bluuebunny/crossref_metadata_2025 huggingface dataset:
New triangular steroid-based A(LS)3 type gelators for selective fluoride sensing application
Authors: Devi Manisha , Dhir Abhimanew , Pooja Pooja , Pradeep Chullikkattil P.
Published: June 2014

A new series of triangular steroid-based A(LS)3 type gelators has been developed which exhibited selective fluoride sensing abilities. The gelation, self-assembly and anion sensing properties of these gelators could be controlled by systematically altering their molecular structures.
On the study of the relationship between the thermal stability of Au catalysts and the basic nature of their supports for aerobic oxidation of benzyl alcohol
Authors: Xu Chunli , Wang Zhen , Huangfu Xiuting , Wang Hanfei
Published: June 2014

Gold catalysts were loaded on supports of hydrotalcite (HT), MgO, or γ-Al2O3 using methods of sol-immobilisation, deposition–precipitation or impregnation.
High photocatalytic performance by engineering Bi2WO6 nanoneedles onto graphene sheets
Authors: Sun Zhihua , Guo Jingjing , Zhu Shenmin , Ma Jun , Liao Yongliang , Zhang Di
Published: June 2014

A sonochemical method was described to engineer Bi2WO6 nanoneedles on graphene sheets, which showed improved performances both in H2 and O2 creation.
Epitaxial growth of high-quality AlN films on metallic nickel substrates by pulsed laser deposition
Authors: Wang Wenliang , Yang Weijia , Liu Zuolian , Lin Yunhao , Zhou Shizhong , Qian Huirong , Wang Haiyan , Lin Zhiting , Li Guoqiang
Published: June 2014

Single-crystalline AlN films with smooth surface and abrupt interface have been grown on metallic nickel (Ni) substrates by pulsed laser deposition with an in-plane epitaxial relationship of AlN[112̄0]//Ni[11̄0].
Nanoporous silica-supported organocatalyst: a heterogeneous and green hybrid catalyst for organic transformations
Authors: Rostamnia Sadegh , Doustkhah Esmail
Published: June 2014

Organically modified hybrid silica mesostructures are becoming increasingly promising candidates as catalysts for various kinds of organic reactions and green chemistry.
Electron-accepting phthalocyanine–pyrene conjugates: towards liquid phase exfoliation of graphite and photoactive nanohybrid formation with graphene
Authors: Roth Alexandra , Ragoussi Maria-Eleni , Wibmer Leonie , Katsukis Georgios , Torre Gema de la , Torres Tomás , Guldi Dirk M.
Published: June 2014

Exfoliation of graphite by ultrasonication in the presence of electron-accepting pyrene–phthalocyanines and photophysical characterization of the resulting nanoconjugate are reported.
Insights into ordered microstructures and ordering mechanisms of ABC star terpolymers by integrating dynamic self-consistent field theory and variable cell shape methods
Authors: Cao Xuguang , Zhang Liangshun , Wang Liquan , Lin Jiaping
Published: June 2014

The ABC star terpolymers self-assemble into tiling patterns. Three types of ordering mechanisms (quick-slow, one step and step-wise) were discovered in the disorder-to-order transition of ABC star terpolymer melts.
A graphene-like MoS2/graphene nanocomposite as a highperformance anode for lithium ion batteries
Authors: Liu Yongchang , Zhao Yanping , Jiao Lifang , Chen Jun
Published: June 2014

A graphene-like MoS2/graphene nanocomposite exhibits excellent electrochemical performance with high capacity, high rate capability and good cyclability as the anode for lithium-ion batteries.
Recent advances in the potential applications of bioinspired superhydrophobic materials
Authors: Darmanin Thierry , Guittard Frederic
Published: June 2014

This review highlights the recent advances made in the potential applications of superhydrophobic materials.
Human stress monitoring through an organic cotton-fiber biosensor
Authors: Coppedè Nicola , Tarabella Giuseppe , Villani Marco , Calestani Davide , Iannotta Salvatore , Zappettini Andrea
Published: June 2014

Selective detection of bioanalytes in physiological fluids, such as blood, sweat or saliva, by means of low-cost and non-invasive devices, is of crucial importance to improve diagnosis and prevention in healthcare.
Chitosan-based biopolysaccharide proton conductors for synaptic transistors on paper substrates
Authors: Wu Guodong , Zhang Jin , Wan Xiang , Yang Yi , Jiang Shuanghe
Published: June 2014

The chitosan-based paper synaptic transistors were successfully used as artificial synapses for emulating biological synaptic functions, including excitatory postsynaptic current, paired-pulse facilitation, dynamic filtering and spatiotemporally correlated signal processing.
An unexpected twist to the activation of IKKβ: TAK1 primes IKKβ for activation by autophosphorylation
Authors: Zhang Jiazhen , Clark Kristopher , Lawrence Toby , Peggie Mark W. , Cohen Philip
Published: June 2014

