bluuebunny/crossref_metadata_2025_split huggingface dataset:
CFD analysis of a void distribution benchmark in a rod bundle
Authors: Krepper E. , Rzehak R. 
Published: December 2013

Abstract
The NUPEC “PWR Subchannel and Bundle Tests” (PSBT) were designed to investigate critical heat flux phenomena in rod bundles and yield data to validate hot channel codes. Some of the tests are suitable for validating a CFD wall boiling model. The paper presents CFD calculations of the void distribution tests of the PSBT benchmark using ANSYS CFX-12.1. First, relevant aspects of the implemented wall boiling model are reviewed highlighting the uncertainties in several model parameters. It is then shown that the measured cross sectionally averaged values can be reproduced well with a single set of calibrated model parameters for different tests cases. For the reproduction of patterns of void distribution cross sections attention has to be focussed on the modelling of turbulence in the narrow channel. Only a turbulence model with the capability to resolve turbulent secondary flows is able to reproduce at least qualitatively the observed void distribution patterns.
Experimental investigations of single and two-phase flow in a heated rod bundle
Authors: Barthel F. , Franz R. , Hampel U. 
Published: December 2013

Abstract
An experimental facility for the study of boiling flows in a 3 × 3 rod bundle geometry was setup. The bundle resembles in essential geometrical parts the geometry in a pressurized water reactor fuel element. The facility is operated with a refrigerant fluid. Beside standard instrumentation for temperature, pressure and flow rate we employed particle image velocimetry for single phase flow studies, gamma ray densitometry for integral gas fraction measurement sand ultrafast X-ray tomography for the study of the void dynamics in the cross-section. Moreover extensive thermo-instrumentation allows axial rod surface temperature measurements for the central heated rod. First results will be discussed in this article.
About the change in boiling behaviour of water with coolant additives in PWR
Authors: Nakath R. , Schuster C. , Hurtado A. 
Published: December 2013

Abstract
The present study investigates the effect of boric acid and lithium hydroxide on flow boiling phenomena in pressurized water reactors. The experiments were conducted in a boiling loop with up to 40 bar and 250 °C. The bubble size distribution was determined with a wire-mesh sensor. The results showed no indication that reactor-typical concentrations of boric acid or lithium hydroxide have a safety-relevant influence on the boiling behavior in pressurized water reactors.
Application of the Henyey-Greenstein and Anlı-Güngör phase functions for the solution of the neutron transport equation with Legendre polynomials: Reflected critical slab problem
Authors: Öztürk H. 
Published: December 2013

Abstract
The criticality problem for one-speed neutrons in a uniform homogeneous slab with reflecting boundary conditions is studied using Henyey-Greenstein (HG) and Anlı-Güngör (AG) phase functions. The critical half-thicknesses of the slab are performed with traditional spherical harmonics (PN) method for various values of the cross-section parameter, reflection coefficient and the scattering parameters of HG and AG phase functions. The numerical results obtained in case of using both HG and AG phase functions are tabulated in the tables and they are compared with each other.
Reassessment of external events in view of the Fukushima accident
Authors: Knochenhauer M. , Olofsson F. , Öhlin T. 
Published: December 2013

Abstract
As a consequence of the EU stress tests following the Fukushima NPP accident, the Nordic BWR Owners Group (NOG) initiated an analysis related to the capability of Swedish and Finnish BWR plants to withstand potential effects from external flooding and other extreme natural events. A review of existing analyses was performed with the intention to identify and reassess assumptions and simplifications made, and to judge whether all significant aspects of external events had been identified and considered. A previous NOG project dealing with methodologies for analyzing certain external events was used as a reference. Additional analyses were performed within three sub-projects addressing extreme water levels in the Baltic Sea and Skagerrak, methodology for the analysis of multiple external events, and main heat sink accessibility. It was concluded that the outcome from the previous NOG project can still be used as a basis, but some issues requiring further analysis were also identified.
Seismic fragility of a reinforced concrete structure
Authors: Kurmann D. , Proske D. , Cervenka J. 
Published: December 2013

