regarding its use in building materials.•A comparison exercise of 23 laboratories was used to determine consensus values for the activity per unit mass of selected radionuclides.•Infrastructure has been built for future development of reference materials in support of naturally occurring radioactive materials