Radon dose in cellars during the war in Croatia

During the war in 1991 and 1992, because of artillery bombardment, the citizens of Croatia have been forced to live underground in shelters and cellars and therefore they have been exposed to an additional radon radiation. Rn concentration in shelters (cellars) and dwellings of Osijek and Zagreb were measured by means of a silicon detector (Radhome) and also, at several locations, by an LR-115 nuclear track detector. Estimated monthly radon exposures in dwellings and cellars of Osijek or Zagreb were (2.88±1.58)×10⁴ Bq h m^–3 and (6.62±3.17)×10⁴ Bq h m^–3, respectively, or (1.94±0.72)×10⁴ Bq h m^–3 and (7.46±7.78)×10⁴ Bq h m^–3. Inhabitants of Osijek and Zagreb have received, on the average, the effective dose equivalent of 4.1 and 2.6 mSv y^–1, respectively.     

Radon concentrations in kindergartens of Osijek and Ljubljana

Indoor radon concentrations in the kidergartens of Osijek, Croatia, have been measured with -scintillation cells, LR-115 nuclear track detectors, as well as a Radhome semiconductor detector. Average values of 50.2, 43.7 and 47 Bq m^–3 were obtained, respectively. Under the worst conditions, the annual radon effective dose equivalent was 10 mSv y^–1. Using bare and filtered LR-115 detectors, the average equilibrium factor was assessed as 0.36 indoors. Measurements of the -dose rate in the kindergartens did not show any significant correlation with the radon concentration. Indoor radon concentrations in the kindergartens of Ljubljana, Slovenia, measured by scintillation cells had an arithmetic mean and standard deviation of 228 and 143 Bq m^–3, respectively.     

More about track etching statistics

Statistical errors of the track etching method were investigated by using the LR-115 nuclear track detector and visual microscopic counting. In the experiment, four persons counted tracks of the same detector and the analysis of variance was applied to the respective means and standard deviations. Another experiment was performed with ten detectors exposed to air in the same room; after standard etching and counting, the relative error of the detector track density was obtained as 11.2%. Taking into account the errors of the detector sensitivity coefficient and background, the total relative error of the track etching method was 19.5% in case of measurements of the indoor radon concentration of 8.2 Bq m^–3.     

Radon in the spa of Bizovac

The radon concentration in the air and water of the Bizovac spa was measured by the Radhome silicon detector and the average values were obtained as 70 Bq/m³ in the indoor pool, 40 Bq/m³ in the hotel room, 135 Bq/m³ in the closed therapeutic bathroom, but the geothermal water had a Rn concentration of 25.3 kBq/m³ and the potable one 2.7 kBq/m³. The Rn transfer factor (f) from water to air in the indoor pool and therapeutic bathroom was 10 and 40 times higher than for normal dwellings (f _n=10^–4), respectively. The effective equivalent dose of inhaled radon for permanent personnel under the worst conditions in the spa was 5.4 mSv/y, but visitors spending two weeks in the spa could receive the dose of 77 Sv.     

Determination of trace concentration of boron in ADU by the nuclear track technique

A method for the determination of boron concentration in extracted (NH₄)₂ U₂O₇·H₂O (ADU) has been used. One ml of the aqueous solution is irradiated with thermal neutrons from a 10 Ci Am/Be neutron source with a flux of 0.2·10⁵ n·cm^–2·s^–1 and thermal column in the IRT-5000 with a flux of about 10⁷ n·cm^–2·s^–1. The alpha-activity due to the reaction¹⁰B(n, )⁷Li is recorded by a CR-39 alpha track detector. After the exposure, the alpha tracks are made visible in an optical microscope at magnification of 800X by etching the detector in 6N NaOH, and the track density is determined using calibration curves of known concentrations of boron. The boron concentration of the extracted ADU was found to be 5 ppm.     

The influence of solvation on the calculated activation energy for the reaction CH3F+F−

The influence of the solvent on the activation energy of the synchronous, concerted, narcissistic reaction: CH₃F + F^–¦CH₃F₂¦^–FCH₃+F^–, has been investigated by means of CNDO/2 method. The reaction path has been fully followed in vacuo, and at a suitable point only, of reaction coordinate, in solution. The geometries of H₂O, F^–, CH₃F, and ¦CH₃F₂¦^–, in vacuo and in different hydrated cages, have been optimized.