Abstract
Structures can be exposed to seismic loading. For structures of major importance, extreme seismic loadings have to be considered. The proof of safety for such loadings requires sophisticated analysis. This paper introduces an analysis method which of course still includes simplifications, but yields to a far more realistic estimation of the seismic load bearing capacity of reinforced concrete structures compared to common methods. It is based on the development of pushover curves and the application of time-histories for the dynamic model to a representative harmonic oscillator. Dynamic parameters of the oscillator, such as modal mass and damping are computed using a soil-structure-interaction analysis. Based on the pushover-curve nonlinear force-deformation-capacities are applied to the oscillator including hysteresis behaviour characteristics. The oscillator is then exposed to time-histories of several earthquakes. Based on this computation the ductility is computed. The ductility can be scaled based upon the scaling of the time-histories. Since both, the uncertainty of the earthquake by using different time-histories and the uncertainty of the structure by using characteristic and mean material values, are considered, the uncertainty of the structure under seismic loading can be explicitly represented by a fragility.
Evaluation of radioactive emissions of lignite-fired power plants in Turkey using the Analytic Hierarchy Process
Authors: Büke T. 
Published: December 2013

Abstract
Radioactive emissions of 13 lignite-fired power plants in Turkey are of great concern to the public and to scientists alike. The purpose of this study is to evaluate these power plants, according to their radioactive emissions by using the Analytic Hierarchy Process. Control criteria are in particular 226Ra, 232Th, 40K and 238U emissions from the power plants. These control criteria are weighted according to the objective assessment. The calculations are repeated for three different objective assessments of control criteria namely the mortality risk coefficients for inhalation, ingestion, external exposure of 226Ra, 232Th, 40K and 238U. It has been calculated that the Çan lignite-fired power plant is ranking first while the Soma-B plant is ranking last according to the radioactive emissions of the power plants when the average of three different objective control criteria are used in the calculations.
Computational modeling of monoenergetic neutral particle inverse transport problems in slab geometry
Authors: Gomes R. R. , Barros R. C. 
Published: December 2013

Abstract
An analytical numerical method applied to three different types of monoenergetic neutral particle inverse transport problems in the discrete ordinates (SN) formulation is presented: (a) boundary condition estimation; (b) interior source estimation; and (c) effective slab length estimation. These three types of inverse problems governed by the linear integrodifferential transport equation in SN formulation are related respectively to medical physics; nuclear waste storage; and non-destructive testing in industry. Numerical results and a brief discussion are given to conclude the paper.
Thermal analysis of VWSB-IP1 at Tarapur
Authors: Verma V. , Singh R. K. , Vaze K. K. 
Published: December 2013

Abstract
High Level Liquid Radioactive Waste (HLLRW) produced during reprocessing of spent fuel from nuclear reactors is encased in the canisters after vitrification. The vitrified waste has high heat generation rate due to decay heat and needs interim storage under surveillance. The waste needs to be cooled continuously until major portion of the decay heat is dissipated. Natural circulation air cooling has been considered to cool the canisters. Canisters are placed in a storage vault and cooled by induced axial flow of air with the help of stack. The capacity of storage vault for Vitrified Waste Storage Block (VWSB) Facility proposed at Integrated Plant-1, Tarapur is designed for interim storage of waste generated of 30 yrs of IP1 plant operation. Canister and concrete temperature should be within the prescribed limit. Parametric studies have been carried out for the relevant parameters such as stack and duct dimensions, plenum height etc. Details canister temperature have been obtained using CFD code CFD-ACE+. Axial and radial temperature variation in the canisters, thimble and ventilation pipe have been evaluated in a location. Effect of natural convection (in air) within the canister and between thimble and canister is also studied. It was found that canister centerline temperature reduces by 20°C.
Fuel cycles of WWER-440: results of basic design modification
Authors: Saprykin V. V. , Yasnopolskaya I. I. , Novikov A. N. , Adeev V. A. 
Published: December 2013

