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Journal Articles

Survey of air dose rate distribution inside and outside of wooden houses in Fukushima Prefecture; Actual condition of dose reduction factor

Kim, M.; Malins, A.*; Machida, Masahiko; Yoshimura, Kazuya; Saito, Kimiaki; Yoshida, Hiroko*

Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 22(4), p.156 - 169, 2023/11

https://doi.org/10.3327/taesj.J23.001

Dose reduction factor of a Japanese house is important information in the external exposure estimation of returning residents. In 2019, a total of 19 wooden houses were surveyed in Iitate Village and Namie Town using a gamma plotter that can continuously measure the air dose rate. In addition, the characteristics of the reduction factor were investigated from the measured air dose rate. In the vicinity of houses, uncontaminated areas exist underneath houses and, the ratio of paved surfaces such as asphalt roads is relatively high; furthermore, the pavement has a tendency for the radiation source to decay quickly. Therefore, the air dose rate near the house showed a relatively low value in common at all sites. Air dose rates above unpaved surfaces showed higher values and larger variations than those above paved surfaces within a radius of 50 m form the center of a house. The reduction factor was widely distributed even for one house, if the ratio of every air dose rate observed inside and outside the house is considered. It is suggested that a realistic reduction factor may not be obtained when the reduction factor is obtained based on the measured values at a small number of points that do not have the representativeness of the radiation field to be measured.

Journal Articles

Implementation of decontamination technologies appropriate to Japanese boundary conditions

Kawase, Keiichi

Global Environmental Research (Internet), 20(1&2), p.83 - 90, 2017/03

http://www.airies.or.jp/ebook/Global_Environmental_Research_Vol.20.pdf

Major challenges to implementing full-scale environmental decontamination were the absence of real-world examples and also lack of experience in planning and implementing decontamination technology appropriate to the physical and social boundary conditions in both Japan and Fukushima. The Japan Atomic Energy Agency was thus charged with conducting a range of Decontamination Pilot Project to examine the applicability of decontamination technologies, with a special focus on reducing dose rates and thus allowing evacuees to return to re-establish their normal lifestyles as quickly as possible, whilst simultaneously maintaining worker safety. In this report, re-edit the report of the Decontamination Pilot Project (Nakayama et al.,2014), do the commentary for the decontamination technology.

Journal Articles

Measurements and evaluations of air dose rates around the Fukushima NPP site, 6; Status and issues on evaluation of individual doses due to external exposures

Saito, Kimiaki; Kurihara, Osamu*; Matsuda, Norihiro; Takahara, Shogo; Sato, Tetsuro*

Radioisotopes, 65(2), p.93 - 112, 2016/02

https://doi.org/10.3769/radioisotopes.65.93

Late information is introduced on dose evaluation due to external exposures which employ an important role in the exposures due to the Fukushima accident. First, merits and demerits of the currently used two methods, that is the estimation based air dose rates and the measurements using personal dosimeters, are discussed indicating some basic data after a fundamental concept of external dose evaluation is provided. Next, main activities are summarized on external dose measurements and evaluations after the accident. Finally, a new trial on dose evaluation in introduced.

JAEA Reports

Development of FEMAG; Calculation code of magnetic field generated by ferritic plates in the tokamak devices

Urata, Kazuhiro*

JAERI-Data/Code 2003-005, 36 Pages, 2003/03

JAERI-Data-Code-2003-005.pdf:2.96MB

In design of the fusion devises in which ferritic steel is planned to use as the plasma facing material and/or the inserts for ripple reduction, the appreciation of the error field effect and the optimization of ferritic plate arrangement to reduce the toroidal field ripple require calculation of ferritic magnetic field. However iterative calculations by the non-linearity in B-H curve disturbs high-speed calculation. In the strong toroidal magnetic field in the tokamak, fully magnetic saturation of ferritic steel occurs. Hence a distribution of magnetic charges as magnetic field source is determined straightforward. Additionally objective ferritic steel geometry is limited to the thin plate and they are installed along the toroidal magnetic field. Taking them into account, high-speed calculation code FEMAG has been developed. In this report, the formalization of FEMAG, how to use FEMAG, and the validity check in comparison with a 3D FEM code, with the measurements of the magnetic field in JFT-2M are described. The presented examples are design studies for JT-60 modification.

Journal Articles