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Journal Articles

Evaluation of uncertainties derived from meteorological forecast inputs in plume directions predicted by atmospheric dispersion simulations

Yoshida, Toshiya; Nagai, Haruyasu; Terada, Hiroaki; Tsuzuki, Katsunori; Sawa, Hiroki*

Journal of Nuclear Science and Technology, 59(1), p.55 - 66, 2022/01

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Atmospheric transport, dispersion, and deposition models (ATDMs) can support decision-making during nuclear emergencies; however, uncertainties in the ATDM results need to be carefully evaluated. To investigate the uncertainties derived from meteorological forecast inputs, we conducted three-day forecast simulations every day for one year with hypothetical releases of radionuclides (one-hour releases every 6 h) from a nuclear facility. The forecast outputs were compared with the analysis outputs during the same period. The difference between the outputs is treated as the uncertainty in the forecasts and is represented as an angle based on the discrepancy in the plume directions between the analysis and forecast outputs. Using meteorological inputs made by Japan Meteorological Agency, the discrepancy angle (Ang) increased by approximately 10$$^circ$$ per day on an annual average basis. Meanwhile, the Ang values were occasionally 4-5 times higher than the annual average during short time periods. Since the Ang time series show seasonal and diurnal changes, the statistical characteristics likely depend on the geographical and meteorological conditions, as well as the types of meteorological inputs. Additionally, a main factor in the uncertainty is the wind-direction difference between the analysis and forecast outputs on scales of more than or less than 100 km.

Journal Articles

Large-eddy simulation of plume dispersion in the central district of Oklahoma City by coupling with a mesoscale meteorological simulation model and observation

Nakayama, Hiromasa; Takemi, Tetsuya*; Yoshida, Toshiya

Atmosphere (Internet), 12(7), p.889_1 - 889_15, 2021/07

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

Contaminant gas dispersion within urban area resulting from accidental or intentional release is of great concern to public health and social security. When estimating plume dispersion in a built-up urban area under real meteorological conditions by computational fluid dynamics (CFD), a crucial issue is how to prescribe the model input conditions. There are typically two approaches: using the outputs of a meso-scale meteorological simulation (MMS) model and meteorological observations (OBS). However, the influence of the different approaches on the simulation results have not been fully demonstrated. In this study, we conducted large-eddy simulations (LESs) of plume dispersion in the urban central district under real meteorological conditions by coupling with a MMS model and OBS obtained at a single stationary point, and evaluated the two different coupling simulations in comparison with the field experimental data. The LES-MMS coupling showed better performance than the LES-OBS one. However, the latter one also showed a reasonable performance comparable to the acceptance criteria on the model prediction within a factor of two of the experimental data. These facts indicate that the approach of using observations at a single stationary point still has enough potential to drive CFD models for plume dispersion under real meteorological conditions.

Journal Articles

Toward development of a framework for prediction system of local-scale atmospheric dispersion based on a coupling of LES-database and on-site meteorological observation

Nakayama, Hiromasa; Yoshida, Toshiya; Terada, Hiroaki; Kadowaki, Masanao

Atmosphere (Internet), 12(7), p.899_1 - 899_16, 2021/07

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

In this study, first, we conducted meteorological observations by a Doppler LiDAR and simple plume release experiments by a mist spraying system at the site of Japan Atomic Energy Agency. Then, we developed a framework for prediction system of local-scale atmospheric dispersion based on a coupling of large-eddy simulation (LES) database and on-site meteorological observation. The LES-database was also created by pre-calculating high-resolution turbulent flows in the target site at mean wind directions of class interval. We provided the meteorological observed data with the LES database in consideration of building conditions and calculated three-dimensional distribution of the plume by a Lagrangian dispersion model. Compared to the instantaneous shot of the plume taken by a digital camera, it was shown that the mist plume transport direction was accurately simulated. It was concluded that our proposed framework for prediction system based on a coupling of LES-database and on-site meteorological observation is effective.

Journal Articles

Spatial characteristics of turbulent organized structures within the roughness sublayer over idealized urban surface with obstacle-height variability

