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Szames, E., K. Ammar, D. Tomatis e J. M. Martinez. "FEW-GROUP CROSS SECTIONS MODELING BY ARTIFICIAL NEURAL NETWORKS". EPJ Web of Conferences 247 (2021): 06029. http://dx.doi.org/10.1051/epjconf/202124706029.
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This work deals with the modeling of homogenized few-group cross sections by Artificial Neural Networks (ANN). A comprehensive sensitivity study on data normalization, network architectures and training hyper-parameters specifically for Deep and Shallow Feed Forward ANN is presented. The optimal models in terms of reduction in the library size and training time are compared to multi-linear interpolation on a Cartesian grid. The use case is provided by the OECD-NEA Burn-up Credit Criticality Benchmark [1]. The Pytorch [2] machine learning framework is used.
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Tomatis, Daniele. "A multivariate representation of compressed pin-by-pin cross sections". EPJ Nuclear Sciences & Technologies 7 (2021): 8. http://dx.doi.org/10.1051/epjn/2021006.
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Since the 80’s, industrial core calculations employ the two-step scheme based on prior cross sections preparation with few energy groups and in homogenized reference geometries. Spatial homogenization in the fuel assembly quarters is the most frequent calculation option nowadays, relying on efficient nodal solvers using a coarse mesh. Pin-wise reaction rates are then reconstructed by dehomogenization techniques. The future trend of core calculations is moving however toward pin-by-pin explicit representations, where few-group cross sections are homogenized in the single pins at many physical conditions and many nuclides are selected for the simplified depletion chains. The resulting data model requires a considerable memory occupation on disk-files and the time needed to evaluate all data exceeds the limits for practical feasibility of multi-physics reactor calculations. In this work, we study the compression of pin-by-pin homogenized cross sections by the Hotelling transform in typical PWR fuel assemblies. The reconstruction of these quantities at different physical states of the assembly is then addressed by interpolation of only a few compressed coefficients, instead of interpolating separately each homogenized cross section. Savings in memory higher than 90% are observed, which result in important gains in runtime when interpolating the few-group data.
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Nguyen, Dinh Quoc Dang, e Emiliano Masiello. "Representation of few-group homogenized cross section by multi-variate polynomial regression". EPJ Web of Conferences 302 (2024): 02002. http://dx.doi.org/10.1051/epjconf/202430202002.
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In this paper, a representation of few-group homogenized cross section by multi-variate polynomial regression is presented. The method is applied on the few-group assembly homogenized cross sections of the assembly 22UA from the benchmark X2VVER[1], generated by the lattice transport code APOLLO3®[2], and conducted over a Cartesian grid of parametric state-points. The regression model [3, 4] allow to input a significantly larger number of points for training compared to the number of monomials, thus yielding higher accuracy than polynomial interpolation without being affected by the choice of points in the training set. Additionally, it can reduce data preparation time because the size of the training set can be smaller than the number of points in the complete Cartesian grid, while still providing a good approximation. Furthermore, its evaluation algorithm can be adapted for GPU utilization, similar to polynomial interpolation with the Newton method [5].
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Szames, E., K. Ammar, D. Tomatis e J. M. Martinez. "FEW-GROUP CROSS SECTIONS LIBRARY BY ACTIVE LEARNING WITH SPLINE KERNELS". EPJ Web of Conferences 247 (2021): 06012. http://dx.doi.org/10.1051/epjconf/202124706012.
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This work deals with the representation of homogenized few-groups cross sections libraries by machine learning. A Reproducing Kernel Hilbert Space (RKHS) is used for different Pool Active Learning strategies to obtain an optimal support. Specifically a spline kernel is used and results are compared to multi-linear interpolation as used in industry, discussing the reduction of the library size and of the overall performance. A standard PWR fuel assembly provides the use case (OECD-NEA Burn-up Credit Criticality Benchmark [1]).
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Nguyen, Dinh Q. D., Emiliano Masiello e Daniele Tomatis. "MPOGen: A Python package to prepare few-group homogenized cross sections for core calculations by APOLLO3®". Nuclear Engineering and Design 417 (fevereiro de 2024): 112802. http://dx.doi.org/10.1016/j.nucengdes.2023.112802.
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Henry, Romain, Yann Périn, Kiril Velkov e Sergei Pavlovich Nikonov. "3-D COUPLED SIMULATION OF A VVER 1000 WITH PARCS/ATHLET". EPJ Web of Conferences 247 (2021): 06015. http://dx.doi.org/10.1051/epjconf/202124706015.
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A new OECD/NEA benchmark entitled “Reactivity compensation with diluted boron by stepwise insertion of control rod cluster” is starting. This benchmark, based on high quality measurements performed at the NPP Rostov Unit 2, aims to validate and assess high fidelity multi-physics simulation code capabilities. The Benchmark is divided in two phases: assembly wise and pin-by-pin resolution of steady-state and transient multi-physics problems. Multi-physics simulation requires the generation of parametrized few-group cross-sections. This task used to be done with deterministic (2-D) lattice codes, but in the past few years the Monte-Carlo code SERPENT has demonstrate its ability to generate accurate few-group homogenized cross-section without approximations, neither on the geometry nor in the nuclear data. Since the whole core SERPENT models for production of such cross-section libraries would be computationally costly (and the standard 2-D approach may introduce unnecessary large approximations), 3-D models of each assembly type in infinite radial lattice configurations have been created. These cross-sections are then used to evaluate effective multiplication factors for different core configurations with the diffusion code PARCS. The results are compared with the reference SERPENT calculations. In the next step, a thermal-hydraulic model with the system code ATHLET applying an assembly-wise description of the core (i.e. one channel per fuel assembly) has been developed for coupled PARCS/ATHLET transient test calculations. This paper describes in detail the models and techniques used for the generation of the few-group parameterized cross section libraries, the PARCS model and the ATHLET model. Additionally, a simple exercise with coupled code system PARCS/ATHLET is presented and analysed.
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Galchenko, V. V., А. М. Abdulaev e І. І. Shlapak. "USING SOFTWARE BASED ON THE MONTE CARLO METHOD FOR RECEIVING THE FEW-GROUP HOMOGENIZED MACROSCOPIC INTERACTION CROSS-SECTIONS". Odes’kyi Politechnichnyi Universytet Pratsi, n.º 3(53) (2017): 37–42. http://dx.doi.org/10.15276/opu.3.53.2017.05.
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Cao, Liangzhi, Yong Liu, Wei Shen e Qingming He. "Development of a hybrid method to improve the sensitivity and uncertainty analysis for homogenized few-group cross sections". Journal of Nuclear Science and Technology 54, n.º 7 (24 de abril de 2017): 769–83. http://dx.doi.org/10.1080/00223131.2017.1315973.
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Truffinet, Olivier, Karim Ammar, Jean-Philippe Argaud, Nicolas Gérard Castaing e Bertrand Bouriquet. "Multi-output gaussian processes for the reconstruction of homogenized cross-sections". EPJ Web of Conferences 302 (2024): 02006. http://dx.doi.org/10.1051/epjconf/202430202006.
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Deterministic nuclear reactor simulators employing the prevalent two-step scheme often generate a substantial amount of intermediate data at the interface of their two subcodes, which can impede the overall performance of the software. The bulk of this data comprises “few-groups homogenized cross-sections” or HXS, which are stored as tabulated multivariate functions and interpolated inside the core simulator. A number of mathematical tools have been studied for this interpolation purpose over the years, but few meet all the challenging requirements of neutronics computation chains: extreme accuracy, low memory footprint, fast predictions… We here present a new framework to tackle this task, based on multi-outputs gaussian processes (MOGP). This machine learning model enables us to interpolate HXS’s with improved accuracy compared to the current multilinear standard, using only a fraction of its training data – meaning that the amount of required precomputation is reduced by a factor of several dozens. It also necessitates an even smaller fraction of its storage requirements, preserves its reconstruction speed, and unlocks new functionalities such as adaptive sampling and facilitated uncertainty quantification. We demonstrate the efficiency of this approach on a rich test case reproducing the VERA benchmark, proving in particular its scalability to datasets of millions of HXS.
