Variation of internal doses caused by differences in physical characteristics between the average Japanese and the ICRP's reference man which is based on the standard data of Caucasians in the dosimetric methodology in conformity to the 2007 Recommendations

Manabe, Kentaro; Sato, Kaoru; Takahashi, Fumiaki

Journal of Nuclear Science and Technology, 59(5), p.656 - 664, 2022/05

https://doi.org/10.1080/00223131.2021.1997663

It is known that internal doses depend on the physical characteristics of an evaluation subject. Internal dose coefficients provided by the International Commission on Radiological Protection (ICRP) are evaluated using the characteristics of the standard Caucasian. It is important to grasp the variations of doses due to the differences in characteristics between Japanese and Caucasian when the dose coefficients of ICRP are applied to Japanese. This study evaluated dose coefficients using specific absorbed fraction (SAF) data based on the average adult Japanese physique which was developed by modification of the existing Japanese SAF data with additional calculations to make the existing data fit to the current dosimetric methodology of ICRP and compared them to those provided by ICRP. As a result, the discrepancies in dose coefficients were smaller than plus or minus 10% in most intake conditions. However, some intake conditions indicated varieties over 40% due to the differences in organ masses, amount of adipose tissues around the thoracic cavity, and so on. This information is useful in application of ICRP's dose coefficients to population of which physical characteristics are different from those of Caucasian. Further, the Japanese SAF data is published as an appendix of this paper.

Japanese population dose from natural radiation

Omori, Yasutaka*; Hosoda, Masahiro*; Takahashi, Fumiaki; Sanada, Tetsuya*; Hirao, Shigekazu*; Ono, Koji*; Furukawa, Masahide*

Journal of Radiological Protection, 40(3), p.R99 - R140, 2020/09

https://doi.org/10.1088/1361-6498/ab73b1

UNSCEAR and the Nuclear Safety Research Association report the annual effective doses from cosmic rays, terrestrial radiation, inhalation and ingestion from natural sources. In this study, radiation doses from natural radiation sources in Japan were reviewed with the latest knowledge and data. Total annual effective dose from cosmic-ray exposure can be evaluated as 0.29 mSv. The annual effective dose from external exposure to terrestrial radiation for Japanese population can be evaluated as 0.33 mSv using the data of nationwide survey by the National Institute of Radiological Sciences. The Japan Chemical Analysis Center (JCAC) performed the nationwide radon survey using a unified method for radon measurements in indoor, outdoor and workplace. The annual effective dose for radon inhalation was estimated using a current dose conversion factor, and the values were estimated to be 0.50 mSv. The annual effective dose from thoron was reported as 0.09 mSv by UNSCEAR and then the annual effective dose from inhalation can be described as 0.59 mSv. According to the report of large scale survey of foodstuff by JCAC, the effective dose from main radionuclides due to dietary intake can be evaluated to be 0.99 mSv. Finally, Japanese population dose from natural radiation can be assessed as 2.2 mSv which is near to the world average value of 2.4 mSv.

Estimating internal dose coefficients of short-lived radionuclides in accordance with ICRP 2007 Recommendations

Manabe, Kentaro; Sato, Kaoru; Takahashi, Fumiaki

Journal of Nuclear Science and Technology, 56(5), p.385 - 393, 2019/05

https://doi.org/10.1080/00223131.2019.1585988

At high energy accelerator facilities, various radionuclides are produced by nuclear reactions of high energy particles with structure and/or ambient air of the facilities. Consequently, the radionuclides are potential sources of internal exposure for works of the facilities. However, the International Commission on Radiological Protection (ICRP) do not provide dose coefficients, which are committed effective doses per intake, for the short-lived radionuclides whose half-lives are shorter than 10 minutes in accordance with the ICRP 2007 Recommendations. Then, we estimated the dose coefficients for inhalation and ingestion of these short-lived radionuclides in accordance with the ICRP 2007 Recommendations. In addition, we compared the dose coefficients with those in accordance with the ICRP 1990 Recommendations. As a result, a decreasing tendency was shown in the dose coefficients for inhalation cases; an increasing tendency was observed in those for ingestion cases. It was found that these changes in dose coefficients were mainly caused by the revision of the dose calculation procedures, alimentary tract models. The result of this study will be useful for planning of radiation protection at the high energy facilities.

