The Experts below are selected from a list of 53643 Experts worldwide ranked by ideXlab platform
Mitsuru Kambe - One of the best experts on this subject based on the ideXlab platform.
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Conceptual Design of a Modular Island Core Fast Breeder Reactor "RAPID-M"
2020Co-Authors: Mitsuru KambeAbstract:A metal fueled modular island Core sodium cooled fast breeder reactor concept RAPID-M to improve reactor performance and proliferation resistance and to accommodate various power requirements has been demonstrated. The essential feature of the RAPID-M concept is that the reactor Core consists of integrated fuel assemblies (IFAs) instead of conventional fuel subassemblies. The RAPID concept enables quick and simplified refueling by replacing IFAs in which all the Core and blanket fuel elements are comprised. In this paper, the 600 MWe RAPID-M design consists of 7 IFAs is presented. Significant reactor mass savings and the improvement of inherent safety features are discussed. Plant dynamics analyses using the multi-point reactor kinetics equations to accommodate the modular Core Configuration demonstrated a favorable transient response in case of unprotected transient over power (UTOP)
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conceptual design of a modular island Core fast breeder reactor rapid m
Journal of Nuclear Science and Technology, 2002Co-Authors: Mitsuru KambeAbstract:A metal fueled modular island Core sodium cooled fast breeder reactor concept RAPID-M to improve reactor performance and proliferation resistance and to accommodate various power requirements has been demonstrated. The essential feature of the RAPID-M concept is that the reactor Core consists of integrated fuel assemblies (IFAs) instead of conventional fuel subassemblies. The RAPID concept enables quick and simplified refueling by replacing IFAs in which all the Core and blanket fuel elements are comprised. In this paper, the 600 MWe RAPID-M design consists of 7 IFAs is presented. Significant reactor mass savings and the improvement of inherent safety features are discussed. Plant dynamics analyses using the multi-point reactor kinetics equations to accommodate the modular Core Configuration demonstrated a favorable transient response in case of unprotected transient over power (UTOP).
W Satula - One of the best experts on this subject based on the ideXlab platform.
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gamow teller response in the Configuration space of a density functional theory rooted no Core Configuration interaction model
Physical Review C, 2018Co-Authors: M Konieczka, W Satula, M KortelainenAbstract:Background: The atomic nucleus is a unique laboratory in which to study fundamental aspects of the electroweak interaction. This includes a question concerning in medium renormalization of the axial-vector current, which still lacks satisfactory explanation. Study of spin-isospin or Gamow-Teller (GT) response may provide valuable information on both the quenching of the axial-vector coupling constant as well as on nuclear structure and nuclear astrophysics.Purpose: We have performed a seminal calculation of the GT response by using the no-Core Configuration-interaction approach rooted in multireference density functional theory (DFT-NCCI). The model treats properly isospin and rotational symmetries and can be applied to calculate both the nuclear spectra and transition rates in atomic nuclei, irrespectively of their mass and particle-number parity.Methods: The DFT-NCCI calculation proceeds as follows: First, one builds a Configuration space by computing relevant, for a given physical problem, (multi)particle-(multi)hole Slater determinants. Next, one applies the isospin and angular-momentum projections and performs the isospin and $K$ mixing in order to construct a model space composed of linearly dependent states of good angular momentum. Eventually, one mixes the projected states by solving the Hill-Wheeler-Griffin equation.Results: The method is applied to compute the GT strength distribution in selected $N\ensuremath{\approx}Z$ nuclei including the $p$-shell $^{8}\mathrm{Li}$ and $^{8}\mathrm{Be}$ nuclei and the $sd$-shell well-deformed nucleus $^{24}\mathrm{Mg}$. In order to demonstrate a flexibility of the approach we present also a calculation of the superallowed GT $\ensuremath{\beta}$ decay in doubly-magic spherical $^{100}\mathrm{Sn}$ and the low-spin spectrum in $^{100}\mathrm{In}$.Conclusions: It is demonstrated that the DFT-NCCI model is capable of capturing the GT response satisfactorily well by using a relatively small Configuration space, exhausting simultaneously the GT sum rule. The model, due to its flexibility and broad range of applicability, may either serve as a complement or even as an alternative to other theoretical approaches, including the conventional nuclear shell model.