IKKβ {IκB [inhibitor of NF-κB (nuclear factor κB)] kinase β} is required to activate the transcription factor NF-κB, but how IKKβ itself is activated in vivo is still unclear. It was found to require phosphorylation by one or more ‘upstream’ protein kinases in some reports, but by autophosphorylation in others. In the present study, we resolve this contro-versy by demonstrating that the activation of IKKβ induced by IL-1 (interleukin-1) or TNF (tumour necrosis factor) in embryonic fibroblasts, or by ligands that activate Toll-like receptors in macrophages, requires two distinct phosphorylation events: first, the TAK1 [TGFβ (transforming growth factor β)-activated kinase-1]-catalysed phosphorylation of Ser177 and, secondly, the IKKβ-catalysed autophosphorylation of Ser181. The phosphorylation of Ser177 by TAK1 is a priming event required for the subsequent autophosphorylation of Ser181, which enables IKKβ to phosphorylate exogenous substrates. We also provide genetic evidence which indicates that the IL-1-stimulated, LUBAC (linear ubiquitin chain assembly complex)-catalysed formation of linear ubiquitin chains and their interaction with the NEMO (NF-κB essential modulator) component of the canonical IKK complex permits the TAK1-catalysed priming phosphorylation of IKKβ at Ser177 and IKKα at Ser176. These findings may be of general significance for the activation of other protein kinases.
Endoplasmic reticulum stress response in yeast and humans
Authors: Wu Haoxi , Ng Benjamin S. H. , Thibault Guillaume
Published: June 2014

Stress pathways monitor intracellular systems and deploy a range of regulatory mechanisms in response to stress. One of the best-characterized pathways, the UPR (unfolded protein response), is an intracellular signal transduction pathway that monitors ER (endoplasmic reticulum) homoeostasis. Its activation is required to alleviate the effects of ER stress and is highly conserved from yeast to human. Although metazoans have three UPR outputs, yeast cells rely exclusively on the Ire1 (inositol-requiring enzyme-1) pathway, which is conserved in all Eukaryotes. In general, the UPR program activates hundreds of genes to alleviate ER stress but it can lead to apoptosis if the system fails to restore homoeostasis. In this review, we summarize the major advances in understanding the response to ER stress in Sc (Saccharomyces cerevisiae), Sp (Schizosaccharomyces pombe) and humans. The contribution of solved protein structures to a better understanding of the UPR pathway is discussed. Finally, we cover the interplay of ER stress in the development of diseases.
Mutation‐based compact genetic algorithm for spectroscopy variable selection in determining protein concentration in wheat grain
Authors: Soares A.S. , de Lima T.W. , Soares F.A.A.M.N. , Coelho C.J. , Federson F.M. , Delbem A.C.B. , Van Baalen J.
Published: June 2014

Wheat is the third most produced grain in the world after maize and rice. Determining the protein concentration in wheat grain is one of the major challenges for measuring its industrial quality. Samples of wheat can be collected using a spectrophotometer device. The challenge is to associate the energy absorbed by the device with the protein concentration in wheat. The device measures hundreds of variable intensities that can be related to the physicochemical properties. The selection of a subset of uncorrelated variables has been shown to be fundamental for establishing correct correlations and reducing prediction error. A new formulation of a compact genetic algorithm that uses only a mutation operator is proposed. The results produced by the proposed approach are compared with traditional techniques for spectroscopy variable selection as successive projection algorithms, partial least square and classical formulations of genetic algorithms. For near‐infrared spectral analysis of the protein concentration in wheat, the prediction errors decreased from 0.28 to 0.10 on average, a reduction of 63%.
Space‐time model of the first‐order sea clutter in onshore bistatic high frequency surface wave radar
Authors: Xie Junhao , Sun Minglei , Ji Zhenyuan
Published: June 2014

Land or sea clutter Doppler frequency shift and spectrum spread are traditionally attributed to the radar platform motion relative to the clutter scatterer. However, another spreading mechanism of the clutter Doppler spectrum exists in onshore bistatic high frequency surface wave radar (HFSWR), which is presented in this study. Based on the space‐time distribution of the first‐order sea clutter in onshore bistatic HFSWR, the spreading model is proposed, which is verified by the simulation and experimental results. It demonstrates that the space‐time model would be of fundamental importance to the future experimental investigations, not only of target detection but also of ocean remote sensing with onshore bistatic HFSWR.
Research on the visibility of low‐orbit debris using space‐borne radar
Authors: Zhao Huipeng , Fu Xiongjun , Gao Meiguo , Ding Shuai
Published: June 2014

Space debris with size larger than 1 cm poses a threat to spacecraft. Recently, space debris surveillance, tracking and early warning become far more urgent than ever before owing to the explosive growth of the number of debris. At the base of these problems is how to determine the visibility of debris to observation equipment, which will be discussed in this study. The statistics related to the orbital altitude, inclination and eccentricity of space debris are presented first, and then the principles of orbital parameter design of the space‐borne radar (SBR) are given. Next, systemic parameters of SBR, such as wavelength, antenna type, are determined upon the observation aim. Detectable debris subset is preliminarily selected in accordance with some constraints. At last, based on the simplified general perturbations (SGP4) model, the range and velocity vectors of debris to SBR at specific time are calculated. Another expression form of relative position between debris and radar, range, azimuth and elevation (RAE) course is obtained by means of coordinate rotation which can be accomplished by directing projection or rotational matrix. The RAE data guide file can be used to carry on guidance tracking. Furthermore, the conversion accuracy of two different coordinate transformation methods is also analysed.
Accurate measurement of original current pulses because of positive corona in the coaxial cylindrical arrangement
Authors: Liu Yang , Cui Xiang , Lu Tiebing , Wang Xiaobo , Xiang Yu , Zhou Xiangxian , Li Xuebao
Published: June 2014