Abstract
This paper presents the current status of works performed to date to further upgrade fuel assemblies and fuel cycle of WWER-440 reactors, and also considers some innovations – both envisaged and implemented in practice – intended to improve their neutronic and operating parameters. Reactors were assumed to operate at 100% power in a steady-state refueling mode. Trial operation of third-generation fuel assemblies (FA-3), including a comparison between some calculated and measured results, is described as an example illustrating these new developments.
CFD analysis of temperature deviations in Gd assembly heads
Authors: Tóth S. , Aszódi A. 
Published: December 2013

Abstract
A CFD model for the head part of the VVER-440 fuel assemblies with Gd burnable poison has been developed. Using this model calculations are performed for some recent Gd assemblies of the Paks NPP with the code ANSYS CFX. The temperature distributions in the assembly heads are determined and the in-core thermocouple signals are evaluated. The computed signals are compared to the in-core measured data of Paks NPP. The study shows that the deviations between the in-core thermocouple signals and the cross-sectional average temperatures at the measurement level depend on the burn-ups of the fuel assemblies. These deviations are significant in the cases of low burn-ups and negligible in the cases of higher burn-ups. This behavior is caused by the depletion of Gd from the three fuel rods near the assembly center.
Uncertainties of the neutronic calculations at core level determined by the KARATE code system and the KIKO3D code
Authors: Panka I. , Keresztúri A. 
Published: December 2013

Abstract
In this paper the uncertainties of the neutronic calculations at core level – originating from the uncertainties of the basic nuclear data – are presented. The investigations have been made for a VVER-1000 core (Kozloduy-6) defined in the frame of the OECD NEA UAM benchmark. In the first part of the paper, the uncertainties of the effective multiplication factor, the assembly-wise radial power distribution, the axial power distribution and the rod worth are shown. After that the preliminary evaluation of the uncertainties of the neutron kinetic calculations are presented for a rod movement transient at HZP (Hot Zero Power) state, where the uncertainties of the time dependent core and assembly powers and the dynamic reactivity were evaluated. In both cases, we will see that the most important quantities –at core level and at HZP state – have a considerable uncertainty which is originating from the uncertainties of the basic cross section library in these investigations.
Comparison of sensitivity and uncertainty in Gd and Er containing fuels for VVER-1000 using TSUNAMI-2D
Authors: Frýbort J. 
Published: December 2013

Abstract
Computer calculations important for safe operation of nuclear reactors are inherently affected by uncertainties. These originate mostly in numerical method applied, the calculated system model developed by the user, and finally there are fundamental uncertainties in nuclear data. This analysis is aimed at comparison of uncertainties in nuclear data affecting model of VVER-1000 fuel assembly containing either gadolinium or erbium as a burnable absorber using TSUNAMI-2D. This tool for quantitative determination of nuclear data uncertainties is being developed in Oak Ridge National Laboratory (USA). This tool works with 1D and 2D deterministic calculations and 3D Monte-Carlo calculations and processes the results. Output of the calculation is a complete characterization of the solved system with an overall uncertainty of multiplication factor determination. Furthermore, different system responses can be defined (e.g. pin power peaking) and their sensitivity to nuclear data in dependence on neutron energy is determined.
The impact on the competence on severe accidents following the Fukushima event
Authors: Band S. , Schaffrath A. , Sonnenkalb M. , Weiß F.-P. 
Published: December 2013

Abstract
Fukushima related questions are currently being addressed at Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH within several research projects funded by the Federal Ministry for Environment, Nature Conservation and Nuclear Safety (BMU) and Federal Ministry of Economics (BMWi). In the following section first results of selected issues are presented.
On the creep resistance in cast Ni-base superalloys
Authors: Yuan C. , Guo J. T. 
Published: December 2013

Abstract
In this paper, we attempt to apply the modified hardening theory to estimate the creep resistance, which is considered as a key factor for controlling the creep deformation mechanism in cast nickel-base superalloys. It is suggested that, when the applied stress is high enough for the dislocations to cut into the γ′ particles, the creep resistance is almost a constant and independent of applied stress. At low applied stress, creep deformation is mainly controlled by dislocations climb, where the creep resistance has two components of a threshold stress and a friction stress. The model is verified for two cast nickel-base superalloys DZ17G and IN738. The results of detailed calculations are in good agreement with the experimental data.
Formation, stability, and presence of magnesium nitride in magnesium recycling processes
Authors: Bauer Christoph , Mogessie Aberra , Galovsky Ulrike 
Published: December 2013