Yoshida, Toshiya; Takemi, Tetsuya*

Environmental Fluid Mechanics, 21(1), p.129 - 154, 2021/02

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

The effects of obstacle-height variability on spatial characteristics of turbulent organized structures were investigated with the use of a large-eddy simulation technique for airflows over roughness obstacles. Two-types simulation cases were considered: one is uniform-height case in which uniform-height obstacles are aligned in streamwise direction, the other is height-variability case with staggered higher-height obstacles. Streaky structures were observed above the roughness sublayer (RSL) regardless of obstacle-height variability. When obstacles are uniform, flow fields within the RSL contain low- and high-speed regions along the streamwise streets. When obstacle heights vary, airflow within the RSL collides with the front-facing surfaces of taller obstacles. The statistical features of low- and high-speed structures were examined using the spatial correlations of flow fields centering on strong ejection and sweep, respectively. The ejection- and sweep-center spatial correlations extend forward and backward in the streamwise direction, respectively. Length scales were obtained from the ejection-center and sweep-center spatial correlations. The streamwise lengths vary significantly below the canopy height when obstacles are uniform. In contrast, the streamwise length scales remain nearly constant when obstacle heights vary. The horizontal aspect ratios below the canopy heights indicate that turbulent organized structures over obstacles with variable heights are more isotropic than those over uniform obstacles. The inclination angles of the organized structures were also deduced using the spatial correlations. The angles of sweep-center structures are steeper than those of the ejection-center structures. The angles of the ejection-center structures at the RSL heights become larger with obstacle-height variability.

Journal Articles

Development of a combined LES/RANS model to predict atmospheric dispersion over urban areas

Yoshida, Toshiya; Nakayama, Hiromasa

Nihon Keisan Kogakkai Rombunshu (Internet), 2020, p.20200013_1 - 20200013_9, 2020/07

To quickly and accurately predict the dispersion of hazardous materials released over urban areas, we propose a combined method in which dispersion fields are simulated using a Reynolds-averaged Navier-Stokes model with pre-calculated flow fields from a large-eddy simulation (LES) model. First, the combined model is conducted for dispersion in a simple street canyon. The results of the combined model are compared with those of a wind-tunnel experiment to adjust empirical parameters in the turbulent scalar flux. The horizontal dispersion fields predicted in the combined model with the best parameters are well consistent with those calculated from our LES model. We then apply the combined model to predict the scalar dispersion over a real urban area. The combined model well predicts the results obtained from the LES model with less calculation time. Therefore, we find that the combined model is potentially effective for emergency response to hazardous-material release over urban areas.

Journal Articles

Bipartite magnetic parent phases in the iron oxypnictide superconductor

Hiraishi, Masatoshi*; Iimura, Soshi*; Kojima, Kenji*; Yamaura, Junichi*; Hiraka, Haruhiro*; Ikeda, Kazutaka*; Miao, P.*; Ishikawa, Yoshihisa*; Torii, Shuki*; Miyazaki, Masanori*; et al.

Nature Physics, 10(4), p.300 - 303, 2014/04

 Times Cited Count:94 Percentile:96.38(Physics, Multidisciplinary)

Journal Articles

Instrumental upgrades of the RIXS spectrometer at BL11XU at SPring-8

Ishii, Kenji; Jarrige, I.*; Yoshida, Masahiro*; Ikeuchi, Kazuhiko*; Inami, Toshiya; Murakami, Yoichi*; Mizuki, Junichiro

Journal of Electron Spectroscopy and Related Phenomena, 188, p.127 - 132, 2013/06

 Times Cited Count:12 Percentile:62.69(Spectroscopy)

Journal Articles

Development of a hand-held fast neutron survey meter

Yoshida, Tadayoshi; Tsujimura, Norio; Yamano, Toshiya*

Radiation Protection Dosimetry, 146(1-3), p.72 - 75, 2011/07

 Times Cited Count:2 Percentile:20.43(Environmental Sciences)

A neutron survey meter with a ZnS(Ag) scintillator to measure recoil protons was built. The detection probe weighs approximately 2 kg, therefore providing us with true portability. Performance tests exhibited satisfactory neutron dosimetry characteristics in unmoderated or lightly moderated fission neutron fields and in particular work environments at a MOX fuel facility. This new survey meter will augment a routine of neutron monitoring that is inconveniently being carried out by moderator-based neutron survey meters.

Journal Articles

Polarization-analyzed resonant inelastic X-ray scattering of the orbital excitations in KCuF$$_3$$

Ishii, Kenji; Ishihara, Sumio*; Murakami, Yoichi*; Ikeuchi, Kazuhiko*; Kuzushita, Kaori*; Inami, Toshiya; Owada, Kenji; Yoshida, Masahiro; Jarrige, I.; Tatami, Naka*; et al.

Physical Review B, 83(24), p.241101_1 - 241101_4, 2011/06

 Times Cited Count:21 Percentile:68.08(Materials Science, Multidisciplinary)

Journal Articles

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.

Journal Articles

Development of a hand-held fast neutron survey meter

Yoshida, Tadayoshi; Tsujimura, Norio; Yamano, Toshiya*

Proceedings of 3rd Asian and Oceanic Congress on Radiation Protection (AOCRP-3) (CD-ROM), 3 Pages, 2010/05

A neutron survey meter with a ZnS(Ag) scintillator to measure recoil protons was built. The detection probe weighs approx. 2 kg, therefore providing us with true portability. Performance tests exhibited satisfactory neutron dosimetry characteristics at unmoderated or lightly moderated fission neutron fields and in particular work environments at a MOX fuel facility. This new survey meter will augment a routine neutron monitoring inconveniently being carried out by moderator-based neutron survey meters.

