The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Akio Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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Application of correction technique using leakage index combined with SPH or discontinuity factors for energy collapsing on pin-by-pin BWR core analysis
Journal of Nuclear Science and Technology, 2014Co-Authors: Tatsuya Fujita, Tomohiro Endo, Akio YamamotoAbstract:A correction technique to capture the spectral interference effect on collapsed cross sections is combined with the superhomogenization (SPH) factor or the discontinuity factor (DF) and is applied to the pin-by-pin core analysis for boiling water reactors (BWRs). The spectral interference effect has relationship with variations of Neutron leakage in each pin-cell from the viewpoint of Neutron Balance. In order to correct collapsed cross sections, a new correction technique, in which the Neutron leakage in each pin-cell is used as a correction index, was proposed in the previous study. By this correction technique, the reference coarse group cross sections are well reproduced and the calculation accuracies are improved. However, the reference fine group calculation results could not be reproduced since the correction technique cannot reduce energy collapsing errors. Thus, we combine the correction technique with the SPH factor or the DF to reduce energy collapsing errors. In order to verify and discuss the...
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A new technique for spectral interference correction on pin-by-pin BWR core analysis
Journal of Nuclear Science and Technology, 2014Co-Authors: Tatsuya Fujita, Tomohiro Endo, Akio YamamotoAbstract:A new correction technique to capture the spectral interference effect on collapsed cross sections, which focuses on application to the pin-by-pin boiling water reactor (BWR) core analysis, is proposed. The spectral interference effect, which is caused by adjacent loadings of different types of fuel assemblies, has relationship with variations of Neutron leakage in each pin-cell from the viewpoint of Neutron Balance. Variation of Neutron leakage affects Neutron spectrum and thus the Neutron leakage is considered to be important to correct coarse-group cross sections used in core calculations. We focus on the Neutron leakage in each pin-cell and use it as a correction index (i.e., a leakage index (LI)), which is defined as the volume-averaged Neutron leakage in a pin-cell. By utilizing the leakage index, we represent the variations of coarse-group cross sections as the linear combination of LIs. In order to verify and discuss the applicability of the present correction technique, two-dimensional benchmark ...
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improvement of spatial discretization error on the semi analytic nodal method using the scattered source subtraction method
Journal of Nuclear Science and Technology, 2006Co-Authors: Akio Yamamoto, Masahiro TatsumiAbstract:In this paper, the scattered source subtraction (SSS) method is newly proposed to improve the spatial discretization error of the semi-analytic nodal method with the flat-source approximation. In the SSS method, the scattered source is subtracted from both side of the diffusion or the transport equation to make spatial variation of the source term to be small. The same Neutron Balance equation is still used in the SSS method. Since the SSS method just modifies coefficients of node coupling equations (those used in evaluation for the response of partial currents), its implementation is easy. Validity of the present method is verified through test calculations that are carried out in PWR multi-assemblies configurations. The calculation results show that the SSS method can significantly improve the spatial discretization error. Since the SSS method does not have any negative impact on execution time, convergence behavior and memory requirement, it will be useful to reduce the spatial discretization error of ...
Tatsuya Fujita - One of the best experts on this subject based on the ideXlab platform.
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Application of correction technique using leakage index combined with SPH or discontinuity factors for energy collapsing on pin-by-pin BWR core analysis
Journal of Nuclear Science and Technology, 2014Co-Authors: Tatsuya Fujita, Tomohiro Endo, Akio YamamotoAbstract:A correction technique to capture the spectral interference effect on collapsed cross sections is combined with the superhomogenization (SPH) factor or the discontinuity factor (DF) and is applied to the pin-by-pin core analysis for boiling water reactors (BWRs). The spectral interference effect has relationship with variations of Neutron leakage in each pin-cell from the viewpoint of Neutron Balance. In order to correct collapsed cross sections, a new correction technique, in which the Neutron leakage in each pin-cell is used as a correction index, was proposed in the previous study. By this correction technique, the reference coarse group cross sections are well reproduced and the calculation accuracies are improved. However, the reference fine group calculation results could not be reproduced since the correction technique cannot reduce energy collapsing errors. Thus, we combine the correction technique with the SPH factor or the DF to reduce energy collapsing errors. In order to verify and discuss the...
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A new technique for spectral interference correction on pin-by-pin BWR core analysis
Journal of Nuclear Science and Technology, 2014Co-Authors: Tatsuya Fujita, Tomohiro Endo, Akio YamamotoAbstract:A new correction technique to capture the spectral interference effect on collapsed cross sections, which focuses on application to the pin-by-pin boiling water reactor (BWR) core analysis, is proposed. The spectral interference effect, which is caused by adjacent loadings of different types of fuel assemblies, has relationship with variations of Neutron leakage in each pin-cell from the viewpoint of Neutron Balance. Variation of Neutron leakage affects Neutron spectrum and thus the Neutron leakage is considered to be important to correct coarse-group cross sections used in core calculations. We focus on the Neutron leakage in each pin-cell and use it as a correction index (i.e., a leakage index (LI)), which is defined as the volume-averaged Neutron leakage in a pin-cell. By utilizing the leakage index, we represent the variations of coarse-group cross sections as the linear combination of LIs. In order to verify and discuss the applicability of the present correction technique, two-dimensional benchmark ...
