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Kenji Konashi - One of the best experts on this subject based on the ideXlab platform.
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concept of hydride fuel target subassemblies in a fast reactor core for effective Transmutation of ma
Journal of Alloys and Compounds, 1998Co-Authors: Michio Yamawaki, Hadi Suwarno, Toshio Sanda, Koji Fujimura, Katsuyuki Kawashima, T Yamamoto, Kenji KonashiAbstract:Abstract U–Th–Zr alloys with four different compositions were hydrogenated and examined for their hydrogen holding capacities, microstructural and hardness changes with irradiation and thermal diffusivities. Considerably high hydrogen capacity was confirmed up to about 1173 K. A certain degree of irradiation stability was observed, and relatively high thermal diffusivity was ascertained for these hydrogenated ternary alloys. Based on these results, a new concept for effective Transmutations of MA was proposed, where target assemblies containing Np and Am in hydrogenated form are loaded in a fast reactor core. This concept has a great potential to achieve the best Transmutation of MA with improvement of safety characteristics in a fast reactor core.
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Transmutation of 99Tc with the Use of an Accelerator
Nuclear Science and Engineering, 1994Co-Authors: Takeshi Kase, Kenji KonashiAbstract:Two Transmutation methods, the spallation neutron and the muon-catalyzed fusion methods, both which use an accelerator, are employed for the Transmutation of long-lived nuclides in high-level radioactive wastes. The Transmutation energies and the effective half-lives of [sup 99][Tc] for both Transmutation methods are calculated by the Monte Carlo simulation codes for particle transport, the NMTC/JAERI code and the MCNP code. Both methods could obtain short effective half-lives, which are 17 times smaller than those of a fission reactor. The Transmutation energies are calculated to be 25 to 55 MeV for both methods. These calculated Transmutation energies reveal that it is possible for the foregoing two methods for Transmutation of [sup 99][Tc] to meet the energy balance criterion.
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Design of a high flux reactor for the Transmutation of fission products
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 1993Co-Authors: H. Takashita, Kenji Konashi, K. KawashimaAbstract:We studied the Transmutation of 137Cs into a stable nuclide in a fission reactor. The reactor we considered is a high-flux fast reactor with an inner thermal region for the Transmutation. Neutronic calculations for the reactor were carried out. The average thermal neutron flux was 2.5 × 1015 n/cm2s in the Cs region under the constraints that the burnup reactivity and the peaking factor are within 3.0 and 1.7% Δk/kk′, respectively, which correspond to conditions in ordinary fast reactors. The reactor gives a Transmutation rate of 2.8%/yr for 137Cs.
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Transmutation of Cesium-137 Using Proton Accelerator
Journal of Nuclear Science and Technology, 1993Co-Authors: Takeshi Kase, Kenji Konashi, Hiroshi Takahashi, Yasuo HiraoAbstract:Abstract Two Transmutation methods of 137Cs using a proton accelerator were evaluated in terms of the effective half life and the Transmutation energy. One was the proton method which mainly used high energy proton spallation reaction for Transmutation, and the other was the spallation neutron method which mainly used thermal neutron capture reaction. The Transmutation energies and the effective half lives for the two Transmutation methods were calculated by Monte Carlo simulation codes for particle transport, the NMTC/JAERI code and the MCNP code. The calculated Transmutation energies were 510 MeV and 570 MeV for the spallation neutron method and the proton method, respectively, for an effective half life of 2 yr for 137Cs.
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Transmutation of 90Sr by Inertial Confinement Fusion
Fusion Technology, 1993Co-Authors: Hirofumi Takashita, Kenji KonashiAbstract:Transmutation of [sup 90]Sr by inertial confinement fusion is discussed. A pellet composed of deuterium-tritium fuel surrounded by [sup 90]Sr is compressed by a laser or a particle beam. It is shown that a high Transmutation rate and a small Transmutation energy are obtained because of the highly compressed [sup 90]Sr, which has a large probability of a Transmutation reaction. The number of cycles, including recovering and refabrication of the target, is also discussed. 16 refs., 8 figs., 2 tabs.
Toshio Wakabayashi - One of the best experts on this subject based on the ideXlab platform.
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Study on method to achieve high Transmutation of LLFP using fast reactor
Scientific Reports, 2019Co-Authors: Toshio Wakabayashi, Yoshiaki Tachi, Satoshi Chiba, Makoto Takahashi, Naoyuki TakakiAbstract:The purpose of this study is to clarify the method to achieve high Transmutation rates of four long-lived fission products (^79Se, ^99Tc, ^107Pd, and ^129I) using a fast reactor. New LLFP target assemblies were invented in consideration of the suppression of thermal spikes in adjacent fuel assemblies by combining YD_2 and YH_2 moderators or using a thermal neutron filter material. It was clarified that the high Transmutation rate of about 8%/year was achieved, if the new LLFP target assemblies of 4 nuclides were loaded in the blanket region of the sodium cooled, MOX fueled fast reactor. The feasibility of the LLFP Transmutation target was clarified through experiments on material properties and fabrication of the LLFP target, YH_2 and YD_2 moderators.
