The Sorben-Tec system for rapid dosimetric evaluation of <Superscript>137</Superscript>Cs in drinking water

The Sorben-Tec system was developed for rapid evaluation of ¹³⁷Cs in drinking water using a domestic personal dosimeter or beta-radiometer. Linear calibration curves were obtained for dosimetric and beta-radiometric measurement of caesium. In case of 20 L drinking water sample, detection limits of ¹³⁷Cs were found to be 12.3 and 2.0 Bq L^?1 for dosimetric and beta-radiometric measurement respectively. This system is recommended for using by non-professionals who are living at radioactively contaminated areas or near nuclear power plants.     

Radium isotopes and <Superscript>222</Superscript>Rn in Austrian drinking waters

The activity concentrations of the Ra isotopes, ²²⁶Ra and ²²⁸Ra, as well as of ²²²Rn were measured in Austrian tap waters. Rn was extracted into a mineral oil cocktail not miscible with water and measured by liquid scintillation counting using pulse-shape analysis for α/β-separation. Ra isotopes were co-precipitated with BaSO₄ or concentrated by filtration through an element specific filter. EDTA solution was used to redissolve the precipitate as well as to release the Ra from the filter. After mixing with a cocktail, the EDTA solution was measured by liquid scintillation counting, too. From our results the effective ingestion doses for adults and 3 months old babies were calculated.     

Determination and differentiation of <Superscript>226</Superscript>Ra and <Superscript>222</Superscript>Rn by gamma-ray spectrometry in drinking water

The analysis of ²²⁶Ra in natural waters can be tedious and time-consuming. For the determination and differentiation of activities of ²²⁶Ra and ²²²Rn in drinking water by γ-ray spectrometry a simple and fast method is presented. Activities of ²²⁶Ra > 0.5 Bq L⁻¹ can be determined according to stabilization of the sample without further procedures. For a more sensitive detection sample volumes of up to 5 litres are applicable by a rapid precipitation procedure without large expenditure. Further laborious enrichment methods are not necessary. Thus, detection limits of 0.1 Bq L⁻¹ can be obtained when using sample volumes of 5 litres. Therefore the method is suitable for the monitoring of radioactivity in drinking water samples in accordance with the legal guidance of the European Union.     

Determination of <Superscript>3</Superscript>H, <Superscript>226</Superscript>Ra, <Superscript>222</Superscript>Rn and <Superscript>238</Superscript>U in Austrian ground- and drinking water

Screening measurements for ³H, ²²⁶Ra, ²²²Rn and ²³⁸U in ground water were performed within a ground- and drinking water project in Austria. The aim of this project is to get an overview of the distribution of natural radionuclide activity concentration levels in ground water bodies. In some cases this water is used for drinking water abstraction. In this paper methods and results of the screening measurements are presented. Regions with high activity concentrations were identified and in these regions further investigation for ²²⁸Ra, ²¹⁰Pb and ²¹⁰Po will be conducted.     

A multi-detector continuous monitor for assessment of <Superscript>222</Superscript>Rn in the coastal ocean

Summary Radon-222 is a good natural tracer of groundwater discharge and other physical processes in the coastal ocean. Unfortunately, its usefulness is limited by the time consuming nature of collecting individual samples and traditional analysis schemes. We demonstrate here an automated multi-detector system that can be used in a continuous survey basis to assess radon activities in coastal ocean waters. The system analyses ²²²Rn from a constant stream of water delivered by a submersible pump to an air-water exchanger where radon in the water phase equilibrates with radon in a closed air loop. The air stream is fed to 3 commercial radon-in-air monitors connected in parallel to determine the activity of ²²²Rn. By running the detectors out of phase, we are able to obtain as many as 6 readings per hour with a precision of approximately ±5-15% for typical coastal seawater concentrations.     