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Truffinet, Olivier, Karim Ammar, Jean-Philippe Argaud, Nicolas Gérard Castaing e Bertrand Bouriquet. "Adaptive sampling of homogenized cross-sections with multi-output gaussian processes". EPJ Web of Conferences 302 (2024): 02010. http://dx.doi.org/10.1051/epjconf/202430202010.
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In another talk submitted to this conference, we presented an efficient new framework based on multi-outputs gaussian processes (MOGP) for the interpolation of few-groups homogenized cross-sections (HXS) inside deterministic core simulators. We indicated that this methodology authorized a principled selection of interpolation points through adaptive sampling. We here develop this idea by trying simple sampling schemes on our problem. In particular, we compare sample scoring functions with and without integration of leave-one-out errors, and obtained with single-output and multi-output gaussian process models. We test these methods on a realistic PWR assembly with gadolinium-added fuel rods, comparing them with non-adaptive supports. Results are promising, as the sampling algorithms allow to significantly reduce the size of interpolation supports with almost preserved accuracy. However, they exhibit phenomena of instability and stagnation, which calls for further investigation of the sampling dynamics and trying other scoring functions for the selection of samples.
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Guo, Hui, Yuyang Shen, Yiwei Wu, Qufei Song e Hanyang Gu. "Generating multi-group cross-sections using continuous-energy Monte Carlo method for fast reactor analysis". EPJ Web of Conferences 302 (2024): 02003. http://dx.doi.org/10.1051/epjconf/202430202003.
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The deterministic two-step method, comprising multigroup cross-section generation and core calculation, is widely applied in fast reactor design and analysis. Monte Carlo (MC) methods with continuous energy and fine geometry provide high-precision cross-sections essential for advanced fast reactor neutronics analysis. This paper presents an analysis of integrating MC-generated homogenized cross-sections with various core solvers, demonstrating their effectiveness and potential improvements in fast reactor simulations. For diffusion core calculations, the superhomogénéisation (SPH) technique reduces control rod worth overestimation from 13.5% to 0.35% in the MET-1000 benchmark, improving power distribution predictions. In transport core calculations, the flux-moment homogenization technique (MHT) addresses reactivity overestimation by incorporating cross-section anisotropy, reducing error by 698 pcm. For Method of Characteristics (MOC) core calculations, transport-corrected multigroup cross-sections yield high precision in pin-by-pin power distribution for a 100 MWe lead-based fast reactor benchmark. While MC methods require significant computational resources, such as 62 CPU-hours for the MET-1000 core and 85.5 CPU-hours for the 100 MWe lead-based fast reactor core, they offer flexibility in geometry modeling. This work highlights MC multigroup cross-section generation methods applicable to diffusion, MOC, and transport core calculations for fast reactor analysis, suggesting further exploration into their performance in various reactor parameters and computational efficiency.
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Ardiansyah, H., V. Seker, T. Downar, S. Skutnik e W. Wieselquist. "Evaluation of PBMR-400 Core Design Steady State Condition with Serpent and AGREE". Journal of Physics: Conference Series 2048, n.º 1 (1 de outubro de 2021): 012024. http://dx.doi.org/10.1088/1742-6596/2048/1/012024.
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Abstract The significant recent advances in computer speed and memory have made possible an increasing fidelity and accuracy in reactor core simulation with minimal increase in the computational burden. This has been important for modeling some of the smaller advanced reactor designs for which simplified approximations such as few groups homogenized diffusion theory are not as accurate as they were for large light water reactor cores. For narrow cylindrical cores with large surface to volume ratios such the Ped Bed Modular Reactor (PBMR), neutron leakage from the core can be significant, particularly with the harder neutron spectrum and longer mean free path than a light water reactor. In this paper the core from the OECD PBMR-400 benchmark was analyzed using multigroup Monte Carlo cross sections in the HTR reactor core simulation code AGREE. Homogenized cross sections were generated for each of the discrete regions of the AGREE model using a full core SERPENT Monte Carlo model. The cross sections were generated for a variety of group structures in AGREE to assess the importance of finer group discretization on the accuracy of the core eigenvalue and flux predictions compared to the SERPENT full core Monte Carlo solution. A significant increase in the accuracy was observed by increasing the number of energy groups, with as much as a 530 pcm improvement in the eigenvalue calculation when increasing the number of energy groups from 2 to 14. Significant improvements were also observed in the AGREE neutron flux distributions compared to the SERPENT full core calculation.
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Hernandez-Solis, Augusto, Yohannes Molla, Edoaurd Malambu, Alexey Stankovskiy e Gert Van den Eynde. "VERIFICATION OF THE OpenMC HOMOGENIZED MYRRHA-1.6 CORE MODEL". EPJ Web of Conferences 247 (2021): 04002. http://dx.doi.org/10.1051/epjconf/202124704002.
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The OpenMC code is being employed both as a multi-group nodal macroscopic cross-section generator and a reference multi-group Monte Carlo (MGMC) solution. The aim is to do a neutronic benchmark verification study versus a deterministic model (based on the MYRRHA-1.6 core) performed by the PHISICS simulator. MYRRHA, a novel research accelerator driven system concept that is also foreseen to work as a critical configuration, offers a rich opportunity of testing state-of-the art methods for reactor physics analysis due to its strong heterogeneous configuration utilized for both thermal and fast spectra irradiation purposes. The original core configuration representing MYRRHA-1.6 and formed by 169 assemblies, was launched in OpenMC for producing a homogenous nodal model that, when executed in its multi-group Monte Carlo mode, it produced a keff that differs in almost 500 pcm from the original case. This means that in the future, such approximation should correct the nodal cross-sections to preserve the reaction rates in order to match those ones from the heterogeneous model. Nevertheless, such MGMC mode of operation offered by OpenMC could be exploited in order to verify deterministic core simulators. By inputting the same nodal multi-group cross-section model into the transport solver of the PHISICS toolkit, the neutronic benchmark showed a difference of 171 pcm in eigenvalue while comparing it to its OpenMC MGMC counterpart. Also, local multi-group and energy-integrated nodal profiles of the neutron flux showed a maximum relative difference between methodologies of 15% and 1%, respectively. This means that the MGMC capabilities offered by OpenMC can be employed to verify other deterministic methodologies.
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Zhuang, Kun, Xiaobin Tang e Liangzhi Cao. "Development and verification of a model for generation of MSFR few-group homogenized cross-sections based on a Monte Carlo code OpenMC". Annals of Nuclear Energy 124 (fevereiro de 2019): 187–97. http://dx.doi.org/10.1016/j.anucene.2018.09.037.
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Hwang, Dae Hee, e Ser Gi Hong. "SMALL MODULAR PWR DESIGN FOR TRU RECYCLING WITH McCARD-MASTER TWO-STEP PROCEDURE". EPJ Web of Conferences 247 (2021): 01003. http://dx.doi.org/10.1051/epjconf/202124701003.
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In our previous study, a small modular PWR core was designed for TRU (Transuranics) recycling with multi-recycling scheme with a typical two-step procedure using DeCART2D/MASTER code system in which the lattice analysis for producing homogenized group constant was performed by DeCART2D while whole core analysis was conducted by MASTER code. However, the neutron spectrum hardening of the LWR core loaded with TRU requires validating the multi-group cross section library and resonance self-shielding treatment method in lattice calculation. In this study, a new procedure using McCARD/MASTER was used to analyze the SMR core, in which the lattice calculation was performed by a Monte Carlo code called McCARD with a continuous energy library to generate homogenized two-group assembly cross sections. The SMR core analysis was performed to show neutronic characteristics and TRU mass flow in the SMR core with TRU multi-recycling. The result shows that the analyses on the neutronic characteristics and TRU mass flow using the McCARD/MASTER code system showed good agreement with the previous ones using the DeCART2D/MASTER code system. The neutronic characteristics of each cycle of the core satisfied the typical limit of a commercial PWR core and the SMR core consumes effectively TRU with net TRU consumption rates of 8.46~14.33 %.