5.1.2 Properties and characteristics of radiations

Takahashi, Fumiaki

Genshiryoku No Ima To Ashita, p.106 - 109, 2019/03

The Atomic Energy Society of Japan has planned to publish a document for public, entitled "Current and tomorrow of atomic energy, -Experiences from the accident at the Tokyo Electronic Power Company Fukushima Dai-ichi NPPs-". The documents give us basics and usages of radiations, in addition to nuclear power plants and the accident at TEPCO Fukushima Dai-ichi NPPs. This manuscript explains interactions and penetrations in material for -rays, -rays, -rays and neutrons. In addition, exposure characteristics that is determined by properties of radiations are expressed here. This manuscript also explains characteristics in internal exposure and countermeasures of radiation protection following the TEPCO accident for Iodine-131 and Cesium-137.

Construction of adult Japanese voxel phantoms with various body sizes and their applications to evaluation of organ doses due to external photon irradiation

Sato, Kaoru; Takahashi, Fumiaki

Hoken Butsuri, 52(4), p.247 - 258, 2017/12

https://doi.org/10.5453/jhps.52.247

Organ doses for dose assessment in radiation protection are derived from ICRP reference phantoms (Male:RCP-AM, Female:RCP-AF) with standard Caucasian physiques. In adult, Japanese are smaller than Caucasian. To study impact of differences in physiques between Caucasian and Japanese on organ doses, we previously constructed Japanese phantoms (Male:JM-103, Female:JF-103) with average adult Japanese physiques. In addition, adult Japanese physiques have also wide distribution. Thus, we newly modeled DJM (Male) and DJF (Female) with 8 physiques by changing the perimeters of JM-103 and JF-103. Organ doses due to external photon irradiation of DJM and DJF were calculated, and were compared with those of RCP-AM and RCP-AF. In ISO geometry at 0.3 MeV, it was found that doses of breast, colon, lung, stomach, gonad, urinary bladder, esophagus, liver and thyroid in DJM and DJF with physiques, which are applicable to most adult Japanese, agreed with those of RCP-AM and RCP-AF within 10%.

Assessment of specific absorbed fractions for photons and electrons using average adult Japanese female phantom

Manabe, Kentaro; Sato, Kaoru; Takahashi, Fumiaki

JAEA-Data/Code 2016-013, 48 Pages, 2016/12

JAEA-Data-Code-2016-013.pdf:1.3MB
JAEA-Data-Code-2016-013-appendix(CD-ROM).zip:0.47MB

In the 2007 Recommendations of the International Commission on Radiological Protection (ICRP), an effective dose is defined as a sum of equivalent doses which are calculated by using male and female reference phantoms based on Caucasian physiological data and averaged over the sexes by tissue weighting factors. Specific absorbed fractions (SAFs), which are essential for internal dosimetry, depend on the body weight and organ masses of phantoms. Then, the dose coefficients, which are committed effective doses per unit intake of radionuclides, developed by ICRP on the basis of the 2007 Recommendations reflect the physical characteristics of Caucasians and are averaged over the sexes. Meanwhile, the physiques of adult Japanese are generally smaller than those of adult Caucasians, and organ masses are also different from each other. Knowledge of the influence of race differences on dose coefficients is important to apply the sex averaged dose coefficients of ICRP to the Japanese system of radiation protection. In this study, SAFs for 25 kinds of mono-energetic electrons and photons ranging from 10 keV to 10 MeV were calculated about the combinations of 67 source regions and 42 target organs using the average adult Japanese female phantom, JF-103, incorporated with a general purpose radiation transport code, MCNPX 2.6.0. The data of this report and the previously published data of JM-103 are applicable to evaluate sex-specific and sex-averaged dose coefficients reflecting the physical characteristics of the average adult Japanese for intakes of all radionuclides not to emit other than photons and electrons.

