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Tanaka, Yasunori*; Smirnov, R. D.*; Pigarov, A. Y.*; Takenaga, Hidenobu; Asakura, Nobuyuki; Uesugi, Yoshihiko*; Ono, Noriyasu*
Journal of Nuclear Materials, 415(Suppl.1), p.S1106 - S1110, 2011/08
Times Cited Count：10 Percentile：60.68(Materials Science, Multidisciplinary)Dust can be an important contributor to impurity contamination of the core and scrape-off-layer (SOL) plasmas in tokamak fusion devices. This is the first report about investigation of transport of carbon dust particles in case of JT-60U tokamak using the dust transport code (DUSTT). The DUSTT code takes into account various plasma-dust interaction processes. In the present report, background plasma parameters in JT-60U such as densities and temperatures of electron, ion and neutral atom were computed with the UEDGE code. Three dimensional trajectories, temperature evolution, and radius variation of dust particles launched from different positions at the inner divertor, the outer divertor and the dome structure in JT-60U tokamak were simulated numerically to study dynamics and transport of dust particles there. As a result, the lifetime of dust particles is dependent mainly on the ion density in trajectories in final term.
Tobita, Kenji; Nishio, Satoshi*; Enoeda, Mikio; Nakamura, Hirofumi; Hayashi, Takumi; Asakura, Nobuyuki; Uto, Hiroyasu; Tanigawa, Hiroyasu; Nishitani, Takeo; Isono, Takaaki; et al.
JAEA-Research 2010-019, 194 Pages, 2010/08
JAEA-Research-2010-019-01.pdf:48.47MBJAEA-Research-2010-019-02.pdf:19.4MB
This report describes the results of the conceptual design study of the SlimCS fusion DEMO reactor aiming at demonstrating fusion power production in a plant scale and allowing to assess the economic prospects of a fusion power plant. The design study has focused on a compact and low aspect ratio tokamak reactor concept with a reduced-sized central solenoid, which is novel compared with previous tokamak reactor concept such as SSTR (Steady State Tokamak Reactor). The reactor has the main parameters of a major radius of 5.5 m, aspect ratio of 2.6, elongation of 2.0, normalized beta of 4.3, fusion out put of 2.95 GW and average neutron wall load of 3 MW/m
. This report covers various aspects of design study including systemic design, physics design, torus configuration, blanket, superconducting magnet, maintenance and building, which were carried out increase the engineering feasibility of the concept.
Hoshi, Harutaka*; Wei, Y.-Z.*; Kumagai, Mikio*; Asakura, Toshihide; Morita, Yasuji
Journal of Alloys and Compounds, 444-445, p.663 - 667, 2007/10
Times Cited Count：4 Percentile：33.15(Chemistry, Physical)no abstracts in English
Shimada, Michiya; Campbell, D. J.*; Mukhovatov, V.*; Fujiwara, Masami*; Kirneva, N.*; Lackner, K.*; Nagami, Masayuki; Pustovitov, V. D.*; Uckan, N.*; Wesley, J.*; et al.
Nuclear Fusion, 47(6), p.S1 - S17, 2007/06
Times Cited Count：749 Percentile：99.93(Physics, Fluids & Plasmas)The Progress in the ITER Physics Basis document is an update of the ITER Physics Basis (IPB), which was published in 1999. The IPB provided methodologies for projecting the performance of burning plasmas, developed largely through coordinated experimental, modeling and theoretical activities carried out on today's tokamaks (ITER Physics R&D). In the IPB, projections for ITER (1998 Design) were also presented. The IPB also pointed out some outstanding issues. These issues have been addressed by the International Tokamak Physics Activities (ITPA), which were initiated by the European Union, Japan, Russia and the U.S.A.. The new methodologies of projection and control developed through the ITPA are applied to ITER, which was redesigned under revised technical objectives, but will nonetheless meet the programmatic objective of providing an integrated demonstration of the scientific and technological feasibility of fusion energy.
Lipschultz, B.*; Asakura, Nobuyuki; Bonnin, X.*; Coster, D. P.*; Counsell, G.*; Doerner, R.*; Dux, R.*; Federici, G.*; Fenstermacher, M. E.*; Fundamenski, W.*; et al.
Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03
The work of the ITPA SOL/divertor group is reviewed. The high-n nature of ELMs has been elucidated and new measurements have determined that they carry 10-20% of the ELM energy to the far SOL with implications for ITER limiters and the upper divertor. Analysis of ELM measurements imply that the ELM continuously loses energy as it travels across the SOL. The prediction of ITER divertor disruption power loads have been reduced as a result of finding that the divertor footprint broadens during the thermal quench and that the plasma can lose up to 80% of its thermal energy before the thermal quench (not for VDEs or ITBs). Disruption mitigation through massive gas puffing has been successful at reducing divertor heat loads but estimates of the effect on the main chamber walls indicate 10s of kG of Be would be melted/mitigation. Long-pulse studies have shown that the fraction of injected gas that can be recovered after a discharge decreases with discharge length. The use of mixed materials gives rise to a number of potential processes.
Hoshi, Harutaka*; Wei, Y.*; Kumagai, Mikio*; Asakura, Toshihide; Morita, Yasuji
Recent Advances in Actinide Science, p.596 - 598, 2006/06
Recently, extraction selectivity for trivalent minor actinides (MA = Am and Cm) over lanthanides (Ln) has been found in some extractants containing soft donor, such as S or N, ligands. Kolarik et al. reported that a new N-donor ligand 2,6-bis(5,6-dialkyl-1,2,4-triazine-3-yl)-pyridine (R-BTP) shows high selectivity for MA (III) over Ln(III) [1]. However, protonation of R-BTP results in its acidic hydrolysis in acidic medium. Stability in acidic solution was improved by substitution of long normal chain or branched chain [2]. In this work, separation of MA(III) and Ln(III) from nitric acid solution was studied by using novel R-BTP impregnated resin. Branched R-BTP resin had high affinity for Am from up to 4 M HNO
solution and its distribution coefficient was over 10
.
Hoshi, Harutaka*; Wei, Y.*; Kumagai, Mikio*; Asakura, Toshihide; Morita, Yasuji
Journal of Alloys and Compounds, 408-412, p.1274 - 1277, 2006/02
Times Cited Count：39 Percentile：84.4(Chemistry, Physical)For the development of advanced aqueous reprocessing system, it is one of the most important subjects to separate minor trivalent actinides (MA = Am and Cm). Recently, extraction selectivity for MA(III) over Ln(III) has been found in some extractants containing soft donor, such as S or N, ligands. Kolarik et al. reported that a new N-donor ligand 2,6-bis(5,6-dialkyl-1,2,4-triazine-3-yl)-pyridine (R-BTP) shows high selectivity for MA (III) over Ln(III). The novel silica-based extraction resins were prepared by impregnating some R-BTP molecules into a macroreticular styrene-divinylbenzene copolymer which is immobilized in porous silica particles with a mean diameter of 50 
m. Separation of simulated high level liquid waste solution containing Ln(III) and trace amount of Am(III) was studied. Am(III) was mutually separated from Ln(III) through a packed column with R-BTP impregnating resin, very high decontamination factor (
10
) for Am, and all the elements were recovered quantitatively.
-dimethylformamideKim, S.-Y.; Asakura, Toshihide; Morita, Yasuji; Ikeda, Yasuhisa*
Journal of Alloys and Compounds, 408-412, p.1291 - 1295, 2006/02
Times Cited Count：10 Percentile：54.57(Chemistry, Physical)The electrochemical reactions of UO
(
-diketonato)DMF, UO(trop)DMF and UO(sap)(DMF), (DMF = N,N-dimethylformamide, -diketonate = thenoyltrifluoroacetonate (ttfa), benzoyltrifluoroacetonate (btfa), and dibenzoylmethanate(dbm), trop = tropolonate, and sap = 2-salicylidenaminophenolate) complexes in DMF solution containing tetrabutyl ammonium perchlorate as a supporting electrolyte have been studied with cyclic voltammetry. These uranyl(VI) complexes were found to be quasi-reversibly reduced to U(V) species. The formal redox potentials (E
, 
. ferrocene/ferrocenium) for U(VI)/U(V) couples were determined to be -1.18 V for UO(ttfa)DMF, -1.18 V for UO(btfa)DMF, -1.46 V for UO (dbm)DMF, -1.46 V for UO(trop)DMF, and -1.59 V for UO(sap)(DMF).
