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Journal Articles

Atmospheric-dispersion database system that can immediately provide calculation results for various source term and meteorological conditions

Terada, Hiroaki; Nagai, Haruyasu; Tanaka, Atsunori*; Tsuzuki, Katsunori; Kadowaki, Masanao

Journal of Nuclear Science and Technology, 57(6), p.745 - 754, 2020/06

 Times Cited Count:3 Percentile:76.41(Nuclear Science & Technology)

We have estimated source term and analyzed processes of atmospheric dispersion of radioactive materials released during the Fukushima Daiichi Nuclear Power Station (FDNPS) accident by the Worldwide version of System for Environmental Emergency Dose Information. On the basis of this experience, we developed an dispersion calculation method that can respond to various needs in a nuclear emergency and provide useful information for emergency-response planning. By this method, if a release point is known, it is possible to immediately obtain the prediction results by applying provided source term to the database of dispersion-calculation results prepared in advance. With this function, it is easy to compare results by applying various source term with monitoring data, and to find out the optimum source term, which was applied for the source term estimation of the FDNPS accident. By performing this calculation with past meteorological-analysis data, it is possible to immediately get dispersion-calculation results for various source term and meteorological conditions. This database can be used for pre-accident planning, such as optimization of a monitoring plan and understanding of events to be supposed in considering emergency countermeasures.

JAEA Reports

Development of a calculation method for atmospheric dispersion database that can immediately provide calculation results for any source term and period from hindcast to short-term forecast (Joint research)

Terada, Hiroaki; Tsuzuki, Katsunori; Kadowaki, Masanao; Nagai, Haruyasu; Tanaka, Atsunori*

JAEA-Data/Code 2017-013, 31 Pages, 2018/01

JAEA-Data-Code-2017-013.pdf:9.52MB

We developed an atmospheric dispersion calculation method that can respond to various needs for dispersion prediction in nuclear emergency and prepare database of information useful for planning of emergency response. In this method, it is possible to immediately get the prediction results for provided source term by creating a database of dispersion calculation results without specifying radionuclides, release rate and period except release point. By performing this calculation steadily along with meteorological data update, it is possible to immediately get calculation results for any source term and period from hindcast to short-term forecast. This function can be used for pre-accident planning such as optimization of monitoring plan and understanding events to be supposed for emergency response. Spatiotemporal distribution of radioactive materials reproduced by source term estimated inversely from monitoring based on this method is useful as a supplement to monitoring.

Journal Articles

Particle transport of LHD

Tanaka, Kenji*; Kawahata, Kazuo*; Tokuzawa, Tokihiko*; Akiyama, Tsuyoshi*; Yokoyama, Masayuki*; Shoji, Mamoru*; Michael, C. A.*; Vyacheslavov, L. N.*; Murakami, Sadayoshi*; Wakasa, Arimitsu*; et al.

Fusion Science and Technology, 58(1), p.70 - 90, 2010/07

 Times Cited Count:17 Percentile:78.18(Nuclear Science & Technology)

Particle confinement processes were studied in detail on LHD. Diffusion coefficients (D) and convection velocities (V) were estimated from density modulation experiments. The magnetic configuration and collisionality were widely scanned in order to investigate parameter dependences of D and V. In order to study the effect of the magnetic configuration, magnetic axis positions (R$$_{ax}$$) were scanned from 3.5 m to 3.9 m. This scan changed the magnetic ripples quite significantly, enabling the effects of neoclassical properties on measured values to be widely elucidated. Dependences of electron temperature (T$$_{e}$$) and helically trapped normalized collsionality ($$nu$$$$_{h}^{*}$$), where $$nu$$$$_{h}^{*}$$=1 indicates a rough boundary between the 1/$$nu$$ and plateau regimes, were examined using the heating power scan of neutral beam injection (NBI). It was found out that generally larger (or smaller) contributions of neoclassical transport resulted in more hollow (or peaked) density profiles. The larger neoclassical contribution was found to be situated at a more outwardly shifted R$$_{ax}$$ for the same T$$_{e}$$, and higher T$$_{e}$$ or lower $$nu$$$$_{h}^{*}$$ at each R$$_{ax}$$. However, it is to be noted that R$$_{ax}$$=3.5 m showed different characteristics from these trends in that this case showed a more peaked density profile at higher T$$_{e}$$.