Current pulse because of positive corona discharge is a main source of radio interference (RI). An accurate measurement of the original corona pulse is necessary to study corona‐generated RI. However, the corona pulse is likely to be distorted by either LC oscillation or reflection. In this study, an experiment system with single corona source is built which can provide a nearly free‐reflection path for the current pulses, and measurements are carried out in the system. The magnitude of the measured waveform is close to one half of the original pulse, which proves the accuracy of the measurement method. In order to obtain the original current pulse, a comprehensive model for the current pulses’ path, taking the stray capacitance and stray inductance into consideration, is established. Based on the model, an inversion method to derive the original pulse is proposed. In combination with the obtained original pulse, the model gives the calculated results for other experimental conditions. The calculated results agree well with the measured results, which provide solid validation for the accuracy of the measurement. Another advantage of the proposed measurement method is that the long cables enable the accurate measurements to be achieved under any terminal conditions.
CFD study of isothermal water flow in rod bundle with split-type spacer grid
Authors: Batta A. , Class A. G.
Published: June 2014

The design of rod bundles in nuclear application nowadays is assessed by CFD (computational fluid dynamics). The accuracy of CFD models need validation. Within the OECD/NEA benchmark MATiS-H (Measurement and Analysis of Turbulent Mixing in Sub-channels – Horizontal) a single-phase water flow in a 5x5 rod bundle is studied. In the benchmark, two types of spacer grids are tested, the swirl type and the split type, where the current study focuses on the split type spacer grid. Comparison of CFD results obtained at Karlsruhe Institut of Technology (KIT) with experimental results of KAERI (Korea Atomic Energy Research Institute) are presented. In the benchmark velocities components along selected lines downstream of the spacer grid are measured and compared to CFD results. The CFD code STAR CCM+ with the Realized k-ε model is used. Comparisons with experimental results show quantitative and qualitative agreement for the averaged values of velocity components. Comparisons of results to other benchmark partners using different modeling show that the selected mesh size and models for the analysis of the current case gives relatively accurate results. However, the used turbulent model (Realized k-ε does not capture the turbulent intensity correctly. Computation shows that the flow has very high mixing due to the spacer grid, which does not decay within the measurements domain (z/ DH =0-10 downstream of spacer grid). The same conclusion can be drawn from experimental data.
Contribution to study of heat transfer and fluid flow during GTA welding
Authors: Koudadje Koffi , Delalondre Clarisse , Médale Marc , Carpreau Jean-Michel
Published: June 2014

In this paper, the effect of surface-active elements especially sulfur on weld pool shape has been reported. In our contribution, we analyze the influence of the weld pool chemical composition (Mn, Si, …), welding energy, sulphur gradient and electromagnetic effect.

The computed results are in good agreement with the corresponding experimental results, indicating the validity of the modeling approach.
Constrained non-collinear magnetism in disordered Fe and Fe-Cr alloys
Authors: Nguyen-Manh D. , Ma Pui-Wai , Lavrentiev M.Yu. , Dudarev S.L.
Published: June 2014

The development of quantitative models for radiation damage effects in iron, iron alloys and steels, particularly for the high temperature properties of the alloys, requires understanding of magnetic interactions, which control the phase stability of ferritic-martensitic, ferritic, and austenitic steels. In this work, disordered magnetic configurations of pure iron and Fe-Cr alloys are investigated using Density Functional Theory (DFT) formalism, in the form of constrained non-collinear magnetic calculations, with the objective of creating a database of atomic magnetic moments and forces acting between the atoms. From a given disordered atomic configuration of either pure Fe or Fe-Cr alloy, a penalty contribution to the usual spin-polarized DFT total energy has been calculated by constraining the magnitude and direction of magnetic moments. An extensive database of non-collinear magnetic moment and force components for various atomic configurations has been generated and used for interpolating the spatially-dependent magnetic interaction parameters, for applications in large-scale spin-lattice dynamics and magnetic Monte-Carlo simulations.
Computational Models of Thermodynamic Properties of Uranium Nitride
Authors: Mei Zhi-Gang , Stan Marius
Published: June 2014

The structural, elastic, electronic, phonon and thermodynamic properties of uranium nitride (UN) have been systematically studied by density functional theory (DFT) calculations. The calculated electronic band structure shows that UN is a metallic phase. The ground state structural and elastic properties predicted by DFT agree well with experiments. The thermodynamic properties of UN are studied by quasiharmonic approximation by including both lattice vibrational and thermal electronic contributions to free energies. The calculated enthalpy, entropy, Gibbs energy and heat capacity show an excellent agreement with experimental results. The thermal electronic contribution due to 5f electrons of U is found to be critical to describe the free energy of UN due to its metallic character.
Evaluation of Thermal Fatigue Failure Probability at a Mixing Tee Subjected to Random Fluid Temperature Fluctuation
Authors: Suzuki Masaaki , Chihara Rui
Published: June 2014

