Publications (15)5.49 Total impact

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    ABSTRACT: The experimental data on 235U enrichment by isotopic exchange 235U/238U in U4+ - UO22+ system on cation exchange resin C-100 (produced by Purolite) and in the system U4+-[UO2Clx]2-x, on anion exchange resin Dowex-1 (Sigma) are presented. In both cases a thermostated glass lumn was utilised. Cation exchange resin was passed in R-Ti3+ form, then the column was feeded with 0.047M UO2Cl2 solution. According to the isotopic exchange between U4+ fixed on resin and UO22+ from solution 235U is enriched in the solution phase at the front of U band, and 238U in the resin phase at the rear of uranium band. The uranium solution which has passed through the column was fractioned, by means of an automatic sample colector, in 100 small fractions. For each sample fraction uranium content, and uranium isotopic ratio 235U/238U were determined. In the case of Dowex-1 the resin was converted in R-Cl form with 5M HCl solution, then 0.1 M UO2Cl2 solution in 5M HCl was feeded in the column, and on the resin were fixed the following complex anions: [UO2Cl3]-, [UO2Cl4]2-. When all resin was passed in R-U(IV) form, the column was feeded with 0.1 M TiCl3 solution in 5 M HCl. According to the isotopic exchange between [UO2Clx]2-x fixed on resin and U4+ from solution 235U will be enriched in the resin phase, at the rear edge of uranium band. The effluent from the bottom of the column was collected in small fractions on which uranium content and isotopic ratio 235U/238U were determined. All isotopic analysis were performed on SMIT-1 thermoionization mass spectrometer. In both cases presented here, 235U enrichments were experimentally determined. Temperature increase with 10°C had not a significant effect on 235U enrichment in U4+-UO22+ exchange system on cation exchange resin C-100. The 235U enrichment was diminished when feed flow rate of the column with Dowex-1 increased two times. The eluent volume, corresponding to the uranium 235U maximum enrichment was 1428 mL on cation exchange resin, and 692 mL on anion exchange resin.
    No preview · Article · Jul 2001
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    ABSTRACT: The design and operational characteristics of a high repetition rate TEA CO2 laser are described. The laser operates at variable pulse repetition frequencies up to 100 Hz. Stable operation is obtained in a closed cycle which includes a gas mixture regenerator. Energies of up to 10 J/pulse are obtained in pulses having 25 MW peak powers. Average powers as high as 500 W are reached at the maximum pulse repetition frequency. The performance of optical components at various pulse repetition frequencies is presented.
    No preview · Article · Nov 2000 · Journal of Physics E Scientific Instruments
  • S. Dronca · D. Axente · A. Bâldea · C. Teacǎ
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    ABSTRACT: The experimental data regarding 13C separation by 13C/12C isotopic exchange in CO2-Di-n-butyl amine carbamate in methanol system, using two laboratory plants: a pyrex glass unit, for atmospheric pressure and a stainless steel one for measurements at pressure, are presented. At atmospheric pressure the concentration increase of DNBA-Methanol solution from 1 M.I-1 to 2 M.I-1 has not a significant influence on the height equivalent to a theoretical plate, unlike solution of DNBA in Heptan, where at 2 M.I-1 a 67% decrease of HETP was observed. The pressure increase from 0,1 MPa to 0,2 MPa determined diminution of HETP for 1 M.I-1 and 2 M.I-1 solution of DNBA in Methanol at 25 and 5°C. The isotopic transfer between two phases, circulated in counter current in the separation column, is improved at higher pressure according to increased carbon dioxide concentration in the amine solution. HETP of 5,02 cm for 2 M.I-1 DNBA in Methanol at 1,4 mM carbamat · cm-2 · min-1 flow rate recomends this system for 12C separation on comercial plant.
    No preview · Article · Jan 2000
  • D. Axente · A. Bâldea · C. Teacă · M. Abrudean · R. Horga
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    ABSTRACT: The basic isotopic exchange reaction is responsible for the separation of15N in the Nitrox system that between gaseous nitrogen oxides and aqueous nitric acid with a single stage separation factor α=1.055 for 10M nitric acid, at 25°C and atmospheric pressure takes place. In order to know what happens in15N separation at higher pressure, when the isotopic transport between two phases is improved, a stainless steel laboratory experimental plant with a 1000 mm long × 18 mm i.d. column, packed with triangular wire springs 1.8×1.8×0.2 mm2, was utilised. At 1.5 atm (absolute), and 2.36 ml·cm−2·min−1 flow rate HETP was 7% smaller than at atmospheric pressure and 1.5 times smaller flow rate. HETP at 3.14 ml·cm−2·min−1 flow rate and 1.8 atm is practically equal with that obtained at atmospheric pressure and 2 times smaller flow rate. The operation of the15N separation plant at 1.8 atm (absolute), instead of atmospheric pressure, will permit doubling of the 10M nitric acid flow rate and of15N production of the given column.
    No preview · Article · Jun 1999 · Journal of Radioanalytical and Nuclear Chemistry
  • S. Dronca · D. Axente · A. Bâldea · M. Abrudean
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    ABSTRACT: The absorption of CO2 in solutions of di-n-butyl-amine in methanol, octane and triethylamine at 0.5÷2 ML-1 concentration, , -20÷25°C teperature range and 0.101÷0,404 MPa CO2 pressure, using a stainless steel vibrated contactor is studied. The absorption rate law is shown to be: n = k[DNBA] PCO2 for both systems studied: DNBA-methanol and DNBA-octane and experimental conditions above mentioned. Both equilibrium and kinetic measurements show the possibility of utilization of studied systems for 13C enrichment by isotopic exchange between CO2 and carbamate.
    No preview · Article · Jan 1998
  • D. Axente · M. Abrudean · A. Baldea
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    ABSTRACT: The rate of nitrogen isotope exchange between NO and HNO3 has been measured as a function of nitric oxide pressure 0.1-0.4 MPa for 1 and 2 M.l(-1) HNO3. It is concluded that N-15/N-14 change rate in NO-HNO3 system has a linear dependence of NO pressure as indicated by rate measurements at different NO partial pressure and constant overall pressure, by adding helium in reactor. Using the rate law: R = k[HNO3](2)[N2O3] the N-15/N-14 exchange rates for nitric acid concentrations 1.5-10 M.l(-1) were calculated.
    No preview · Article · Aug 1997 · Journal of Radioanalytical and Nuclear Chemistry
  • D. Axente · M. Abrudean · A. Baldea
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    ABSTRACT: The rate or nitrogen isotope exchange between NO and HNO3 has been measured as a function of nitric oxide pressure 0.1-0.4 MPa for 1 and 2 M · l-1 HNO3. It is concluded that 15N/14N exchange rate in NO-HNO3 system has a linear dependence of NO pressure as indicated by rate measurements at different NO partial pressure and constant overall pressure, by adding helium in reactor. Using the rate law: R = k[HNO3]2[N2O3] the 15N/14N exchange rates for nitric acid concentrations 1.5-10 M l-1 were calculated.
    No preview · Article · Jan 1997
  • D. Axente · M. Abrudean · A. Bâldea
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    ABSTRACT: The rate of nitrogen isotope exchange between NO and HNO3 has been measured as a function of nitric acid concentration of 1.5–4M·1–1. The exchange rate law is shown to beR=k[HNO3]2[N2O3] and the measured activation energy isE=67.78kJ ·M–1 (16.2 kcal·M–1). It is concluded that N2O3 participates in15N/14N exchange between NO and HNO3 at nitric acid concentrations higher than 1.5M·1–1.
    No preview · Article · Jul 1996 · Journal of Radioanalytical and Nuclear Chemistry
  • A. Bâldea · M. Abrudean · S. Dronca · D. Axente