Journal Articles

Dynamics of ion internal transport barrier in LHD heliotron and JT-60U tokamak plasmas

Ida, Katsumi*; Sakamoto, Yoshiteru; Yoshinuma, Mikiro*; Takenaga, Hidenobu; Nagaoka, Kenichi*; Hayashi, Nobuhiko; Oyama, Naoyuki; Osakabe, Masaki*; Yokoyama, Masayuki*; Funaba, Hisamichi*; et al.

Nuclear Fusion, 49(9), p.095024_1 - 095024_9, 2009/09

 Times Cited Count:26 Percentile:72.4(Physics, Fluids & Plasmas)

Dynamics of ion internal transport barrier (ITB) formation and impurity transport both in the Large Helical Device (LHD) heliotron and JT-60U tokamak are described. Significant differences between heliotron and tokamak plasmas are observed. The location of the ITB moves outward during the ITB formation regardless of the sign of magnetic shear in JT-60U and the ITB becomes more localized in the plasma with negative magnetic shear. In LHD, the low Te/Ti ratio ($$<$$ 1) of the target plasma for the high power heating is found to be necessary condition to achieve the ITB plasma and the ITB location tends to expand outward or inward depending on the condition of the target plasmas. Associated with the formation of ITB, the carbon density tends to be peaked due to inward convection in JT-60U, while the carbon density becomes hollow due to outward convection in LHD. The outward convection observed in LHD contradicts the prediction by neoclassical theory.

Journal Articles

Dynamic transport study of the plasmas with transport improvement in LHD and JT-60U

Ida, Katsumi*; Sakamoto, Yoshiteru; Inagaki, Shigeru*; Takenaga, Hidenobu; Isayama, Akihiko; Matsunaga, Go; Sakamoto, Ryuichi*; Tanaka, Kenji*; Ide, Shunsuke; Fujita, Takaaki; et al.

Nuclear Fusion, 49(1), p.015005_1 - 015005_7, 2009/01

 Times Cited Count:13 Percentile:49.07(Physics, Fluids & Plasmas)

Transport analysis during the transient phase of heating (a dynamic transport study) applied to the plasma with internal transport barriers (ITBs) in the Large Helical Device (LHD) heliotron and the JT-60U tokamak is described. In the dynamic transport study the time of transition from the L-mode plasma to the ITB plasma is clearly determined by the onset of flattening of the temperature profile in the core region and a spontaneous phase transition from a zero curvature ITB (hyperbolic tangent shaped ITB) or a positive curvature ITB (concaved shaped ITB) to a negative curvature ITB (convex shaped ITB) and its back-transition are observed. The flattening of the core region of the ITB transition and the back-transition between a zero curvature ITB and a convex ITB suggest the strong interaction of turbulent transport in space.

Journal Articles

Experimental investigation of particle pinch associated with turbulence in LHD heliotron and JT-60U tokamak plasmas

Tanaka, Kenji*; Takenaga, Hidenobu; Muraoka, Katsunori*; Michael, C.*; Vyacheslavov, L. N.*; Yokoyama, Masayuki*; Yamada, Hiroshi*; Oyama, Naoyuki; Urano, Hajime; Kamada, Yutaka; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