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no Core Configuration interaction model for the isospin and angular momentum projected states
Physical Review C, 2016Co-Authors: W Satula, J Dobaczewski, P Bączyk, M KonieczkaAbstract:Background: Single-reference density functional theory is very successful in reproducing bulk nuclear properties like binding energies, radii, or quadrupole moments throughout the entire periodic table. Its extension to the multireference level allows for restoring symmetries and, in turn, for calculating transition rates.Purpose: We propose a new variant of the no-Core-Configuration-interaction (NCCI) model treating properly isospin and rotational symmetries. The model is applicable to any nucleus irrespective of its mass and neutron- and proton-number parity. It properly includes polarization effects caused by an interplay between the long- and short-range forces acting in the atomic nucleus.Methods: The method is based on solving the Hill-Wheeler-Griffin equation within a model space built of linearly dependent states having good angular momentum and properly treated isobaric spin. The states are generated by means of the isospin and angular-momentum projection applied to a set of low-lying (multi)particle-(multi)hole deformed Slater determinants calculated using the self-consistent Skyrme-Hartree-Fock approach.Results: The theory is applied to calculate energy spectra in $N\ensuremath{\approx}Z$ nuclei that are relevant from the point of view of a study of superallowed Fermi $\ensuremath{\beta}$ decays. In particular, a new set of the isospin-symmetry-breaking corrections to these decays is given.Conclusions: It is demonstrated that the NCCI model is capable of capturing main features of low-lying energy spectra in light and medium-mass nuclei using relatively small model space and without any local readjustment of its low-energy coupling constants. Its flexibility and a range of applicability makes it an interesting alternative to the conventional nuclear shell model.
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beta decay study within multireference density functional theory and beyond
Physical Review C, 2016Co-Authors: M Konieczka, W Satula, P BączykAbstract:A pioneering study of Gamow-Teller (GT) and Fermi matrix elements (MEs) using no-Core-Configuration-interaction formalism rooted in multireference density functional theory is presented. After a successful test performed for $^{6}\mathrm{He}\ensuremath{\rightarrow}^{6}\mathrm{Li}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$ decay, the model is applied to compute MEs in the $sd$- and $pf$-shell $T=1/2$ mirror nuclei. The calculated GT MEs and the isospin-symmetry-breaking corrections to the Fermi branch are found to be in very good agreement with shell-model predictions in spite of fundamental differences between these models concerning model space, treatment of correlations, or inclusion of a Core. This result indirectly supports the two-body-current-based scenarios behind the quenching of the axial-vector coupling constant.
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beta decay studies in n z nuclei using no Core Configuration interaction model
Proceedings of the Conference on Advances in Radioactive Isotope Science (ARIS2014), 2015Co-Authors: W Satula, J Dobaczewski, M KonieczkaAbstract:The no-Core Configuration-interaction model based on the isospinand angular-momentum projected density functional formalism is introduced. Two applications of the model are presented: (i) determination of spectra of 0 states in 62Zn and (ii) determination of isospin-symmetry-breaking corrections to superallowed β-decay between isobaric-analogue 0 states in 38Ca and 38K. It is shown that, without readjusting a single parameter of the underlying Skyrme interaction, in all three nuclei, the model reproduces the 0 spectra surprisingly well.
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beta decay studies in n z nuclei using no Core Configuration interaction model
arXiv: Nuclear Theory, 2014Co-Authors: W Satula, J Dobaczewski, M KonieczkaAbstract:The no-Core Configuration-interaction model based on the isospin- and angular-momentum projected density functional formalism is introduced. Two applications of the model are presented: (i) determination of spectra of 0+ states in 62Zn and (ii) determination of isospin-symmetry-breaking corrections to superallowed beta-decay between isobaric-analogue 0+ states in 38Ca and 38K. It is shown that, without readjusting a single parameter of the underlying Skyrme interaction, in all three nuclei, the model reproduces the 0+ spectra surprisingly well.
G Nouet - One of the best experts on this subject based on the ideXlab platform.
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Core properties and mobility of the basal screw dislocation in wurtzite gan a density functional theory study
Modelling and Simulation in Materials Science and Engineering, 2016Co-Authors: I Belabbas, J Chen, M I Heggie, C D Latham, M J Rayson, P R Briddon, G NouetAbstract:We have performed first principles simulations, based on density functional theory (DFT), to investigate the Core properties of the basal a -type screw dislocation in wurtzite gallium nitride. Our calculations demonstrate that the fully coordinated shuffle Core Configuration is the most energetically favourable. The calculated electronic structure of the a -type screw dislocation was found to exhibit exclusively shallow gap states which are not associated with any extended metallization. This may explain why a -type screw dislocations are less detrimental to the performance of GaN based electronic devices than c -type screw dislocations.