Calculation of fatigue damage and fatigue life of a mixing tee considering uncertainty on loading and strength parameters has been achieved by conducting Monte Carlo simulations with the aim of clarifying the effect of the uncertainties on the prediction of fatigue damage and quantifying the level of safety of mixing tee designs.
Monte Carlo simulation of spinodal decomposition in a ternary alloy within a three-phases field: comparison to phase transformation of ferrite in duplex stainless steels
Authors: Emo Jonathan , Pareige Cristelle , Saillet Sébastien , Domain Christophe , Pareige Philippe
Published: June 2014

This work proposes to model phase transformations occurring in duplex stainless steels using atomistic kinetic Monte Carlo in a ternary model alloy. Kinetics are simulated in the three-phase field of a ternary system. Influence of the precipitation of the third phase on the kinetic of spinodal decomposition between the two other phases is studied in order to understand the synergy between spinodal decomposition and G-phase precipitation which exists in duplex stainless steels. Simulation results are compared to experimental data obtained with atom probe tomography.
Application of the Monte Carlo method to analyze materials used in flat panel detectors to obtain X-ray spectra
Authors: Gallardo Sergio , Pozuelo Fausto , Querol Andrea , Ródenas José , Verdú Gumersindo
Published: June 2014

An accurate knowledge of the photon spectra emitted by X-ray tubes in radiodiagnostic is essential to better estimate the imparted dose to patients and to improve the quality image obtained with these devices. In this work, it is proposed the use of a flat panel detector together with a PMMA wedge to estimate the actual X-ray spectrum using the Monte Carlo method and unfolding techniques. The MCNP5 code has been used to model different flat panels (based on indirect and direct methods to produce charge carriers from absorbed X-rays) and to obtain the dose curves and system response functions. Most of the actual flat panel devices use scintillator materials that present K-edge discontinuities in the mass energy-absorption coefficient, which strongly affect the response matrix. In this paper, the applicability of different flat panels for reconstructing X-ray spectra is studied. The effect of the mass energy-absorption coefficient of the scintillator material has been studied on the response matrix and consequently, in the reconstructed spectra. Different unfolding methods are tested to reconstruct the actual X-ray spectrum knowing the dose curve and the response function. It has been concluded that the regularization method MTSVD is appropriate to unfold X-ray spectra in all the scintillators studied.
New capabilities of the Liège intranuclear-cascade model for particle-transport codes
Authors: Mancusi D. , Boudard A. , Cugnon J. , David J.-C. , Hagiwara M. , Leprince A. , Leray S.
Published: June 2014

We review and discuss the latest developments of the Liège Intranuclear Cascade model. The new capabilities are illustrated by comparisons with selected experimental data. We also present examples of thick-target calculations performed using particle-transport codes.
Combs: open source python library for RVE generation. Application to microscale diffusion simulations in cementitious materials
Authors: Bourcier C. , Dridi W. , Chomat L. , Laucoin E. , Bary B. , Adam E.
Published: June 2014

The developed tools are used to create a representative volume element (RVE) of cementitious materials and then assess the diffusive properties. The algorithms developed in Combs target a fast placement of the inclusions and a fast generation of the RVE shape and its mesh. Two application cases are considered: the unaltered material diffusivity and the degraded material diffusivity. The first case of application focuses on the description of the capillary porosity. The second application case focuses on the description of the degradation of cementitious material (mineral and porosity) and the diffusive properties associated. The reliability of the analytical effective medium approximations (MT and SC) is confirmed from 3D finite elements (FE) calculations performed on a matrix-inclusions microstructure obtained by RVE generation with Combs. The results also show the need to take into account the percolation behavior.
Facing Challenges for Monte Carlo Analysis of Full PWR Cores : Towards Optimal Detail Level for Coupled Neutronics and Proper Diffusion Data for Nodal Kinetics
Authors: Nuttin A. , Capellan N. , David S. , Doligez X. , El Mhari C. , Méplan O.
Published: June 2014

Safety analysis of innovative reactor designs requires three dimensional modeling to ensure a sufficiently realistic description, starting from steady state. Actual Monte Carlo (MC) neutron transport codes are suitable candidates to simulate large complex geometries, with eventual innovative fuel. But if local values such as power densities over small regions are needed, reliable results get more difficult to obtain within an acceptable computation time. In this scope, NEA has proposed a performance test of full PWR core calculations based on Monte Carlo neutron transport, which we have used to define an optimal detail level for convergence of steady state coupled neutronics. Coupling between MCNP for neutronics and the subchannel code COBRA for thermal-hydraulics has been performed using the C++ tool MURE, developed for about ten years at LPSC and IPNO. In parallel with this study and within the same MURE framework, a simplified code of nodal kinetics based on two-group and few-point diffusion equations has been developed and validated on a typical CANDU LOCA. Methods for the computation of necessary diffusion data have been defined and applied to NU (Nat. U) and Th fuel CANDU after assembly evolutions by MURE. Simplicity of CANDU LOCA model has made possible a comparison of these two fuel behaviours during such a transient.
A generalization of 3D prismatic characteristics along a nonuniform projection mesh
Authors: Lajoie Marc-André , Févotte François , Marleau Guy
Published: June 2014