Comparative studies were carried out in LHD heliotron and JT-60U tokamak plasmas to elucidate the most essential parameter(s) for control of density profiles in toroidal systems. A difference in the collisionality dependence was found between the two devices. In LHD, the density peaking factor decreased with decrease of the collisionality at the magnetic axis position (R$$_{rm au}$$) 3.6 m, while the density peaking factor gradually increased with a decreased of collisionality at R$$_{rm au}$$ = 3.5 m. On the other hand, in JT-60U, the density peaking factor clearly increased with a decrease of the collisionality. The difference in the collisionality dependence between R$$_{rm au}$$ = 3.5 and R$$_{rm au}$$ = 3.6 m is likely due to the contribution of the anomalous transport. At R$$_{rm au}$$ = 3.5 m, larger anomalous transport caused a similar collisionality dependence. Change of the fluctuation property was observed with different density profiles in the plasma core region on both devices. In JT-60U, the increase of the radial coherence was observed with higher density peaking profile suggesting enhanced diffusion and inward directed pinch. For a magnetic axis positions (R$$_{rm au}$$) at 3.6 m in LHD, the increase of the fluctuation power with an increase in P$$_{rm NB}$$ was observed for a hollow density profile suggesting an increase on diffusion due to anomalous processes. Change of density profiles from peaked to hollow indicates change in the convection direction. This is due to increase in neoclassical processes. The reduction of the density peaking factor with increase of P$$_{rm NB}$$ in LHD is partly due to the neoclassical effect and partly due to the anomalous effect.

Journal Articles

Particle transport and fluctuation characteristics around the neoclassically optimized configurations in LHD

Tanaka, Kenji*; Michael, C.*; Vyacheslavov, L. N.*; Yokoyama, Masayuki*; Murakami, Sadayoshi*; Wakasa, Arimitsu*; Takenaga, Hidenobu; Muraoka, Katsunori*; Kawahata, Kazuo*; Tokuzawa, Tokihiko*; et al.

Plasma and Fusion Research (Internet), 3, p.S1069_1 - S1069_7, 2008/08

Density profiles in LHD were measured and particle transport coefficients were estimated from density modulation experiments in LHD. The dataset of different magnetic axis, toroidal magnetic filed and heating power provided data set of widely scanned neoclassical transport. At minimized neoclassical transport configuration ($$R$$$$_{rm ax}$$ = 3.5 m, $$B$$$$_{rm t}$$ = 2.8 T) showed peaked density profile. Its peaking factor increased gradually with decrease of collisional frequency. This is a similar result observed in JT-60U. At other configuration, peaking factor reduced with decrease of collsional frequency. Data set showed that larger contribution of neoclassical transport produced hollowed density profile. Comparison between neoclassical and estimated particle diffusivity showed different minimum condition. Clear difference of spatial profile of turbulence was observed between hollowed and peaked density profiles. Major part of fluctuation existed in the unstable region of ion temperature gradient mode.

Journal Articles

Comparisons of density profiles in JT-60U tokamak and LHD helical plasmas with low collisionality

Takenaga, Hidenobu; Tanaka, Kenji*; Muraoka, Katsunori*; Urano, Hajime; Oyama, Naoyuki; Kamada, Yutaka; Yokoyama, Masayuki*; Yamada, Hiroshi*; Tokuzawa, Tokihiko*; Yamada, Ichihiro*

Nuclear Fusion, 48(7), p.075004_1 - 075004_11, 2008/07

 Times Cited Count:28 Percentile:73.66(Physics, Fluids & Plasmas)

In order to understand particle transport systematically in toroidal plasmas, electron density profiles were compared in JT-60U tokamak and LHD helical plasmas with low collisionality. Peakedness of density profiles increased with decreasing collisionality in ELMy H-mode plasmas of JT-60U, when the collisionality at half the minor radius was in the collisionless regime. Collisionality dependence of density profiles in LHD plasmas was similar to that in JT-60U plasmas in the same collisionality regime, when neoclassical transport was suppressed by geometrical optimization. On the other hand, in the LHD plasmas having relatively larger neoclassical transport than that in the above case, peakedness of density profiles decreased with decreasing collisionality. Neoclassical transport enhanced by the non-axisymmetric effect significantly affected density profiles with low collisionality in LHD plasmas. Density profiles in LHD plasmas tended to approach those in JT-60U, which are dominated by anomalous transport, as the contribution of neoclassical transport was reduced.