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Method to Reduce Long-lived Fission Products by Nuclear Transmutations with Fast Spectrum Reactors
Scientific Reports, 2017Co-Authors: Satoshi Chiba, Atsunori Terashima, Shin Okumura, Toshio Wakabayashi, Naoyuki Takaki, Yoshiaki Tachi, Tadashi YoshidaAbstract:Transmutation of long-lived fission products (LLFPs: ^79Se, ^93Zr, ^99Tc, ^107Pd, ^129I, and ^135Cs) into short-lived or non-radioactive nuclides by fast neutron spectrum reactors without isotope separation has been proposed as a solution to the problem of radioactive wastes disposal. Despite investigation of many methods, such Transmutation remains technologically difficult. To establish an effective and efficient Transmutation system, we propose a novel neutron moderator material, yttrium deuteride (YD_2), to soften the neutron spectrum leaking from the reactor core. Neutron energy spectra and effective half-lives of LLFPs, Transmutation rates, and support ratios were evaluated with the continuous-energy Monte Carlo code MVP-II/MVP-BURN and the JENDL–4.0 cross section library. With the YD_2 moderator in the radial blanket and shield regions, effective half-lives drastically decreased from 10^6 to 10^2 years and the support ratios reached 1.0 for all six LLFPs. This successful development and implementation of a Transmutation system for LLFPs without isotope separation contributes to a the ability of fast spectrum reactors to reduce radioactive waste by consuming their own LLFPs.
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Transmutation characteristics of MA and LLFP in a fast reactor
Progress in Nuclear Energy, 2002Co-Authors: Toshio WakabayashiAbstract:Abstract Systematic studies were implemented to investigate the flexibility and attractive core concepts of MA and LLFP Transmutation in fast reactors. The MA Transmutation in the fast reactor core has no serious drawbacks in terms of core performance, provided that the homogeneous loading method can be employed with a small fraction of MA fuel (2~5wt%). The recycling of MA in the fast reactor is feasible from neutronic and thermal-hydraulic points of view. For FP Transmutation, the introduction of target subassemblies using duplex pellets — a moderator annulus surrounding a Tc-99 core — gives the maximum Transmutation rate of Tc-99 in the radial shield region of the fast reactor. The fast reactor has an excellent potential for transmuting MA and LLFP effectively. The fast reactor will be able to play an important role for reduction of environmental burden in future energy system.
Sergii M. Torba - One of the best experts on this subject based on the ideXlab platform.
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construction of Transmutation operators and hyperbolic pseudoanalytic functions
Complex Analysis and Operator Theory, 2015Co-Authors: Vladislav V. Kravchenko, Sergii M. TorbaAbstract:A representation for integral kernels of Delsarte Transmutation operators is obtained in the form of a functional series with exact formulae for the terms of the series. It is based on the application of hyperbolic pseudoanalytic function theory and recent results on mapping properties of the Transmutation operators. The kernel \(K_{1}\) of the Transmutation operator relating \(A=-\frac{d^{2} }{dx^{2}}+q_{1}(x)\) and \(B=-\frac{d^{2}}{dx^{2}}\) turns out to be one of the complex components of a bicomplex-valued hyperbolic pseudoanalytic function satisfying a Vekua-type hyperbolic equation of a special form. The other component of the pseudoanalytic function is the kernel of the Transmutation operator relating \(C=-\frac{d^{2}}{dx^{2}}+q_{2}(x)\) and \(B\) where \(q_{2}\) is obtained from \(q_{1}\) by a Darboux transformation. We prove an expansion theorem and a Runge-type theorem for this special hyperbolic Vekua equation and using several known results from hyperbolic pseudoanalytic function theory together with the recently discovered mapping properties of the Transmutation operators we obtain a new representation for their kernels. Several examples are given. Moreover, approaches for numerical computation of the Transmutation kernels and for numerical solution of spectral problems are proposed.