Large scale tri-dimensional transport calculations in unstructured meshes are limited in scale mostly by the amountof data to process (memory space limitations), the number of operations to perform (computational time limitations), or both. A method relying on a prismatic projection of non-uniform 3-D geometries is proposed, that reduces both memory space and computation time without introducing new approximations and opens new possibilities regarding large scale parallel processing.
Computation of the Doppler-broadened scattering kernel and its Legendre moments
Authors: Previti Alberto , Sanchez Richard , Mostacci Domiziano
Published: June 2014

A numerical computation of the Doppler convolution of the elastic scattering kernel based on the gas model is presented, without making assumptions on the variation of the cross section with energy and for a general scattering law in the center of mass system. The range of integration has been optimized employing a numerical cutoff, allowing for a faster numerical evaluation of the convolution integral. Legendre moments of the transfer kernel are subsequently obtained by direct quadrature and a numerical analysis of the convergence is presented.
Monte Carlo Neutronics and Thermal Hydraulics Analysis of Reactor Cores with Multilevel Grids
Authors: Bernnat W. , Mattes M. , Guilliard N. , Lapins J. , Zwermann W. , Pasichnyk I. , Velkov K.
Published: June 2014

Power reactors are composed of assemblies with fuel pin lattices or other repeated structures with several grid levels, which can be modeled in detail by Monte Carlo neutronics codes such as MCNP6 using corresponding lattice options, even for large cores. Except for fresh cores at beginning of life, there is a varying material distribution due to burnup in the different fuel pins. Additionally, for power states the fuel and moderator temperatures and moderator densities vary according to the power distribution and cooling conditions. Therefore, a coupling of the neutronics code with a thermal hydraulics code is necessary. Depending on the level of detail of the analysis, a very large number of cells with different materials and temperatures must be regarded. The assignment of different material properties to all elements of a multilevel grid is very elaborate and may exceed program limits if the standard input procedure is used. Therefore, an internal assignment is used which overrides uniform input parameters. The temperature dependency of continuous energy cross sections, probability tables for the unresolved resonance region and thermal neutron scattering laws is taken into account by interpolation, requiring only a limited number of data sets generated for different temperatures. The method is applied with MCNP6 and proven for several full core reactor models. For the coupling of MCNP6 with thermal hydraulics appropriate interfaces were developed for the GRS system code ATHLET for liquid coolant and the IKE thermal hydraulics code ATTICA-3D for gaseous coolant. Examples will be shown for different applications for PWRs with square and hexagonal lattices, fast reactors (SFR) with hexagonal lattices and HTRs with pebble bed and prismatic lattices.
ARTEMISTM Core Simulator: Latest Developments
Authors: Hobson Greg , Bolloni Hans-Wilhelm , Breith Karl-Albert , Dall’Osso Aldo , Geemert René van , Haase Hartmut , Hartmann Bettina , Leberig Mario , Porsch Dieter , Pothet Baptiste , Riedmann Michael , Sieber Galina , Tomatis Daniele
Published: June 2014

AREVA has developed a new coupled neutronics/thermal-hydraulics code system, ARCADIA®. It makes use of modern computing resources to enable more realistic reactor analysis as improved understanding of nuclear reactor behavior is the basis for efficient margin management, i.e. optimization of safety and performance. One of the principal components of this new system is the core simulator, ARTEMIS™. The purpose of this paper is to recall its features, present the latest developments and give a summary of the validation tests.
Pathways and Uncertainty Prediction in Fispact-II
Authors: Eastwood James W. , Guy Morgan J.
Published: June 2014

This paper describes how the new inventory code Fispact-II provides predictions of radiological quantities and their uncertainties using TENDL data. Central to the method is a novel fast pathways search algorithm using directed graphs. The pathways output provides (1) an aid to identifying important reactions, (2) fast estimates of uncertainties, (3) reduced models that retain important nuclides and reactions for use in the code’s monte-carlo sensitivity analysis. Described are the methods that are being implemented for improving uncertainty predictions using the covariance data that the recent TENDL nuclear data libraries contain.
Development of Depletion Code Surrogate Models for Uncertainty Propagation in Scenario Studies
Authors: Krivtchik Guillaume , Coquelet-Pascal Christine , Blaise Patrick , Garzenne Claude , Le Mer Joël , Freynet David
Published: June 2014

The result of transition scenario studies, which enable the comparison of different options of the reactor fleet evolution and management of the future fuel cycle materials, allow to perform technical and economic feasibility studies. The COSI code is developed by CEA and used to perform scenario calculations. It allows to model any fuel type, reactor fleet, fuel facility, and permits the tracking of U, Pu, minor actinides and fission products nuclides on a large time scale. COSI is coupled with the CESAR code which performs the depletion calculations based on one-group cross-section libraries and nuclear data. Different types of uncertainties have an impact on scenario studies: nuclear data and scenario assumptions. Therefore, it is necessary to evaluate their impact on the major scenario results. The methodology adopted to propagate these uncertainties throughout the scenario calculations is a stochastic approach. Considering the amount of inputs to be sampled in order to perform a stochastic calculation of the propagated uncertainty, it appears necessary to reduce the calculation time. Given that evolution calculations represent approximately 95% of the total scenario simulation time, an optimization can be done, with the development and implementation of a surrogate models library of CESAR in COSI. The input parameters of CESAR are sampled with URANIE, the CEA uncertainty platform, and for every sample, the isotopic composition after evolution evaluated with CESAR is stored. Then statistical analysis of the input and output tables allow to model the behavior of CESAR on each CESAR library, i.e. building a surrogate model. Several quality tests are performed on each surrogate model to insure the prediction power is satisfying. Afterward, a new routine implemented in COSI reads these surrogate models and using them in replacement of CESAR calculations. A preliminary study of the calculation time gain shows that the use of surrogate models allows stochastic calculation of the uncertainty propagation. Once the set of surrogate models is complete, one of the first expected results is the comparison of global sensitivity indices of nuclear data and scenario assumptions.
Nuclear data uncertainties for local power densities in the Martin-Hoogenboom benchmark
Authors: van der Marck Steven C. , Rochman Dimitri A.
Published: June 2014