Oral presentation

Particle transport in LHD and comparisons with tokamaks

Tanaka, Kenji*; Takenaga, Hidenobu; Muraoka, Katsunori*; Urano, Hajime; Michael, C.*; Vyacheslavov, L. N.*; Yokoyama, Masayuki*; Yamagishi, Osamu*; Murakami, Sadayoshi*; Wakasa, Arimitsu*; et al.

no journal, , 

In order to understand particle transport systematically in toroidal plasmas, a density profile was compared in LHD helical and JT-60U tokamak plasmas. In large tokamak devices such as JT-60U, the density profile is always peaked and the peaked density profile can be explained based on outward diffusion flux and inward convection flux driven by microinstability. A peaking factor of the density profile was increased with decreasing collisionality. On the other hand, the density profile was changed from peaked one to hollow one depending on discharge conditions in LHD. The hollow density profile can be explained based on outward convection flux driven by neoclassical transport and inward diffusion flux driven by microinstability. In the configuration with a small helical ripple, where the neoclassical transport is reduced, the density profile tended to be peaked and dependence of the peaking factor on the collisionality was similar to that in tokamak plasmas. These results indicated that magnetic field ripple and microinstability are some of the main mechanisms determining the density profile.

Oral presentation

Electron density profile and turbulence in toroidal plasmas

Tanaka, Kenji*; Takenaga, Hidenobu; Muraoka, Katsunori*; Michael, C.*; Vyacheslavov, L. N.*; Yokoyama, Masayuki*; Yamada, Hiroshi*; Murakami, Sadayoshi*; Wakasa, Arimitsu*; Kawahata, Kazuo*; et al.

no journal, , 

In order to understand mechanisms for determining density profiles in toroidal plasmas, density profiles were compared in JT-60U tokamak and LHD helical plasmas. Transport theory indicates that neoclassical transport is enhanced in helical plasmas with low collisionality due to helical ripple. In JT-60U plasmas, density peaking increased with decreasing the collisionality. In LHD plasmas for magnetic axis (Rax) of 3.5m with small effective helical ripple, density peaking slightly increased with decreasing the collisionality as similar to that in tokamak plasmas. On the other hand, in LHD plasmas for Rax$$>$$3.6m with relatively large effective helical ripple, density profile became hollow as the collisionality decreased. Different turbulence structures are observed for Rax=3.5m and Rax=3.6m in LHD plasmas. Turbulence propagated towards electron diamagnetic direction for Rax=3.5m and towards ion diamagnetic direction for Rax=3.6m. This difference could be related to the difference of density profiles, as well as difference of neoclassical transport. Furthermore, when density decreased in the core region due to increase of electron temperature, it was found that turbulence was first modified in the edge region and then in the core region.

Oral presentation

Response of turbulence under change of density profiles in toroidal devices

Tanaka, Kenji*; Takenaga, Hidenobu; Muraoka, Katsunori*; Michael, C.*; Vyacheslavov, L. N.*; Mishchenko, A.*; Yokoyama, Masayuki*; Yamada, Hiroshi*; Oyama, Naoyuki; Urano, Hajime; et al.

no journal, , 

Comparative studies were carried out in LHD heliotron and JT-60U tokamak plasmas to elucidate effects of turbulence transport on density profiles in toroidal systems. A difference in the collisionality dependence was found between the two devices. In LHD, the density peaking factor decreased with decrease of the collisionality at the magnetic axis position (R$$_{ax}$$) of 3.6 m. On the other hand, in JT-60U, the density peaking factor clearly increased with a decrease of the collisionality. For R$$_{ax}$$=3.6 m in LHD, the increase of the fluctuation power with an increase in P$$_{NB}$$ was observed for a hollow density profile suggesting an increase on diffusion due to anomalous processes. In JT-60U, the increase of the radial coherence was observed with higher density peaking profile suggesting enhanced diffusion and inward directed pinch. The effects of curvature pinch on density profiles were also investigated in both devices. The curvature pinch produces a peaked density profile in JT-60U and a hollow density profile in LHD depending on their magnetic shear. However, these effects were too small to explain the density profiles observed in both devices.

