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JAEA Reports

Evaluation on review of screening level of simple measurement of radioactive iodine radioactivity in the thyroid in the case of a nuclear accident

Hokama, Tomonori; Kimura, Masanori; Togawa, Orihiko

JAEA-Research 2023-010, 57 Pages, 2024/02

JAEA-Research-2023-010.pdf:3.29MB

In the case of a nuclear accident, itis planned to perform simple measurement of radioactive iodine radioactivity in the thyroid of residents. The screening level for simple measurement is set at 0.20 Sv/h as a reference, and it is required to be reviewed appropriately according to the situation such as a nuclear accident. However, a specific method for reviewing the screening level is not shown. When reviewing the screening level, it is important to take into account factors related to the feasibility of simple measurement, such as the judgment level for internal exposure dose of the thyroid and the duration of the measurement period. In this study, we organized the derivation process of 0.20 Sv/h, which was set as the reference for screening level, and considered the feasibility of the reviewing of screening level. We calculated the relationship between the judgment level and the duration of simple measurement for each screening level, ranging from 0.025 to 0.50 Sv/h. Then, the feasibility of the reviewing of screening level was considered. It was found that reviewing the screening level is technically feasible, provided that the judgment level and the duration of simple measurement are appropriate. However, assuming that simple measurement will be performed in an actual nuclear accident, we assessed that it would be reasonable to review the screening level within the range of 0.030 to 0.20 Sv/h, in a situation where the duration of simple measurement must be extended.

Journal Articles

Chemical species of cesium and iodine in condensed vaporized microparticles formed by melting nuclear fuel components with concrete materials

Onuki, Toshihiko*; Ye, J.*; Kato, Tomoaki; Liu, J.; Takano, Masahide; Kozai, Naofumi; Utsunomiya, Satoshi*

Environmental Science; Processes & Impacts, 25(7), p.1204 - 1212, 2023/07

https://doi.org/10.1039/D3EM00074E

Times Cited Count：1 Percentile：0(Chemistry, Analytical)

To elucidate chemical forms of Cs and I in microparticles produced via the Fukushima Daiichi Nuclear Power Plant accident and released into the atmosphere, we analyzed Cs and I in condensed vaporized particles (CVP) produced by melting experiments using nuclear fuel components containing CsI with concrete. CVPs consisted of many round particles containing Cs and I of diameters less than several tens of micrometers. Two kinds of particles were present: one containing large amounts of Cs and I, suggesting the presence of CsI, and the other containing small amounts of Cs and I with large Si contents. Most of CsI from both particles were dissolved in water. On the contrary, some fractions of Cs remained from the latter particles. These results suggest that Cs was incorporated in CVPs along with Si to form water low-soluble CVPs

Journal Articles

Iodate respiration by sp. DN11 and its potential use for removal of radioiodine from contaminated aquifers

Sasamura, Seiya*; Onuki, Toshihiko*; Kozai, Naofumi; Amachi, Seigo*

Frontiers in Microbiology (Internet), 14, p.1162788_1 - 1162788_7, 2023/04

https://doi.org/10.3389/fmicb.2023.1162788

Times Cited Count：2 Percentile：75.4(Microbiology)

sp. DN11 previously isolated from gasoline-contaminated groundwater contained a gene cluster involved in bacterial iodate (IO $_{3}$ $^{-}$ ) respiration. This study determined if strain DN11 performed iodate respiration and assessed its potential use to remove and sequester radioactive iodine ( $^{129}$ I) from subsurface contaminated aquifers. Strain DN11 grew anaerobically with iodate as the sole electron acceptor. After the growth of strain DN11 on iodate, silver-impregnated zeolite was added to the spent medium to remove iodide from the aqueous phase. In the presence of 200 M iodate as the electron acceptor, more than 98% of iodine was successfully removed from the aqueous phase. These results suggest that strain DN11 is potentially helpful for bioaugmentation of $^{129}$ I-contaminated subsurface aquifers.

Journal Articles

Development of portable thyroid monitoring system with detector shields

Tanimura, Yoshihiko

FBNews, (548), p.1 - 5, 2022/08

In the situation of a severe nuclear accident, radioiodine monitoring in thyroid should be performed for a large number of people immediately after accident. The portable thyroid dose monitoring system with the radiation shield which can be used in a high dose rate condition has been developed. In this paper, the outline of the monitoring system and the performance test results using the system will be described.