Abstract
In this study an attempt has been made to identify analytical methods for detecting magnesium nitride, and document in which part of the magnesium recycling process this phase is concentrated. The samples were taken from a continuous fluxfree recycling session, where an AZ91D magnesium alloy was remelted and purified by blowing nitrogen through the melt. Exothermic reactions took place when magnesium nitride reacted to ammonia and Brucite and also when aluminium nitride reacted to ammonia and Gibbsite in a moisture-bearing environment. Because of this, it was essential to avoid any contact with moisture during the whole sampling and preparation process. The samples were exclusively handled in an argon atmosphere. Due to their crystallinity and Raman activity the nitrides were detected with X-ray diffraction and Raman spectroscopy, respectively. With the scanning electron microscope it was difficult to analyze small concentrations of nitrides since large, stable crystals were absent and the carbon coating absorbs the nitrogen Kα line.
The Mg-alloy was found to be free of impurities. Although nitrides were expected to be concentrated in the slag because of their greater density, they were found adhering at the nitrogen bubbles and accumulating in the dross. Large amounts of oxides were concentrated in the slag.
From waste to high strength alloy – recycling of magnesium chips
Authors: Lu L. , Lai M. O. , Lim S. H. , Chua B. W. , Yan C. , Ye L. 
Published: December 2013

Abstract
Ultrafine grained magnesium alloy was synthesized via mechanical milling of AZ91 chips. Mechanical property measurement revealed enhanced yield strength of 470 MPa after mechanical milling. The increase in yield strength is associated with reduction in grain size which restricts twining and dislocation gliding. The present investigation demonstrates that magnesium alloys can be cost-effectively recycled through the process of mechanical milling.
Liquid–liquid transition in elemental liquids investigated by sound velocity measurements: trends in the periodic table
Authors: Tsuchiya Y. 
Published: December 2013

Abstract
The velocity of sound has been measured as a function of temperature to investigate structural changes in the molten As–Sb alloy. The overall profile of temperature dependence of the sound velocity changes smoothly from Sb to As. The results indicate that a tendency to change structures in the supercooled state develops with increasing As fraction, and confirm the previous conclusion that molten As changes rapidly its structure in the undercooled state and is already in the high-temperature side of an assumed liquid–liquid transition at the melting point.
Bulk and surface properties of liquid Ga–Tl and Zn–Cd alloys
Authors: Akinlade O. , Awe O. E. 
Published: December 2013

Abstract
A simple thermodynamic model, based on the formation of self-associates, has been used to correlate the bulk and surface properties of mixing of liquid Ga–Tl and Zn–Cd alloys at temperatures of 973K and 900K, respectively. The model enables us to explain the positive deviation of the properties of mixing of the two liquid alloys from the ideal solution behavior. Our calculations indicate that the degree of phase separation in Zn–Cd, as measured using the Warren–Cowley short-range order parameter, is less than that in Ga–Tl. With regards to the surface, we show that the surface decomposition in Zn–Cd liquid alloys is greater than in Ga–Tl. We explain the contrast in the bulk and surface properties in terms of the possible roles of the entropic and enthalpic effects on the properties of mixing.
Fragility, kinetic stability and phase separations in the undercooled state of bulk glass formers – a case study on metallic model systems
Authors: Wilde Gerhard , Madge Shantanu V. 
Published: December 2013

