1. Simulation of flow conditions in nuclear power plant reactor pressure vessel lower plenum experimental facility : master's thesisBlaž Kamenik, 2019, magistrsko delo Opis: The flow conditions during the experiment LIVE2D on reactor core melt behaviour in the lower plenum of a reactor pressure vessel, performed at the Karlsruhe Institute of Technology (Germany), were simulated with a Computational Fluid Dynamics computer code. In this hypothetical severe accident scenario in a pressurized water reactor nuclear power plant, the melt is divided into an oxidic layer and a metallic layer on top of it, and the oxidic layer is volumetrically heated due to decay heat. In the experiment, oil and salt were used as simulant materials for metallic and oxidic melt, respectively. The main goal of performed simulations was to investigate the so-called “focusing effect”, where a thin layer of the reactor vessel steel wall is exposed to high heat flux. Due to the length of experiment, which exceeds 100 hours, only intervals of the melt behaviour were simulated. Four cases were simulated. The first case investigated different boundary conditions for the oil layer behaviour for layer thickness 35 mm. The second case investigated the same conditions with added modelling of the reactor vessel steel wall and salt crust from the lower layer. The third case used similar modelling as the second case to investigate the oil layer behaviour for layer thickness 75 mm. The fourth case investigated both salt and oil layers for oil layer thickness 75 mm. Different analytical and numerical calculations were performed to determine heat losses from simulant liquids to the surroundings, which played an important part in the experiment.
Ključne besede: nuclear power plant, severe accident, reactor core melt, lower plenum, heat flux focusing effect
Objavljeno v DKUM: 17.09.2019; Ogledov: 1417; Prenosov: 204
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2. Analysis of interface at explosive welded plates from low-carbon steel and titaniumBorut Kosec, Ladislav Kosec, Gabrijela Čevnik, Peter Fajfar, Mirko Gojić, Ivan Anžel, 2004, izvirni znanstveni članek Opis: On the basis of experimentally obtained data, it was established that a very thin layer of a melt is generated at the explosive welding of two metals at the bond interface within which impurities flow at the bond during melting. Rapid cooling after the collision generates an alloy of different structure and very small grains of an average thickness app. 1 to 2 micro m. The generation of such an amorphous layer in the bond area has been noticed with various metal combinations and represents a fundamental mechanism of explosive welding of metals. Using the metallographic analysis, the development of the vortices which were formed by the explosive welding of low-carbon steel and titanium plates is described in the paper.
Ključne besede: metallurgy, explosion welding, plates, composites, low-carbon steel, titanium, melt, vortex
Objavljeno v DKUM: 03.07.2017; Ogledov: 1400; Prenosov: 84
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3. Shapes of the icosahedral quasicrystalline phase in melt-spun ribbonsTonica Bončina, 2013, drugi znanstveni članki Opis: The shapes of icosahedral quasicrystalline (IQC) particles were determined in melt-spun ribbons of alloys based on the Al-Mn-Be alloy system. The sizes of the quasicrystalline particles ranged from a few tenths of nanometres up to 1m. Therefore, different methods were employed for characterizing their shapes: projection of quasicrystalline particles using transmission electron microscopy (TEM), cross-sections of IQCs on metallographically polished surfaces, and observation of deep-etched samples and extracted particles using a scanning electron microscope (SEM). It was discovered that icosahedral quasicrystalline particles preferentially grow in three-fold directions and have a tendency for faceting and adopting the shape of a pentagonal dodecahedron. The evolution of quasicrystalline shapes is systematically presented.
Ključne besede: Al-alloy, metallography, ribon, icosahedral quasicrystalline phase, shape, melt-spinning
Objavljeno v DKUM: 10.07.2015; Ogledov: 1440; Prenosov: 104
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4. Microstructure of rapidly solidified Cu-Al-Ni shape memory alloy ribbonsGorazd Lojen, Ivan Anžel, Albert C. Kneissl, Elfride Unterweger, Borut Kosec, Milan Bizjak, 2005, izvirni znanstveni članek Opis: Cu-Al-Ni shape memory alloys (SMAs) are currently the only available high temperature SMAs, showing a good resistance against functional fatigue. In polycrystalline state, they are very brittle and exhibit, in general, only small reversible deformations. By melt spinning, thin Cu-Al-Ni ribbons can be manufactured directly from the melt. Appropriate casting parameters can ensurea single layer columnar structure with a fibre texture, which significantly increases the maximal reversible strain in longitudinal direction. Cu-Al-Ni ribbons, containing 13, 14 and 15 wt.% Al were cast by free jet melt spinning. Because of the alloys' low thermal conductivity, the cooling rate was surprisingly low - considering the crystal grain size - significantly below 103 K/s. Therefore, wide ribbons having a single layer columnar and (except the ribbons containing 13 wt.% Al) completely martensiticstructure could not be obtained. Regardless the chemical composition, the ribbons have a single layer columnar structure only if the thickness does not exceed approximately 50 m, otherwise the structure consists of at least two layers of equiaxed grains. In as-cast condition, only ribbons containing 13 wt.% Al seem to be completely martensitic. Heat treatments at temperatures up to 900 °C improved the structure of 13 and 14 wt.% Al ribbons. All ribbons exhibit one-way shape memory effect in as-cast condition. Heat-treated ribbons containing 13 wt.% Al exhibited two-way shape memory effect already after one bending and heating cycle.
Ključne besede: metallurgy, shape memory alloys, Cu-Al-Ni alloy, microstructure, melt spinning
Objavljeno v DKUM: 01.06.2012; Ogledov: 2526; Prenosov: 115
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5. Characterization of Cu-Al-Ni melt-spun ribbons using a focussed ion beam (FIB)Franc Zupanič, Elfride Unterweger, Albert C. Kneissl, Ivan Anžel, Gorazd Lojen, 2007, izvirni znanstveni članek Opis: This work investigates the possibilities for applying a focussed ion beam (FIB) for the metallographic preparation and characterization of Cu-Al-Ni melt-spun ribbons. Two alloys were selected for this reason: CuAl13Ni4 and CuAl15Ni4. The microstructure of the first alloy was fully martensitic and the microstructure of the second consisted of two phases: martensite and ▫$\gamma_2$▫. It was discovered that with FIB-etching the microstructures of both alloys can be clearly revealed on polished cross-sections of the melt-spun ribbons, as well as on their wheel-side and air-side surfaces. However, better results were obtained when the etched surface was smoother, and finer details were visible when using smaller ion currents. In addition, a study was made into the influence of platinum deposition on the quality of 3D-cross sections. It was found that Pt-deposition is necessary when the edge of the trench should be straight and sharp, and the surface of the 3D cross-section smooth. However, in this case, the microstructure of the ribbons free surface cannot be seen.
Ključne besede: focussed ion beam, FIB, metallography, melt-spinning, shape memory alloy, Cu-Al-Ni
Objavljeno v DKUM: 31.05.2012; Ogledov: 1880; Prenosov: 25
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