The recently developed method of fast Total Monte Carlo to propagate nuclear data uncertainties was applied to the Martin-Hoogenboom benchmark. For each of the more than 6 million local power tallies, the uncertainty due to nuclear data uncertainties was calculated, based on random variation of data for 235U, 238U, 239Pu and H in H2O thermal scattering. In the center of the core region, the nuclear data uncertainty is 0.9%. Towards the edges of the core, this uncertainty increases to roughly 3%.
Probability Tables: a generic tool for representing and propagating uncertainties
Authors: Coste-Delclaux M. , Diop C.M. , Lahaye S.
Published: June 2014

Probability tables are a generic tool that allows representing any random variable whose probability density function is known. In the field of Nuclear Reactor Physics, this tool is currently used to represent the variation of cross-sections versus energy (TRIPOLI4®, MCNP, APOLLO2, ECCO/ERANOS, …). In the present article we show how we can propagate uncertainties, thanks to a probability table representation, through two very simple mathematical problems: an eigenvalue problem (neutron multiplication factor, …) or a depletion problem.
Efficient Geometry and Data Handling for Large-Scale Monte Carlo – Thermal-Hydraulics Coupling
Authors: Eduard Hoogenboom J.
Published: June 2014

Detailed coupling of thermal-hydraulics calculations to Monte Carlo reactor criticality calculations requires each axial layer of each fuel pin to be defined separately in the input to the Monte Carlo code in order to assign to each volume the temperature according to the result of the TH calculation, and if the volume contains coolant, also the density of the coolant. This leads to huge input files for even small systems. In this paper a methodology for dynamical assignment of temperatures with respect to cross section data is demonstrated to overcome this problem. The method is implemented in MCNP5.

The method is verified for an infinite lattice with 3x3 BWR-type fuel pins with fuel, cladding and moderator/coolant explicitly modeled. For each pin 60 axial zones are considered with different temperatures and coolant densities. The results of the axial power distribution per fuel pin are compared to a standard MCNP5 run in which all 9x60 cells for fuel, cladding and coolant are explicitly defined and their respective temperatures determined from the TH calculation. Full agreement is obtained.

For large-scale application the method is demonstrated for an infinite lattice with 17x17 PWR-type fuel assemblies with 25 rods replaced by guide tubes. Again all geometrical detailed is retained. The method was used in a procedure for coupled Monte Carlo and thermal-hydraulics iterations. Using an optimised iteration technique, convergence was obtained in 11 iteration steps.
Effect of the Target Motion Sampling Temperature Treatment Method on the Statistics and Performance
Authors: Viitanen Tuomas , Leppänen Jaakko
Published: June 2014

Target Motion Sampling (TMS) is a stochastic on-the-fly temperature treatment technique that is being developed as a part of the Monte Carlo reactor physics code Serpent. The method provides for modeling of arbitrary temperatures in continuous-energy Monte Carlo tracking routines with only one set of cross sections stored in the computer memory.

Previously, only the performance of the TMS method in terms of CPU time per transported neutron has been discussed. Since the effective cross sections are not calculated at any point of a transport simulation with TMS, reaction rate estimators must be scored using sampled cross sections, which is expected to increase the variances and, consequently, to decrease the figures-of-merit. This paper examines the effects of the TMS on the statistics and performance in practical calculations involving reaction rate estimation with collision estimators.

Against all expectations it turned out that the usage of sampled response values has no practical effect on the performance of reaction rate estimators when using TMS with elevated basis cross section temperatures (EBT), i.e. the usual way. With 0 Kelvin cross sections a significant increase in the variances of capture rate estimators was observed right below the energy region of unresolved resonances, but at these energies the figures-of-merit could be increased using a simple resampling technique to decrease the variances of the responses. It was, however, noticed that the usage of the TMS method increases the statistical deviances of all estimators, including the flux estimator, by tens of percents in the vicinity of very strong resonances. This effect is actually not related to the usage of sampled responses, but is instead an inherent property of the TMS tracking method and concerns both EBT and 0 K calculations.
Calculation of Reactor Kinetics Parameters βeff and Λ with Monte Carlo Differential Operator Sampling
Authors: Nagaya Yasunobu
Published: June 2014