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Nikitin, E., E. Fridman, K. Mikityuk, S. Radman e C. Fiorina. "NEUTRONIC MODELLING OF THE FFTF CONTROL ROD WORTH MEASUREMENTS WITH DIFFUSION CODES". EPJ Web of Conferences 247 (2021): 10017. http://dx.doi.org/10.1051/epjconf/202124710017.
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This paper presents an assessment of three deterministic core simulators with the focus on the neutronic performance in steady-state calculations of small Sodium cooled Fast Reactor cores. The selected codes are DYN3D, PARCS and the novel multi-physics solver GeN-Foam. By using these codes, the multi-group diffusion solutions are obtained for the selected twenty control rod worth measurements performed during the isothermal physics tests of the Fast Flux Test Facility (FFTF). The identical set of homogenized few-group cross sections applied in the calculations is generated with the Serpent Monte Carlo code. The numerical results are compared with each other as well as with the measured values. The obtained numerical results, such as the multiplication factors and control rod worth values, are in good agreement as compared to the experimental data. Furthermore, a comparison of the radial power distributions is presented between DYN3D, PARCS and GeN-Foam. Ultimately, the power distributions are compared to the full core Serpent solution, demonstrating an adequate performance of the selected deterministic tools. In overall, this study presents a verification and validation of the neutronic solvers applied by DYN3D, PARCS and GeN-Foam to steady-state calculations of SFR cores.
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Hernández-Solís, Augusto, Christophe Demazière e Christian Ekberg. "Uncertainty Analyses Applied to the UAM/TMI-1 Lattice Calculations Using the DRAGON (Version 4.05) Code and Based on JENDL-4 and ENDF/B-VII.1 Covariance Data". Science and Technology of Nuclear Installations 2013 (2013): 1–21. http://dx.doi.org/10.1155/2013/437854.
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The OECD/NEA Uncertainty Analysis in Modeling (UAM) expert group organized and launched the UAM benchmark. Its main objective is to perform uncertainty analysis in light water reactor (LWR) predictions at all modeling stages. In this paper, multigroup microscopic cross-sectional uncertainties are propagated through the DRAGON (version 4.05) lattice code in order to perform uncertainty analysis on and 2-group homogenized macroscopic cross-sections. The chosen test case corresponds to the Three Mile Island-1 (TMI-1) lattice, which is a 15 15 pressurized water reactor (PWR) fuel assembly segment with poison and at full power conditions. A statistical methodology is employed for the uncertainty assessment, where cross-sections of certain isotopes of various elements belonging to the 172-group DRAGLIB library format are considered as normal random variables. Two libraries were created for such purposes, one based on JENDL-4 data and the other one based on the recently released ENDF/B-VII.1 data. Therefore, multigroup uncertainties based on both nuclear data libraries needed to be computed for the different isotopic reactions by means of ERRORJ. The uncertainty assessment performed on and macroscopic cross-sections, that is based on JENDL-4 data, was much higher than the assessment based on ENDF/B-VII.1 data. It was found that the computed Uranium 235 fission covariance matrix based on JENDL-4 is much larger at the thermal and resonant regions than, for instance, the covariance matrix based on ENDF/B-VII.1 data. This can be the main cause of significant discrepancies between different uncertainty assessments.
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Seubert, A., Y. Périn e R. Henry. "HIGH-FIDELITY MULTI-PHYSICS PIN-BY-PIN MODEL OF A SVEA-96 OPTIMA2 ASSEMBLY WITH TORT-TD/CTF". EPJ Web of Conferences 247 (2021): 06035. http://dx.doi.org/10.1051/epjconf/202124706035.
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This paper describes the development of a 3-d high-fidelity multi-physics pin-by-pin neu-tronic and sub-channel thermal hydraulic model of a SVEA-96 Optima2 fuel assembly for the coupled code system TORT-TD/CTF. No pin power reconstruction is applied. Detailed descriptions are given on (a) the generation of few-group parameterized pin cell-homogenized cross section data using HELIOS, (b) the 3-d neutronic pin-by-pin and ther-mal-hydraulic sub-channel model of a single SVEA-96 Optima2 assembly and its qualifica-tion by Monte Carlo models using Serpent, (c) coupled steady-state results for a single as-sembly and (d) coupled steady-state and transient simulations of a 4-by-4 mini core model of SVEA-96 Optima2 assemblies in a partially rodded state.
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Radaideh, Majdi I., Tomasz Kozlowski, William A. Wieselquist e Matthew A. Jessee. "Data-Driven and Precursor-Group Uncertainty Propagation of Lattice Kinetic Parameters in UAM Benchmark". Science and Technology of Nuclear Installations 2019 (2 de maio de 2019): 1–21. http://dx.doi.org/10.1155/2019/3702014.
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A new data-driven sampling-based framework was developed for uncertainty quantification (UQ) of the homogenized kinetic parameters calculated by lattice physics codes such as TRITON and Polaris. In this study, extension of the database for the delayed neutron data (DND) is performed by exploring more delayed neutron experiments and adding additional isotopes/actinides to the data libraries. Afterwards, the framework is utilized to obtain a deeper knowledge of the kinetic parameters’ sensitivity and uncertainty. The kinetic parameters include precursor-group-wise delayed neutron fraction (DNF) and decay constant. Input uncertainties include nuclear data (i.e., cross-sections) and DND (i.e., precursor group parameters and fractional delayed neutron yield). It is found that kinetic parameters, especially DNFs, have large uncertainties. The DNF uncertainty is driven by the cross-section uncertainties for LWR designs, while decay constant uncertainty is dominated by the DND uncertainties. The usage of correlated U-235 thermal DND in the UQ process significantly reduces the DND uncertainty contribution on the kinetic parameters. Large void fraction and presence of neutron absorber (e.g., control rod) increase the DNF uncertainty due to the hardening of neutron spectrum. High correlation between the DNF groups (β1,..,β6) is observed, while the decay constant groups (λ1,..,λ6) show weak correlation to each other and also to DNF groups. The DNF uncertainties of the dominant precursor group 4 for PWR, BWR, and VVER are about 7.5%, 9.4%, and 7.6%, respectively. The DNF uncertainty grows to larger values after fuel burnup. Kinetic parameters’ values and uncertainties provided here can be efficiently used in subsequent core calculations, point reactor kinetics, and other applications.
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Kim, Wonkyeong, Jinsu Park, Tomasz Kozlowski, Hyun Chul Lee e Deokjung Lee. "Comparative Neutronics Analysis of DIMPLE S06 Criticality Benchmark with Contemporary Reactor Core Analysis Computer Code Systems". Science and Technology of Nuclear Installations 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/180979.
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A high-leakage core has been known to be a challenging problem not only for a two-step homogenization approach but also for a direct heterogeneous approach. In this paper the DIMPLE S06 core, which is a small high-leakage core, has been analyzed by a direct heterogeneous modeling approach and by a two-step homogenization modeling approach, using contemporary code systems developed for reactor core analysis. The focus of this work is a comprehensive comparative analysis of the conventional approaches and codes with a small core design, DIMPLE S06 critical experiment. The calculation procedure for the two approaches is explicitly presented in this paper. Comprehensive comparative analysis is performed by neutronics parameters: multiplication factor and assembly power distribution. Comparison of two-group homogenized cross sections from each lattice physics codes shows that the generated transport cross section has significant difference according to the transport approximation to treat anisotropic scattering effect. The necessity of the ADF to correct the discontinuity at the assembly interfaces is clearly presented by the flux distributions and the result of two-step approach. Finally, the two approaches show consistent results for all codes, while the comparison with the reference generated by MCNP shows significant error except for another Monte Carlo code, SERPENT2.
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Jang, Seongdong, e Yonghee Kim. "A STUDY OF LEAKAGE-CORRECTED TWO-STEP METHOD BASED ON THE NODAL EQUIVALENCE THEORY FOR FAST REACTOR ANALYSIS". EPJ Web of Conferences 247 (2021): 02026. http://dx.doi.org/10.1051/epjconf/202124702026.
