This article presents a SPH study of a liquid jet break-up, the control of which is improved by applying external vibrations. The numerical method is simple: a standard weakly compressible SPH approach where the gaseous phase is neglected. The density calculation near the free surface is based on an improved geometrical method, which was previously published by the authors. The later allows one to increase the stability of the simulations and thus to widen the range of parameters (We and Oh) compared with previous studies based on SPH. The simulation results show the capability of this approach to simulate the jet break-up phenomenon accurately. This study is a step forward, toward the simulation of liquid atomization in industrial conditions with the SPH method.

316L grade stainless steel powders were produced by centrifugal atomization during the melting of a rotating rod heated by a high-power LASER beam. The feasibility has been demonstrated by atomizing a range of stainless steel rods. The atomization process has been observed via high-speed imaging and fragmentation regimes have been identified according to a literature review on the rotating electrode process (REP). Results were compared with literature data and an existing prediction model for such a process. High-speed observation can monitor the present process and it is shown that a solidified layer of metal is formed at the edge of the rod during the process inducing metal flake ejection due to the centrifugal stresses. Effects of incident LASER beam power density, ejection speed and oxygen content of the surrounding atmosphere on the particle size distribution and the sample surface have been studied and compared with literature data on classical REP atomizers. The study focuses on the production of irregular particles during the atomization process and highlights the influence of the oxygen content in the surrounding atmosphere on the fragmentation regime and the resulting particle size distribution.(c) 2022 Published by Elsevier B.V. on behalf of The Society of Powder Technology Japan All rights reserved.

In this paper, a new density formulation for free surface simulations using SPH is presented. This new approach is applicable to surface-tension driven free surface flows with strong topological changes. The density is corrected for each particle by analytically calculating the missing volume of the support domain. This calculation depends on two parameters: the local curvature and the distance of each particle to the free surface. This method was validated and compared with the density evolution method for two test cases: the square droplet and the Rayleigh–Plateau instability. It shows more stable results and a better representation of the free surface.

The Smoothed Particle Hydrodynamics method (SPH) is a meshfree Lagrangian simulation method widely applied for fluid simulations due to the advantages presented by this method for solving problems with free and deformable surfaces. In many scientific and engineering applications, surface tension forces play an important or even dominating role in the dynamics of the system. For instance, the breakage (instability) of a liquid jet or film is strongly affected by the strength of the surface tension at the liquid-air interface. Simulating deforming phase interfaces with strong topological changes is still today a challenging task. As a promising numerical method, here we use SPH to predict the interface instability at a water-air interface. With SPH, the main challenge in modelling surface tension at a free-surface is the accurate description of the interface (normal direction and curvature). When only the liquid phase is modelled (to decrease the computational cost), the standard SPH approximations to calculate the normal direction and curvature of the interface suffer from a lacking “full support”, i.e. the omitted and therefore missing gas particles. Various models for such free surface surface tension corrections were presented, see e.g. among others Sirotkin et al., Ordoubadi et al. or Ehigiamusoe et al. Many of these models follow the classical Continuum Surface Force (CSF) approach (Morris, Adami et al.) and incorporate different corrections/treatments at the surface. The objective of our ongoing study is to investigate the influence of different interface descriptions. We compare different free surface particle detection schemes, normal vector calculations and curvature estimations for the quality of the resulting surface-tension effect. In this work, we focus on two-dimensional problems and consider a static drop and oscillating drops as test cases.

The minimization of proliferation risks for research reactors necessitates the reduction of the enrichment of the uranium fuels. In the EU, this conversion from high to low enriched uranium has already begun and is currently on its way towards the qualification phase. This concerns both medium and high power research reactors. Neither for medium nor for high power research reactors are off-the-shelf low enriched uranium fuel elements available. Indeed, introducing a new type of fuel element in a research reactor implies the conservation or improvement of both safety and performance on one of a kind units within specific safety legislation. The H2020 European LEU-FOREvER Project (2017-2021), associating major actors of the European research reactors field –Areva-NP, CEA, Centrum výzkumu Řež, ILL, NCBJ, SCK∙CEN, TechnicAtome, TUM, aims to foster the development of sustainable and innovative low enriched uranium fuel elements for the whole spectrum of European research reactors.

Significant progresses in the performances under in-pile irradiation of particular U-Mo based fuels have been observed over the last fifteen years. One of the remaining issues has still to be tackled for use as a LEU fuel in the high power research reactors: the U-Mo recrystallization and its associated swelling have to be controlled or delayed. One way to mitigate this problem would be to optimize the initial microstructure of U-Mo atomized particle, by homogenizing Mo concentration and increasing grain size. This paper mainly focuses on U-Mo grain growth. Based on samples prepared in the framework of KOMO-5 and EMPIrE tests, a methodological work based on the use of EBSD is presented. In particular, surface preparation procedures are proposed for powders and rods, this last one being most likely readily applicable for plate analysis. As-atomized microstructures are analyzed in detail and subsequently compared to those obtained on particles annealed at 1000 degrees C under various conditions. It is found that 1 h annealing under vacuum is a good compromise of temperature and time to meet the development goals, provided that few impurity precipitates are present within U-Mo particles, since these can impact grain growth. (C) 2017 Elsevier B.V. All rights reserved.

