Seasonal variations in radon and thoron exhalation rates from solid concrete interior walls observed using in situ measurements

Sakoda, Akihiro; Ishimori, Yuu; Hasan, Md. M.*; Jin, Q.*; Iimoto, Takeshi*

Atmosphere (Internet), 15(6), p.701_1 - 701_12, 2024/06

https://doi.org/10.3390/atmos15060701

Building materials such as brick and concrete are known indoor radon (Rn) and thoron (Rn) sources. Most radon and thoron exhalation studies are based on the laboratory testing of pieces and blocks of such materials. To discuss if laboratory findings can be applied to a real-world environment, we conducted intensive in-situ exhalation tests on two solid concrete interior walls of an apartment in Japan for over a year. Exhalation rates of radon () and thoron () were measured by a measurement system, mainly consisting of an accumulation chamber and dedicated monitors. The indoor air temperature () and absolute humidity () were measured in parallel, and the wall-surface temperature and water content were occasionally measured. All data obtained here were investigated to reveal environmental and material-associated factors affecting exhalation from the concrete walls. There were weak correlations between or and T or at one tested wall, and moderate correlations of and strong correlations of with or at the other wall. Our findings on were consistent with those in a previous laboratory work where a concrete sample was subject to various temperatures, although a corresponding laboratory study of could not be collected. Additionally, moderate or strong correlation between and was observed for both tested walls. The comparison of the measured data and theoretical calculations revealed a new issue on how much impact each process of the emanation and migration within concrete pore spaces has on radon and thoron exhalation. This study provides an insight into parameterizing radon and thoron source inputs in modeling the spatiotemporal dynamics of indoor radon and thoron.

Optimizing calibration factors of plastic scintillation fibers for improved accuracy of radiocesium concentration measurements in bottom sediments of agricultural ponds

Katengeza, E. W.*; Sanada, Yukihisa; Ochi, Kotaro; Iimoto, Takeshi*

Cogent Engineering (Internet), 11(1), p.2340203_1 - 2340203_9, 2024/04

https://doi.org/10.1080/23311916.2024.2340203

The uncertainty of radioactivity measurements can be influenced by the vertical distribution of the target radionuclide in the sediments. This study used 2015-2019 field measurement data from 47 ponds to evaluate the depth dependence of calibration factors of plastic scintillation fiber (PSF) and its influence on measurement uncertainty. By changing the depth of focus from 10 cm to 15-20 cm when calculating the conversion factor, the normalized mean square error of the radiocesium concentration estimated by the PSF with respect to the radiocesium concentration in core sediments sampled at the same location was found to be smaller.

Review of articles related to the accident of TEPCO's Fukushima Daiichi Nuclear Power Station published on Japanese Journal of Health Physics; Opinion and others

Takahara, Shogo; Iimoto, Takeshi*; Igarashi, Takayuki*; Kawabata, Masako*

Hoken Butsuri (Internet), 58(2), p.50 - 58, 2023/08

https://doi.org/10.5453/jhps.58.50

The Health Physics Society of Japan established a working group to obtain the insights and findings from the articles, which are related to the Fukushima Daiichi Nuclear Power Station (1F) accident, published in the Japanese Journal of Health Physics. This paper describes the results of the review on 47 articles, which are classified into the field without risk communication, environmental measurement and monitoring, radiation dose measurement and assessment, radiation medicine and radioactive waste. In the reviewed articles, there are various insights and issues depending on the standpoint of the authors and social interests in the timing those published. It is important to face these insights and issues to consider prudently "what is health physics or radiation protection?" for the future development of the Health Physics society.

Activity review of Working Group on Accidents Relating X-ray Equipment, Japan Health Physics Society

Igarashi, Yu; Yamaguchi, Ichiro*; Oda, Keiji*; Fukushi, Masahiro*; Sakama, Minoru*; Iimoto, Takeshi*

Nihon Hoshasen Anzen Kanri Gakkai-Shi, 21(2), p.74 - 76, 2022/11

https://doi.org//10.11269/jjrsm.21.69

no abstracts in English

Status of radon exposure in Bangladeshi locations and dwellings

Hasan, Md. M.*; Janik, M.*; Sakoda, Akihiro; Iimoto, Takeshi*

Environmental Monitoring and Assessment, 193(12), p.770_1 - 770_10, 2021/12

https://doi.org/10.1007/s10661-021-09571-4

Potentially higher cancer risk due to exposure from natural background radiation was indicated for Bangladeshi population by estimations based on the countrywide study. Several regions with elevated natural background exhibited higher soil radium and thorium contents than the world average. Being the decay products of these radioactive elements, natural radon isotopes could constitute environmental risk factors for internal radiation exposure to the lungs of people living in these areas. Although lung cancer is one of most prevalent types of cancer in Bangladesh, its status and features are still unclear. To clarify the present status of one of the potential risk factors for lung cancer in the country, this review intends to ascertain the countrywide radon exposure, and its pathways by types of local dwelling and by regions; which would provide an indication of the internal exposures in areas of elevated natural background radiation and radionuclides of soil as well as an understanding of the preliminary contribution of environmental radon on the country's lung cancer prevalence. In this review, countrywide air radon exposures for Bangladeshi dwellings and workplaces are organized from peer-reviewed published papers. Radon has been identified as one of influential sources of radiation dose in Bangladesh with its higher radon exhalation and emanation rate from soil. A novel nationwide depiction of the overall indoor and soil radon levels for Bangladesh has been made through radiation maps. This would be helpful for designing future systematic radon/radiological surveys and research on the country's lung cancer prevalence.