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construction of Transmutation operators and hyperbolic pseudoanalytic functions
arXiv: Analysis of PDEs, 2012Co-Authors: Vladislav V. Kravchenko, Sergii M. TorbaAbstract:A representation for integral kernels of Delsarte Transmutation operators is obtained in the form of a functional series with the exact formulas for the terms of the series. It is based on the application of hyperbolic pseudoanalytic function theory and recent results on mapping properties of the Transmutation operators. The kernel $K_1$ of the Transmutation operator relating $A=-\frac{d^2}{dx^2}+q_1(x)$ and $B=-\frac{d^2}{dx^2}$ results to be one of the complex components of a bicomplex-valued hyperbolic pseudoanalytic function satisfying a Vekua-type hyperbolic equation of a special form. The other component of the pseudoanalytic function is the kernel of the Transmutation operator relating $C=-\frac{d^2}{dx^2}+q_2(x)$ and $B$ where $q_2$ is obtained from $q_1$ by a Darboux transformation. We prove the expansion theorem and a Runge-type theorem for this special hyperbolic Vekua equation and using several known results from hyperbolic pseudoanalytic function theory together with the recently discovered mapping properties of the Transmutation operators obtain the new representation for their kernels. Several examples are given. Moreover, based on the presented results approaches for numerical computation of the Transmutation kernels and for numerical solution of spectral problems are proposed.
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Transmutations for Darboux transformed operators with applications
Journal of Physics A: Mathematical and Theoretical, 2012Co-Authors: Vladislav V. Kravchenko, Sergii M. TorbaAbstract:We solve the following problem. Let q1 be a continuous complex-valued potential of a stationary Schr?dinger operator defined on a segment [ ? a, a] and q2 be the potential of a Darboux transformed Schr?dinger operator, that is , where f is a nonvanishing solution of the equation . Suppose a Transmutation operator T1 is known such that for any u ? C2[ ? a, a]. Find an analogous Transmutation operator for . It is well known that the Transmutation operators can be realized in the form of Volterra integral operators with continuously differentiable kernels. Given a kernel K1 of the Transmutation operator T1, we find the kernel K2 of T2 in a closed form in terms of K1. As a corollary, interesting commutation relations between T1 and T2 are obtained which then are used in order to construct the Transmutation operator for the one-dimensional Dirac system with a scalar potential.
Kenji Nishihara - One of the best experts on this subject based on the ideXlab platform.
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Transmutation Scenarios after Closing Nuclear Power Plants
Nuclear Back-end and Transmutation Technology for Waste Disposal, 2014Co-Authors: Kenji Nishihara, Kazufumi Tsujimoto, Hiroyuki OigawaAbstract:With consideration of the phase-out option from nuclear power (NP) utilization in Japan, an accelerator-driven system (ADS) for Pu Transmutation has been designed and scenario analysis performed. The ADS is designed based on the existing ADS design for MA Transmutation, and the six-batch ADS was selected as a reference design for scenario analysis. In the scenario analysis, the once-through scenario of light water reactor (LWR) spent fuel is referred to as a conventional scenario with a LWR-MOX utilization scenario. As the Transmutation scenario, three cases of transmuters that are only-FR, only-ADS, and both-FR+ADS are analyzed. The numbers of necessary transmuters are obtained as 15 to 32 units, and the necessary period for Transmutation as 180–240 years. The benefit on repository by reduction of Pu and MA is reduction of repository area by a factor of five and of decay time of toxicity by one order of magnitude. The FR+ADS scenario would be a modest solution, although the ADS scenario is preferable if rapid Transmutation is required.
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impact of partitioning and Transmutation on lwr high level waste disposal
Journal of Nuclear Science and Technology, 2008Co-Authors: Kenji Nishihara, Hiroyuki Oigawa, Shinichi Nakayama, Yasuji Morita, Tomohiko IwasakiAbstract:Partitioning and/or Transmutation (PT) technology affects the disposal concept of high-level radioactive waste (HLW). We studied how cooling in the predisposal storage period may affect the design of the emplacement area in a repository for radioactive wastes produced by a light-water-reactor nuclear system that uses PT technology. Three different fuel cycle scenarios involving PT technology were analyzed: 1) partitioning process only (separation of some fission products), 2) Transmutation process only (separation and Transmutation of minor actinides), and 3) both partitioning and Transmutation. The necessary predisposal storage periods for some predefined emplacement configurations were determined through transient thermal analysis, and the relation between the storage period and the emplacement area was obtained. For each scenario, we also estimated the storage capacity required for the dry storage of the heat-generating waste forms. The contributions of PT technology on the storage and disposal were di...
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Transmutation of 129I Using an Accelerator-Driven System
Nuclear Technology, 2002Co-Authors: Kenji Nishihara, Hideki TakanoAbstract:A conceptual blanket design for {sup 129}I Transmutation is proposed for an accelerator-driven system (ADS) that is designed to transmute minor actinides (MAs). In this ADS, 250 kg/yr of MA and 56 kg/yr of iodine are simultaneously transmuted, and they correspond to the quantities generated from {approx}10 units of existing light water reactors. Furthermore, an introduction scenario and the benefit of iodine Transmutation are studied for future introduction of fast breeder reactors. It is shown that the Transmutation of iodine benefits the concept of underground disposal.
