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Journal Articles

Effects of human model configuration in Monte Carlo calculations for organ doses from CT examinations

Takahashi, Fumiaki; Sato, Kaoru; Endo, Akira; Ono, Koji*; Yoshitake, Takayasu*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Ban, Nobuhiko*; Kai, Michiaki*

Progress in Nuclear Science and Technology (Internet), 2, p.153 - 159, 2011/10

Computed Tomography (CT) is one of the most useful tools for medical diagnosis, and is becoming a major source of medical exposure in developed countries. Appropriate radiation protection in CT examinations is emphasized by international organizations, such as the International Atomic Energy Agency (IAEA), because the patients receive higher radiation doses than in conventional radiography. Medical staffs can acquire dose information on the conditions of some CT examinations with available dosimetry systems, which had been already developed. These systems utilize datasets of organ and tissue doses, which were derived with Monte Carlo calculations. Methods in computational analyses, however, have been improved, since these calculations had been performed. Then, our new dosimetry system for CT examination, WAZA-ARI, is being developed to estimate radiation dose based upon the state-of-art numerical analyses. Our analysis adopts Particle and Heavy Ion Transport code System (PHITS) coupled with a voxel-type phantom, JM phantom, for the organ dose calculation. PHITS has advantageous to define the model of photon emission from X-ray tube in a CT device for radiation transport calculations. The physique and mass of organs for JM phantom are similar to those for average Japanese male adults. Since the goal of WAZA-ARI is to provide dosimetric information of arbitrary patient, it is important to evaluate uncertainty due to different configurations in human bodies between JM phantom and individual patients. For this purpose, the organ doses are calculated and compared for different human models; another Japanese male adult voxel phantom and the ICRP reference voxel phantom, which is constructed on the basis of Caucasian data.

Journal Articles

Application and validation of event generator in the PHITS code for the low-energy neutron-induced reactions

Iwamoto, Yosuke; Niita, Koji*; Sato, Tatsuhiko; Matsuda, Norihiro; Iwase, Hiroshi*; Nakashima, Hiroshi; Sakamoto, Yukio

Progress in Nuclear Science and Technology (Internet), 2, p.931 - 935, 2011/10

The "Event Generator Mode (E-mode)" has been introduced into the PHITS code in the treatment of transport phenomena of low energy neutrons below 20 MeV. In the E-mode, the evaluated nuclear data for neutron-induced reactions and a special evaporation model are combined so as to trace all correlations of ejectiles and residuals in a collision under the energy and the momentum conservation. For the validation of the E-mode below 20 MeV, we have calculated neutron-induced activation cross sections by the E-mode, and compared them with the experimental data and the evaluated nuclear data library of activation cross sections. All calculated results agreed well with the experimental data and the evaluated data of activation cross sections below 20 MeV. As an application of the E-mode, we indicate a new approach to the deposit energy distribution of the thermal neutron transport for the boron-neutron capture therapy.

Journal Articles

Development of an atmosphere-soil-vegetation model for investigation of radioactive materials transport in the terrestrial biosphere

Katata, Genki; Nagai, Haruyasu; Zhang, L.*; Held, A.*; Ser$c{c}$a, D.*; Klemm, O.*

Progress in Nuclear Science and Technology (Internet), 2, p.530 - 537, 2011/10

In order to investigate the transport of radioactive materials we have developed a one-dimensional numerical model that predicts the transfer of water, heat, and gaseous and particulate matters in atmosphere-soil-vegetation continuous system. The model calculates dry, wet and fog deposition of gaseous and particulate matters onto vegetation, taken into account the dependency of plant species such as leaf shape and leaf surface area. As a result of performance tests of the model under various environmental conditions, the model predicted the observed temporal changes in heat, water and CO$$_{2}$$ fluxes over vegetative and non-vegetative surface, and temperature, water content, and CO$$_{2}$$ concentration in the soil under the temperate and arid climate. The model also reproduced observational data of mass fluxes of fog water and atmospheric gases such as ozone and $$SO_{2}$$, and number flux of nano-sized aerosols over the vegetation.

Journal Articles

Fluence-to-dose conversion coefficients for muons and pions calculated based on ICRP Publication 103 using the PHITS code

Sato, Tatsuhiko; Endo, Akira; Niita, Koji*

Progress in Nuclear Science and Technology (Internet), 2, p.432 - 436, 2011/10

The evaluation of the fluence-to-dose conversion coefficients for muons and pions is of great importance for the estimation of the aircrew doses from cosmic-ray exposure. Recently, ICRP released a new set of fundamental recommendations for a system of radiological protection in ICRP Publication 103. In this issue, the definition of effective dose was revised. We therefore calculated the dose conversion coefficients for muons and pions up to 100 GeV using the PHITS code, following the instructions given in ICRP103. The calculated dose conversion coefficients will be implemented in a route-dose calculation code JISCARD-EX developed by NIRS, which is currently used for the evaluation of aircrew doses for Japanese airline companies.