    No preview · Article · Jan 1996
  • A. Bâldea · M. Abrudean · D. Axente · S. Dronca

    No preview · Article · Jan 1996 · Acta Geologica Hungarica
  • A. Baldea · D. Axente · M. Abrudean · V. Mercea · C. Bratu
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    ABSTRACT: Thermal decomposition of uranium double fluoride in a screw reactor in the temperature range of 250–500 °C is presented. Using integral reactor relation, kinetic parameters are discussed in terms of the shrinking core grain model. Arrhenius global activation energy is also determined.
    No preview · Article · Apr 1987 · Journal of Radioanalytical and Nuclear Chemistry
  • M. Abrudean · A. Bâldea · D. Axente
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    ABSTRACT: Nitrogen and hydrogen adsorption tests were performed in static and dynamic conditions, on clinoptilolite from Mřşid, district Sǎlaj, Romania, in natural and KCl ion exchanged form. Static adsorption capacities of hydrogen and nitrogen and adsorbed nitrogen quantity (dynamic capacity) in flow conditions were determined for several pressures. The separation of hydrogen (min. 98%) from hydrogen—nitrogen mixture using adsorption on clinoptilolite has been demonstrated.
    No preview · Article · Jul 1985 · Zeolites
  • D. Axente · M. Abrudean · A. Bâldea
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    ABSTRACT: Adsorption of carbon dioxide, sulphur dioxide, ammonia, and nitric oxide from air, and of hydrogen sulphide from methane, on Romanian natural zeolite in natural and modified form, is reported. The adsorption capacities, at 20°C, in flow conditions for several partial pressures of pollutants and for different linear velocity of the gaseous mixtures in the adsorption bed, were determined. The adsorption parameters of the studied zeolite indicates its suitability as a good adsorbant in air and methane purification plants.
    No preview · Article · Jul 1983 · Zeolites
  • D. Axente · M. Abrudean · A. Bâldea · L. Calancea · D. Stroescu
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    ABSTRACT: The utilization of O labelled potassium phosphate KH2PO4, instead of radiophosphorus, P, labelled phosphate in biochemical and ecological studies concerning fertilizer phosphorus assimilation by plants is presented.The 30–60 mg dry plant samples were heated under 10 mm Hg vacuum in Pyrex ampoules to form carbon dioxide (COO) for O mass spectromietric analyses. Potassium phosphate labelled with 1.36 O atom per cent is sufficient to obtain a significant increase of the O plant content, the added O quantity in 0.5 kg soil being 1.4 × 10 g O in this case.
    No preview · Article · Jan 1979 · Isotopenpraxis
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    ABSTRACT: The rate of the15N/14N isotopic exchange between NO−HNO3 at high nitric acid concentration (2–10M) have been measured. The experimental data were obtained by contacting nitric oxide at atmospheric pressure with nitric acid solution labelled with15N, in a glass contactor.
    No preview · Article · Mar 1976