Ueta, Shohei; Sasaki, Koei; Arita, Yuji*
Nihon Genshiryoku Gakkai-Shi ATOMO, 63(8), p.615 - 620, 2021/08
no abstracts in English
Annals of Nuclear Energy, 149, p.107818_1 - 107818_7, 2020/12
Treatment of surplus plutonium has been one of the most important issues in the utilization of nuclear power in Japan. This study investigates a molten salt accelerator-driven system (ADS) to transmute transuranic (TRU) nuclides to address the issue. MARDS (Molten salt Accelerator Driven System) concept employs lead chloride (PbCl) as a fuel salt to achieve a hard spectrum. Since the fuel salt is used as a spallation target, a dedicated spallation target is not required in this concept. Furthermore, a beam window which is a boundary between an accelerator and subcritical core is designed to avoid touching the fuel salt. It mitigates the difficulties of the beam design for ADS. Neutronics calculation for the MARDS concept was performed for a condition of 400 MW thermal power with 800 MeV proton beam. The calculation results showed that the proton beam current was about 7 mA and about 4400 kg plutonium could be transmuted during 40-year operation.
Alcaraz, O.*; Trulls, J.*; Tahara, Shuta*; Kawakita, Yukinobu; Takeda, Shinichi*
Journal of Chemical Physics, 145(9), p.094503_1 - 094503_7, 2016/09
Annals of Nuclear Energy, 81, p.301 - 305, 2015/07
Development of a simple method to incorporate the out-of-core cooling effect on the thorium conversion in multi-pass fueled reactors and investigation on characteristics of the effect have been performed. For multi-pass fueled reactors, such as Molten Salt Breeder Reactor (MSBR) and Pebble-Bed Modular Reactor (PBMR), fuel moves in the core and exits from the core. The nuclides decay also out of the core, and it should be also considered if it is important for core characteristics. In the present study, Pa is considered to evaluate the thorium conversion accurately. To take the effect into account, in the present study, an effective decay constant is proposed to make equilibrium concentration of Pa without out-of-core cooling equal to that of out-of-core cooling. With the effective decay constant, the out-of-core cooling effect can be incorporated even with the code system using macroscopic cross sections generated by cell burn-up calculations without any code modification. In addition, the characteristic of out-of-core cooling effect for the thorium conversion is evaluated for thorium fueled reactors of MSBR and PBMR. It is concluded that the out-of-core cooling effect is suitable for MSBR to enhance thorium conversion because of the fast flow rate of fuel salt. On the other hand, the effect is not important and not realistic to employ for PBMR because the in-core residence time of approximately 100 days is longer than the half-life of Pa of 27.0 days, and the effect cannot improve the conversion ratio drastically.
Research Group for Actinides Science
JAERI-Conf 2005-008, 216 Pages, 2005/09
This report is the Proceedings of the 4th Workshop on Molten Salts Technology and Computer Simulation, which was held on December 20, 2004, at Tokai Research Establishment of Japan Atomic Energy Research Institute (JAERI). The purpose of this workshop is to exchange information and views on molten salts technology and computer simulation among the specialists from domestic organizations, and to discuss the recent and future research status for this research field. The intensive discussion was made among approximately 55 participants. The presentations were 14 papers including one keynote lecture.
Kuznetsov, S. A.*; Hayashi, Hirokazu; Minato, Kazuo; Gaune-Escard, M.*
Journal of Nuclear Materials, 344(1-3), p.169 - 172, 2005/09
The knowledge of separation coefficients of actinides and rare-earth metals is important for developing pyrometallurgical process of spent nuclear fuel. Electrochemical experiments were carried out at 723-823 K to estimate separation coefficients in LiCl-KCl eutectic melt containing uranium and lanthanum trichlorides. Uranium and lanthanum separation coefficients is calcurated with the voltammetric peak potentials of U (III) and La (III), their concentration in the melt and kinetic parameters for U(III) discharge such as diffusion coefficients, and standard rate constants of charge transfer. The diffusion coefficients of U (III) were determined by some electrochemical measurements. The standard rate constants of charge transfer for electroreduction of uranium U(III) +3e =U were calculated by impedance spectroscopy method.