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The conventional two-step method based on the generalized equivalence theory (GET) cannot be directly applied to the fast reactor analysis since the assumption of the space-energy separability is not very valid due to a relatively long neutron mean free path. This study aims to develop a leakage-corrected two-step method for the fast reactor analysis with the aid of the albedo-corrected parameterized equivalence constants (APEC) method. The critical idea of the APEC method is to correct the homogenized group constants (HGCs) including discontinuity factors (DFs) during the nodal calculation through predetermined APEC functions. The APEC functions are functionalized in terms of the normalized leakage parameters such as a current-to-flux (CFR) ratio so that they can correct the cross-sections (XSs) and discontinuity factors by reflecting the in-situ neutron leakage information of the nodal analysis. The feasibility of the APEC-corrected two-step method was investigated by solving 5-group diffusion equations for a two-dimensional sodium-cooled fast reactor with a 6-triangle finite difference method. The 5-group HGCs for fuel assemblies were determined by using a continuous-energy Monte Carl code, and the conventional assembly discontinuity factors are also introduced for each hexagonal fuel assembly. First of all, it was demonstrated that the simple FDM scheme could reproduce the reference nodal quantities with the GET. And the APEC functions are formulated using the reference solutions to evaluate the feasibility of simple APEC functional for both XSs and DFs. Then, a smaller color-set problem was defined to determine practical APEC functions for the original benchmark, and various numerical evaluations are performed in terms of the k-eff value and nodal power distribution.
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Botes, Danniëll, e Pavel M. Bokov. "Polynomial interpolation of few-group neutron cross sections on sparse grids". Annals of Nuclear Energy 64 (fevereiro de 2014): 156–68. http://dx.doi.org/10.1016/j.anucene.2013.09.033.
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Kim, Myung H., e A. F. Henry. "Flux-Adjoint Weighted Few-Group Cross Sections Used for Reactor Transient Analysis". Nuclear Science and Engineering 103, n.º 3 (novembro de 1989): 276–82. http://dx.doi.org/10.13182/nse89-a23678.
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Du, Xianan, Xuewen Wu, Youqi Zheng e Yongping Wang. "Reactivity Effect Evaluation of Fast Reactor Based on Angular-Dependent Few-Group Cross Sections Generation". Energies 14, n.º 13 (4 de julho de 2021): 4042. http://dx.doi.org/10.3390/en14134042.
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Among all the possible occurring reactivity effects of a fast reactor, the situations whereby the control rod was inserted, or the coolant was voided could lead to strong anisotropy of neutron flux distribution, therefore the angular dependence on neutron flux should be considered during the few-group cross-sections generation. Therefore, the purpose of this paper is to compare the influence whether the angular dependence on neutron flux is considered in the calculation of few-group cross sections for the reactivity effect calculation. In the study, the 1-D SN finite difference neutron transport equation solver was implemented in the TULIP of SARAX code system so that the high-order neutron flux could be obtained. Meanwhile, the improved Tone’s method was also applied. The numerical results were obtained based on three experimental FR cores, the JOYO MK-I core, ZPPR-9 core, and ZPPR-10B core. Both control rod worth and sodium void reactivity were calculated and compared with the measurement data. By summarizing and comparing the results of 46 cases, significant differences were found between different consideration of the neutronic analysis. The consideration of angular dependence on neutron flux distribution in the few-group cross-sections generation was beneficial to the neutronic design analysis of FR, especially for the reactivity effect calculation.
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Du, Xianan, Liangzhi Cao, Youqi Zheng e Hongchun Wu. "A hybrid method to generate few-group cross sections for fast reactor analysis". Journal of Nuclear Science and Technology 55, n.º 8 (11 de abril de 2018): 931–44. http://dx.doi.org/10.1080/00223131.2018.1452650.
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Radaideh, Majdi I., Stuti Surani, Daniel O’Grady e Tomasz Kozlowski. "Shapley effect application for variance-based sensitivity analysis of the few-group cross-sections". Annals of Nuclear Energy 129 (julho de 2019): 264–79. http://dx.doi.org/10.1016/j.anucene.2019.02.002.
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Pautz, Andreas, e Winfried Zwermann. "TRANSIENT CALCULATIONS OF SPERT III EXPERIMENTS". EPJ Web of Conferences 247 (2021): 07017. http://dx.doi.org/10.1051/epjconf/202124707017.
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Cold-startup and hot-standby reactivity accident tests conducted at the SPERT III E-core research reactor are analysed with the coupled neutron-kinetic/thermal-hydraulic code system DYN3D-ATHLET. Homogenised 2-group cross sections for DYN3D are thereby generated with the Monte Carlo neutron transport code Serpent 2 in combination with the ENDF/B-VII.1 cross section library. Results in terms of maximum power, energy release, and reactivity compensation are in good agreement with the experimental values. The time-dependent contributions to the reactivity feedback are investigated for both a cold-startup test and a hot-standby test. These findings prove the suitability of the combined application of the simulation codes to predict the reactor dynamic behaviour in the event of prompt-critical and super-prompt critical transients even for small reactor cores. Furthermore, static core characteristics of the SPERT III E-core reactor at cold-startup condition are analysed with using a static DYN3D model, a detailed Serpent reference model, and a simplified Serpent model consistent with the DYN3D model. The critical control rod position and the excess reactivities of both the control rods and the transient rod obtained with the Serpent reference model are consistent with the experimental values. For the same parameters, the DYN3D model is in good agreement with the Serpent simplified model.
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Nguyen, Tung Dong Cao, Hyunsuk Lee, Xianan Du, Vutheam Dos, Tuan Quoc Tran e Deokjung Lee. "MACROSCOPIC CROSS SECTIONS GENERATION BY MONTE CARLO CODE MCS FOR FAST REACTOR ANALYSIS". EPJ Web of Conferences 247 (2021): 02007. http://dx.doi.org/10.1051/epjconf/202124702007.
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Recent researches have become more interested in the feasibility of using Monte Carlo (MC) code to generate multi-group (MG) cross sections (XSs) for fast reactor analysis using nodal diffusion codes. The current study, therefore, presents a brief methodology for MG XSs generation by the in-house UNIST MC code MCS, which can be compatibly utilized in nodal diffusion codes, PARCS and RAST-K. The applicability of the methodology is quantified on the sodium fast reactor (SFR) ABR-1000 design with a metallic fuel from the OECD/NEA SRF benchmark. The few-group XSs generated by MCS with a two-dimensional (2D) fuel assembly geometry are well consistent with those of SERPENT 2. Furthermore, the simulation of beginning-of-cycle (BOC) steady-state three-dimensional (3D) whole-core problem with PARCS and RAST-K is conducted using the generated 24-group XSs by MCS. The nodal diffusion solutions, including the core keff, power profiles and various of reactivity parameters, are compared to reference whole-core results obtained by MC code MCS. Overall, the code-to-code comparison indicates a reasonable agreement between deterministic and stochastic codes, with the difference in keff less than 100 pcm and the root-mean-square (RMS) error in assembly power less than 1.15%. Therefore, it is successfully demonstrated that the employment of the MG XSs generation by MCS for nodal diffusion codes is feasible to accurately perform analyses for fast reactors.
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Shchurovskaya, M. V., N. I. Geraskin, M. S. Siddiquee e A. E. Kruglikov. "Few group cross sections generation using MCU-PTR and Serpent for diffusion calculation of light water research reactor". Journal of Physics: Conference Series 1133 (novembro de 2018): 012002. http://dx.doi.org/10.1088/1742-6596/1133/1/012002.
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Shchurovskaya, M. V., N. I. Geraskin e A. E. Kruglikov. "Comparison of research reactor full-core diffusion calculations with few-group cross sections generated using Serpent and MCU-PTR". Annals of Nuclear Energy 141 (junho de 2020): 107361. http://dx.doi.org/10.1016/j.anucene.2020.107361.
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Maragkos, Fotis, Michael Kokkoris e Anastasios Lagogiannis. "MottCalc: A new tool for calculating Mott scattering differential cross sections for analytical purposes". HNPS Proceedings 27 (17 de abril de 2020): 112. http://dx.doi.org/10.12681/hnps.2986.