Journal Articles

Development of coupled modeling system for regional water cycle and material transport in the atmospheric, terrestrial, and oceanic environment

Nagai, Haruyasu; Kobayashi, Takuya; Tsuzuki, Katsunori; Terada, Hiroaki

Progress in Nuclear Science and Technology (Internet), 2, p.556 - 567, 2011/10

A general-purpose model coupling program (JAEA-Coupler) has been developed to construct local to regional scale coupled models for environmental studies. In this coupled model, calculations of component models are carried out by different processors of parallel computers and the coupler controls these processes and handles data exchanges among component models using MPI. The coupler handles the data distribution to target models with interfacing spatial, temporal, and physical discrepancies among component models. By using JAEA-Coupler, an integrated coupled model system to simulate regional water cycle and material transport has been constructed. Test calculations were carried out to simulate water movement after heavy rainfall and dissolved material transport after a hypothetical release to the atmosphere. These results show the validity of the coupled model system in appropriate data exchanges among component models and reasonable reproduction of the target phenomena.

Journal Articles

Large-Eddy Simulation of plume dispersion within a regular array of cubic buildings

Nakayama, Hiromasa; Nagai, Haruyasu

Progress in Nuclear Science and Technology (Internet), 2, p.463 - 469, 2011/10

There is a potential problem that the intentional release of radioactive materials by terror attacks and the accidental spillage from the transportation or storage of flammable and toxic gas occur within populated urban area. For the assessment of human health hazard or the safety analysis of the hazardous gas, not only mean but also fluctuating concentrations should be estimated. Therefore, we have developed a high resolution atmospheric dispersion model using Large Eddy Simulation (LES) model and perform its simulation on plume dispersion within a regular array of cubic buildings as a first step and investigate the characteristics of mean and fluctuating concentrations. As a result, we can capture the unsteady behaviors of turbulent flow and plume dispersion within the building array and show the spatial distribution of mean and fluctuating concentrations.

Journal Articles

A Study of released radionuclide in the coastal area from a discharge pipe of nuclear fuel reprocessing plant in Rokkasho, Aomori, Japan

Kobayashi, Takuya; In, Teiji*; Ishikawa, Yoichi*; Kawamura, Hideyuki; Nakayama, Tomoharu*; Shima, Shigeki*; Awaji, Toshiyuki*; Togawa, Orihiko

Progress in Nuclear Science and Technology (Internet), 2, p.682 - 687, 2011/10

When the reprocessing plant is in routine operation, radionuclides are released to the coastal ocean as scheduled. Released radionuclides migrate in the ocean by physical, chemical and biological processes. Thus, for environmental safety, it is important to understand the migration behavior due to routine releases of radionuclides to the coastal ocean from the reprocessing plant. A numerical simulation model system that consists of an ocean general circulation model and a particle random-walk model to describe the radionuclide migration behavior in Rokkasho coastal region has been developed. The particle random-walk model, SEA-GEARN, calculates the radionuclides migration in the ocean. The system has been applied to simulate the nowcast of Rokkasho coastal region in 2007 and hypothetical radionuclide release has been carried out.

Journal Articles

Application and validation of particle transport code PHITS in design of J-PARC 1 MW spallation neutron source

Harada, Masahide; Maekawa, Fujio; Oikawa, Kenichi; Meigo, Shinichiro; Takada, Hiroshi; Futakawa, Masatoshi

Progress in Nuclear Science and Technology (Internet), 2, p.872 - 878, 2011/10

In the previous stage of the JSNS design, there was no reliable and convenient nucleon and meson nuclear particle transport code in the energy region above 20 MeV. Therefore, with the progress of the J-PARC project, the NMTC/JAM code (the PHITS code in present) had been developed. Aiming to the best neutronic performance, the PHITS code was fully applied to JSNS neutronics designs and several thousand calculation cases were done with complicated models for neutronic performance, shielding calculation, nuclear heat estimation and so on. JSNS is one of the first facilities in the world fully adapted such a simulation code to the neutronics design. In these calculations, note that the particle energies change by 12 decades and neutron fluxes reduce by 10 decades. To confirm the reliability of these calculations, neutron spectral intensity, radiation dose, residual radio-activity and so on were measured. As a result, the measured values were good agreement with the calculated values.

Journal Articles

Journal Articles

A New approach for building an atomic model from a three-dimensional electron microscopy data

Matsumoto, Atsushi

Progress in Nuclear Science and Technology (Internet), 2, p.486 - 490, 2011/10

Journal Articles

Simulating plasma turbulence with the global Eulerian gyrokinetic code GT5D

Jolliet, S.; Idomura, Yasuhiro

Progress in Nuclear Science and Technology (Internet), 2, p.85 - 89, 2011/10

Journal Articles

Performance evaluations of advanced massively parallel platforms based on gyrokinetic toroidal five-dimensional eulerian code GT5D

Idomura, Yasuhiro; Jolliet, S.