Oral presentation

Density profiles and turbulence in tokamak and helical plasmas

Tanaka, Kenji*; Takenaga, Hidenobu; Muraoka, Katsunori*; Michael, C.*; Vyacheslavov, L. N.*

no journal, , 

In order to understand transport properties in toroidal plasmas, density profiles were compared in tokamak and helical plasmas. The density profiles tended to be peaked as the contribution of anomalous transport increases in JT-60U and LHD plasmas. In JT-60U ELMy H-mode plasmas and LHD plasmas at magnetic axis Rax=3.5 m, where the contribution of anomalous transport is large, a peaking factor of the density profile increased with decreasing normalized collisionality $$nu_{b}$$*. In LHD plasmas at Rax=3.6 m, where the contribution of anomalous transport is small, this factor decreased with decreasing $$nu_{b}$$* and the density profile became hollow one. In JT-60U ELMy H-mode plasmas, coherence increased as the density profile becomes peaked one. On the other hand, when the peaking factor of the density profile decreased with increasing heating power in LHD plasmas at Rax=3.6 m, anomalous diffusion increased due to increase in turbulence level and the direction of the convection velocity changed from inward to outward due to neoclassical transport.

Oral presentation

Spectroscopic measurement of LX-rays emitted by transuranium elements using TES microcalorimeter

Maeda, Makoto*; Maehata, Keisuke*; Iyomoto, Naoko*; Ishibashi, Kenji*; Takasaki, Koji; Nakamura, Keisuke; Aoki, Katsunori; Mitsuda, Kazuhisa*; Tanaka, Keiichi*

no journal, , 

no abstracts in English

Oral presentation

The Spectroscopy of LX-rays emitted from transuranium element using transition edge sensor microcalorimeter

Nakamura, Keisuke; Maeda, Makoto*; Aoki, Katsunori; Yasumune, Takashi; Takasaki, Koji; Maehata, Keisuke*; Iyomoto, Naoko*; Ishibashi, Kenji*; Mitsuda, Kazuhisa*; Tanaka, Keiichi*

no journal, , 

no abstracts in English

Oral presentation

Measuring of capping phenomena in powder compaction process using X-ray computed tomography

Suzuki, Michitaka*; Tanaka, Yutaka*; Iimura, Kenji*; Satone, Hiroshi*; Ishii, Katsunori

no journal, , 

The capping phenomenon is one of the important causes of the powder molding trouble. The research of the capping such as how to occur and what kind of condition related to the phenomena is not cleared still now. The packing particles for our tests were 20-150um spherical Alumina granules and the sieved narrow sized granules were also used. The compression tests were performed by a material-tester. The capping region could be detected from X-ray computed tomographic images and the depth of capping area was measured. It's clear that the capping phenomena are easy to occur at small compression displacement in the case of wider size distributed granules 20-150um. It comes from the higher adhesion force between fine powder and the piston or the mold surface. The depth of capping is decreasing with the increase in displacement. In the conclusion, the capping phenomena can be prevented to use coarser mono-sized granules for compression molding.

Oral presentation

Response of turbulence associated with the change of density profiles in LHD heliotron and JT-60U tokamak

Tanaka, Kenji*; Takenaga, Hidenobu; Muraoka, Katsunori*; Yoshida, Maiko; Michael, C.*; Vyacheslavov, L. N.*; Mikkelsen, D. R.*; Yokoyama, Masayuki*; Oyama, Naoyuki; Urano, Hajime; et al.

no journal, , 

Density profile and turbulence was compared in JT-60U tokamak and LHD heliotron. Density peaking increases with decrease of collisionality in JT-60U. Density gradient predicted from zero flux condition agrees within factor 2 for Te/Ti=1, but large discrepancies are found for Te/Ti $$<$$ =0.5. In LHD, peaked profile and increase of density peaking with decrease of collisionality are found in strong magnetic hill configuration (Rax = 3.5 m). Hollowed-peaked density profile and increase of density peaking with increase of collisionality are found in weak magnetic hill configuration (Rax = 3.6 m). Fluctuation is localized in core gradient region and edge gradient region. Density gradient predicted from zero flux condition are compared. Then both cases agrees the sign and absolute values within factor 2.