Preparation and analysis of <Superscript>226</Superscript>Ra-<Superscript>222</Superscript>Rn emanation standards for calibrating passive radon detectors

Summary In order to calibrate vials containing charcoal for measurement of radon, emanation sources of radon were produced in-house using ²²⁶Ra salts. Calibrated emanation standards containing solution of ²²⁶Ra(NO₃)₂ absorbed into inorganic compounds were prepared. The emanation coefficient of ²²²Rn for these standards vary from 0.23-0.25. The emanation sources were found to be suitable for calibrating radon monitors.     

Determining <Superscript>222</Superscript>Rn daughter activities by simultaneous alpha- and beta-counting and modeling

The introduced method to determine the individual activities of the short-lived radon daughters in air is based on simultaneous α- and β-counting of the sampled air collected on a filter. The measured curves of gross-α and gross-β intensities were decomposed by sum of exponentials and the individual activities of the progenies were assessed. Furthermore, computer simulations were carried out supplemented with aerosol measurements to describe the physical processes of radon progenies in air during the experiments and to verify the suitability of the method.     

Field alpha-spectroscopy of radon (<Superscript>222</Superscript>Rn) and actinon (<Superscript>219</Superscript>Rn) progeny in soil gas: Locating a radon source

Summary The activities of²¹⁸Po,²¹⁴Po and²¹¹Bi were determined in samples obtained of soil/gas. Sampling work was taken in Jáchymov (Czech Republic) at the outcrop of the Geister-vein,by electrostatic precipitation from filtered soil gas on stainless steel disks.The samples were measured in a field laboratory using a semi-conductor alpha-spectrometer.The activities of²¹⁸Po,²¹⁴Po and²¹¹Bi were calculated.Samples taken from active dump material (near-by radon source) exhibited a high²¹¹Bi/²¹⁴Po ratio, while those of the vein outcrop (a relatively deeper source) had a low ratio.A mathematical model was employed to determine the radon age calculated from the actinon/radon input ratio.This varied in a range of 5.6 to -7.7 seconds.Negative age values are probably caused by the preference for actinon, which rapidly comes into equilibrium with the source of this gas.     

Synthesis and characterisation of scintillating microspheres made of polystyrene/polycarbonate for <Superscript>222</Superscript>Rn measurements

Several studies have demonstrated that polycarbonate-based polymers have good capacities for the absorption of ²²²Rn. Meanwhile, polystyrene polymers are reported to be the most appropriate for developing plastic scintillator materials for the detection of radioactivity. The objective of this work was to develop plastic scintillators in the form of microspheres (PSm) composed of polystyrene and polycarbonate that could be used to measure ²²²Rn and improve this performance thanks to the combination of characteristics of both polymers. Our results show that PSm of polystyrene and polycarbonate can be made via the evaporation/extraction method, despite the two polymers not being miscible. From the point of view of the radioactive measurements, we observed that the addition of polycarbonate causes quenching, although it does not significantly affect the detection efficiency for alpha and high-energy beta emitters. From the point of view of ²²²Rn absorption, we observed that synthesis of the PSm through the evaporation/extraction method changes the ²²²Rn absorption of the raw material. This result demonstrates that the method of production of the polymer and the resulting physical characteristics are a key parameter for its final ²²²Rn absorption properties.     

Assessment of <Superscript>222</Superscript>Rn concentration and terrestrial gamma-radiation dose rates in the seismically active area

²²²Rn concentrations along the seismic active area (some distinct in East Anatolian Active Fault System (EAFS), Turkey) were determined by using passive and active (prompt) methods including CR-39 and Markus-10, respectively. It was observed that the changing of ²²²Rn concentration along the fault lines, crossing the main East Anatolian Fault Line, has shown similar characteristics for both methods. The mean ²²²Rn concentrations were found to be between 1.2 and 3.6 kBq·m⁻³ and, 2 and 70 kBq·m⁻³ by using passive and prompt methods, respectively. Nevertheless, some measured terrestrial gamma-radiation dose rate in the same area has weak positive correlation to ²²²Rn concentration. Terrestrial gamma-dose rate at 1 m above the ground in the same sampling point, as for ²²²Rn concentration measurement were made, varied from 8.5 to 10.6 μR·h⁻¹.     