The methods to calculate the kinetics parameters of βeff and Λ with the differential operator sampling have been reviewed. The comparison of the results obtained with the differential operator sampling and iterated fission probability approaches has been performed. It is shown that the differential operator sampling approach gives the same results as the iterated fission probability approach within the statistical uncertainty. In addition, the prediction accuracy of the evaluated nuclear data library JENDL-4.0 for the measured βeff/Λ and βeff values is also examined. It is shown that JENDL-4.0 gives a good prediction except for the uranium-233 systems. The present results imply the need for revisiting the uranium-233 nuclear data evaluation and performing the detailed sensitivity analysis.
Research on Acceleration Algorithms of RMC Complex Geometry
Authors: Sun Jialong , Yu Ganglin , Wang Kan , Xu Qi
Published: June 2014

The function of constructive solid geometry is researched and implemented in the Monte Carlo code RMC. In addition, for the computing efficiency in case of reactor assembly and whole-core analysis, RMC introduces two acceleration techniques in repeated and nested geometry processing. Numerical experiment is carried out with two models, the 17x17 Daya-bay PWR assembly and the Daya-bay whole-core. Satisfying results can be obtained with the two acceleration algorithms.
An Adaptive Zero-Variance Importance Sampling Approximation for Static Network Dependability Evaluation
Authors: L’Ecuyer Pierre , Saggadi Samira , Tuffin Bruno
Published: June 2014

We propose an adaptive parameterized method to approximate the zero-variance change of measure for the evaluation of static network reliability models, with links subject to failures. The method uses two rough approximations of the unreliability function, conditional on the states of any subset of links being fixed. One of these approximation, based on mincuts, under-estimates the true unknown unreliability, whereas the other one, based on minpaths, over-estimates it. Our proposed change of measure takes a convex linear combination of the two, estimates the optimal (graph-dependent) coefficient in this combination from pilot runs, and uses the resulting conditional unreliability approximation at each step of a dynamic importance sampling algorithm. This new scheme is more general and more flexible than a previously-proposed zero-variance approximation scheme, based on mincuts only.
PNS and statistical experiments simulation in subcritical systems using Monte-Carlo method on example of Yalina-Thermal assembly
Authors: Sadovich Sergey , Talamo A. , Burnos V. , Kiyavitskaya H. , Fokov Yu.
Published: June 2014

In subcritical systems driven by an external neutron source, the experimental methods based on pulsed neutron source and statistical techniques play an important role for reactivity measurement. Simulation of these methods is very time-consumed procedure. For simulations in Monte-Carlo programs several improvements for neutronic calculations have been made. This paper introduces a new method for simulation PNS and statistical measurements. In this method all events occurred in the detector during simulation are stored in a file using PTRAC feature in the MCNP. After that with a special code (or post-processing) PNS and statistical methods can be simulated. Additionally different shapes of neutron pulses and its lengths as well as dead time of detectors can be included into simulation.

The methods described above were tested on subcritical assembly Yalina-Thermal, located in Joint Institute for Power and Nuclear Research SOSNY, Minsk, Belarus. A good agreement between experimental and simulated results was shown.
Development of a SCALE Tool for Continuous–Energy Eigenvalue Sensitivity Coefficient Calculations
Authors: Perfetti Christopher M. , Rearden Bradley T.
Published: June 2014

Two methods for calculating eigenvalue sensitivity coefficients in continuous-energy Monte Carlo applications were implemented in the KENO code within the SCALE code package. The methods were used to calculate sensitivity coefficients for several criticality safety problems and produced sensitivity coefficients that agreed well with both reference sensitivities and multigroup TSUNAMI-3D sensitivity coefficients. The newly developed CLUTCH method was observed to produce sensitivity coefficients with high figures of merit and low memory requirements, and both continuous-energy sensitivity methods met or exceeded the accuracy of the multigroup TSUNAMI-3D calculations.
Vectorization of a 2D–1D Iterative Algorithm for the 3D Neutron Transport Problem in Prismatic Geometries
Authors: Moustafa Salli , Févotte François , Lathuilière Bruno , Plagne Laurent
Published: June 2014

The past few years have been marked by a noticeable increase in the interest in 3D whole-core heterogeneous deterministic neutron transport solvers for reference calculations. Due to the extremely large problem sizes tackled by such solvers, they need to use adapted numerical methods and need to be efficiently implemented to take advantage of the full computing power of modern systems.

As for numerical methods, one possible approach consists in iterating over resolutions of 2D and 1D MOC problems by taking advantage of prismatic geometries. The MICADO solver, developed at EDF R&D, is a parallel implementation of such a method in distributed and shared memory systems. However it is currently unable to use SIMD vectorization to leverage the full computing power of modern CPUs.

In this paper, we describe our first effort to support vectorization in MICADO, typically targeting Intel©SSE CPUs.