---

Zusammenfassung Der Einfluß des Lösungsmittels auf die Aktivierungsenergie der synchronverlaufenden Reaktionen CH₃F+F^–¦CH₃F₂¦FCH₃+ F^–, wurde mit der CNDO/2 Methode geprüft. Der Reaktions-Ablauf wurde in Vakuum vollkommen und in der Lösung an einem geeigneten Punkt der Reaktionskoordinate durchgeführt. Die Geometrien von H₂O, F^–, CH₃F, und ¦CH₃F₂¦^– im Vakuum und in verschiedenen hydrierten Käfigen wurden optimalisiert.

---

Résumé L'influence du solvent sur l'énergie d'activation de la réaction synchronique, concertée, narcissistique: CH₃F+ F^–¦CH₃F₂¦^–FCH₃+F^– a été examinée par la méthode CNDO/2. On a suivie l'entier chemin de réaction in vacuo, alors qu'on a observé un seul point convenable de la coordonée de réaction en solution. On a optimize les geometries de H₂O, F^–, CH₃F, et ¦CH₃F₂¦^– in vacuo et en differentes cages hydratés.

---

---

Financial aid from Italian Centro Nazionale delle Ricerche is gratefully acknowledged.     

Radon Dose and Aerosols

The equilibrium factor value (F) was measured in the NRPB radon chamber and the corresponding track density ratio (r = D/D ₀) of bare (D) and diffusion (D ₀) LR-115 nuclear track detectors was determined, as well as the regression equation F(r). Experiments with LR-115 nuclear track detectors and aerosol sources (burning candle and cigarette) were carried out in the Osijek University radon chamber and afterwards an empirical relationship between the equilibrium factor and aerosol concentration was derived. For the purpose of radon dose equivalent assessment, procedures for determining the unattached fraction of radon progeny were introduced using two nuclear track detectors.     

Experimental and theoretical considerations on the calibration factor K between α-activity concentration and track density for application in radon dosimetry

This paper describes a new version of the measurement of the calibration factor, K, between radon activity concentration and track density. The use of Solid State Nuclear Track Detectors (SSNTDs) is one of the most convenient techniques to assess the radiation level of -activities in the environment. Exposed plastic films are chemically and electrochemically etched in an alkali solution and the -tracks are evaluated under an optical microscope. The detailed procedure for this study and the caliabration of the etched films for conversion of track density to radon exposure in (Bq·m^–3) are given in this paper. It was found the experimental and theoretical values of K were 1.37 and 1.27 (track·cm^–2·kBq^–1·h^–1·m³), respectively, for plastic detectors CR-39.     

Complexation processes in KF-SbF<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system studied by calorimetric titration

Complexation in a KF-SbF₃-H₂O system is studied in a range of molar ratios of fluorides KF : SbF₃= (0.1–2) : 1 by calorimetric titration. The equilibrium formation constants of complexes KSb₂F₇, KSbF₄, and K₂SbF₅ (5.8×10⁵±800, 3.3×10⁴±500, and 1.9×10⁶± 950, respectively) and the changes in enthalpy (–31.75± 0.74, –28.15±0.44, and –25.5±0.64 J mol^–1, respectively) and entropy (4±7, –8±5, and –35±9 J mol^–1 K^–1, respectively) are determined. The thermodynamic stability of the antimony(III) fluoride complexes is found to increase on going from KSb₂F₇ to K₂SbF₅.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 3, 2005, pp. 168–171.Original Russian Text Copyright © 2005 by Kovaleva, Zemnukhova, Lebedeva, Fedorishcheva.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Nitric acid transport across TBP—Kerosene oil supported liquid membranes

HNO₃ transport across tri-n-butyl phosphate kerosene oil supported liquid membrane with or without uranyl ion transport has been studied. Parameters studied are the effect of TBP in the membrane, nitric acid in the feed solution and nitrate ion concentration in the feed solution. The flux of protons for 1 to 10 mol·dm^–3 HNO₃ solution is in the range of (0–25)·10^–4 mol·m^–2·s^–1 and for the TBP concentration range of 0.359 to 3.59 mol·dm^–3, the flux determined is (8.9 to 22)·10^–4 mol·m^–2·s^–1. From the experimental data and using theoretical equations the complex under transport through the membrane appears to be 2TBP·HNO₃ both in the presence and absence of uranyl ions. The diffusion coefficient for H⁺ ions through the membrane as a function of TBP concentration varies from (53 to 6)·10^–12 m²·s^–1, based on experimental flux and permeability data. The values of this coefficient supposing 2TBP·HNO₃ as diffusing species, based on viscosity data and theoretical estimation varies from (82.50 to 3.30)·10^–12 m²·s^–1. The value of distribution coefficient varies in the reverse direction from 0.06 to 1.46 at the same TBP concentration.     