Y. Fujii-e - One of the best experts on this subject based on the ideXlab platform.
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Transmutation of long-lived fission products with use of available excess Neutrons in BWR core
Progress in Nuclear Energy, 1998Co-Authors: T. Mochida, Masaki Saito, Junichi Yamashita, M. Yokomi, Y. Fujii-eAbstract:Abstract Feasibility of transmutation of long-lived Fps in BWR is studied from the view point of neuron Balance. Pointing out the equilibrium mass amount of LLFP such as 129 I, 99 Tc, and 126 Sn in BWR core, the Neutron Balance analysis shows that the available Neutrons produced by the current BWR core modification is satisfactory to the required amount of Neutrons for LLFP transmutation. Core performance of the LLFP-recycled BWR is then analyzed and the result shows satisfactory results for the present core design criteria. The results confirm the potential of the transmutation of LLFP in BWR and that the eventual radioactive hazard of the radwaste coming form the LLFP recycled BWR can be reduced well below the hazard level of the burned uranium.
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Scientific feasibility of incineration in scnes
Progress in Nuclear Energy, 1995Co-Authors: Hiroshi Akatsuka, Masaaki Suzuki, Toshiro Ohsaki, Toru Obara, Masayuki Igashira, Y. Fujii-eAbstract:Abstract We confirm the simultaneous realization of burning or transmutation of radioactive nuclides and of net energy generation. An investigation of the Neutron Balance in a reactor core is carried out. It is numerically shown that the Neutrons can burn all the transuranium elements (TRU's) produced in the core as fuel in the SCNES reactor. It is numerically found that the fission products (FP's) whose half-lives are longer than one year can be contained and transmuted into harmless nuclides in the core without losing the Neutron Balance. It is shown that isotope separation of the FP's is required to realize the SCNES. As an example, we investigate the required energy for a scheme of the atomic vapor laser isotope separation (AVLIS) of FP's. It is shown that, in principle, the energy required for the isotope separation is much lower than the generated fission energy. The SCNES is scientifically realized in principle.
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Self-consistent nuclear energy systems
Progress in Nuclear Energy, 1995Co-Authors: Akinao Shimizu, Y. Fujii-eAbstract:Abstract A concept of self-consistent nuclear energy system (SCNES) has been proposed as an ultimate goal of the nuclear energy system in the coming centuries. SCNES should realize a stable and unlimited energy supply without endangering the human race and the global environment. It is defined as a system that realizes at least the following four objectives simultaneously: 1. a) Energy generation — attain high efficiency in the utilization of fission energy, 2. b) Fuel production — secure inexhaustible energy source: breeding of fissile material with the breeding ratio greater than one and complete burning of tansuranium through recycling, 3. c) Burning of radionuclides — zero release of radionuclides from the system: complete burning of transuranium and elimination of radioactive fission products by Neutron capture reactions through recycling, 4. d) System safety — achieve system safety both for the public and experts: eliminate criticality-related safety issues by using natural laws and simple logic. This paper describes the concept of SCNES and discusses the feasibility of the system. Both “Neutron Balance” and “energy Balance” of the system are introduced as the necessary conditions to be satisfied at least by SCNES. Evaluations made so far indicate that both the Neutron Balance and the energy Balance can be realized by fast reactors but not by thermal reactors. Concerning the system safety, two safety concepts: “self controllability” and “self-term inability” are introduced to eliminate the criticality-related safety issues in fast reactors.
Tomohiro Endo - One of the best experts on this subject based on the ideXlab platform.
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Application of correction technique using leakage index combined with SPH or discontinuity factors for energy collapsing on pin-by-pin BWR core analysis
Journal of Nuclear Science and Technology, 2014Co-Authors: Tatsuya Fujita, Tomohiro Endo, Akio YamamotoAbstract:A correction technique to capture the spectral interference effect on collapsed cross sections is combined with the superhomogenization (SPH) factor or the discontinuity factor (DF) and is applied to the pin-by-pin core analysis for boiling water reactors (BWRs). The spectral interference effect has relationship with variations of Neutron leakage in each pin-cell from the viewpoint of Neutron Balance. In order to correct collapsed cross sections, a new correction technique, in which the Neutron leakage in each pin-cell is used as a correction index, was proposed in the previous study. By this correction technique, the reference coarse group cross sections are well reproduced and the calculation accuracies are improved. However, the reference fine group calculation results could not be reproduced since the correction technique cannot reduce energy collapsing errors. Thus, we combine the correction technique with the SPH factor or the DF to reduce energy collapsing errors. In order to verify and discuss the...
