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    Wyświetlanie 1-9 z 9
    Tytuł:
    Bonding xenon on the surface of uranium dioxide single crystal
    Autorzy:
    Dąbrowski, L.
    Szuta, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/147186.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    noble gases
    uranium dioxide
    chemical bond
    density functional theory (DFT)
    generalized gradient approximation (GGA)
    Opis:
    We present density functional theory (DFT) calculation results of xenon atom interaction with the surface of uranium dioxide single crystal. A pseudo-potential approach in the generalized gradient approximation (GGA) was applied using the ABINIT program package. It has been revealed that close to the surface a potential well is formed for xenon atom due to its interaction with the atoms of oxygen and uranium. Depth and shape of the well is the subject of “ab initio” calculations. The calculations were performed both for the case of oxygenic and metallic surfaces. It has been shown, that the potential well for the oxygenic surface is deeper than for the metallic surface.
    Źródło:
    Nukleonika; 2013, 58, 4; 453-458
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Bonding xenon and krypton on the surface of uranium dioxide single crystal
    Autorzy:
    Dąbrowski, L.
    Szuta, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/147310.pdf
    Data publikacji:
    2014
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    noble gases
    uranium dioxide
    chemical bond
    DFT
    GGA
    Opis:
    We present density functional theory (DFT) calculation results of krypton and xenon atoms interaction on the surface of uranium dioxide single crystal. A pseudo-potential approach in the generalised gradient approximation (GGA) was applied using the ABINIT program package. To compute the unit cell parameters, the 25 atom super-cell was chosen. It has been revealed that close to the surface of a potential well is formed for xenon and krypton atom due to its interaction with the atoms of oxygen and uranium. Depth and shape of the well is the subject of ab initio calculations in adiabatic approximation. The calculations were performed both for the case of oxygenic and metallic surfaces. It has been shown that the potential well for the oxygenic surface is deeper than for the metallic surface. The thermal stability of immobilising the atoms of krypton and xenon in the potential wells were evaluated. The results are shown in graphs.
    Źródło:
    Nukleonika; 2014, 59, 3; 83-89
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of Thin Surface Layer on Fission Gas Release from Uranium Dioxide Single Crystal during Irradiation
    Autorzy:
    Szuta, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1945277.pdf
    Data publikacji:
    1996-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    25.85.Ec
    66.30.Lw
    Opis:
    In the present paper it is assumed that in the fluence range of 4×10$\text{}^{19}$ - 0.5×10$\text{}^{21}$ fissions/cm$\text{}^{3}$ the main contribution to the fission gas release from an uranium dioxide single crystal is from the bubble traps by knock-out process. An analysis of bubble distribution in the single crystal for different temperatures shows that some experimental peculiarities of the fission gas release during irradiation arise from different conditions of the thin surface layer and the interior of the considered solid. The thin surface layer is assigned by the fission fragment range.
    Źródło:
    Acta Physica Polonica A; 1996, 89, 3; 451-455
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Neutronic analysis of LBE-uranium spallation target accelerator driven system loaded with uranium dioxide in TRISO particles
    Autorzy:
    Bakir, G.
    Selçuklu, S.
    Genç, G.
    Yapici, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/1068556.pdf
    Data publikacji:
    2016-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    28.20.-v
    28.20.Np
    28.65.+a
    29.20.dg
    29.85.Fj
    Opis:
    This study presents the neutronic performances of fissile breeding and energy production of a gas cooled accelerator-driven system with LBE-uranium dioxide (UO₂) spallation target. The accelerator-driven system is designed and optimized by considering various target materials, in terms of neutronic. Two different materials, LBE + natural UO₂ and LBE + 15% enrichment UO₂ are selected as target materials. The target zone is divided into two parts, one within the other; the outer part is pure LBE target part, and the inner part is UO₂ target part cooled with the helium gas. Tristructural-isotropic (TRISO)-coated fuel particles, containing UO₂ fuel, are embedded in a carbon matrix pebble with the packing fraction of a 29%, and the pebbles are placed in the UO₂ target part and in the fuel core with the packing fraction of a 60%. The fuel core is cooled with helium that is a high-temperature coolant. The target is bombarded with the continuous beams of a 1 GeV protons to produce high-flux neutrons that enter the fuel core. The fuel core is surrounded with a graphite reflector zone serving as both effective moderation and reflection of these neutrons. Furthermore, the whole system is enclosed by boron carbide, B₄C (shielding zone), to prevent the neutrons leakage out of the accelerator-driven system. The high-energy Monte Carlo code MCNPX along with the LA150 library is used for neutronic calculations. The numerical results bring out that the investigated accelerator-driven system has a high neutronic performance, from the energy production and fissile breeding points of view. Namely, it can be obtained over the thermal power of a 350 MW and produced over the fissile breeding of a 300 g/day.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 1; 30-32
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modification of Recrystallization Temperature of Uranium Dioxide in Function of Burn-Up and Its Impact on Fission Gas Release
    Autorzy:
    Szuta, M.
    El-Koliel, M. S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2011009.pdf
    Data publikacji:
    1999-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    25.85.Ec
    66.30.Lw
    Opis:
    In the present paper it is assumed that the recrystallization temperature of uranium dioxide decreases with burn-up. Two opposing effects of enhancement and inhibition of irradiation damage introduced by fission effect on grain growth are described. Mathematical model of fission gas release from the UO$\text{}_{2}$ fuel affected by grain growth is presented. Theoretical results are compared with the experimental data.
