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

https://doi.org/10.15669/pnst.2.153

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.

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.*; Sera, D.*; Klemm, O.*

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

https://doi.org/10.15669/pnst.2.530

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 fluxes over vegetative and non-vegetative surface, and temperature, water content, and CO 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 , and number flux of nano-sized aerosols over the vegetation.

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

http://doi.org/10.15669/pnst.2.556

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.

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

https://doi.org/10.15669/pnst.2.682

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.

Monte Carlo code for the damage of bio-molecules irradiated by X-ray free electron lasers; Incorporation of election impact ionization processes

Moribayashi, Kengo

Progress in Nuclear Science and Technology (Internet), 2, p.893 - 897, 2011/10

https://doi.org/10.15669/pnst.2.893

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

https://doi.org/10.15669/pnst.2.85

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

https://doi.org/10.15669/pnst.2.470

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

https://doi.org/10.15669/pnst.2.375

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.

LDA+ 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

https://doi.org/10.15669/pnst.2.16

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 -orbital electrons are taken into account using the LDA+ 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.

Thermal properties of UO 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

https://doi.org/10.15669/pnst.2.598

Interatomic potential function of UO 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 was considered usable.