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In the last few years, the popularity of ERDA applications has soared along with the implementation of time of flight (TOF) type measurements. However, ERDA and other forward scattering IBA techniques suffer from the possibility of the occurence of Mott scattering. This leads to deviations in the elastic differential cross sections which in turn demand special care in the treatment of the obtained experimental spectra. To address this issue, a new code has been developed, called MottCalc (Mott Calculator). Based on the analytical formula, first developed by Mott, which describes the phenomenon, the code is capable of producing theoretical angular and energy distributions of such differential cross sections along with the appropriate R33 files, which in turn can be implemented in all the widely used analytical codes (SIMNRA, DF, POTKU etc.). The electronic screening effect is taken into account in these calculations by implementing the Andersen model. A list of 314 different isotopes is available to choose from as projectile and target nuclei. The list can be expanded with radioactive isotopes. The program is available in two distinct versions, an Excel Spreadsheet and a stand-alone application. Both versions of the program can be freely downloaded from the webpage of the Nuclear Physics group of NTUA (nuclearphysics.ntua.gr/downloads.php). The implementation of the code as well as the features and capabilities of both versions of the program are presented in the current work along with a brief synopsis of the elastic Mott scattering phenomenon.
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Zherdev, Gennady, Tamara Kislitsyna e Mark Nikolayev. "ROCOCO system of combined neutron constants – current status and results of testing using geometrical module of the MMK code". Nuclear Energy and Technology 4, n.º 3 (7 de dezembro de 2018): 217–22. http://dx.doi.org/10.3897/nucet.4.31861.
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Results of studies aimed at the further refinement of the ROCOCO system (routine for calculation and organization of combined constants including cross-sections in group and subgroup representation with detailed description of energy dependence of neutron cross-sections) (Zherdev et al. 2018, Kislitsina et al. 2016) are presented in the paper. Inclusion of this system as a physical module into a set of Monte Carlo calculation codes with OOBG geometric module from the MMK code (Zherdev et al. 2003) is discussed. OOBG module is designed for calculation of neutron multiplication systems with heterogenous cores arranged as hexagonal grids with different degrees of complexity. The name ROCOCO-MMK was assigned to the complex. Results of testing the complex in the calculations of multi-zone neutron multiplication systems (including those with zones containing neutron moderator, zones with close composition but with different temperature, etc.) are described. Accounting for the dependence of constants for one and the same nuclide in the zones with different compositions and temperatures required substantial modernization of routines for preparation of constants for calculation described in (Zherdev et al. 2018). Algorithm for preparation of subgroup constants was modified, methodology for taking into account resonance self-screening of cross-sections within the range of unresolved resonances was improved, and other changes were introduced in the process of this modernization. Results of calculations are compared with data obtained using the MCNP-5 precision program (MCNP 1987), which is linked to the same library of evaluated neutron data ROSFOND as that used in ROCOCO. The ROCOCO-MMK includes procedures for registering different neutron flux functionals (also based on ROCOCO data), which allowed including it in the SCALA computation complex (Zherdev et al. 2003, Zherdev 2005), and performing step-by-step calculation of evolution of fuel nuclide composition during the fuel residence campaign. Directions for further development of the system are outlined in conclusion and, in particular, some possibilities of using the created software for further improvement of methods for preparation of few-group constants for calculations in diffusion approximation are examined.
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Haeberli, W. "Parity violation in proton scattering: low energy region". Canadian Journal of Physics 66, n.º 6 (1 de junho de 1988): 485–94. http://dx.doi.org/10.1139/p88-080.
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Measurements of the parity-violating longitudinal analyzing power, Az, in the scattering of low-energy protons (Ep < 50 MeV) are reviewed. The experiments are based on the determination of the relative scattering cross sections σ+ and σ− for incident protons of positive and hegative helicity, respectively. The first results were reported from Los Alamos, where a significant analyzing power [Az = (−1.7 ± 0.8) × 10−7] was found for p–p scattering at 15 MeV. All other results are for a proton energy near 45 MeV, primarily by the group working at Schweizerisches Institut für Nuklearforschung, which recently reported a new, very accurate result for p–p scattering of Az = (−1.50 ± 0.22) × 10−7. A review is presented of the methods that have been developed by this group over the last 10 years to reduce systematic errors in the determination of Az to a few times 10−9.
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Prasad Joshi, Arun, Neer Shobha Chitrakar, Jitendra Pariyar, Isha Shrestha, Rima Maharjan e Pabitra Maharjan. "Perinatal Outcome: A Comparative Study between Emergency and Elective Caesarean Section at A Tertiary Care Hospital". Journal of Perinatal Society of Nepal 1, n.º 1 (1 de junho de 2023): 1–5. http://dx.doi.org/10.59881/jpeson1.
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Introduction: Caesarean delivery is the most commonly performed lifesaving procedure in obstetrics. Caesarean section can be done in emergency and elective basis. There has been rising trend of caesarean section over the last few decades. Both the caesarean sections are associated with fetal risks than vaginal delivery.
Objectives: To assess and compare the perinatal outcomes of emergency and elective caesarean sections.
Methods: It was a cross-sectional comparative study done in Civil Service Hospital of Nepal over the period of one year starting from January 2021 to December 2021. All the patients who underwent caesarean section during the study period were taken into study. Data regarding perinatal outcomes were analysed by SPSS software.
Results: During the study period, there were 1349 total deliveries. Caesarean sections accounted for 52.2% (n=705) of all deliveries. There were a total of 373 (52.9%) emergency CS and 332 (47.1%) elective CS. Most common indications of emergency and elective caesarean section were fetal distress and previous caesarean section respectively.Out of 713 new-born’s, 26 (6.9%) were preterm in emergency CS, 4 (2.1%) in elective group which was statistically significant (X2 <0.001). Regarding APGAR score, need of resuscitation, nursery admission, respiratory distress syndrome, and neonatal intensive care unit transfer, neonates delivered by emergency basis had more number of babies than elective. However, there was no significant difference. There was one early neonatal death in the study period.
Conclusion: Caesarean section is in rising trend of late. However, timely decision making skills can certainly lead to better perinatal outcome in caesarean sections.
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Lee, Do Kyung, Jun Ho Kim, Byung Hoon Lee, Hyeonsoo Kim, Min Jae Jang, Sung-Sahn Lee e Joon Ho Wang. "Influence of Graft Bending Angle on Femoral Tunnel Widening After Double-Bundle ACL Reconstruction: Comparison of Transportal and Outside-In Techniques". Orthopaedic Journal of Sports Medicine 9, n.º 10 (1 de outubro de 2021): 232596712110357. http://dx.doi.org/10.1177/23259671211035780.
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Background: Previous studies have suggested that increased mechanical stress due to acute graft bending angle (GBA) is associated with tunnel widening and graft failure after anterior cruciate ligament (ACL) reconstruction. Few studies have compared the GBA between the outside-in (OI) and the transportal (TP) techniques. Purpose: To evaluate the influence of GBA on clinical outcomes and tunnel widening after ACL reconstruction with OI versus TP technique. Study Design: Cohort study; Level of evidence, 3. Methods: Included in the study were 56 patients who underwent double-bundle ACL reconstruction (n = 28 in the OI group and n = 28 in the TP group). Clinical outcomes (Lysholm, International Knee Documentation Committee, Tegner score, and knee laxity) 1 year postoperatively were evaluated. Computed tomography scans at 5 days and 1 year postoperatively were used for imaging measurements, and the femoral tunnel was divided into the proximal third, middle, and aperture sections. The GBA and cross-sectional area (CSA) were measured using image analysis software and were compared between groups. A correlation analysis was performed to determine if the GBA affected clinical outcomes or tunnel widening. Results: No significant difference was observed in clinical outcomes between the groups. The GBA of both the anteromedial (AM) and posterolateral bundles were more acute in the OI group compared with the TP group ( P < .05). The CSA at the AM tunnel aperture increased significantly in the OI group (84.2% ± 64.3%) compared with the TP group (51.4% ± 36.7%) ( P = .04). However, there were no differences in the other sections. In the Pearson correlation test, GBA was not correlated with tunnel widening or clinical outcomes. Conclusion: Regardless of technique, the GBA did not have a significant influence on tunnel widening or clinical outcomes. Considering a wider AM tunnel aperture, a more proximal and posterior AM tunnel position might be appropriate with the OI technique.
