Radon leakage as a source of additional uncertainty in simultaneous determination of ²²⁶Ra and ²²⁸Ra by gamma spectrometry--validation of analysis procedure

Bias in 238U decay chain members measured by γ-ray spectrometry due to 222Rn leakage

In this work we investigate and quantify how effectively the noble gas ²²²Rn is trapped inside measurement beakers used in high-resolution gamma-ray spectrometry. We test six types of different beakers commonly utilized in γ spectrometry, including one novel construction, the γBeaker. We assessed ²²²Rn leakage by injecting ²²²Rn rich air into the examined beakers and investigated the abnormal decrease in ²²²Rn daughters - ²¹⁴Pb and ²¹⁴Bi. The measured decay times were used to estimate the ²²²Rn leakage. In addition, we investigated the influence of an additional beaker sealed with tape. However, the additional beaker sealing only slightly reduced the ²²²Rn escape and was not reproducible. Almost every tested beaker exhibited heavy ²²²Rn leakage. This may lead to an underestimation and radioactivity over-dispersion of ²³⁸U decay chain members when they are measured via their ²²²Rn daughter products.

Long-term monitoring of water treatment technology designed for radium removal-removal efficiencies and NORM formation

A drinking water treatment plant in Viimsi, Estonia, was monitored over three years for iron, manganese, radium-226, radium-228, as well as their daughter nuclides, in order to determine the efficiency of the treatment process, gain an insight into the removal mechanisms and interactions between radium, iron, and manganese, and assess the overall longevity and performance of the technology along with the possible build-up of NORM in the treatment process. During the study, samples were collected from raw water, first and second stage filtrate, consumer water, backwash water and filter materials. The results show consistent removal efficiency for iron and manganese, as well as an average of over 85% removal for radium with a slight decline over time. The backwash process has been optimised for maximum radium removal from the filters, while keeping concentrations in the backwash water below exemption levels. However, the accumulation of radium and thorium occurs in the filter material, exceeding exemption levels in the top layer of the filter columns in less than a year. By the end of the observation period, activity concentrations in the top layer of the columns were above 30 000 Bq kg-1 for Ra-226 and Ra-228, and around 15 000 Bq kg-1 for Th-228. Radionuclides are not homogenously distributed in the filter columns. In order to estimate the average activity concentrations in the filter media, the height distribution of radionuclides has to be accounted for. Two years and two months after commissioning the treatment plant, the average activity concentrations of Ra isotopes in the filter columns were in the range 10 000 Bq kg-1, while Th-228 activity concentration was roughly 3500 Bq kg-1.

Temporal changes in radiological and chemical composition of Cambrian-Vendian groundwater in conditions of intensive water consumption

Intensive groundwater uptake is a process at the intersection of the anthroposphere, hydrosphere, and lithosphere. In this study, groundwater uptake on a peninsula where only one aquifer system - the Cambrian-Vendian (CmV) - is available for drinking water uptake is observed for a period of four years for relevant radionuclides and chemical parameters (Cl, Mn, Fe, δ¹⁸O). Intensive groundwater uptake from the CmV aquifer system may lead to water inflow either from the sea, through ancient buried valleys or from the under-laying crystalline basement rock which is rich in natural radionuclides. Changes in the geochemical conditions in the aquifer may in turn bring about desorption of Ra from sediment surface. Knowing the hydrogeological background of the wells helps to predict possible changes in water quality which in turn are important for sustainable groundwater management and optimization of water treatment processes. Changes in Cl and Ra concentrations are critical parameters to monitor for sustainable management of the CmV groundwater. Radionuclide activity concentrations in groundwater are often considered rather stable, minimum monitoring frequency of the total indicative dose from drinking water is set at once every ten years. The present study demonstrates that this is not sufficient for ensuring stable drinking water quality in case of aquifer systems as sensitive as the CmV aquifer system. Changes in Cl concentrations can be used as a tool to predict Ra activity concentrations and distribute the production between different wells opening to the same aquifer system.

Validation of a method for measuring (226)Ra in drinking waters by LSC

A simple method for measuring (226)Ra in drinking waters has been validated and validation parameters are provided. It is based on the measurement by LSC of (222)Rn, at equilibrium with (226)Ra, which is absorbed into a water immiscible scintillation cocktail (Ultima Gold F) inside the counting vial. The validated application field ranges between the detection limit (2·10(-3) Bq/kg) to 150 Bq/kg. The method has proven to be reliable, effective and suitable for wide-range measuring campaigns. A summary of results obtained in recent years is also given.

(226)Ra measurement by LSC as a tool to assess the efficiency of a water treatment technology for removing radionuclides from groundwater

A simple (226)Ra analysis procedure by LSC with an extractive scintillator was tested for evaluating the long-term radionuclides removal efficiency of a water treatment facility at Viimsi, Estonia. During the 14 months of operation, total radium removal efficiency of the treatment process has stayed over 90%, but the removal efficiencies of the different purification steps have varied notably. This demonstrates the need for routine monitoring of radium content in the water treatment plant.