Asakura, Toshihide; Kim, S.-Y.; Morita, Yasuji; Ozawa, Masaki*
Journal of Nuclear and Radiochemical Sciences, 6(3), p.267 - 269, 2005/12
An electrolytic extraction (EE) method, i.e. electro-reductive deposition, of Tc from nitric acid aqueous solution was studied for future reprocessing. After 30 min of constant potential electrolysis by carbon electrode at -0.3 V vs. SSE (Standard Silver Electrode), Tc concentration in 3 M nitric acid decreased to 93 % of the initial value, which corresponds to 7 % of deposition. With co-existence of Pd, the value reached to 15 % of deposition equivalent by electrolysis at 
0.0 V vs. SSE for 60 min. An acceleration effect of Pd on Tc deposition (promoter effect) was suggested. The concentration, however, increased to the initial value after further electrolysis and competing re-dissolution of deposited Tc was also suggested. In cyclic voltammetry measurements, it was found that the deposit from Tc-Pd-Ru-Rh solution dissolved easier than that from Pd-Ru-Rh did. In electrolyzed Tc solution, an absorption peak at 482 nm was found. It can be attributed to the complex with nitrite anion, and the complex formation is proposed as one possible mechanism of Tc re-dissolution.
Kim, S.-Y.; Asakura, Toshihide; Morita, Yasuji
Radiochimica Acta, 93(12), p.767 - 770, 2005/12
Times Cited Count：10 Percentile：56.65(Chemistry, Inorganic & Nuclear)Electrochemical and spectroelectrochemical has been used to investigate the behaviour of Neptunium (VI) in concentration 1-8 M HNO solutions. The electrochemical reactions of Np(VI) ions were found to occur quasi-reversibly. The formal redox potentials (E
) for Np(VI)/Np(V) couples were determined to be +0.906, +0.908, +0.909, +0.902, +0.896, +0.895, +0.888, and +0.884 V (vs. Ag/AgCl) for Np(VI) ions in 1, 2, 3, 4, 5, 6, 7, 8 M HNO solutions, respectively. The reduction processes of Np(VI) ions were followed spectroelectrochemically by using an optical transparent thin layer electrode cell. It was found that the absorption spectra measured at the applied potentials from +1.10 to +0.60 V versus Ag/AgCl reference electrode redox couple for Np(VI) in HNO solution have clear isosbestic points. These results indicate that the reduction product of Np(VI) is Np(V), which is considerably stable in HNO solution.
Hoshi, Harutaka*; Wei, Y.*; Kumagai, Mikio*; Asakura, Toshihide; Morita, Yasuji
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10
For the development of nuclear fuel cycle, it is one of the most important tasks to improve reprocessing more economically and efficiently. Especially, to establish the Fast Breeder Reactor (FBR) cycle system for the future, it is strongly desirable to develop a new reprocessing which uses more compact equipments and produces less radioactive wastes compared to the present PUREX process. For this purpose, we have proposed a novel aqueous reprocessing system named ERIX Process to treat spent FBR-MOX fuels. This process consists of (1) Pd removal by selective adsorption using a specific anion exchanger; (2) electrolytic reduction for the valence adjustment of the major actinides including U, Pu, Np and some fission products (FP) such as Tc and Ru; (3) anion exchange separation for the recovery of U, Pu and Np using a new type of anion exchanger, AR-01; and (4) selective separation of long-lived minor actinides (MA = Am and Cm) by extraction chromatography. In this work, MA separation process was studied.
Kim, S.-Y.; Asakura, Toshihide; Morita, Yasuji
JAERI-Conf 2005-007, p.341 - 344, 2005/08
Electrochemistry has been used to investigate the behavior of plutonium(IV) in 1-7 M HNO solutions. These Pu(IV) complexes were found to be reduced quasi-reversibly to Pu(III) species. The formal redox potentials (E) for Pu(IV)/Pu(III) couples were determined to be +0.721, +0.712, +0.706, +0.705, +0.704, 0.694, and +0.696 V (vs. Ag/AgCl(SSE)) for Pu(IV) complexes in 1, 2, 3, 4, 5, 6, 7 M HNO solutions, respectively. These results indicate that the reduction product of Pu(IV) is Pu(III), which is considerably stable in HNO solution.
Kim, S.-Y.; Asakura, Toshihide; Morita, Yasuji; Uchiyama, Gunzo*; Ikeda, Yasuhisa*
Radiochimica Acta, 93(2), p.75 - 81, 2005/02
Times Cited Count：9 Percentile：53.1(Chemistry, Inorganic & Nuclear)no abstracts in English
Hoshi, Harutaka*; Wei, Y.*; Kumagai, Mikio*; Asakura, Toshihide; Morita, Yasuji
Journal of Radioanalytical and Nuclear Chemistry, 262(3), p.601 - 605, 2005/01
Electroreduction of Tc(VII) in nitric acid solution using grassy carbon electrode was studied. The electroreduction was conducted at a constant potential -300 mV (vs. Ag/AgCl) with a potentiostat. It was found that difference of the Tc concentration in the solutions before and after the electrolysis was negligibly small. This means that there were almost no TcO or Tc deposited on the carbon fiber electrode during the electroreduction. Absorption spectra and distribution coefficients obtained by ion-exchange analysis indicated that Tc(VII) was reduced to Tc(IV).