The phase relations within the U-Al-Ge ternary system were studied for two isothermal sections, at 673K for the whole Gibbs triangle and at 1173K for the concentration range 25–100at% U. The identification of the phases, their composition ranges and stability were determined by x-ray powder diffraction, scanning electron microscopy coupled to energy dispersive spectroscopy and differential thermal analysis. The tie-lines and the solubility domains were determined for the U-Ge and U-Al binaries, the UAl3-UGe3 solid-solution and for the unique ternary intermediate phase U3Al2−xGe3+x. The experimental isopleth section of the pseudo-binary UAl3-UGe3 reveals an isomorphous solid solution based on the Cu3Au-type below the solidus. The U3Al2−xGe3+x solid solution extends for −0.1≤x≤1.35 and −0.2≤x≤1.5 at 673K and 1173K respectively. It crystallizes in the I-centered tetragonal symmetry. The reciprocal lattice of several compositions of the U3Al2−xGe3+x solid solution was examined by electron diffraction at room temperature, revealing the presence of a c-glide plane. Their crystal structure was refined by single crystal x-ray diffraction suggesting an isomorphous solid solution best described with the non-centrosymmetric space group I4cm in the paramagnetic domain. The magnetic measurements confirm the ferromagnetic ordering of the solid solution U3Al2−xGe3+x with an increase of Tc with the Al content. The thermal variation of the specific heat bear out the magnetic transitions with some delocalized character of the uranium 5f electrons.

Isothermal sections at 673 K and 1073 K of the ternary U-Zr-Al system were established in the whole concentration range, by means of powder X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy and differential thermal analysis. All measured compositions and unit-cell refinements were performed at room temperature from quenched samples annealed at 1073 K and 673 K for four and eight weeks respectively. For both temperatures, the Al-rich corner of the phase diagram is characterized by extended homogeneity ranges due to mutual exchange between U and Zr in UAl3 (cubic, AuCu3-type) and in the Laves phase UAl2 (cubic, MgCu2-type). Minute U solubility in ZrAl2 (hexagonal, MgZn2-type) and in Zr2Al (hexagonal, Ni2In-type) was evaluated to be of the order of 1 at.% U. For the other binary compounds, the solubility of the third component was found negligible. At 1073 K, the solid solution based on gamma U (cubic, W-type) which covers the U-Zr binary axis up to 95.5 at.% Zr, allows also some limited solubility of Al [maximum of 5 at.%]. For Al-content below 66 at.%, most of the phase relations comprise equilibria between the Zr-Al binaries and the gamma(U,Zr,Al) solid solution. At 673 K, the U-Zr axis is found in agreement with the literature data and no Al solubility could be detected in alpha U, alpha Zr and UZr2 (delta phase). The phase relations are mainly established between Zr-Al binaries and all For monolithic UMo fuel with a Zr diffusion barrier foil cladded with Al, the main interaction product is expected to involve the U-based alloy with the Zr-Al binary compounds and the pseudo-binary U1-xZrxAl2 and U1-xZrxAl3 phases. (C) 2015 Elsevier B.V. All rights reserved.

UMo-Al based fuel plates prepared with ground U8wt%Mo, ground U8wt%MoX (X = 1 wt%Pt, 1 wt%Ti, 1.5 wt%Nb or 3 wt%Nb) and atomized U7wt%Mo have been examined.The first finding is that that during the fuel plate production the metastable gamma-UMo phases partly decomposed into two different gamma-UMo phases, U2Mo and alpha'-U in ground powder or alpha ''-U in atomized powder. Alloying small amounts of a third element to the UMo had no measurable effect on the stability of the gamma-UMo phase.Second, the addition of some Si inside the Al matrix and the presence of oxide layers in ground and atomized samples is studied. In the case with at least 2 wt%Si inside the matrix a Silicon rich layer (SiRL) forms at the interface between the UMo and the Al during the fuel plate production. The SiRL forms more easily when an Al-Si alloy matrix - which is characterized by Si precipitates with a diameter <= 1 mu m - is used than when an Al-Si mixed powder matrix - which is characterized by Si particles with some mu m diameter - is used. The presence of an oxide layer on the surface of the UMo particles hinders the formation of the SiRL. (C) 2013 Elsevier B.V. All rights reserved.

The optimisation of high density metallic U-Mo/Al(Si) nuclear fuels, developed for use in high neutron flux research reactor without proliferation issues, requires an excellent control of the manufacturing conditions for getting a full benefit of Si powder additions. Eleven full size plates (from the IRIS and E-FUTURE experimental programs) have been analysed by diffraction using synchrotron high energy X-rays. For the first time, both the levels of the gamma U-Mo phase destabilisation in the U-Mo particle and characteristics (size and composition) of the Si rich protective layers around these particles have been quantified at a macroscopic scale. These results enable to evaluate the influence of the different parameters implied in the manufacturing process and could also provide solutions for producing enhanced fuels. (C) 2012 Elsevier B.V. All rights reserved.