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a new atomistic model for the threading screw dislocation Core in wurtzite gan
Computational Materials Science, 2012Co-Authors: I Belabbas, J Chen, G NouetAbstract:We report a new atomistic model for the threading screw dislocation Core in wurtzite gallium nitride. By combining elasticity theory and atomistic simulations, we have revealed the new Core Configuration, with a double 6-atoms ring structure, to be more energetically favourable than the previously known one with a single 6-atoms ring structure, introduced about ten years ago. The new Core Configuration is fully coordinated and has both Ga–Ga and N–N homo-nuclear bonds in its centre. As the double 6-atoms ring Core is free from dangling bonds, it was found to introduce less dispersed energy levels in the bandgap than the single 6-atoms ring Core.
Parks G - One of the best experts on this subject based on the ideXlab platform.
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Development of a deep space nuclear electric propulsion (Nep) system – a nuaer plasma nep reactor
2020Co-Authors: Joseph Kalyan Raj, Parks GAbstract:The application of nuclear fission to meet the propulsion and power requirements of spacecraft has returned to the forefront of research studies in space technology. This project draws on a concept developed by researchers at the University of Florida called a ‘nuclear-activation enhanced’ MHD cycle, in which a partially-ionized rubidium (Rb) vapor from a boiling fast reactor is used to power a magnetohydrodynamic (MHD) generator. In the present study, a molten salt fast reactor concept, called the NuAER plasma NEP-MHD system, is developed based on previous studies of molten salt reactors. A critical reactor Core Configuration is designed and simulated using the Monte Carlo code SERPENT®. Thermodynamic analysis is performed to assess the feasibility of a Rb vapor MHD cycle with the properties of Rb vapor, at the desired temperatures and pressures, determined from predicted values. Basic heat exchanger calculations are performed to qualify the heat transfer requirements of a simple NuAER plasma NEP reactor concept. The results obtained show that the NuAER plasma NEP-MHD system employing a molten salt fast reactor is a viable fission reactor option for the ‘nuclear-activation enhanced’ MHD cycle
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Development of a deep space nuclear electric propulsion (Nep) system – a nuaer plasma nep reactor
2020Co-Authors: Joseph Kalyan Raj, Parks GAbstract:© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. The application of nuclear fission to meet the propulsion and power requirements of spacecraft has returned to the forefront of research studies in space technology. This project draws on a concept developed by researchers at the University of Florida called a ‘nuclear-activation enhanced’ MHD cycle, in which a partially-ionized rubidium (Rb) vapor from a boiling fast reactor is used to power a magnetohydrodynamic (MHD) generator. In the present study, a molten salt fast reactor concept, called the NuAER plasma NEP-MHD system, is developed based on previous studies of molten salt reactors. A critical reactor Core Configuration is designed and simulated using the Monte Carlo code SERPENT®. Thermodynamic analysis is performed to assess the feasibility of a Rb vapor MHD cycle with the properties of Rb vapor, at the desired temperatures and pressures, determined from predicted values. Basic heat exchanger calculations are performed to qualify the heat transfer requirements of a simple NuAER plasma NEP reactor concept. The results obtained show that the NuAER plasma NEP-MHD system employing a molten salt fast reactor is a viable fission reactor option for the ‘nuclear-activation enhanced’ MHD cycle
I Belabbas - One of the best experts on this subject based on the ideXlab platform.
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Core properties and mobility of the basal screw dislocation in wurtzite gan a density functional theory study
Modelling and Simulation in Materials Science and Engineering, 2016Co-Authors: I Belabbas, J Chen, M I Heggie, C D Latham, M J Rayson, P R Briddon, G NouetAbstract:We have performed first principles simulations, based on density functional theory (DFT), to investigate the Core properties of the basal a -type screw dislocation in wurtzite gallium nitride. Our calculations demonstrate that the fully coordinated shuffle Core Configuration is the most energetically favourable. The calculated electronic structure of the a -type screw dislocation was found to exhibit exclusively shallow gap states which are not associated with any extended metallization. This may explain why a -type screw dislocations are less detrimental to the performance of GaN based electronic devices than c -type screw dislocations.
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a new atomistic model for the threading screw dislocation Core in wurtzite gan
Computational Materials Science, 2012Co-Authors: I Belabbas, J Chen, G NouetAbstract:We report a new atomistic model for the threading screw dislocation Core in wurtzite gallium nitride. By combining elasticity theory and atomistic simulations, we have revealed the new Core Configuration, with a double 6-atoms ring structure, to be more energetically favourable than the previously known one with a single 6-atoms ring structure, introduced about ten years ago. The new Core Configuration is fully coordinated and has both Ga–Ga and N–N homo-nuclear bonds in its centre. As the double 6-atoms ring Core is free from dangling bonds, it was found to introduce less dispersed energy levels in the bandgap than the single 6-atoms ring Core.