Both the 2D and 1D algorithms are vectorized, allowing for high expected speedups for the whole spatial solver. We present benchmark computations, which show nearly optimal speedups for our vectorized implementation on the TAKEDA case.
A parallelization approach to the COBRA-TF thermal-hydraulic subchannel code
Authors: Ramos Enrique , Abarca Agustín , Roman Jose E. , Miró Rafael
Published: June 2014

In order to reduce the response time when simulating large reactors in detail, we have developed a parallel version of the thermal-hydraulic subchannel code COBRA-TF, with standard message passing technology (MPI). The parallelization is oriented to reactor cells, so it is best suited for models consisting of many cells. The generation of the Jacobian is parallelized, in such a way that each processor is in charge of generating the data associated to a subset of cells. Also, the solution of the linear system of equations is done in parallel, using the PETSc toolkit.
Accelerating COBAYA3 on multi-core CPU and GPU systems using PARALUTION
Authors: Trost Nico , Jiménez Javier , Lukarski Dimitar , Sanchez Victor
Published: June 2014

COBAYA3 is a multi-physics system of codes which includes two 3D multi-group neutron diffusion codes, ANDES and COBAYA3-PBP, coupled with COBRA-TF, COBRA-IIIc and SUBCHANFLOW sub-channel thermal-hydraulic codes, for the simulation of LWR core transients. The 3D multi-group neutron diffusion equations are expressed in terms of a sparse linear system which can be solved using different iterative Krylov subspace solvers. The mathematical SPARSKIT library has been used for these purposes as it implements among others, external GMRES, PGMRES and BiCGStab solvers.

Multi-core CPUs and graphical processing units (GPUs) provide high performance capabilities which are able to accelerate many scientific computations. To take advantage of these new hardware features in daily use computer codes, the integration of the PARALUTION library to solve sparse systems of linear equations is a good choice. It features several types of iterative solvers and preconditioners which can run on both multi-core CPUs and GPU devices without any modification from the interface point of view. This feature is due to the great portability obtained by the modular and flexible design of the library.

By exploring this technology, namely the implementation of the PARALUTION library in COBAYA3, we are able to decrease the solution time of the sparse linear systems by a factor 5.15x on GPU and 2.56x on multi-core CPU using standard hardware. These obtained speedup factors in addition to the implementation details are discussed in this paper.
The energy band memory server algorithm for parallel Monte Carlo transport calculations
Authors: Felker Kyle G. , Siegel Andrew R. , Smith Kord S. , Romano Paul K. , Forget Benoit
Published: June 2014

An algorithm is developed to significantly reduce the on-node footprint of cross section memory in Monte Carlo particle tracking algorithms. The classic method of per-node replication of cross section data is replaced by a memory server model, in which the read-only lookup tables reside on a remote set of disjoint processors. The main particle tracking algorithm is then modified in such a way as to enable efficient use of the remotely stored data in the particle tracking algorithm. Results of a prototype code on a Blue Gene/Q installation reveal that the penalty for remote storage is reasonable in the context of time scales for real-world applications, thus yielding a path forward for a broad range of applications that are memory bound using current techniques.
Research on GPU Acceleration for Monte Carlo Criticality Calculation
Authors: Xu Qi , Yu Ganglin , Wang Kan
Published: June 2014

The Monte Carlo neutron transport method can be naturally parallelized by multi-core architectures due to the dependency between particles during the simulation. The GPU+CPU heterogeneous parallel mode has become an increasingly popular way of parallelism in the field of scientific supercomputing. Thus, this work focuses on the GPU acceleration method for the Monte Carlo criticality simulation, as well as the computational efficiency that GPUs can bring. The “neutron transport step” is introduced to increase the GPU thread occupancy. In order to test the sensitivity of the MC code’s complexity, a 1D one-group code and a 3D multi-group general purpose code are respectively transplanted to GPUs, and the acceleration effects are compared. The result of numerical experiments shows considerable acceleration effect of the “neutron transport step” strategy. However, the performance comparison between the 1D code and the 3D code indicates the poor scalability of MC codes on GPUs.
3D Neutron Transport PWR Full-core Calculation with RMC code
Authors: Qiu Yishu , She Ding , Fan Xiao , Wang Kan , Li Zeguang , Liang Jingang , Leroyer Hadrien
Published: June 2014

Nowadays, there are more and more interests in the use of Monte Carlo codes to calculate the detailed power density distributions in full-core reactors. With the Inspur TS1000 HPC Server of Tsinghua University, several calculations have been done based on the EDF 3D Neutron Transport PWR Full-core benchmark through large-scale parallelism. To investigate and compare the results of the deterministic method and Monte Carlo method, EDF R&D and Department of Engineering Physics of Tsinghua University are having a collaboration to make code to code verification. So in this paper, two codes are used. One is the code COCAGNE developed by the EDF R&D, a deterministic core code, and the other is the Monte Carlo code RMC developed by Department of Engineering Physics in Tsinghua University. First, the full-core model is described and a 26-group calculation was performed by these two codes using the same 26-group cross-section library provided by EDF R&D. Then the parallel and tally performance of RMC is discussed. RMC employs a novel algorithm which can cut down most of the communications. It can be seen clearly that the speedup ratio almost linearly increases with the nodes. Furthermore the cell-mapping method applied by RMC consumes little time to tally even millions of cells. The results of the codes COCAGNE and RMC are compared in three ways. The results of these two codes agree well with each other. It can be concluded that both COCAGNE and RMC are able to provide 3D-transport solutions associated with detailed power density distributions calculation in PWR full-core reactors. Finally, to investigate how many histories are needed to obtain a given standard deviation for a full 3D solution, the non-symmetrized condensed 2-group fluxes of RMC are discussed.