Gas-phase reactions of CF3 and CF2 with atomic and molecular fluorine: Their significance in plasma etching

Reaction rate coefficients have been measured at 295 K for both CF₃ and CF₂ with atomic and molecular fluorine. The reaction between CF₃ and F was studied over a gas number density range of (2.4–23)×10¹⁶ cm^–3 with helium as the bath gas. The measured rate coefficient increased from (1.1–1.7)×10^–11 cm³ s^–1 as the gas number density increased over this range. In contrast to this relatively small change in rate coefficient with gas number density, the rate coefficient for CF₂+F increased from (0.4–2.3)×10^–12 cm³ s^–1 as the helium gas number density increased from (3.4–28.4)×10¹⁶ cm^–3. Even for the highest bath gas number density employed, the rate coefficient was still more than an order of magnitude lower than earlier measurements of this coefficient performed at comparable gas number densities.Both these association reactions are examined from the standpoint of the Gorin model for association of radicals and use is made of unimolecular dissociation theory to examine the expected dependence on gas number density. The calculations reveal that CF₃+F can be explained satisfactorily in these terms but CF₂+F is not well described by the simple Gorin model for association.CF₃ was found to react with molecular fluorine with a rate coefficient of (7±2)×10^–14 cm³ s^–1 whereas only an upper limit of 2×10^–15 cm³ s^–1 could be placed on the rate coefficient for the reaction between CF₂ and F₂. The values obtained for this set of reactions mean that the reaction between CF₃ and F will play an important role in plasmas containing CF₄. The high rate coefficient will mean that, under certain conditions, this particular reaction will control the amount of CF₄ consumed. On the other hand, the much lower rate coefficient for reactions between CF₂ and F means that CF₂ will attain much higher concentrations than CF₃ in plasmas where these combination reactions are dominant.     

A structural study of saturated aqueous solutions of some alkali halides by X-ray diffraction

The structure of nearly saturated or supersaturated aqueous solutions of NaCI [6.18 mol (kg H₂O)^–1], KCI [4.56 mol (kg H₂O)^–1], KF [16.15 mol (kg H₂O)^–1] and CsF [31.96 mol (kg H₂O)^–1] has been investigated by means of solution X-ray diffraction at 25°C. In the NaCI and KCI solutions about 30% and 60%, respectively, of the ions form ion pairs and the Na⁺–Cl^– and K⁺–Cl^– distances have been determined to be 282 and 315 pm, respectively. The average hydration numbers of Na⁺ and Cl^– ions are 4.6 and 5.3, respectively, in the NaCI solution and those of K⁺ and Cl^– ions in the KCI solution are both 5.8. In the KF solution, clusters containing some cations and anions, besides 1:1 (K⁺–F^–) ion pairs, are formed. The K⁺–F^– interatomic distance has been determined to be 269 pm, and nonbonding K⁺...K⁺ and F^–...F^– distances in the clusters are 388 and 432 pm, respectively, and the average coordination numbers n _KF , n _KK and n _FF have been estimated to be 2.3, 1.9, and 1.6, respectively. In the highly supersaturated CsF solution an appreciable amount of clusters containing several caesium and fluoride ions are formed. The Cs⁺–F^– distance in the cluster has been determined to be 312 pm, while the nonbonding Cs⁺...Cs⁺ and F^–...F^– distances are estimated to be 442 and 548 pm, respectively, the distances being about and times the Cs⁺–F^– distance, respectively. The coordination numbers n _CsF , n _CsCs , and n _FF in the first coordination sphere of each ion are 3.3, 2.3 and 5.3, respectively, and the result shows the formation of clusters of higher order than 1:1 and 2:2 ion pairs. These ion pairs and clusters may be regarded as embryos for the formation of nuclei of crystals and the results obtained in the present diffraction study support observations for the nucleation of the alkali halide crystals studied by molecular dynamics simulations previously examined.     

High-ResolutionF MAS andF–Cd REDOR NMR Study of Oxygen/Fluorine Ordering in Oxyfluorides