Oral presentation

Comparison study of turbulence driven particle transport study by gyrokinetic linear/quasi linear simulation in JT-60U and LHD

Tanaka, Kenji*; Takenaga, Hidenobu; Muraoka, Katsunori*; Oyama, Naoyuki; Yoshida, Maiko; Mikkelsen, D. R.*; Michael, C. A.*; Vyacheslavov, L. N.*

no journal, , 

Density profile and turbulence was compared in JT-60U tokamak and LHD heliotron. Density peaking increases with decrease of collisionality in JT-60U. Density gradient predicted from zero flux condition agrees within factor 2 for Te/Ti=1, but large discrepancies are found for Te/Ti $$<$$ = 0.5. In LHD, peaked profile and increase of density peaking with decrease of collisionality are found in strong magnetic hill configuration (Rax = 3.5 m). Hollowed-peaked density profile and increase of density peaking with increase of collisionality are found in weak magnetic hill configuration (Rax = 3.6 m). Fluctuation is localized in core gradient region and edge gradient region. Density gradient predicted from zero flux condition are compared. Then both cases agrees the sign and absolute values within factor 2.

Oral presentation

Study of high resolution spectroscopy of LX-rays emitted from TRU using TES microcalorimeter

Nakamura, Keisuke; Aoki, Katsunori; Takasaki, Koji; Maeda, Makoto*; Maehata, Keisuke*; Iyomoto, Naoko*; Ishibashi, Kenji*; Mitsuda, Kazuhisa*; Tanaka, Keiichi*

no journal, , 

no abstracts in English

Oral presentation

Development of the Integrated System for Repository Engineering (ISRE), 1; Conceptual design of the ISRE utilizing CIM technology

Sugita, Yutaka; Chijiwa, Tatsunori; Honda, Akira; Shibata, Masahiro; Kawaguchi, Tatsuya; Maekawa, Keisuke; Hatanaka, Koichiro; Ebashi, Takeshi; Semba, Takeshi; Makino, Hitoshi

no journal, , 

This paper reports on the development of ISRE (the Integrated System for Repository Engineering), as a knowledge management tool on repository design and engineering technology, which manages and inherits the information and knowledge of each phase of the disposal project of radioactive waste lasting around 100 years, and which also enables reasonable design of the repository by using accumulated and integrated information. The content of this paper is the conceptual design of the ISRE utilizing CIM (Computer Information Modeling) technology.

Oral presentation

R&D of lithium target and test facilities for the fusion neutron source

Wakai, Eiichi; Kondo, Hiroo; Kanemura, Takuji; Hirakawa, Yasushi; Furukawa, Tomohiro; Kikuchi, Takayuki; Ito, Yuzuru*; Hoashi, Eiji*; Yoshihashi, Sachiko*; Horiike, Hiroshi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Study on in-vessel coolability by decay heat removal systems in sodium-cooled fast reactors; Preliminary investigation of experimental requirements for a sodium test facility with different in-vessel direct heat exchangers

Tanaka, Masaaki; Amano, Katsunori*; Ishikawa, Nobuyuki; Nabeshima, Kunihiko; Ohshima, Hiroyuki; Oyama, Kazuhiro*; Nakamura, Hironori*; Ichihara, Takashi*

no journal, , 

In the investigation of measures to enhance safety of a sodium cooled fast reactor, conceptual design of a test apparatus for sodium experiment named AtheNa-RV/DHRS has been conducted at JAEA in corporation with MFBR for feasibility study of the diverse systems for decay heat removal under various operating conditions including the sever accident. Important thermal-hydraulic problems to be studied using AtheNa-RV/DHRS and significant points in the design of it were investigated based on knowledge from the existing investigations regarding decay heat removal systems and results of the preliminary numerical simulation of AtheNa-RV/DHRS in temporal design.

21 (Records 1-20 displayed on this page)