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.     

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.     

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.     

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.     

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.     

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.     

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.     

Use of the Sorben-Tec system for rapid dosimetric evaluation of <Superscript>222</Superscript>Rn level in drinking water

The Sorben-Tec system was tested for rapid dosimetric evaluation of ²²²Rn level in drinking water in domestic conditions using a dosimeter of beta radiometer as a measurement equipment. It was shown that the method is cheap, rapid and very simple, therefore it can be used by population for rapid radiation safety assessment of drinking water. The sorption-active Sorben-Tec system contains iron hexacyanoferrate allowing for separation of approximately 40% of both ²¹⁴Pb and ²¹⁴Bi, the short-lived decay products of ²²²Rn from 5 L water sample. It was assessed that the Sorben-Tec system provides detection limits of radon in 5 L water samples of 35–40 and 10 Bq L^?1 for dosimetric and radiometric measurements respectively. The total time consumption of analysis does not exceed 1 h excluding the time for ²¹⁴Pb and ²¹⁴Bi ingrowth in the water sample (min. 3 h). Due to an insignificant sorption of radon, it is possible to reuse spent Sorben-Tec system again 3–4 h after previous analysis.     

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.     

Effect of cigarette smoke on the measured equivalent volume activity of222Rn in air

The effect of cigarette smoke in air on the increase of the measured equivalent volume activity of²²²Rn is demonstrated. After introduction of the smoke from one cigarette into 1 m³ of air, this value increased up to ten times as shown by the method of sucking air through a filter.     

<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.     

Mixing of atmospheric <Superscript>210</Superscript>Pb and <Superscript>7</Superscript>Be and <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr fission products in four characteristic soil types

Depth distribution of atmospheric ²¹⁰Pb and ⁷Be and ⁹⁰Sr and ¹³⁷Cs fission products was measured in two types of aeolian soils (desert dust and volcanic ash), irrigated paddy soil and strongly acidic soil. The depth dependence of ²¹⁰Pb, ⁷Be and ¹³⁷Cs show that these radionuclides have been diffused as solid soil particles in surface soil layers. In aeolian soil layers, about 50% of ⁹⁰Sr were diffused in surface soil layer and the remaining 50% had penetrated to deeper layers. The half of the fission particles containing ⁹⁰Sr were shown to have decomposed over the past 35 years.     

Seasonal variation and activity size distribution of <Superscript>7</Superscript>Be in ambient air

The seasonal variation of the ⁷Be activities in air and the size distribution of the ⁷Be aerosols were studied by using a continuous air sampler and a five stage cascade impactor. The mean monthly activity level of ⁷Be at the Korea Atomic Energy Research Institute (KAERI) site varied from 0.5 to 4.8 Bq·m⁻³ and revealed a seasonal variation, in which the ⁷Be activity levels were high in winter and low in summer. The mass size distribution showed a bi-modal distribution with a higher peak around 0.49 μm and a smaller peak between 3 μm and 7.2 μm. The activity median aerodynamic diameter (AMAD) decreased with increasing ambient ⁷Be concentrations. The mean residence times by using a mean growth rate of 0.004 μm·h⁻¹ were estimated to be 2.5–6.4 days. The AMAD has an increasing tendency with higher relative humidity. It seemed that the high humidity condition facilitated the growth of the aerosol, resulting in increased deposition rates of the aerosols and the low ⁷Be content in the surface air. The AMAD of the ⁷Be aerosols increased with an increasing temperature, but the temperature dependency of AMAD should be explained with geological and meteorological conditions.     