Fast determination of indoor radon (<Superscript>222</Superscript>Rn) concentration using liquid scintillation counting

The indoor ²²²Rn radionuclide was directly absorbed in typical 20 ml glass scintillation vials by passing ?3 dm³ of ambient air through 16 ml of water-immiscible non-volataile scintillation cocktail Ultima-Gold F for 10 min. The activity of radon and its two α-emitting daughters: ²¹⁸Po and ²¹⁴Po, was determined with the BetaScout low-background liquid scintillation counter. The limit of ²²²Rn detection is 9 Bq/m³, and the quantification limit with 20% relative accuracy is 28 Bq/m³. The results of the indoor Rn measurement in different houses showed good consistency with results obtained from a Sarad EQF 3220 device.     

Effect of atmospheric pressure variations on the <Superscript>222</Superscript>Rn activity concentration in the air of a wine cellar

We have measured the variation of atmospheric pressure and of ²²²Rn activity concentration in the air of a wine cellar with an AlphaGAURD type ionization chamber radon monitor. We have found that the ²²²Rn activity concentration varies inversely with pressure. To explain this behavior we have done model calculations. We have compared the results of model calculations with the results of experimental measurements, and we have found that the model is capable to reproduce some part of the variation of ²²²Rn activity concentration.     

Comparison of three methods for measuring 222Rn in drinking water

Three techniques were used to measure ²²²Rn in drinking water: the degassing method followed by counting in an ionisation chamber (IC); gamma spectrometry (GS); and liquid scintillation counting (LSC). Environmental samples were measured in the field using the IC, and the same samples were measured in the laboratory using GS and LSC. The results obtained using the three techniques are compared and discussed in the context of the new Euratom Drinking Water Directive (2013/51/Euratom), which sets out general principles for monitoring radioactive substances such as radon.

     

Proficiency testing for measurement of radon (222Rn) in drinking water

The Finnish Environment Institute in collaboration with the Radiation and nuclear safety authority (STUK) carried out the proficiency test for measurement of radon (²²²Rn) in water. Samples were taken from two drilled wells in November 2007. STUK has supplied the regional laboratories with RADEK MKGB-01 equipment based on gamma spectrometry. Two samples for this PT were taken from two drilled wells. Ground water moves irregularly in the process and cracks of the bedrock which is why each participant received an individual sample. Each participant’s sample was measured also by STUK using liquid scintillation counter (LSC) as the reference method in this proficiency test. In estimating laboratory performance the results that deviated less than ±10% from the value measured by STUK using LSC were regarded satisfactory. In total, 73% of the results in the analysis of the sample R1 and 82% in the analysis of the sample R2 deviated less than 10% from the values measured by STUK. The results reported by the participants were generally smaller than the results measured by STUK. The deviation between each participant’s result and the result measured by STUK with the LSC was ?7.4% (Sample R1) and ?6.2% (Sample R2). Due to the lack of certified reference materials and a reliable proficiency testing data, it is impossible to check the traceability of radon measurements by using the reference method (LSC) at this moment.     

Ultra low level deep water <Superscript>137</Superscript>Cs activity in the South Pacific Ocean

We determined ¹³⁷Cs concentrations in deep water samples of the subtropical gyre in the South Pacific collected during the BEAGLE2003 cruise. This was done at an underground facility to achieve extremely low background γ-spectrometry, and we, therefore, obtained reliable values of ¹³⁷Cs activity in the deeper layers. ¹³⁷Cs activity in the layers between 2000 and 4500 m ranged from 7 ± 4 mBq m⁻³ to 25 ± 11 mBq m⁻³. The inventory of ¹³⁷Cs in the water column from 2000 m to the sea bottom was estimated to be 20 ± 8 Bq m⁻² to 94 ± 41 Bq m⁻² in this region.     

