Simulation study of the effects of buildings, trees and paved surfaces on ambient dose equivalent rates outdoors at three suburban sites near Fukushima Dai-ichi

Kim, M.; Malins, A.; Yoshimura, Kazuya; Sakuma, Kazuyuki; Kurikami, Hiroshi; Kitamura, Akihiro; Machida, Masahiko; Hasegawa, Yukihiro*; Yanagi, Hideaki*

Journal of Environmental Radioactivity, 210, p.105803_1 - 105803_10, 2019/12

https://doi.org/10.1016/j.jenvrad.2018.09.001

To improve the accuracy of simulations for air dose rates over fallout contaminated areas, the distribution of the radionuclides within the environment should be modelled realistically, e.g. considering differences in radioactivity levels between agricultural land, urban surfaces, and forest compartments. Moreover simulations should model the shielding of rays by buildings, trees and land topography. Here we outline a system for generating three dimensional models of urban and rural areas in Fukushima Prefecture. The Cs and Cs radioactivity distribution can be set flexibly across the different components of the model. The models incorporate realistic representations of local buildings, based on nine common Japanese designs, individual conifer and broadleaf trees, and the topography of the land surface. Models are generated from Digital Elevation Model (DEM) and Digital Surface Model (DSM) datasets, and refined by users assisted with ortho-photographs of target sites. Completed models are exported from the system in a format suitable for the Particle and Heavy Ion Transport code System (PHITS) for the calculation of air dose rates and other radiological quantities. The system is demonstrated by modelling a suburban area 4 km from the Fukushima Daiichi Nuclear Power Plant that has yet to be decontaminated. Air dose rates calculated in PHITS were correlated with measurements taken across the site in a car-borne survey.

Development of an air dose rate evaluation system (3D-ADRES) for complex real environments in Fukushima Prefecture; Using remote sensing data and evaluating the influence of different features (topography, soil, buildings, trees, etc.)

Kim, M.; Malins, A.; Sakuma, Kazuyuki; Kitamura, Akihiro; Machida, Masahiko; Hasegawa, Yukihiro*; Yanagi, Hideaki*

RIST News, (64), p.3 - 16, 2018/09

To improve the accuracy of simulations for air dose rates over fallout contaminated areas, the distribution of the radionuclides within the environment should be modelled realistically, e.g. considering differences in radioactivity levels between agricultural land, urban surfaces, and forest compartments. Moreover simulations should model the shielding of rays by buildings, trees and land topography. Here we outline a system for generating three dimensional models of urban and rural areas in Fukushima Prefecture. The Cs and Cs radioactivity distribution can be set flexibly across the different components of the model. The models incorporate realistic representations of local buildings, based on nine common Japanese designs, individual conifer and broadleaf trees, and the topography of the land surface. Models are generated from Digital Elevation Model (DEM) and Digital Surface Model (DSM) datasets, and refined by users assisted with ortho-photographs of target sites. Completed models are exported from the system in a format suitable for the Particle and Heavy Ion Transport code System (PHITS) for the calculation of air dose rates and other radiological quantities. The system is demonstrated by modelling a suburban area 4 km from the Fukushima Daiichi Nuclear Power Plant that has yet to be decontaminated. Air dose rates calculated in PHITS were correlated with measurements taken across the site in a car-borne survey.

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage; Progress report on NUMO-JAEA collaborative research in FY2011 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Hayano, Akira; Mitsui, Seiichiro; Taniguchi, Naoki; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.

JAEA-Research 2012-032, 298 Pages, 2012/09

JAEA-Research-2012-032.pdf:33.68MB

JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation phase. The topics and the conducted research are follows; (1) Study on selection of host rock: in terms of hydraulic properties, items for assessing rock property, and assessment methodology of groundwater travel time has been organized with interaction from site investigation. (2) Study on development of scenario: the existing approach has been embodied, in addition, the phenomenological understanding regarding dissolution of and nuclide release from vitrified waste, corrosion of the overpack, long-term performance of the buffer are summarized. (3) Study on setting nuclide migration parameters: the approach for parameter setting has been improved for sorption and diffusion coefficient of buffer/rock, and applied and tested for parameter setting of key radionuclides. (4) Study on ensuring quality of knowledge: framework for ensuring quality of knowledge has been studied and examined aimed at the likely disposal facility condition.

R&D project on irradiation damage management technology for structural materials of long-life nuclear plant, 2; Plan and execution of coupling irradiation (JRR-3 and JOYO) and Hot facilities work (WASTEF, JMTR-HL, MMF and FMF)

Matsui, Yoshinori; Nabeya, Hideaki; Kusunoki, Tsuyoshi; Takahashi, Hiroyuki; Aizawa, Masao; Nakata, Masahito; Numata, Masami; Usami, Koji; Endo, Shinya; Ito, Kazuhiro; et al.

no journal, , 

We are proceeding with the study of "R&D Project on Irradiation Damage Management Technology for Structural Materials of Long-life Nuclear Plant". For the study, it is important that the irradiated specimens are gotten by the coupling of JRR-3 and JOYO. This reports the total irradiation plan in the study, and the executed work for the coupling irradiation (JRR-3 and JOYO) including the Hot facilities work of Tokai and Oarai in the 2006 fiscal year.

Inspection and repair techniques in reactor vessel of sodium cooled fast reactor, 1; Current status of in-vessel observation techniques in the experimental fast reactor Joyo

Maeda, Yukimoto; Kitamura, Ryoichi; Nagai, Akinori; Ito, Hideaki; Sekine, Takashi; Suzuki, Soju

no journal, , 

no abstracts in English

Recovery of damaged components in reactor vessel of the experimental fast reactor Joyo

Aoyama, Takafumi; Ashida, Takashi; Ito, Hideaki; Kitamura, Ryoichi

no journal, , 

The experimental fast reactor Joyo is the first sodium cooled fast reactor in Japan. When the R/P was jacked down during the 15th periodical inspection, measured load of the hold-down shaft revealed an abnormal decrease. This indicated that anomaly occurred in the upper part of the in-reactor vessel storage rack. In order to investigate the cause of this, in reactor vessel observation was conducted. As a result of the MARICO-2 lift-up test, the basic function, mechanism and the procedure to retrieve bent subassembly stayed in the in-vessel storage pot is confirmed and it will be used to design and fabricate the retrieval device with the shielding cask as the next step. The experience obtained through the restoration work in Joyo will provided valuable prospect for further improvements of in-reactor vessel inspection and repair techniques in sodium-cooled fast reactors.