Abstract
Several Pd-base alloys display a large tendency for glass formation that renders them especially suitable for investigations concerning (metastable) equilibrium properties of the deeply undercooled liquid including the glass transition, since the detrimental interference of premature crystallization can be avoided rather easily compared to other alloy systems. Here, thermodynamic, dynamic, and transport properties were analysed and compared to an Al-rich marginal glass former in the context of a possible relation between fragility, thermodynamic excess and kinetic stability against crystallization. Additionally, the possibility for liquid-phase separation occurring in the undercooled state of bulk glass-forming alloys is analysed as a function of thermal history, and critically discussed with respect of alternative mechanisms that are often summarized as ‘short-range ordering’.
Isothermal crystallization behavior of undercooled liquid Pd40Cu30Ni10P20 in terms of crystal growth, overall volume crystallization kinetics and their relation to the viscosity temperature dependence
Authors: Russew Krassimir , Stojanova Liljana , Kovacheva Rositza 
Published: December 2013

Abstract
The crystallization behavior of undercooled liquid Pd40Cu30Ni10P20 metallic alloy has been studied with the aid of differential scanning calorimetry, optical metallography, and electron microscopy methods. The crystallization occurs as a single-stage process starting preferably on the surface of casting voids in the sample volume and on the outer sample cutting planes. The linear crystal growth velocity of crystallizing cells was measured at several constant temperatures in the range 590–620 K. It is constant at constant temperatures and its temperature dependence is in good agreement with the theoretical concepts of Uhlmann using the temperature dependence of the viscosity of the alloy studied. A differential scanning calorimetry study of isothermal overall volume transformation kinetics of samples pre-annealed at 600K for 600s was carried out at several constant temperatures. The experimental data are interpreted on the basis of the equation of Kolmogorov-Avrami-Johnson-Mehl for the case of three-dimensional growth of a fixed number of pre-existing nuclei. The possibility to re-vitrify the crystallized samples by their melting in differential scanning calorimeter, followed by quick cooling with cooling rate of 5Ks−1 is shown. The volume transformation kinetics of revitrified samples has been also studied.
The magnesium-ytterbium system: A contribution to the thermodynamics of solid alloys
Authors: Borzone Gabriella , Parodi Nadia , Ferro Riccardo 
Published: December 2013

Abstract
Magnesium-ytterbium alloys were investigated in order to determine the enthalpy of formation of YbMg2 and to check the phase diagram of the system. The system was investigated by using differential scanning calorimetry, electron microscopy, electron microprobe analysis, and X-ray diffraction analysis. The enthalpy of formation was measured by high temperature drop calorimetry. A value of −13.5 ± 0.5kJ/mol of atoms was obtained for the standard formation enthalpy of YbMg2.
Twinning in ultrathin silicon nanowires
Authors: Zhan Jinhua , Bando Yoshio , Hu Junqing , Golberg Dmitri 
Published: December 2013

Abstract
Galium nanodroplets induced the anisotropic growth of ultrathin (diameter (<5nm) silicon nanowires in accordance with the vapor-liquid-solid (VLS) mechanism. X-ray diffraction and dispersion spectroscopy, and scanning, and transmission electron microscopy (TEM) were used to characterize the product. High-resolution TEM analysis revealed the existence of twins in the nanowires. In contrast to the theoretically predicated 5-fold twinning in ultrathin Si nanowires (diameter (<6nm), no twinning on the {111} planes along the wire axial directions was observed. The possible reasons for the formation of novel nanostructures are discussed.
Enthalpies of formation measurements and thermodynamic description of the Ag–Cu–Zn system
Authors: Witusiewicz Victor T. , Fries Suzana G. , Hecht Ulrike , Drevermann Anne , Rex Stephan 
Published: December 2013

Abstract
The enthalpies of formation of β and γ alloys of the Ag–Cu–Zn system were determined by dissolution calorimetry. The melting and solid-state transformation temperatures as well as the enthalpies of the order/disorder and β/χ transformations were measured by differential scanning calorimetry. Thermodynamic descriptions are presented for the binary Ag–Zn system and for the ternary Ag–Cu–Zn system in the entire composition ranges. The thermodynamic model parameters of the constituent binaries Ag–Cu and Cu–Zn are taken from earlier assessments. Those for Ag–Zn and the Ag–Cu–Zn system are established based on relevant experimental data available in the literature completed with experimental data obtained in the present work. Several vertical and isothermal sections as well as the liquidus surface and thermodynamic properties are calculated using the evaluated parameters and show reasonably good agreement with experimental data available.