<Superscript>234</Superscript>U/<Superscript>238</Superscript>U and <Superscript>235</Superscript>U/<Superscript>238</Superscript>U ratios in domestic water from the environs of Obuasi mine in Ghana

Activity concentrations of ²³⁸U, ²³⁵U and ²³⁴U were determined in different sources of drinking water at the Obuasi gold mines and its surrounding areas in Ghana. Water samples collected from the mines and its surrounding areas were analyzed using direct gamma-ray spectrometry and neutron activation analysis. The ²³⁴U/²³⁸U and ²³⁵U/²³⁸U ratios were calculated and the mean values range from 1.27 to 1.38 and from 0.044 to 0.045 respectively. The average ²³⁴U/²³⁸U ratio was from 1.27 for groundwater to 1.38 for treated water, demonstrating the lack of equilibrium. The average ²³⁵U/²³⁸U activity ratio is 0.045, indicating that only natural uranium was detected in the samples investigated.     

Low level detection of <Superscript>135</Superscript>Cs and <Superscript>137</Superscript>Cs in environmental samples by ICP-MS

The measurement of fission product cesium isotopes ¹³⁵Cs and ¹³⁷Cs at low femtogram (fg) 10⁻¹⁵ levels in ground water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is reported. To eliminate the natural barium isobaric interference on the cesium isotopes, in-line chromatographic separation of the cesium from barium was performed followed by high sensitivity ICP-MS analysis. A high efficiency desolvating nebulizer system was employed to maximize ICP-MS sensitivity ~10 cps/fg. The three sigma detection limit for ¹³⁵Cs was 2 fg/mL (0.1 μBq/mL) and for ¹³⁷Cs 0.9 fg/mL (0.0027 Bq/mL) measured from the standard with analysis time of less than 30 min/sample. Cesium detection and 135/137 isotope ratio measurement at very low femtogram levels using this method in a spiked ground water matrix is also demonstrated.     

Stability of Ag<Superscript>+</Superscript> Complexes with Cryptand 222 in Ionic Liquids

Stability constants of silver(I) complexes with cryptand 222 were measured in a number of ionic liquids, applying potentiometric titration. The ionic liquids were based on 1-butyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-butyl-1-methyl-pyrrolidinium and 1-methyl-1-propyl-pyrrolidinium cations, as well as on tetrafluoroborate, triflate and bis(trifluoromethane sulfonyl) imide. The stability constants, expressed in log K scale, were within the broad range of 8.4–17.2. The formation of the Ag⁺222 cryptates was not detected in ionic liquids based on halide anions. Free enthalpy of silver(I) transfer from dimethylsulfoxide as a reference molecular solvent to ionic liquids was calculated applying the cryptate assumption. The results were discussed in terms of the competition between silver(I) complexation by ion forming ionic liquid and its complexation by cryptand 222.in final form: 6 December 2004This revised version was published online in July 2005 with a corrected issue number.     

<Superscript>234</Superscript>U/<Superscript>235</Superscript>U activity ratios as a probe for the <Superscript>238</Superscript>U/<Superscript>235</Superscript>U half-life ratio

High-resolution alpha-particle spectrometry was performed on three uranium materials enriched in ²³⁵U. Besides the ²³⁵U peaks, separate peaks belonging to impurity traces of ²³⁴U could be quantified. Relying on the isotopic composition of the uranium, as determined by mass spectrometry, the ratio of the half-lives of ²³⁸U and ²³⁵U was determined via the activity ratio of ²³⁴U and ²³⁵U in the materials. As an intermediate link, the ²³⁴U/²³⁸U half-life ratio was taken from published mass spectrometric analyses of ‘secular equilibrium’ uranium material. The resulting half-life ratio T _1/2(²³⁸U)/T _1/2(²³⁵U) = 6.351±0.031 is in agreement with the commonly adopted half-life values determined by Jaffey et al.