Kato, Tetsuya*; Iizuka, Masatoshi*; Inoue, Tadashi*; Iwai, Takashi; Arai, Yasuo
Journal of Nuclear Materials, 340(2-3), p.259 - 265, 2005/04
no abstracts in English
Shiwaku, Hideaki; Okamoto, Yoshihiro; Yaita, Tsuyoshi; Suzuki, Shinichi; Minato, Kazuo; Tanida, Hajime*
Zeitschrift fr Naturforschung, A, 60a(1-2), p.81 - 84, 2005/01
no abstracts in English
Ishitsuka, Etsuo; Kawamura, Hiroshi; Tanaka, Satoru*
JAERI-Conf 2004-006, 347 Pages, 2004/03
This report is the Proceedings of the Sixth International Energy Agency International Workshop on Beryllium Technology for Fusion. The workshop was held on December 2-5, 2003, at SEAGAIA in Miyazaki City, Japan with 69 participants who attended from Europe, the Russian Federation, Kazakhstan, Ukraine, China, the United States and Japan. The topics for papers were arranged into nine sessions; Status of beryllium study, Plasma and tritium interactions, ITER oriented issues, Neutron irradiation effects, Beryllide application, Disposal and recycling, Molten salt, Health and safety issues and Panel discussion. The issues in these topics were discussed intensively on the bases of 49 presentations. In the Panel discussion, the international collaboration for three topics, i.e., Neutron irradiation effects, Beryllide application, Recycling and Disposal, were discussed, and necessary items for the international collaboration were proposed.
Shirai, Osamu; Uozumi, Koichi*; Iwai, Takashi; Arai, Yasuo
Journal of Applied Electrochemistry, 34(3), p.323 - 330, 2004/03
The electrode reactions of the Np/Np couple at liquid Cd and Bi electrodes were investigated by cyclic voltammetry at 723, 773 and 823 K in LiCl-KCl eutectic melt. It was found that the diffusion of Np in the salt phase was a rate-determining step in the cathodic reaction when the concentration of NpCl was less than about 1 wt.% and the liquid Cd or Bi phase was not saturated with Np. The redox potentials of the Np/Np couple at liquid Cd electrode at 723, 773 and 823 K were observed more positively than those at Mo electrode by 0.158, 0.140 and 0.126 V, respectively. The potential shift would result from a lowering of activity of Np in Cd phase according to the alloy formation of NpCd at 723 K and NpCd at 773 and 823 K. The redox potentials of the Np/Np couple at liquid Bi electrode at 723, 773 and 823 K were more positive than those at Mo electrode by 0.427, 0.419 and 0.410 V, respectively, which would be attributable to a lowering of activity of Np in Bi phase according to the formation of NpBi.
Kato, Tetsuya*; Uozumi, Koichi*; Inoue, Tadashi*; Shirai, Osamu*; Iwai, Takashi; Arai, Yasuo
Proceedings of GLOBAL2003 Atoms for Prosperity; Updating Eisenhower's Global Vision for Nuclear Energy (CD-ROM), p.1591 - 1595, 2003/11
Electrolysis experiments were carried to recover plutonium and uranium into liquid cadmium cathodes from molten salt at high cathode current densities. In the electrolysis at 101mA/cm, 10.4wt.% of heavy metals in the cathode was recovered at almost 100% of current efficiency. In the electrolysis at 156mA/cm, the cathode potential ascended after approximately 8wt.% of heavy metals was recovered and some deposit was observed outside of the crucible.
Minato, Kazuo; Arai, Yasuo
Genshikaku Kenkyu, 47(6), p.31 - 38, 2003/06
no abstracts in English
Mehmood, M.*; Kawaguchi, Nobuaki*; Maekawa, Hideki*; Sato, Yuzuru*; Yamamura, Tsutomu*; Kawai, Masayoshi*; Kikuchi, Kenji
Materials Transactions, 44(2), p.259 - 267, 2003/02
Electrochemical study has been carried out on the electro-deposition of tantalum in LiF-NaF-CaF melt containing KTaF at 700C. This has been done for determining the mechanistic features for preparing electrolytic coating of tantalum on nickel and tungsten substrates. Electro-deposition of metallic tantalum occurs primarily by electro-reduction of Ta(V). Pure metallic tantalum without any entrapped salt is successfully deposited on tungsten by galvanostatic polarization at reasonably low current densities. An additional feature on nickel is the formation of an intermetallic compound at potential 0.25V nobler than that of pure tantalum as a result of underpotential deposition of tantalum. This intermetallic compound covers the surface within a short time followed by deposition of pure tantalum, although intermetallic compound keeps growing at the interface of pure tantalum deposit and the substrate as a result of diffusion.