Journal Articles

The Design of the neutron total scattering spectrometer for hydrogenous materials at J-PARC-JSNS

Suzuya, Kentaro; Kameda, Yasuo*; Otomo, Toshiya*; Yoshida, Koji*; Ito, Keiji*; Fukunaga, Toshiharu*; Misawa, Masakatsu*

Journal of Neutron Research, 13(1-3), p.123 - 128, 2005/03

The design, performance, philosophy, lessons learned and advantages of the neutron total scattering spectrometer for hydrogenous materials, FAST, under consideration for the J-PARC-JSNS, are described. In particular, novel instrumentation concept such as the small fractional scattered neutron flight path, $$gamma$$= L$$_{2}$$/(L$$_{1}$$+L$$_{2}$$), where L$$_{1}$$ is the incident flight path, moderator to sample, L$$_{2}$$ is the scattered neutron flight path from sample to detector, is presented and their expected performance at the JSNS is considered.

Journal Articles

Development of Portable Neutron Ambient Dose Equivalent Rate Meter Using Two Li-glass Scintillators Embedded in Stacked Polyethylene Cylinders

Tsujimura, Norio; Yoshida, T.; Yamano, Toshiya*; Matsubara, S.*

Saikuru Kiko Giho, (26), p.87 - 89, 2005/00

The concept of air transport of A Type package containing nuclear fuel materials according to the nuclear disaster countermeasures law, and the experience of a transportation of plutonium solution from France are shown.

Journal Articles

Evaluation of energy responses for neutron dose-equivalent meters made in Japan

Saegusa, Jun; Yoshizawa, Michio; Tanimura, Yoshihiko; Yoshida, Makoto; Yamano, Toshiya*; Nakaoka, Hiroshi*

Nuclear Instruments and Methods in Physics Research A, 516(1), p.193 - 202, 2004/01

 Times Cited Count:12 Percentile:64.04(Instruments & Instrumentation)

Energy responses of three types of Japanese rem counters were evaluated by Monte Carlo simulations and measurements. The energy responses for thermal neutrons, monoenergetic neutrons with energies up to 15.2 MeV were evaluated as well as for neutrons from such radionuclide sources as $$^{252}$$Cf. The calculated results were corroborated with the measured ones. Angular dependence of the response and dose equivalent response was also evaluated. As a result, the reliable energy responses were obtained by careful simulations of the proportional counter, moderator and absorber of the rem counters. Furthermore, discussions were made about the relationship between pressure of counting gas and sensitivity of the rem counter. By using the obtained responses, relations of predicted readings of the rem counters and true dose equivalent were studied for various workplace spectra.

Oral presentation

Development of a new portable neutron dose equivalent rate meter based on the recoil proton measurements

Yoshida, Tadayoshi; Tsujimura, Norio; Yamano, Toshiya*

no journal, , 

no abstracts in English

Oral presentation

RIXS of Y1-xCaxVO$$_{3}$$

Ikeuchi, Kazuhiko; Yoshida, Masahiro; Jarrige, I.; Ishii, Kenji; Inami, Toshiya; Mizuki, Junichiro; Bizen, Daisuke*; Murakami, Yoichi*; Miyasaka, Shigeki*; Fujioka, Jun*; et al.

no journal, , 

no abstracts in English

Oral presentation

Polarization-analyzed RIXS for orbital excitaions in KCuF$$_3$$

Ishii, Kenji; Ishihara, Sumio*; Murakami, Yoichi*; Ikeuchi, Kazuhiko*; Kuzushita, Kaori*; Owada, Kenji; Inami, Toshiya; Yoshida, Masahiro; Jarrige, I.; Tatami, Naka*; et al.

no journal, , 

no abstracts in English

Oral presentation

X-ray Raman scattering experiment on the valence transition of EuPd$$_2$$Si$$_2$$

Inami, Toshiya; Ishii, Kenji; Jarrige, I.; Yoshida, Masahiro; Mitsuda, Akihiro*

no journal, , 

Oral presentation

Development of a hand-held fast neutron survey meter

Yoshida, Tadayoshi; Tsujimura, Norio; Yamano, Toshiya*

no journal, , 

no abstracts in English

Oral presentation

X-ray Raman scattering study on the valence transition of EuPd$$_2$$Si$$_2$$

Inami, Toshiya; Ishii, Kenji; Yoshida, Masahiro; Mitsuda, Akihiro*; Taguchi, Munetaka*; Shin, S.*

no journal, , 

no abstracts in English

26 (Records 1-20 displayed on this page)