    Źródło:
    Acta Physica Polonica A; 1999, 96, 1; 143-151
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Microspheres and Pellets of UO2 Prepared Via ADU by Complex Sol-Gel Process and ICHTJ Process
    Autorzy:
    Brykala, M.
    Rogowski, M.
    Wawszczak, D.
    Olczak, T.
    Smolinski, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/357030.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    uranium dioxide
    microspheres
    pellets
    Complex Sol-Gel Process
    ICHTJ Process
    Opis:
    This study is devoted to synthesis and characterization of uranium dioxide microspheres (Ø < 100 μm) and pellets by application of powder-free process called the Complex Sol-Gel Process. The precursors of prepared sols were ascorbic acid solution with dissolved a freshly precipitated ammonium diuranate. The microspheres of uranyl-ascorbate gel were obtained using the ICHTJ Process. The pellets were formed by pressing and sintering of uranium dioxide powder. Studies allowed determining an optimal heat treatment of calcination, reduction and sintering processes at temperatures of 700°C, 900°C and 1300°C, respectively. The main parameters which play a key role in the process of synthesis method and features of the pellets and microspheres of uranium dioxide are described in this article.
    Źródło:
    Archives of Metallurgy and Materials; 2020, 65, 4; 1397-1404
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Diffusion of helium in the perfect uranium and thorium dioxide single crystals
    Autorzy:
    Dąbrowski, L.
    Szuta, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/147700.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    uranium
    thorium dioxide
    diffusion
    tunneling
    DFT+U
    generalized gradient approximation (GGA)
    potential barrier
    incorporated helium
    Opis:
    We present quantum-mechanical evaluation of helium diffusion coefficient in the crystalline UO2 and ThO2. Parameters assignment of Schrödinger’s equation were done using the crystal field potentials which were obtained applying the density functional theory (DFT). “Ab initio” calculations were performed using the Wien2k program package. To compute the unit cell parameters the 13 atom super-cell was chosen. Applying two-site model we evaluated the time for an over-barrier jump and diffusion of interstitial He. The obtained values for diffusion coefficient are compared with the experimentally obtained values and with the theoretical values of other authors. In addition, it is simultaneously shown that helium diffusion in these materials is a quantum diffusion.
    Źródło:
    Nukleonika; 2013, 58, 2; 295-300
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Local structure and cohesive properties of mixed thorium and uranium dioxides calculated by "ab initio" method
    Autorzy:
    Dąbrowski, L.
    Szuta, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/147874.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    uranium
    thorium dioxide
    DFT+U
    LDA
    GGA
    local structure
    cohesive properties
    bulk modulus
    Opis:
    Density functional theory (DFT) results of calculations of the mixed thorium and uranium dioxide Th1-xUxO2 for the following mole ratio x = 0, 0.25, 0.75 and 1 are presented and discussed. "Ab initio" calculations were performed using the Wien2k program package. To compute the unit cell parameters the 12 atom super-cell were chosen. The lattice parameters were calculated through minimization of the total energy by the change of lattice parameters and atom displacement within the unit cell. Calculations were performed for five different exchange energy approximations EXC with and without corrective orbital potential U, and obtained lattice constants are presented graphically and compared with experimental data. It is established that the initially assumed oxygen location within the unit cell plus or minus 0.25 of the mixed compounds are not their equilibrium positions. The oxygen atoms within the unit cell undergo dislocation in the (111) direction. So, the distances oxygen-uranium are smaller than the distances oxygen-thorium. The change of local structure is presented graphically and appropriate parameters values are given in Table. The bulk modulus and the cohesive properties are also counted and shown graphically.
    Źródło:
    Nukleonika; 2012, 57, 1; 101-107
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    „Ab initio” study of helium atoms immobilization in UO2 crystals
    Autorzy:
    Dąbrowski, L.
    Szuta, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/146654.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    uranium
    dioxide
    DFT+U
    LDA
    GGA
    ABINIT
    over-barrier jumps
    incorporated helium
    harmonic oscillator
    Opis:
    We present density functional theory (DFT) calculation results concerning the uranium dioxide crystals with a helium atom incorporated in the octahedral interstitial position. "Ab initio" calculations were performed using the Wien2k program package. For comparison, a pseudo-potential approach in the generalized gradient approximation was applied using the ABINIT program package. To compute the unit cell parameters 13 atom super-cell was chosen. Parameters of the potential barrier, which the helium atom has to overcome while jumping to the next octahedral interstitial position, were calculated by the help of both the program packages. The results, obtained using two different program packages, are shown in the table and presented graphically. For the so described parameters, the quantum mechanical movement of the helium atom around the equilibrium position is considered. The parameters of Schrödinger's equation are collected in Table 2, while the results of mean square deviation and thermal occupation of energetic levels are presented in a graph. It is established that the helium atoms are located (with an accuracy of several percent of lattice constant) nearby the equilibrium position and form a local bound state. Applying a two site-model, we evaluated the time for an over-barrier jump. Graphically presented results show that the helium atom over-barrier jump is not possible even for temperatures as high as 1200 K. Influence of potential barrier height on the jump time was also considered.
    Źródło:
    Nukleonika; 2012, 57, 3; 337-343
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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