Fusion Engineering and Design, 61-62, p.209 - 216, 2002/11
To attain high fusion power density, the divertor must suffer high heat flux from the fusion plasma. It is very difficult to remove a high heat flux more than 20 MW/m using the only solid divertor plate from the viewpoint of severe mechanical state such as thermal stress and crack growth. Therefore, a concept of liquid divertor is proposed to remove high heat flux by liquid films flowing on a solid wall. This paper mainly descries a preliminary thermofluid analysis of the free surface liquid flow, made of the FliBe molten salt, using the finite element analysis code ADINA-F. The heat flux of 25100 MW/m was given on the free surface liquid of the flow. I explored a possibility of applying the secondary flow to enhance the heat transfer of the liquid flow suffering high heat flux. This analysis shows that the heat flux of 100 MW/m can be removed by inducing the secondary flow in the free surface liquid FLiBe. And this paper shows that the liquid divertor using solid-liquid multi-phase flow makes possible large heat removal by utilizing the latent heat of fusion of solid phase.
Hayashi, Hirokazu; Kobayashi, Fumiaki; Ogawa, Toru; Minato, Kazuo
Journal of Nuclear Science and Technology, 39(Suppl.3), p.624 - 627, 2002/11
The behavior of the dissolution of uranium nitrides, which is a component of the MA-U mixed nitride fuel, has been investigated. A mixture of uranium nitride, LiCl-KCl and CdCl was contained in a double walled quartz reaction vessel. During the heating, the carrier gas helium was introduced to a gas chromatography apparatus equipped with an automatic gas sampler. A fraction of the gas was sampled and analyzed by a mass analyzer. Most of nitrogen is recovered as N gas from uranium nitrides dissolving in the LiCl-KCl eutectic melt reacted with CdCl above 550 C, which is higher than that for lanthanide nitrides.
Okamoto, Yoshihiro; Shiwaku, Hideaki; Yaita, Tsuyoshi; Narita, Hirokazu; Tanida, Hajime*
Journal of Molecular Structure, 641(1), p.71 - 76, 2002/10
The local structure of molten LaCl was investigated by X-ray absorption fine structure(XAFS) of the La K-edge. The nearest La-Cl distance andcoordination number were 2.89 and 7.4 from the curve fitting of the 1st peak in the fourier transform magnitude . The coordination number larger than 6 suggests that the local structure of molten LaCl is not a simple octahedral coordination (LaCl), but 7-fold (LaCl) and/or 8-fold (LaCl) complexes. The 1st La-La distance, of which correlation was observed as a weak 2nd peak in the , was evaluated to be 4.9. It suggests that the distorted corner-sharing connection of the complex species is predominant in the melt, inontrast with molten YCl in which the edge-sharing connection of the 6-fold (YCl) mainly exists.
Okamoto, Yoshihiro; Motohashi, Haruhiko*
Zeitschrift fr Naturforschung, A, 579(5), p.277 - 280, 2002/05
The local structure of molten ZrCl in LiCl-KCl eutectic was investigated by using an X-ray absorption fine structure(XAFS) of the Zr K-absorption edge. The nearest Zr-Cl distance and coordination number from the curve fitting analysis were 2.51 and 5.80.6, respectively. These suggest that a 6-fold coordination (ZrCl) is predominant in the mixture melt.
Hayashi, Hirokazu; Ogawa, Toru; Minato, Kazuo
Proceedings of Japan-Korea Workshop on Nuclear Pyroprocessing, p.301 - 303, 2002/00
The Japan Atomic Energy Research Institute (JAERI) has proposed the concept of the double-strata fuel cycle, which includes transmutation cycle for burning long-lived minor actinides (MA: Np, Am and Cm) besides the current Japanese commercial fuel cycle. A combination of the nitride fuel and pyrochemical reprocessing has been chosen as a candidate for the fuel cycle of the MA burner systems. The behavior of uranium in pyrochemical reprocessing of nitride fuels were discussed using the stability diagrams (potential-log(p(N)) diagrams). The diagrams of U-N-Cl system were constructed with the thermochemical data of uranium compounds including UNCl. Experimental data for dissolution of uranium nitride with oxidizing agents in LiCl-KCl eutectic melt were compared with the diagrams.
Hayashi, Hirokazu; Minato, Kazuo
JAERI-Conf 2001-016, 181 Pages, 2001/12
Applications of molten salts technology to separations and syntheses of materials have been studied eagerly, which would develop new fields of materials science. Research Group for Actinides Science, Department of Materials Science, Japan Atomic Energy Research Institute (JAERI), together with Reprocessing and Recycle Technology Division, Atomic Energy Society of Japan, organized the Workshop on Molten Salts Technology and Computer Simulation at Tokai Research Establishment, JAERI on September 18, 2001. In the workshop eleven lectures were made and lively discussions were there on the bases and applications of the molten salts technology that covered the structure and basic properties of molten salts, the pyrochemical reprocessing technology and the relevant computer simulation.
Ogawa, Toru; Minato, Kazuo
Pure and Applied Chemistry, 73(5), p.799 - 806, 2001/05
no abstracts in English