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Bertulani, Carlos A., Francis W. Hall e Benjamin I. Santoyo. "Big Bang nucleosynthesis as a probe of new physics". EPJ Web of Conferences 275 (2023): 01003. http://dx.doi.org/10.1051/epjconf/202327501003.
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The Big Bang Nucleosynthesis (BBN) model is a cornerstone for the understanding of the evolution of the early universe, making seminal predictions that are in outstanding agreement with the present observation of light element abundances in the universe. Perhaps, the only remaining issue to be solved by theory is the so-called “lithium abundance problem". Dedicated experimental efforts to measure the relevant nuclear cross sections used as input of the model have lead to an increased level of accuracy in the prediction of the light element primordial abundances. The rise of indirect experimental techniques during the preceding few decades has permitted the access of reaction information beyond the limitations of direct measurements. New theoreticaldevelopments have also opened a fertile ground for tests of physics beyond the standard model of atomic,nuclear, statistics, and particle physics. We review the latest contributions of our group for possible solutions of the lithium problem.
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Vera von Bargen, Helga, María Espinosa Serrano, Daniel Martin Navarrete, Paz Ahumada Droguett, Carolina Méndez Benavente, Mónica Flores Castillo, Natalia Ramírez González, Gabriela Ulloa Contador e Marcia López Aceiton. "Analysis of prevalence and sociodemographic conditions among women in labor with and without COVID-19 in public hospitals in Chile". Journal of Perinatal Medicine 50, n.º 2 (6 de dezembro de 2021): 132–38. http://dx.doi.org/10.1515/jpm-2021-0286.
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Abstract Objectives The SARS-CoV-2 virus continues wreaking worldwide havoc on health and between March and August 2020, the first outbreak of COVID-19 hit Chile. The pregnant population is especially vulnerable to infection. Studies have been published that associate socioeconomic status, overcrowding, and poverty with a higher prevalence of SARS-CoV-2 infection. There are few studies about the development of this pandemic in Latin American countries so far. This study seeks to show the prevalence and sociodemographic and perinatal characteristics in pregnant women at the time of delivery, comparing both groups with positive and negative COVID-19 PCR results. Methods A prospective, cross-sectional study of pregnant women who delivered at the San Juan de Dios Hospital in Santiago between April 15, 2020 and June 15, 2020. Analysis of epidemiological, sociodemographic, obstetric, perinatal and sociodemographic data of patients with positive and negative COVID-19 PCR results. Results There were 701 patients included in the study. The prevalence of those with a positive COVID-19 PCR was 9.7% and 67.7% being asymptomatic. Pre-term delivery was significantly higher in the group of positive patients (23.5%) vs. negative patients (8.7%), which was not the same rate as with cesarean sections (C-sections). A 13.2% of patients required management of the pathology in the Critical Care Unit (CCU) and there were no cases of maternal or fetal deaths. We found no significant difference between both groups when analyzing socioeconomic variables, though we noted a trend of greater overcrowding among the group of patients with infection. Conclusions The majority of pregnant patients with SARS-CoV-2 infection are asymptomatic. COVID-19 increases the rate of premature births, but this rate is not same with C-sections. Sociodemographic conditions and overcrowding do not show a higher infection rate in a homogeneous population in relation to the economic, social and demographic level.
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Ovdiienko, Yu, M. Yeremenko, V. Khalimonchuk, A. Kuchin e Yu Bilodid. "Effect of Fuel Burnup History on Neutronic Characteristics of WWER-1000 Core". Nuclear and Radiation Safety, n.º 3(63) (1 de setembro de 2014): 14–18. http://dx.doi.org/10.32918/nrs.2014.3(63).03.
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In preparation of few-group cross-section libraries to be used in WWER macro-calculations, change in the nuclide composition during fuel burnup is commonly defined under invariable characteristics, averaged over the entire core (power, fuel and moderator temperature, moderator density etc.). In reality, conditions of fuel burnup are changing and this factor affects the fuel nuclide composition (the so-called spectral history effect). To account for real burnup history, it is necessary to take into consideration the dependence of cross-sections not only on burnup but also on history of neutron spectrum in the fuel burnup process.
This paper analyzes fuel burnup history effect on neutronic characteristics of WWER-1000 core with use of the DYN3D code. The DYN3D code employs the local Pu-239 concentration as an indicator of burnup spectral history. The calculations have been performed for the first four fuel loadings of Khmelnitsky NPP unit 2 and stationary fuel loading with TVSA. The effect of fuel burnup history is shown both on macro-characteristics of the reactor core (boric acid concentration, fuel cycle duration, reactivity coefficients) and on local values of burnup and power.
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Singhvi, Shreyans D., Preksha T. Singh e Gautam Bhandari. "Assessment of multiple factors affecting intelligence quotient of children of rural and urban areas of Rajasthan, India". International Journal of Research in Medical Sciences 8, n.º 7 (26 de junho de 2020): 2557. http://dx.doi.org/10.18203/2320-6012.ijrms20202895.
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Background: Children are the future of our country and hence their mental and physical wellbeing should be our upmost priority. Undernutrition is a major public health problem in our country and is one of the most common reasons for morbidity and mortality in children under 5yrs of age. The first few years of life are particularly important because vital development occurs in all domains. Therefore, this study has aimed to study the Intelligence Quotient (IQ) of the children of the age group 3-5 in urban and rural areas and study the factors associated with it.Methods: A cross section study of the children group of population was performed. Two sections of the children group were taken for the study- children population residing in an urban area and children population residing in a rural community of Rajasthan, India. The data was compiled and analyzed using appropriate statistical methods.Results: In our study, we have found that The following chosen demographic factors were found associated with children Intelligence quotient (IQ) - nutritional status, socioeconomic status, and age, while gender was not found to be associated with IQ.Conclusions: As, cognitive development is fairly important to children and their future, it should be paid more acknowledgment, as well as early preventive methods of it’s associated factors.
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Honj, Renato M., André M. Vaz-dos-Santos e Carmen Lúcia D. B. Rossi-Wongtschowsk. "Identification of the stages of ovarian maturation of the Argentine hake Merluccius hubbsi Marini, 1933 (Teleostei: Merlucciidae): advantages and disadvantages of the use of the macroscopic and microscopic scales". Neotropical Ichthyology 4, n.º 3 (setembro de 2006): 329–37. http://dx.doi.org/10.1590/s1679-62252006000300004.
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The Argentine hake Merluccius hubbsi is a demersal-pelagic species on which few studies have been undertaken, despite its importance for the fisheries of the South-Southeastern Brazilian region, . The species is the most important commercial fishery resource in Uruguay and Argentina, where several studies have permitted the proper monitoring of the species. The ovarian maturation of the Argentine hake is analysed in this study. A scale of maturation is presented in the light of the oocyte development and the use of macro and microscopic scales of ovarian maturation are compared. It was detected that the oocyte types and derived structures present in the ovaries are similar to those already described both for the species and for teleosts in general; group synchronous development and multiple spawning are typical. The identification of ovarian maturation based only on external morphological characteristics of the gonads presents many errors, mainly in the characterization of the stages of maturation, which makes imperative the parallel analysis of the oocyte development, undertaken through histological ovarian cross-sections.
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Virk, Punit, Samara Laskin, Rebecca Gokiert, Chris Richardson, Mandi Newton, Rob Stenstrom, Bruce Wright, Tyler Black e Quynh Doan. "MyHEARTSMAP: development and evaluation of a psychosocial self-assessment tool, for and by youth". BMJ Paediatrics Open 3, n.º 1 (julho de 2019): e000493. http://dx.doi.org/10.1136/bmjpo-2019-000493.
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BackgroundPaediatric mental health-related visits to the emergency department are rising. However, few tools exist to identify concerns early and connect youth with appropriate mental healthcare. Our objective was to develop a digital youth psychosocial assessment and management tool (MyHEARTSMAP) and evaluate its inter-rater reliability when self-administered by a community-based sample of youth and parents.MethodsWe conducted a multiphasic, multimethod study. In phase 1, focus group sessions were used to inform tool development, through an iterative modification process. In phase 2, a cross-sectional study was conducted in two rounds of evaluation, where participants used MyHEARTSMAP to assess 25 fictional cases.ResultsMyHEARTSMAP displays good face and content validity, as supported by feedback from phase 1 focus groups with youth and parents (n=38). Among phase 2 participants (n=30), the tool showed moderate to excellent agreement across all psychosocial sections (κ=0.76–0.98).ConclusionsOur findings show that MyHEARTSMAP is an approachable and interpretable psychosocial assessment and management tool that can be reliably applied by a diverse community sample of youth and parents.