The ordering of fluoride ions on the anion sites in the oxyfluorides Ba₂WO₃F₄, Ba₂MoO₃F₄, CdWO₃F₂, NaMoO₃F, and K₂NbO₃F has been studied with very fast magic angle spinning¹⁹F NMR.¹⁹F MAS NMR of Ba₂WO₃F₄shows that the fluoride ions are disordered within the four equatorial anion positions on the W–O/F chains, but that the anion positions between the chains are fully occupied by fluorine. No difference in fluoride-ion ordering is observed between samples synthesized under a wide variety of conditions (e.g., hydrothermally at 3 kbar at 800°C, and at 227°C at <2 kbar.) In contrast, fluoride ions in the isostructural compound Ba₂MoO₃F₄are almost completely ordered both between and on the W–O/F chains. Two-dimensional NMR is, however, used to demonstrate that a weak¹⁹F resonance corresponding to ≈0.35% of the total fluoride-ion content is not due to a BaF₂impurity but that it results from a small amount of disorder in the tungsten chains. The fluoride ions order on one site in NaMoO₃F and K₂NbO₃F, consistent with earlier studies. The¹⁹F and¹⁹F–¹¹³Cd REDOR NMR of CdWO₃F₂show that the fluoride ions are ordered on two anion sites, each equidistant from a cadmium ion, in contrast to the isostructural compound CuWO₃F₂where ordering on only one anion site has been proposed. A new model for the structure of CdWO₃F₂is proposed.     

Rare earth element complexation by fluoride ions in aqueous solution

Rare earth fluoride stability constants for Ce, Eu, Gd, Tb and Yb at 25°C have been determined by examining the influence of fluoride ions on the distribution of rare earths between tributyl phosphate (TBP) and 0.68M NaClO₄. Our results indicate that rare earth mono and difluoro complexation constants show a steady increase as a function of atomic number from La to Tb but remain relatively constant after Dy. This behavior is similar to that which has been observed for dicarboxylic acids. Stepwise stability constant ratios, K₂/K₁, obtained in our work (where K₁=[MF²⁺][M³⁺]^–1[F^–]^–1 and K₂=[MF ₂ ⁺ ]^–1[MF²⁺]^–1[F^–]^–1) indicated that, for all rare earths, K₂/K₁=0.09±0.03.     

Negative ion formation in compounds relevant to SF6 decomposition in electrical discharges

Dissociative and nondissociative electron attachment in the electron impact energy range 0–14 eV are reported for SOF₂ SOF₄, SO₂F₂, SF₄, SO₂, and SiF₄ compounds which can be formed by electrical discharges in SF₆. The electron energy dependences of the mass-identified negative ions were determined in a time-of-flight mass spectrometer. The ions studied include F^– and SOF ₂ ^–* from SOF₂; SOF ₃ ^– and F^– from SOF₄; SO₂F ₂ ^–* , SO₂F^–, F ₂ ^– , and F^– from SO₂F₂; SF ₄ ^–* and F^– from SF₄; O^–, SO^–, and S^– from SO₂; and SiF ₃ ^– and F^– from SiF₄. Thermochemical data have been determined from the threshold energies of some of the fragment negative ions. Lifetimes of the anions SOF ₂ ^–* , SO₂F ₂ ^–* , and SF ₄ ^–* are also reported.     

Radon in schools and dwellings of Osijek

Indoor radon concentrations were measured in 10 821 pupils primary schools of Osijek by means of the Radhome silicon detector. The values ranged from 15 to 300 Bq/m³ with the arithmetic and geometric means of 93.4 and 70.6 Bq/m³, respectively. Ten years continuous radon measurements performed with the LR-115 nuclear track detector in three houses of different construction and town area gave means of 27, 96 and 23 Bq/m³; the indoor Rn concentration for a heating period was a factor of 1.5 higher than for the warm season. The average effective dose equivalent for the primary school pupils was 2.8 mSv/y (with occupancy factors of 0.6, 0.2 and 0.2 for home, school and outdoors, respectively). For citizens of Osijek it was 1.7 mSv/y.     