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A new technique for spectral interference correction on pin-by-pin BWR core analysis
Journal of Nuclear Science and Technology, 2014Co-Authors: Tatsuya Fujita, Tomohiro Endo, Akio YamamotoAbstract:A new correction technique to capture the spectral interference effect on collapsed cross sections, which focuses on application to the pin-by-pin boiling water reactor (BWR) core analysis, is proposed. The spectral interference effect, which is caused by adjacent loadings of different types of fuel assemblies, has relationship with variations of Neutron leakage in each pin-cell from the viewpoint of Neutron Balance. Variation of Neutron leakage affects Neutron spectrum and thus the Neutron leakage is considered to be important to correct coarse-group cross sections used in core calculations. We focus on the Neutron leakage in each pin-cell and use it as a correction index (i.e., a leakage index (LI)), which is defined as the volume-averaged Neutron leakage in a pin-cell. By utilizing the leakage index, we represent the variations of coarse-group cross sections as the linear combination of LIs. In order to verify and discuss the applicability of the present correction technique, two-dimensional benchmark ...
Masaki Saito - One of the best experts on this subject based on the ideXlab platform.
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Feasibility of uranium spallation target in accelerator-driven system
Progress in Nuclear Energy, 2011Co-Authors: Kairat Ismailov, Masaki Saito, Hiroshi Sagara, Kenji NishiharaAbstract:Abstract A feasibility study on natural uranium spallation target in accelerator-driven system (ADS) for minor actinide (MA) transmutation was performed. As a result of comparative study of uranium and lead-bismuth (PbBi) targets in the bare case without blanket surrounding, it was found that uranium target had better Neutron generation performance, but limited by the geometrical size due to high Neutron absorption in 238U. In ADS for MA transmutation, uranium used as target instead of PbBi also absorbs Neutrons passing the target area. More realistic concept of pin type uranium spallation target cooled by liquid PbBi was considered aiming at enhancing spallation target performance in terms of Neutron generation efficiency and operation temperature. The uranium pin target design had nothing better effects on Neutron Balance of such system than a conventional PbBi target in ADS and it was concluded that uranium target was not suitable for the full-scale ADS.
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Neutron Excess Generation by Fusion Neutron Source for Self-Consistency of Nuclear Energy System
Journal of Nuclear Science and Technology, 1999Co-Authors: Masaki Saito, Vladimir Artisyuk, A. ChmelevAbstract:The present day fission energy technology faces with the problem of transmutation of dangerous radionuclides that requires Neutron excess generation. Nuclear energy system based on fission reactors needs fuel breeding and, therefore, suffers from lack of Neutron excess to apply large-scale transmutation option including elimination of fission products. Fusion Neutron source (FNS) was proposed to improve Neutron Balance in the nuclear energy system. Energy associated with the performance of FNS should be small enough to keep the position of Neutron excess generator, thus, leaving the role of dominant energy producers to fission reactors. The present paper deals with development of general methodology to estimate the effect of Neutron excess generation by FNS on the performance of nuclear energy system as a whole. Multiplication of fusion Neutrons in both non-fissionable and fissionable multipliers was considered. Based on the present methodology it was concluded that Neutron self-consistency with respect t...
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Intensive 14 MeV Neutron source based on deuteron storage ring
Progress in Nuclear Energy, 1998Co-Authors: Yu. A. Korovin, Masaaki Suzuki, Masaki Saito, Vladimir Artisyuk, E. Avdeyev, A. Konobeyev, Alexey StankovskyAbstract:The key element of a Self-Consistent Nuclear Energy System is excess Neutron generation. External Neutron source is supposed to be included in the nuclear energy structure to improve its Neutron Balance. The paper presents accelerator based 14 MeV Neutron source that might contribute to Neutron excess generation required for transmuting of those fission products which are difficult to transmute in ordinary fission reactors.
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Transmutation of long-lived fission products with use of available excess Neutrons in BWR core
Progress in Nuclear Energy, 1998Co-Authors: T. Mochida, Masaki Saito, Junichi Yamashita, M. Yokomi, Y. Fujii-eAbstract:Abstract Feasibility of transmutation of long-lived Fps in BWR is studied from the view point of neuron Balance. Pointing out the equilibrium mass amount of LLFP such as 129 I, 99 Tc, and 126 Sn in BWR core, the Neutron Balance analysis shows that the available Neutrons produced by the current BWR core modification is satisfactory to the required amount of Neutrons for LLFP transmutation. Core performance of the LLFP-recycled BWR is then analyzed and the result shows satisfactory results for the present core design criteria. The results confirm the potential of the transmutation of LLFP in BWR and that the eventual radioactive hazard of the radwaste coming form the LLFP recycled BWR can be reduced well below the hazard level of the burned uranium.