Kim, S.-Y.; Asakura, Toshihide; Morita, Yasuji; Uchiyama, Gunzo*; Ikeda, Yasuhisa*
Journal of Radioanalytical and Nuclear Chemistry, 262(2), p.311 - 315, 2004/11
Times Cited Count：11 Percentile：58.46(Chemistry, Analytical)no abstracts in English
Shimada, Michiya; Campbell, D.*; Stambaugh, R.*; Polevoi, A. R.*; Mukhovatov, V.*; Asakura, Nobuyuki; Costley, A. E.*; Donn
, A. J. H.*; Doyle, E. J.*; Federici, G.*; et al.
Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11
This paper summarises recent progress in the physics basis and its impact on the expected performance of ITER. Significant progress has been made in many outstanding issues and in the development of hybrid and steady state operation scenarios, leading to increased confidence of achieving ITER's goals. Experiments show that tailoring the current profile can improve confinement over the standard H-mode and allow an increase in beta up to the no-wall limit at safety factors 
4. Extrapolation to ITER suggests that at the reduced plasma current of 12MA, high Q 10 and long pulse (1000 s) operation is possible with benign ELMs. Analysis of disruption scenarios has been performed based on guidelines on current quench rates and halo currents, derived from the experimental database. With conservative assumptions, estimated electromagnetic forces on the in-vessel components are below the design target values, confirming the robustness of the ITER design against disruption forces.
Ban, Yasutoshi; Mineo, Hideaki; Asakura, Toshihide; Hotoku, Shinobu; Matsumura, Masakazu; Kim, S.-Y.; Morita, Yasuji
JAERI-Conf 2004-011, p.101 - 102, 2004/07
Experimental studies and numerical analysis on physical and chemical behavior of actinide elements in the solutions of aqueous reprocessing process have been done for compiling technical data that are necessary for evaluating processes such as reprocessing facilities. The objective of the present study is obtaining technical data that are conductive to the construction of reprocessing process that cope with high burn-up nuclear fuel, the evaluation of nuclear fuel cycle, and the drawing up policy on reprocessing.
Asakura, Toshihide; Hotoku, Shinobu; Ban, Yasutoshi; Matsumura, Masakazu*; Kim, S.-Y.; Mineo, Hideaki; Morita, Yasuji
Proceedings of International Conference ATALANTE 2004 Advances for Future Nuclear Fuel Cycles, 5 Pages, 2004/06
In JAERI, PARC process based on PUREX technique has been studied to as the basis of future reprocessing. The key of concept is to obtain the products, U and Pu, within only a single extraction cycle by separating Np and Tc from U and Pu before U/Pu partition. Two flow-sheet tests on the process were performed with 44 GWd/t PWR spent-fuel solutions. It was demonstrated that remaining Np in raffinate from co-extraction could be decreased to 13 % compared to the dissolver solution with increased solvent flow rate and with increased nitric acid concentration of FP scrubbing solution. It was demonstrated that Np separation (selective reduction by n-butyraldehyde) efficiency could be improved from 36 % to 78 % by flow-sheet modification; increasing reductant concentration and scrubbing solution flow rate. The feasibility of the Tc separation technique by high acid scrubbing was demonstrated.
Bcoulet, M.*; Huysmans, G.*; Sarazin, Y.*; Garbet, X.*; Ghendrih, P.*; Rimini, F.*; Joffrin, E.*; Litaudon, X.*; Monier-Garbet, P.*; An, J.-M.*; et al.
Plasma Physics and Controlled Fusion, 45(12A), p.A93 - A113, 2003/12
Times Cited Count：84 Percentile：91.13(Physics, Fluids & Plasmas)no abstracts in English
Asakura, Toshihide; Uchiyama, Gunzo; Hoshi, Harutaka*; Wei, Y.*; Kumagai, Mikio*
Journal of Nuclear Science and Technology, 39(Suppl.3), p.340 - 342, 2002/11
no abstracts in English