A Computational approach using reflection boundaries for dose calculation in infinitely expanded radiation field

Furuta, Takuya; Takahashi, Fumiaki

Radiation Protection Dosimetry, 167(4), p.392 - 398, 2015/12

https://doi.org/10.1093/rpd/ncu337

A new approach was proposed to compute radiation dose to objects of interest in infinitely expanded radiation fields with Monte Carlo transport codes. The particles, which were emitted from the location far from the interested object, could be effectively taken into account by setting reflection boundaries at the borders of the computational area in the newly developed method. Here, the positions and momenta of the particles at each reflection were recorded and used as the sources to simulate particles from the exterior region of the computational area. The validity of new method was checked by radiation transport calculations of objects on the infinitely expanded contaminated ground surface. The results in our new approach agreed within statistical errors of the simulation with those in the conventional approach considering a very large computational area. In addition, an efficiency in computational time was compared between the new and conventional approaches.

Non-destructive examination of jacket sections for ITER central solenoid conductors

Takahashi, Yoshikazu; Suwa, Tomone; Nabara, Yoshihiro; Ozeki, Hidemasa; Hemmi, Tsutomu; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Kawano, Katsumi; Oshikiri, Masayuki; et al.

IEEE Transactions on Applied Superconductivity, 25(3), p.4200904_1 - 4200904_4, 2015/06

https://doi.org/10.1109/TASC.2014.2364632

The Japan Atomic Energy Agency (JAEA) is responsible for procuring all amounts of Central Solenoid (CS) Conductors for ITER, including CS jacket sections. The conductor is cable-in-conduit conductor (CICC) with a central spiral. A total of 576 NbSn strands and 288 copper strands are cabled around the central spiral. The maximum operating current is 40 kA at magnetic field of 13 T. CS jacket section is circular in square type tube made of JK2LB, which is high manganese stainless steel with boron added. Unit length of jacket sections is 7 m and 6,300 sections will be manufactured and inspected. Outer/inner dimension and weight are 51.3/35.3 mm and around 90 kg, respectively. Eddy Current Test (ECT) and Phased Array Ultrasonic Test (PAUT) were developed for non-destructive examination. The defects on inner and outer surfaces can be detected by ECT. The defects inside jacket section can be detected by PAUT. These technology and the inspected results are reported in this paper.

Study of radiation dose reduction of buildings of different sizes and materials

Furuta, Takuya; Takahashi, Fumiaki

Journal of Nuclear Science and Technology, 52(6), p.897 - 904, 2015/06

https://doi.org/10.1080/00223131.2014.990939

Dependence of the radiation dose reduction on sizes and materials of buildings was studied by numerical analyses using the Monte Carlo simulation code PHITS. Three building models were developed: the wooden house, open space concrete building, and thin-wall building, to study the effect of building size and construction material on dose reduction inside these structures. Here the floor area size of the building models were varied to clarify the influence of building configuration on dose reduction. The results demonstrated that the dose rates inside the buildings linearly decreased with increasing floor area on a logarithmic scale for all types of buildings. The calculation of dose distribution inside a building clarified that the distance from outer walls were a determinant factor for the dose rate at each position in the building. The obtained tendency was ensured by comparing to data for the dose reduction of typical buildings in Japan.

Detailed deposition density maps constructed by large-scale soil sampling for -ray emitting radioactive nuclides from the Fukushima Dai-ichi Nuclear Power Plant accident

Saito, Kimiaki; Tanihata, Isao*; Fujiwara, Mamoru; Saito, Takashi*; Shimoura, Susumu*; Otsuka, Takaharu*; Onda, Yuichi*; Hoshi, Masaharu*; Ikeuchi, Yoshihiro*; Takahashi, Fumiaki; et al.

Journal of Environmental Radioactivity, 139, p.308 - 319, 2015/01

https://doi.org/10.1016/j.jenvrad.2014.02.014