Pulverized coal plasma gasification

A number of experiments on the plasma-vapor gasification of brown coals of three types have been carried out using an experimental plant with an electric-arc reactor of the combined type. On the basis of the material and heat balances, process parameters have been obtained: the degree of carbon gasification (_c), the level of sulfur conversion into the gas phase (_s), the synthesis gas concentration (CO+Hz) in the gaseous products, and the specific power consumption for the gasification process. The degree of gasification was 90.5-95.0%, the concentration of the synthesis gas amounted to 84.7–85.7%, and the level of sulfur conversion into the gas phase was 94.3–96.7%. Numerical study of the process of plasma gasification of coals was carried out using a mathematical model of motion, heating, and gasification of polydisperse coal particles in an electric-arc reactor of the combined type with an internal heat source (arc). The initial conditions for a conjugate system of nonlinear differential equations of the gas dynamics and kinetics of a pulverized coal stream interacting with the electric arc and oxidizer (water vapor) agree with the initial conditions of the experiments. The computation results satisfactorily correlate with the experimental data. The mathematical model can be used for the determination of reagent residence time and geometrical dimensions of the plasma reactor for the gasification of coals.Nomenclature c _i volume concentration of components (kmol m^–3) - x longitudinal coordinate (m) - f _i source members, determined by variation of the ith component due to chemical reactions in unit volume in unit time (kmol m^–3s^–1) - velocity (m s^–1) - M _s ash mass in one particle (kg) - C _D particle drag coefficient - 3.14 - r _s particle radius (m) - d particle diameter (m) - density (kg m^–3) - C _p heat capacity of components (J mol^t– K^–1) - Q _j thermal effect of reaction (J kmol^–1) - E_j activation energy of reaction - N _l volume concentration of particles of thelth fraction (m^–3) - T temperature (K) - emissivity factor of coal particles - 5.67 × 10^–8, blackbody emissivity coefficient (W m^–2 K^–4) - P pressure (Pa) - S reactor cross section (m²) - D reactor diameter (m) - V reactor volume (m³) - L _R reactor length (m) - F _W friction force on the wall (N) - f _g friction coefficient - residence time (s) - Nu Nusselt number - Re Reynolds number - Pr Prandtl number - thermal conductivity of gas (J m^– s^–1 K^–1) - R 8.3 × 10³, universal gas constant (J kmol K^–1) - µ _i molecular mass of component (kg kmol^–1) - dynamic viscosity coefficient of gas (kg m^–1 s^–1) - thermal efficiency of plasma reactor - q_arc specific heat flow from arc (W m^–3) - P ₁ heat supplied in vapor at T = 405 K (W) - P ₂ heat loss to wall (W) - P ₃ heat loss in the gas and slag separator chamber (W) - P ₄ heat loss in the synthesis gas oxidation chamber (W) - P ₅ heat loss in the slag catcher (W) - P ₆ heat carried away in the off-gas (W) - P heat input of arc (W) - P _arc electric power of arc (W) - Q_sp specific power consumption (kw Hr kg^–1) - d _w specific heat flow to wall (W m^–2) - _c degree of carbon gasification (%) - _s level of sulfur conversion into gas phase (%)     

Transport of titanium(IV) ions across di-2-ethylhexylphosphoric acid-CCl4 supported liquid membranes

Transport study for Ti(IV) ions using di-2-ethylhexylphosphoric acid (D2EHPA) (carrier)-CCl₄ (diluent) liquid supported membrane in microporous polypropylene hydrophobic film has been performed. The parameters studied are effects of carrier, H₂SO₄, stripping agent (NH₄F) concentrations and temperature variation on flux and permeability coefficients of the metal ion. The optimum concentrations of transport found are 2.04 mol·dm^–3 D2EHPA, 1.0 mol·dm^–3 H₂SO₄ in the feed and 1 mol·dm^–3 NH₄F as stripping agent. The maximum flux and permeability coefficient determined are 1.32·10^–5 mol·m^–2·s^–1 and 8.02·10^–12 mol·m^–2·s^–1, respectively. The transport of this metal ion is increased with increase in temperature. The mechanism of transport appears to be based on coupled counter ion transport phenomenon.     

Measurement of radon in air by α track method enhancement of detection sensitivity using a lamp

A new α track method is proposed for the measurement of radon (²²²Rn) concentration in environmental levels. This involves collecting radon daughters on the surface of pilot lamp and detecting α-particles emitted from the nuclides (²¹⁸Po and²¹⁴Po) by a detector (LR 115). The detection sensitivity of this method is 6 times greater than that of the conventional α track method.     

Conditions for the synthesis of Sb(III) fluoride complexes

Complexation of Sb(III) fluorides with alkali metal, ammonium, and thallium cations in the MF-SbF₃-H₂O systems at the molar ratios MF : SbF₃=(0.01–2) : 1 is studied by preparative chemistry, pH-metry, ₁₉F NMR, IR and X-ray powder diffraction methods. The crystals of Sb₃O₂F₅, MSb₄F₁₃, MSb₃F₁₀, MSb₂F₇, M₂Sb₃F₁₁, M₃Sb₄F₁₅, MSbF₄, M₂SbF₅ are synthesized and the factors influencing their formation are discussed. Some types of Sb(III) fluoride complexes are shown to be formed in the MX-SbF₃-H₂O systems (X = Cl^–, NO₃^–, BF₄^–, SCN^–, ClO₄^–).Translated from Koordinatsionnaya Khimiya, Vol. 30, No. 12, 2004, pp. 833–837.Original Russian Text Copyright © 2004 by Zemnukhova, Kovaleva, Fedorishcheva, Konshin, Davidovich.