Global fallout levels of <Superscript>99</Superscript>Tc and activity ratio of <Superscript>99</Superscript>Tc/<Superscript>137</Superscript>Cs in the Pacific Ocean

Summary Global fallout levels of ⁹⁹Tc and ¹³⁷Cs of surface seawater in the Pacific Ocean were measured. The ⁹⁹Tc concentrations ranged from 0.62 to 3.33 mBq^. m^-3and 5 of 6 samples showed less than 1 mBq^. m^-3except one sample taken in the Great Barrier Reef, Australia. The ¹³⁷Cs concentrations ranged from 2.13 to 3.14 Bq^. m^-3, showing a gradual decrease in the North Pacific toward the equator and a constant level in the South Pacific. The ⁹⁹Tc/¹³⁷Cs activity ratios ranged from 2.5^. 10^-4to 2.9^. 10^-4, which is very close to that calculated theoretically from the fission yield.     

Monitoring of the <Superscript>14</Superscript>C concentration in the stack air of the nuclear power plant VVER Jaslovske Bohunice

¹⁴C releases in the stack air of the NPPs V1 and V2, Jaslovske Bohunice was determined during the year 2004–2010. Radioactivity concentration of ¹⁴C in the stack air was determined in the forms of inorganic ¹⁴CO₂ and ¹⁴C _n H _m . The annual average activity concentration in the stacks air samples varies between 12 and 121 Bq m⁻³. NPP V1, starting with 45 Bq m⁻³ in 2005 is decreasing due to the shutting down of the reactors (the first reactor was shut down in December 2006 and the second reactor in December 2008). The average value of radioactivity concentration for power unit V2 was 32 Bq m⁻³ in 2004 and reached the value of 102 Bq m⁻³ in the first-quarter of the 2010. The average normalized yearly discharge rates were between 0.39 and 0.64 TBq GW_e⁻¹ year⁻¹ (2005–2008), NPP V1 and 0.19–0.61 TBq GW_e⁻¹ year⁻¹ (2004–first-quarter 2010) for NPP V2, Jaslovske Bohunice. Most of the discharged ¹⁴C is in a hydrocarbon form, (95% for Jaslovske Bohunice NPP V2), but the CO₂ fraction may reach 37% in the air stack for Jaslovske Bohunice V1.     

Determination of activity ratios of <Superscript>238,239+240,241</Superscript>Pu, <Superscript>241</Superscript>Am, <Superscript>134,137</Superscript>Cs,and <Superscript>90</Superscript>Sr in Bulgarian soils

The origins of different artificial radionuclides found in soils from Northern and Southern Bulgaria was determined by measurements of their actual concentrations and respective ratios. On the basis of the measured mobility and concentrations of the investigated radionuclides in soils, it was estimated that after the Chernobyl accident the mean depositions of fresh ¹³⁷Cs were 3.0 ± 2.5 kBq/m² for Northern Bulgaria and 15 ± 7 kBq/m² for Southern Bulgaria. As a result of global fallout following atmospheric nuclear weapon tests in the 1950s, mean depositions (corrected to 1965) were calculated for Northern and Southern Bulgaria as follows: for ⁹⁰Sr—1.0 ± 0.5 and 2.3 ± 1.3 kBq/m², ²³⁸Pu—1.3 ± 0.8 and 2.8 ± 1.6 Bq/m², ^239+240Pu—15 ± 14 and 47 ± 38 Bq/m², and ²⁴¹Pu—520 ± 200 and 760 ± 260 Bq/m².     

Determination of <Superscript>90</Superscript>Sr, <Superscript>129</Superscript>I and gross beta radioactivity concentration in some teas

In this study, ⁹⁰Sr (540 keVβ ⁻), ¹²⁹I (150 keVβ ⁻) and the gross beta radioactivity concentrations were determined for the samples of tea as the most leading consumed hot drink in the markets (processed and packaged for sale) in our country. Furthermore, the obtained data were statistically analyzed. For determination of ¹²⁹I (150 keVβ⁻), ⁹⁰Sr (540 keVβ⁻) and gross radioactivity concentrations in tea samples, a sensor system consisting of scintillation detector with BP4 probe sensitive to beta radiation and a radiation meter (ST7) configurable for windows at desired power was used.     

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.