Journal Articles

Background correction method for portable thyroid dose monitor using gamma-ray spectrometer developed at JAEA in high dose rate environment

Tanimura, Yoshihiko; Yoshitomi, Hiroshi; Nishino, Sho; Takahashi, Masa

Radiation Measurements, 137, p.106389_1 - 106389_5, 2020/09

https://doi.org/10.1016/j.radmeas.2020.106389

Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)

A portable thyroid dose monitoring system has been developed at the Japan Atomic Energy Agency (JAEA) to assess the thyroid equivalent dose for workers and members of the public in a high dose rate environment. The background (B.G.) photon correction is required for an accurate measurement in a high dose rate environment at an early stage after a nuclear accident. We developed the B.G. photon correction method using cylindrical PMMA phantoms.

Journal Articles

Processes affecting land-surface dynamics of $^{129}$ I impacted by atmospheric $^{129}$ I releases from a spent nuclear fuel reprocessing plant

Ota, Masakazu; Terada, Hiroaki; Hasegawa, Hidenao*; Kakiuchi, Hideki*

Science of the Total Environment, 704, p.135319_1 - 135319_15, 2020/02

https://doi.org/10.1016/j.scitotenv.2019.135319

Times Cited Count：6 Percentile：29.22(Environmental Sciences)

Land-surface transfers of $^{129}$ I are modeled and incorporated into a land-surface model (SOLVEG-II), and the model was applied to the observed transfer of $^{129}$ I at a vegetated field impacted by atmospheric releases of $^{129}$ I from Rokkasho reprocessing plant during 2007 to investigate the importance of each $^{129}$ I-transfer pathway. The model calculation revealed that contamination of leaves of wild bamboo grasses was mostly caused by foliar adsorption of $^{129}$ I (81%) induced via wet deposition of $^{129}$ I. Wet deposition of $^{129}$ I was the main $^{129}$ I-input to the soil, ten-fold the dry deposition of $^{129}$ I $_{2}$ ; however, the deposition of $^{129}$ I during 2007 was only 2% of the model-assumed $^{129}$ I that pre-existed in the soil; indicating the importance of long-term accumulation of $^{129}$ I in soils. The model calculation also revealed that root uptake of $^{129}$ I, not methylation, control the long-term turnover of soil $^{129}$ I.

Journal Articles

Distribution and fate of $^{129}$ I in the seabed sediment off Fukushima

Otosaka, Shigeyoshi; Sato, Yuhi*; Suzuki, Takashi; Kuwabara, Jun; Nakanishi, Takahiro

Journal of Environmental Radioactivity, 192, p.208 - 218, 2018/12

AA2017-0744.pdf:1.17MB

https://doi.org/10.1016/j.jenvrad.2018.06.025

Times Cited Count：15 Percentile：47.7(Environmental Sciences)

From August 2011 to October 2013, the concentration of iodine-129 ( $^{129}$ I) in the seabed sediment collected from 26 stations located within 160 km from the Fukushima Daiichi Nuclear Power Plant was estimated. The concentrations of $^{129}$ I in seabed sediment off Fukushima in 2011 ranged between 0.02 and 0.45 mBq/kg. Although iodine is a biophilic element, the accident-derived radioiodine negligibly affects the benthic ecosystem. Until October 2013, a slightly increased activity of $^{129}$ I in the surface sediment in the shelf-edge region (bottom depth: 200-400 m) was observed. The increase of the $^{129}$ I concentrations in the shelf-edge sediments was affected by the (1) transport of $^{129}$ I-bound particles from the land through rivers and (2) re-deposition of $^{129}$ I desorbed from the contaminated coastal sediment to the shelf-edge sediments, which were considered to be dominant processes.

JAEA Reports

Radiochemical studies of iodine, tritium and neptunium

Saeki, Masakatsu

JAERI-Review 2004-011, 54 Pages, 2004/03

JAERI-Review-2004-011.pdf:5.21MB

In this review, experimental results on studies of radioactive iodine, tritium and neptunium are summarized. On studies of radioactive iodine, from various experimental results, the process establishing the formation mechanism of organic iodides was fully described. On the basis of formation mechanism, possibilities for the formation of organic iodides under nuclear reactor accidents and so on were also discussed. On studies of tritium, three topics were concisely described on the isotopic composition of tritium gases, the chemical forms and the diffusivity of tritium in various materials, and the sorption and desorption behaviors of tritium on surfaces of various materials. On the neptunium chemistry, the relationship between the structure of neptunium compound and the Moessbauer isomer shift and experimental results on neptunyl(VI) hydroxides were discussed.

Journal Articles