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Biradar, Vidyadhar G., S. S. Hebbal e S. M. Qutubuddin. "Ergonomic Risk Identification and Postural Analysis in Electrical Transformers Manufacturing Company located in Southern India". International Journal of Occupational Safety and Health 14, n.º 2 (25 de março de 2024): 144–51. http://dx.doi.org/10.3126/ijosh.v14i2.53692.
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Introduction: Musculoskeletal disorders are the major factors resulting in discomfort at work in manufacturing industries to workers and these conditions contribute to the poor health of the workforce, subsequently to lower productivity. Therefore, the design of a workstation based on Ergonomic principles is becoming significant to reduce the effects of MSD. This study aimed to identify and assess the ergonomic risks associated with the work tasks in the company through posture analysis and develop recommendations for reducing those risks. Methods: About 36 manufacturing workers from five sections were randomly selected for the cross-sectional study. The chosen team members were from Core building, Core winding, Assembly, Tanking and Tank fabrication sections with experience of more than two years. The presence of MSDs was assessed using a Nordic musculoskeletal questionnaire. For postural analysis, Rapid Upper Limb Assessment (RULA) and Rapid Entire Body Assessment (REBA) were utilized. Few selected postures were analysed using CATIAV5 software and improvements reducing the risks of postures were recommended. Results: All of the 36 workers selected for the study were male with a mean age of 32 years and, average experience of 10 years, and 75% of workers had normal body mass index. The MSD questionnaire indicated discomfort of 86% mostly in the lower back portion of the body. The combined findings of RULA and REBA showed that about 44% of postures were in the high-risk group. Conclusion: Well-defined ergonomic interventions such as redesigning the workstation are suggested to reduce awkward postures and manual handling risks, leading to improvement in job performance and productivity.
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Fortunato, L., J. Casal, W. Horiuchi, E. G. Lanza, G. Singh, Jagjit Singh e A. Vitturi. "Advances on clusters and correlations in nuclear structure and reactions". Journal of Physics: Conference Series 2586, n.º 1 (1 de setembro de 2023): 012030. http://dx.doi.org/10.1088/1742-6596/2586/1/012030.
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Abstract Recent advances obtained in the last few years by the Theoretical Nuclear Physics group in Padova with various collaborators on alpha-cluster models and on nuclear correlations in stable and unstable light nuclei are reviewed in this contribution. The algebraic cluster model assumes triangular and tetrahedral arrangement of α particles for 12C and 16O respectively. The description of the low-lying states achieved in this model, that is a consequence of the requirement of discrete symmetries, is extremely good. We have made several calculations of α-transfer form factors and reaction cross-sections obtaining a good agreement with available data, thus corroborating the main hypotheses of the model [1]. We have speculated about smoking-gun nuclear fluorescence experiment that might shed light on the exact spatial arrangement of alpha particles in 12C [2]. We will also talk about the successful predictions on the positioning of 29F on the southern shore of the island of inversion [3] and on recent calculations on its halo character and dipole response [4, 5]. Extension of these calculations to 31F [6], pointing out the presence of a halo, are also discussed.
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Pinem, Surian, Sukmanto Dibyo, Wahid Luthfi, Veronica Indriati Sri Wardhani e Donny Hartanto. "An Improved Steady-State and Transient Analysis of the RSG-GAS Reactor Core under RIA Conditions Using MTR-DYN and EUREKA-2/RR Codes". Science and Technology of Nuclear Installations 2022 (30 de julho de 2022): 1–12. http://dx.doi.org/10.1155/2022/6030504.
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Steady-state and transient analysis of reactor core under Reactivity-Initiated Accident (RIA) conditions are important for reactor operation safety. The reactor dynamics are influenced by neutronic and thermal-hydraulic aspects of the core. In this study, steady-state and transient analysis under RIA conditions of the RSG-GAS multipurpose reactor was carried out using MTR-DYN and EUREKA-2/RR programs. Neutronic calculations were performed using a few group cross-sections generated by Serpent 2 with the latest cross-section data ENDF/B-VIII.0. Steady-state conditions were carried out with a nominal power of 30 MW, while transient under RIA conditions occurred because the control rod was pulled too quickly while the reactor operated. These transient RIA conditions were performed for two cases, during start-up with an initial power of 1 W, and within power range with an initial power of 1 MW. Thermal-hydraulic parameters considered in this study are reactor power, the temperature of the fuel, cladding, and coolant. The calculated maximum fuel temperature at a steady state is 126.02°C. Meanwhile, the calculated maximum fuel temperature during RIA conditions at the initial power of 1 W and 1 MW are 64.38°C and 137.14°C, respectively. There are no significant differences in thermal-hydraulic parameters between each used program. The thermal-hydraulic parameters such as the maximum temperature of the coolant, cladding, and fuel under this postulated RIA condition are within the acceptable reactor operation safety limits.
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Pellinen-Wannberg, A., A. Westman, G. Wannberg e K. Kaila. "Meteor fluxes and visual magnitudes from EISCAT radar event rates: a comparison with cross-section based magnitude estimates and optical data". Annales Geophysicae 16, n.º 11 (30 de novembro de 1998): 1475–85. http://dx.doi.org/10.1007/s00585-998-1475-x.
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Abstract. Incoherent scatter radars (ISR) are versatile instruments for continuous monitoring of ionisation processes in the Earth's atmosphere. EISCAT, The European Incoherent Scatter facility has proven effective also in meteor studies. The time resolution of the radar can be reduced to a few milliseconds, sufficient to resolve the passage of individual meteors through the narrow ISR beam. Methods for group and phase velocity determination of the meteoroids and the discrepancy between the results related to the target behaviour are presented. The radar cross sections of echoes associated with moving meteoroids ("meteor head echoes") are very small and increase with decreasing wavelength. The parent meteoroids are found to have visual magnitudes far below the detection limit of most optical observations. The equivalent visual magnitude limit of the smallest objects observed by EISCAT in the current experiments has been estimated by two different methods, both from the cross-section measurements and from the measured event rates. Both methods give a limit value of +10 for the smallest objects while the upper limit is +4. The lower limit of the visual magnitude for the collocated optical measurement system is +4. Thus the two detection systems observe two different meteor size ranges, with the radar almost reaching micrometeorite population. Meteor fluxes estimated from the event rates and the radar system parameters agree well with previous extrapolated values for this size range.Key words. Ionosphere (ionization mechanisms). Radio science (ionospheric physics). Space plasma physics (ionization processes)
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Olsen, T., S. Sass, N. Li e J. Duman. "Factors contributing to seasonal increases in inoculative freezing resistance in overwintering fire-colored beetle larvae dendroides canadensis". Journal of Experimental Biology 201, n.º 10 (15 de maio de 1998): 1585–94. http://dx.doi.org/10.1242/jeb.201.10.1585.
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The insects and microarthropods that vary seasonally in susceptibility to cross-cuticular inoculation by external ice (inoculative freezing) represent a phylogenetically diverse group; however, few studies have explored possible mechanisms experimentally. This study documents seasonally variable inoculative freezing resistance in Dendroides canadensis beetle larvae and combines immunofluorescence, in vivo removal of epicuticular lipids and in vitro chamber studies to explore the roles of seasonal modification in the cuticle and in epidermal and hemolymph antifreeze proteins (AFPs). Seasonal cuticular modifications contribute to the inhibition of inoculative freezing since more cold-hardy larvae froze inoculatively when epicuticular waxes were removed with hexane and, in in vitro chamber experiments, cuticle patches (with the underlying epidermis removed) from winter larvae provided greater protection from inoculative freezing than did cuticle patches from summer larvae. The results indicate that seasonal modifications in epidermal and hemolymph AFPs contribute most strongly to the inhibition of inoculative freezing. Subcuticular epidermal AFPs were present in immunocytochemically labeled transverse sections of winter larvae but were absent in summer ones. Winter integument patches (cuticle with epidermis) were more resistant to inoculative freezing than were summer integument patches. Integument patches resisted inoculative freezing as well as live winter-collected larvae only when hemolymph AFP was added. The results also suggest that some integumentary ice nucleators are removed in cold-hardy larvae and that AFP promotes supercooling by inhibiting the activity of these nucleators.