Xiaoping Ouyang - One of the best experts on this subject based on the ideXlab platform.
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Effects of Transmutation elements in tungsten
Computational Materials Science, 2019Co-Authors: Qiang Zhao, Zheng Zhang, Mei Huang, Xiaoping OuyangAbstract:Abstract Tungsten (W) is widely considered as the most promising plasma facing material (PFM), which will be used in nuclear fusion devices. Due to the Transmutation reaction caused by the fusion neutron irradiation, Transmutation elements (such as Re, Os, and Ta) are generated in the W-based PFM during the operation of nuclear fusion devices. In this paper, Transmutation elements effects on mechanical properties of the W and the behavior of hydrogen/helium (H/He) atom in the W were investigated by using the first-principles calculation method. The results show that the ductility of the W is enhanced by Transmutation elements if dislocation and other defects were ignored, while mechanical properties of the W incompletely depend on Transmutation elements content. Compared with the pure W, the formation energy of the H/He in the W is reduced by Transmutation elements, but the most favorable sites of the H/He in the W is not changed. Except for a repulsion between Ta and He in the W, the H/He in the W is attracted by Transmutation elements. In addition, Transmutation elements can change the best diffusion path of the H/He in the W and increase the diffusion rate of the H/He in W. This study provides a theoretical basis for the Tungsten (W) application, and further study on the effects of Transmutation elements in the W will be needed.
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minor actinide Transmutation on pwr burnable poison rods
Annals of Nuclear Energy, 2015Co-Authors: Bin Liu, Xiaoping Ouyang, Fang Liu, Liming Huang, Haiyan MengAbstract:Abstract Minor actinides are the primary contributors to long term radiotoxicity in spent fuel. The majority of commercial reactors in operation in the world are PWRs, so to study the minor actinide Transmutation characteristics in the PWRs and ultimately realize the successful minor actinide Transmutation in PWRs are crucial problem in the area of the nuclear waste disposal. The key issues associated with the minor actinide Transmutation are the appropriate loading patterns when introducing minor actinides to the PWR core. We study two different minor actinide Transmutation materials loading patterns on the PWR burnable poison rods, one is to coat a thin layer of minor actinide in the water gap between the zircaloy cladding and the stainless steel which is filled with water, another one is that minor actinides substitute for burnable poison directly within burnable poison rods. Simulation calculation indicates that the two loading patterns can load approximately equivalent to 5–6 PWR annual minor actinide yields without disturbing the PWR k eff markedly. The PWR k eff can return criticality again by slightly reducing the boric acid concentration in the coolant of PWR or removing some burnable poison rods without coating the minor actinide Transmutation materials from PWR core. In other words, loading minor actinide Transmutation material to PWR does not consume extra neutron, minor actinide just consumes the neutrons which absorbed by the removed control poisons. Both minor actinide loading patterns are technically feasible; most importantly do not need to modify the configuration of the PWR core and composition of nuclear fuel. Furthermore, the two minor actinide loading patterns completely isolate minor actinide Transmutation materials from nuclear fuel, so it also facilitates fuel reprocessing after discharged from PWR core. We believe that loading minor actinide to PWR burnable poison rods for Transmutation is an optimal minor actinide loading pattern.
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Gas mass spectrum analysis of I-127 Transmutation targets irradiated by Xi'an pulse reactor
Journal of Nuclear Science and Technology, 2012Co-Authors: Xuesong Li, Wenshou Zhang, Jing Tu, Xiaoping Ouyang, Zibin ZhangAbstract:Xe-128 in I-127 Transmutation targets irradiated by Xi'an pulse reactor was analyzed by using Quadrupole Mass Spectrometer (QMS) to calculate Transmutation rate and release rate. Transmutation is an alternative method to transform long-lived toxic radio nuclides to short-lived radio nuclides or stable nuclides. 127I targets were irradiated in Xi'an Pulse Reactor for the first time to simulate the Transmutation behavior of 129I. After irradiation, 128Xe in the target was determinate with online isotope dilution method by Quadrupole Mass Spectrometer (QMS), so that the Transmutation rate and release rate could be calculated. Release behaviors of 128Xe were investigated through melting and step-heated modes. The stepwise heating experiment was done by puncturing method. The result shows the release rate in melting mode is 99.9% (RSD = 1%) and increases with the temperature in stepwise heating mode. The technique proposed in this work is suitable for accurate determination of Transmutation rate of 129I.