Development of emergency monitoring system for alpha-particle-emitting radionuclides in the air

Hokama, Tomonori; Fujita, Hiroki; Nakano, Masanao; Iimoto, Takeshi*

Radiation Protection Dosimetry, 196(3-4), p.136 - 140, 2021/11

https://doi.org/10.1093/rpd/ncab139

During the early phase of a nuclear accident, major radioactive materials are released into the environment, necessitating the prompt deployment of various protective actions to avoid or reduce radiation exposure. To implement these actions, the levels of radioactivity in the environment should be determined. However, the radioactivity concentrations of artificial alpha-particle-emitting radionuclides such as plutonium are difficult to measure in airborne samples, because they are interfered with natural radionuclides such as uranium decay products. Therefore, chemical separation is required to measure the concentrations. This study presents a new emergency monitoring system for airborne samples, which performs multiple-pulse time-interval analysis (MTA) without chemical separation. The system is used in conjunction with an alpha/beta-particle survey meter and adopted an analysis method focusing on the detected time interval of each particle. Its features are that a short time to output measurement result, easy handling and nondestructive. The estimated detection limit of the system was 9.510 Bq m. The MTA-based monitoring system could be useful in situations requiring prompt measurement and screening of samples.

The Ecological half-life of radiocesium in surficial bottom sediments of five ponds in Fukushima based on measurements with Plastic Scintillation Fibers

Katengeza, E. W.*; Sanada, Yukihisa; Yoshimura, Kazuya; Ochi, Kotaro; Iimoto, Takeshi*

Environmental Science; Processes & Impacts, 22(7), p.1566 - 1576, 2020/07

https://doi.org/10.1039/D0EM00160K

Integrating radiation protection criteria for radioactive waste management into remediation procedures in existing exposure situations after a nuclear accident

Sugiyama, Daisuke*; Kimura, Hideo; Tachikawa, Hirokazu*; Iimoto, Takeshi*; Kawata, Yosuke*; Ogino, Haruyuki*; Okoshi, Minoru*

Journal of Radiological Protection, 38(1), p.456 - 462, 2018/03

https://doi.org/10.1088/1361-6498/aaa155

Experience after the accident at the Fukushima Daiichi Nuclear Power Station has shown that there is a need to establish radiation protection criteria for radioactive waste management consistent with the criteria adopted for the remediation of existing exposure situations. A stepwise approach to setting such criteria is proposed. Initially, a reference level for annual effective dose from waste management activities in the range 1-10 mSv should be set, with the reference level being less than the reference level for ambient dose. Subsequently, the reference level for annual effective dose from waste management activities should be reduced in one or more steps to achieve a final target value of 1 mSv. The dose criteria at each stage should be determined with relevant stakeholder involvement. Illustrative case studies show how this stepwise approach might be applied in practice.

Summary of study on environmental radioactivity effected from the accident at the TEPCO Fukushima Daiichi Nuclear Power Plant in 5 years after the accident

Iimoto, Takeshi*; Kinoshita, Norikazu*; Sakaguchi, Aya*; Sugihara, Shinji*; Takamiya, Koichi*; Tagami, Keiko*; Nagao, Seiya*; Bessho, Kotaro*; Matsumura, Hiroshi*; Miura, Taichi*; et al.

KEK Report 2016-3, 134 Pages, 2017/03

https://lib-extopc.kek.jp/preprints/PDF/2016/1624/1624003.pdf

This report is summary of study on environmental radioactivity effected from the accident at the TEPCO Fukushima Daiichi Nuclear Power Plant in 5 years after the accident. It was compiled efforts related to the accident reported from the 13th to the 17th "Workshop on Environmental Radioactivity" which was held at the High Energy Accelerator Research and Development Organization.

Interim report of the JHPS expert committee on radiation protection of the lens of the eye, 2; The Dosimetry method for the lens of the eye of workers in Japan

Akahane, Keiichi*; Iimoto, Takeshi*; Ichiji, Takeshi*; Iwai, Satoshi*; Oguchi, Hiroyuki*; Ono, Kazuko*; Kawaura, Chiyo*; Tatsuzaki, Hideo*; Tsujimura, Norio; Hamada, Nobuyuki*; et al.

Hoken Butsuri, 49(3), p.153 - 156, 2014/09

https://doi.org/10.5453/jhps.49.153

A brief review is given of the history and methodology of external dosimetry for the lens of the eye. Under the 1989 revision to domestic radiological protection regulations, the concept on the effective dose equivalent and the dose limit to the lens of the eye (150 mSv/y) both introduced in ICRP 1977 recommendations has changed nationwide the external monitoring methodology in non-uniform exposure situations to the trunk of a radiological worker. In such situations, often created by the presence of a protective apron, the worker is required to use at least two personal dosemeters, one worn on the trunk under the apron and the other, typically, at the collar over the apron. The latter dosemeter serves the dual purpose of providing the dose profile across the trunk for improved effective dose equivalent assessment and of estimating the dose to lens of the eye. The greater or appropriate value between (10) and (0.07), given by the dosemeter, is generally used as a surrogate of (3).