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Kauppila, W. E., C. K. Kwan, D. Przybyla, S. J. Smith e T. S. Stein. "Positron–inert-gas-atom elastic DCS measurements". Canadian Journal of Physics 74, n.º 7-8 (1 de julho de 1996): 474–82. http://dx.doi.org/10.1139/p96-067.
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In this paper we review prior measurements and report new measurements of elastic differential cross sections (DCSs) obtained in our laboratory for positron scattering by the inert gas atoms He, Ne, Ar, Kr, and Xe. The gases (Ne, Ar, Kr, and Xe) for which low-energy measurements have been made below and above the positronium (Ps)-formation thresholds show evidence that the Ps-formation channel is having an observable "absorption" effect on the elastic scattering channel when compared with calculations that only consider the elastic channel. At low energies where only the elastic channel is open, good agreement is found with available calculations. DCS measurements made at high energies (≥200 eV) for He, Ne, and Ar are also found to be consistent with theoretical calculations. At intermediate energies (above the Ps-formation thresholds and below a few hundred eV) theory has not yet been able to match the relative DCSs obtained experimentally owing to the difficulty of including the effects of the most important inelastic channels (i.e., Ps formation and direct ionization). Some initial attempts by our group to obtain absolute elastic DCSs at fixed scattering angles versus positron energy revealed unexpected structure between 55–60 eV for Ar and at 25 and 200 eV for Kr. Our most recent measurements reported here do not confirm the prior observations of these structural features.
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Bassi, Madu M., Dahiru Isa e Clement Pembi. "Development of Nggwaba Orthography: Syllabic, Phonemic and Tones Patterns". Journal of Natural Language and Linguistics 2, n.º 1 (11 de novembro de 2024): 135–42. http://dx.doi.org/10.54536/jnll.v2i1.3484.
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Nggwaba has been described as an Afro-asiatic language. Further classification situates it in the Chadic group precisely Biu-Mandara. The language is spoken in Gombi and Hong Local Government Areas of Adamawa State, North-east, Nigeria. It has been noticed that the language has largely been under-documented and under-investigated. The estimated number of people who speak the language is less than 1000. This paper presents the orthography and a preliminary analysis of a few aspects of the phonology of the language for the early primary education level. It became necessary to study, develop and document the orthography of Nggwaba language in order to prevent it from going into extinction. The study adopted a mixed-method sampling technique, cross-sectional design as well as a descriptive analysis. The paper is divided into three main sections. While the first section deals with background of the study, the second section looks at the literature review. The third section focuses on the methodology through which the study was carried out, and the fourth section discusses the framework, and finally the fifth section focuses on the result of the study. This is the first description of the phonological features of Nggwaba language. The by-product of this study has added knowledge to literature especially the area of areal linguistics.
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Taiwo, Bamigboye J., Oluwole I. Adeyemi, Samson O. A. Odukoya, Olukemi T. Bamigboye-Taiwo, Faith O. Obagunle e Tanwa Animasahun. "Evaluation of a volunteered herbal recipe employed for the treatment of Uterine leiomyoma (Fibroid) in South-West Nigeria". Nigerian Journal of Pharmacy 58, n.º 2 (4 de novembro de 2024): 239–49. http://dx.doi.org/10.51412/psnnjp.2024.22.
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Background: Uterine fibroids, locally known as 'oyun iju' (false pregnancy in Yoruba dialect) are the most prevalent gynecologic tumors affecting 20 to 40 % of women of childbearing age. It is associated with high morbidity rates, high risk of adverse obstetric outcomes and a reduction in a woman's quality of life. However, there are few treatment options that are effective and which preserve the integrity of the uterus and fertility in affected women. Aim of the study: This study investigated the safety and efficacy of a volunteered herbal recipe, 'CKNS' containing four Nigerian medicinal plants, used to manage uterine fibroid locally. Materials and Methods: The crude extract of the recipe was prepared and its toxicity assessment was carried out using the method described by Lorke. Fibrosis was induced in rats with intramuscular administration of 200 µg of estradiol benzoate for 8 weeks. The rats were treated every 48 hours with different doses of extract, fermented corn water, or goserelin for 2 weeks, after which they were sacrificed following anesthesia with diethyl ether. Cardiac puncture was carried out to collect blood into sample tubes. Hematological and biochemical evaluations were carried out on the samples. Histological examination of the cross sections of the uteri of the studied animal was carried out. Data were analyzed using Graphpad Prism version 5.0 for Windows (Graphpad software, San Diego,California, USA). Results: The acute toxicity test showed no death of animal occurred up to 5000 mg/Kg body weight dose. Histological examination confirmed induction of fibroid. Hematological and biochemical values of the studied animals were within normal range for rats, while the cross section of the uteri of the treatment group that received 1000 mg/kg body weight of the extract had normal mucosa, muscularis and adventitia, compared with the control group. Conclusion: The recipe was found to be safe and to effectively reverse the induced fibrosis in rat uterus.
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Shu, Jiao, Li Li, Hui Yu e Dandan Zhang. "Fertility-enhancing potential of ethanol extract of Cuscuta chinensis seeds in a rat model of unilateral cryptorchidism". Tropical Journal of Pharmaceutical Research 20, n.º 5 (26 de janeiro de 2022): 995–1002. http://dx.doi.org/10.4314/tjpr.v20i5.16.
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Purpose: To investigate the fertility-enhancing potential of the ethanol extract of Cuscuta chinensis seeds in a rat model of unilateral cryptorchidism (ULC), and the mechanism(s) of action.
Methods: Healthy male Sprague Dawley rats (n = 48; mean weight = 220 ± 10 g) were randomly assigned to 4 groups (12 rats/group): control, ULC, 100 mg extract/kg and 200 mg extract/kg groups. Unilateral cryptorchidism of right testis was induced via standard method using an operating microscope. Rats in the treatment groups received 100 and 200 mg of ethanol extract of Cuscuta chinensis/kg orally once a day for 60 days. Sperm count and sperm motility were determined in seminal vesicular fluid (SVF) suspension. Oxidative stress markers and histological changes in rat testis were evaluated. The levels of caspase-3 and caspase-9 in testicular tissue were assessed by enzyme-linked immunosorbent assay (ELISA), while the protein expressions of Nrf2 and heme oxygenase 1 (HO-1) were determined using Western blotting.
Results: Body and reproductive organ weights, sperm count, sperm motility, and activities of glutathione peroxidase (GPx), catalase and superoxide dismutase (SOD) were significantly reduced in ULC group, relative to control group, but these parameters were significantly and dose-dependently increased following extract treatment (p < 0.05). Malondialdehyde (MDA), 8-hydroxy-2’-deoxyguanosine (8-OHdG), caspase-3 and caspase-9 levels were significantly higher in ULC group than in control group, but they were reduced significantly and dose-dependently after extract treatment (p < 0.05). Moreover, the protein expressions of Nrf2 and HO-1 were significantly downregulated in ULC group, when compared with control group, but they were significantly and dose-dependently upregulated by the extract (p < 0.05). Cross sections of testicular tissues of rats in ULC group revealed narrowed and thickened seminiferous tubules (disrupted spermatogonia) characterized by increased apoptotic bodies (increased number of necrotic Sertoli and Leydig cells). However, there were few damaged or necrotic Sertoli and Leydig cells, and complete absence of thickening of seminiferous tubules in testicular tissues of rats treated with the extract.
Conclusion: The ethanol extract of Cuscuta chinensis seeds effectively mitigates cryptorchidism in rats via mechanisms involving the regulation of Nrf2/HO-1 signaling pathway, and inhibition of apoptosis and oxidative stress. Thus, the plant extract has potentials for further development for the management of male infertility