Progress in Nuclear Science and Technology (Internet), 2, p.620 - 627, 2011/10

Journal Articles

Molecular dynamics simulation system for structural analysis of biomolecules by high performance computing

Ishida, Hisashi

Progress in Nuclear Science and Technology (Internet), 2, p.470 - 476, 2011/10

Journal Articles

Atomistic simulations of stress concentration induced and dislocation nucleation at grain boundaries

Tsuru, Tomohito; Kaji, Yoshiyuki; Tsukada, Takashi; Shibutani, Yoji*

Progress in Nuclear Science and Technology (Internet), 2, p.20 - 23, 2011/10

Stress concentration and defect nucleation of polycrystalline copper thin film is investigated by parallel molecular statics simulations. Uniaxial tensile deformation is applied to the two-dimensional polycrystalline model. As a result, it is found that the stress concentration is observed at triple point of grain junctions in the elastic and initial stage of plastic deformation. Then partial dislocations are first generated from the small angle grain boundaries. Twin deformations occur at triple points and grain boundaries which result in both another site of stress concentration around grain boundaries and local displacement relevant to the Burgers vector at grain boundary. One distinguishing characteristic of deformation mode of polycrystal is that the stress distribution strongly correlated with the presence of the partial dislocations and twin boundaries.

Journal Articles

Conceptual radiation shielding design of superconducting tokamak fusion device by PHITS

Sukegawa, Atsuhiko; Kawasaki, Hiromitsu*; Okuno, Koichi*

Progress in Nuclear Science and Technology (Internet), 2, p.375 - 381, 2011/10

A complete 3D neutrons and photons transport analysis by Monte Carlo transport code system PHITS (Particle and Heavy Ion Transport code System) have been performed for superconducting tokamak fusion device such as JT-60 Super Advanced (JT-60SA). It is possible to make use of PHITS in the port streaming analysis around the devices for the tokamak fusion device, the duct streaming analysis in the building where the device is installed, and the sky shine analysis for the site boundary. The neutron transport analysis by PHITS makes it clear that the shielding performance of the superconducting tokamak fusion device with the cryostat is improved by the graphical results. From the standpoint of the port streaming and the duct streaming, it is necessary to calculate by 3D codes for the neutronics analysis of superconducting tokamak fusion device.

Journal Articles

Evaluation of solute-atom clusters segregated in $$alpha$$-Fe

Suzuki, Chikashi; Tsuru, Tomohito; Kaji, Yoshiyuki

Progress in Nuclear Science and Technology (Internet), 2, p.34 - 37, 2011/10

no abstracts in English

Journal Articles

LDA+$$U$$ study on plutonium dioxide with spin-orbit couplings

Nakamura, Hiroki; Machida, Masahiko; Kato, Masato

Progress in Nuclear Science and Technology (Internet), 2, p.16 - 19, 2011/10

Plutonium dioxide is a main component of mixed oxide fuels. We perform first-principles density functional calculations on plutonium dioxides considering proper relativistic effects and strong correlations. Though this material is a paramagnetic insulator, standard calculations predict metallic states. The reason of this failure is often considered lack of strong correlations in LDA. However, even if strong correlation effects on plutonium $$f$$-orbital electrons are taken into account using the LDA+$$U$$ method, an insulating state cannot be obtained. In this paper, we point out that not only strong correlations but also spin-orbit couplings as relativistic effects are necessary to obtain paramagnetic insulating states. Based on this proper method, we calculate several physical properties of plutonium dioxide and compare them with other calculations and experiments. We also discuss the effects of oxygen deficiency on the electronic structures and thermal properties.

Journal Articles

Benchmarking of PHITS on pion production for medium-energy physics

Matsuda, Norihiro; Iwamoto, Yosuke; Iwase, Hiroshi*; Sakamoto, Yukio; Nakashima, Hiroshi; Niita, Koji*

Progress in Nuclear Science and Technology (Internet), 2, p.927 - 930, 2011/10

Benchmarking calculation for PHITS was performed on pion production cross sections for C, Al, Cu and Pb target irradiated by 730 MeV protons at wide angles in the interval 15 to 150 $$^{circ}$$. The experimental double differential cross sections were compared with the calculation results calculated by PHITS. As results, the PHITS calculations gave quite satisfactory results on the whole.

Journal Articles

Thermal properties of UO$$_{2}$$ by molecular dynamics simulation

Uchida, Teppei; Sunaoshi, Takeo*; Kato, Masato; Konashi, Kenji*

Progress in Nuclear Science and Technology (Internet), 2, p.598 - 602, 2011/10

Interatomic potential function of UO$$_{2}$$ was determined and thermal expansion, specific heat and thermal conductivity were evaluated by molecular dynamics (MD) simulation. For thermal expansion, a dilatometry was conducted and a measurement result was compared with a result of MD simulation. Thermal expansion value was in good agreement with MD simulation. Specific heat and thermal conductivity was also in good agreement with literature data when the supercell contained Schottky defects. Thermal conductivity, especially, was affected at low temperature range and decreased with increasing Schottky defect concentration. It was considered that vacancies scattered phonon vibrations. The interatomic potential function of UO$$_{2}$$ was considered usable.

Journal Articles

Comparison of photon and electron absorbed fractions in voxel-based and simplified phantoms for small animals

Mohammadi, A.; Kinase, Sakae; Saito, Kimiaki

Progress in Nuclear Science and Technology (Internet), 2, p.365 - 368, 2011/10

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