著者

Tatsuya TSUBOI Hideki WADA Makoto YANAGA

出版者

日本放射線安全管理学会

雑誌

Radiation Safety Management (ISSN:13471511)

巻号頁・発行日

vol.11, no.1, pp.11-18, 2012 (Released:2012-12-21)

参考文献数

9

被引用文献数

3 4 1

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Distribution of radioactive Cs was investigated in the surface soils of urban and vicinity areas of Shizuoka city, Japan. Concentration of 134Cs and 137Cs showed values in the range of 37 to 2435 Bq/m2 (1 to 95 Bq/kg) and 57 to 2242 Bq/m2 (2 to 98 Bq/kg), respectively. The original production ratio of 134Cs and 137Cs was estimated to be 1:1. The high activity areas were mainly observed along the Warashina area and southern slope of the Udo Hills. The pollutant fine particles with radioactive Cs released from the Fukushima Dai-ichi nuclear power plant were arrived at Shizuoka city by northwest wind in the morning and southwest wind in the afternoon on March 15, 2011. The radioactive Cs distribution pattern indicates that these pollutant particles were dropped on land surface of the Warashina area and southern slope of the Udo Hills during ascending wind in the afternoon on March 15, 2011.

著者

Naoko Morita Miwa Miura Toshiro Usa Takashi Kudo Naoki Matsuda

出版者

日本放射線安全管理学会

雑誌

Radiation Safety Management (ISSN:13471511)

巻号頁・発行日

vol.12, no.2, pp.48-55, 2013 (Released:2013-12-19)

参考文献数

20

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The internal doses of 372 persons who were dispatched to the Fukushima prefecture at any time from April 2011 to March 2012 were examined using a whole body counter within 2 months after they left Fukushima. 131I was only detected in April while 134Cs and 137Cs were found up to November 2011. The maximum committed effective dose and thyroid equivalent dose were 22.4 μSv and 0.4 mSv, respectively, which were observed in April 2011 by the scenario of acute inhalation. The internal radioactivity was found in persons staying in almost all of the interior and the coastal regions regardless of the distance from the Fukushima-Daiichi nuclear power plant. Although there was no statistical significance, the detection rate of 134Cs and 137Cs appeared higher in subjects dispatched for relatively long-terms. Comparison of internal doses evaluated by the whole body counter and by prediction from environmental radioactivity indicates that the intake of radioactivity in March, April and possibly May 2011, would be mainly attributable to the inhalation of airborne radioactive particles, whereas in June and later months ingestion of contaminated food would be the major route of radioactive intake. These results suggest that the risk for internal exposure existed for approximately six months after the radiological accident in almost the entire area of Fukushima, however, adverse health consequences by the radiation dose due to internal exposure seem to be negligible. Furthermore, the present risk for internal exposure is quite low in the normal living situation.

著者

Kazuo Kato Maya Ishihara

出版者

日本放射線安全管理学会

雑誌

Radiation Safety Management (ISSN:13471511)

巻号頁・発行日

vol.11, no.1, pp.4-10, 2012 (Released:2012-12-21)

参考文献数

11

被引用文献数

2 2 1

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At a location in the central mountain area of the Chugoku region (Bihoku area), concentrations of 131I, 137Cs and 134Cs in rain and air dust were measured before and after the Tohoku-Pacific Ocean Earthquake that occurred on 11 March 2011. Rainwater was also sampled at a location near the Inland Sea. The rainwater was dried on a Naflon sheet. Airborne particles were collected using an air dust sampler. A pure Ge detector shielded by lead blocks was used to measure the gamma rays from the samples. In both locations of the Chugoku region, initial detections of 131I in rainwater occurred on 8 April 2011. On this date, the 131I concentrations in rainwater were 0.23 ± 0.03 Bq/kg in the mountain area and 0.19 ± 0.01 Bq/kg near the Inland Sea. The concentrations of radioactive cesium in rainwater were high from 19 April to 23 April 2011, and were 0.12 ± 0.02 Bq/kg of 134Cs and 0.12 ± 0.03 Bq/kg of 137Cs at maximum, respectively. The atmospheric concentration of 131I was 9 ± 2 mBq/m3 at maximum (6 April 2011), which was estimated without evaluating the 131I activities of the gaseous molecules that passed through an ordinary filter used in the air dust sampler. Maximum concentrations of 134Cs and 137Cs on 7 April 2011 were 10.2 ± 1.3 mBq/m3 and 9.7 ± 1.4 mBq/m3, respectively. Few radioactive cesium and iodine were observed in March. Western and northwestern winds in March probably prevented these artificial radioactive materials from the Fukushima Daiichi Nuclear Power Plant from reaching the mountain area of the Chugoku region.

著者

Masahiro Hirota Shogo Higaki Takumi Higaki Seiichiro Hasezawa

出版者

日本放射線安全管理学会

雑誌

Radiation Safety Management (ISSN:13471511)

巻号頁・発行日

vol.12, no.2, pp.43-47, 2013 (Released:2013-12-19)

参考文献数

10

被引用文献数

2

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The contamination of spinach collected immediately following the Fukushima Daiichi nuclear disaster was investigated. The radionuclides deposited in the spinach were 132Te, 131I, 132I, 134Cs, 136Cs and 137Cs. Only 40% of these radionuclides were removed when the spinach was washed with water or detergent. The two outside leaves of each spinach stump were contaminated with the radionuclides, but the three inside leaves were nearly uncontaminated. The most significant contamination was observed on the concavities, creases, veins and leaf or stem injuries of the spinach. Most of the radionuclides deposited on the surface, leading to a radioactivity concentration of the epidermal tissue 9 times that of the mesophyll tissue.

著者

Kazuhisa Nakazato

出版者

日本放射線安全管理学会

雑誌

Radiation Safety Management (ISSN:13471511)

巻号頁・発行日

vol.12, no.2, pp.61-80, 2013 (Released:2013-12-19)

参考文献数

20

被引用文献数

2

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A huge amount of radioisotopes(RI), such as 132Te, 131I, 134Cs and 137Cs etc., was released into the atmosphere by the accident of Fukushima Daiichi nuclear power plant of Tokyo electric power company. According to the news immediately after the Fukushima nuclear accident, it was reported that almost all clothes were largely contaminated with the RI, confirmed by the early screenings of the general public evacuated from the Fukushima nuclear accident. On account of a worry about the RI contamination on clothes, many inhabitants could not dry their clothes out of doors in an area indicated the high radiation dose caused by the RI contamination in both Fukushima prefecture and some prefectures next to Fukushima prefecture even after the accidental release of RI was stopped from the accidental Fukushima nuclear power plant.   In order to settle this situation effectively, the Ad Hoc Committee on Safety Measures against Radioactive Iodine and Cesium of the Japanese Society of Radiation Safety Management (JRSM) established a clothes analysis group. The Clothes Analysis Group aimed to analyze the actual RI contamination on clothes, and to develop a simple method to remove the RI by using washing machine sold on market, and so on.   The results were summarized as follows;   (1) The RI contamination was recognized obviously on clothes worn around the accidental Fukushima nuclear power plant immediately after the accident. However, on the clothes worn at July 2011, the RI contamination was not detected by a survey meter, but was detected a little by a Ge semiconductor detector.   (2) The RI on clothes was decontaminated easily by a wash using a usual washing machine and detergent sold on the market. The RI decontamination ratios of the March clothes and the July one in 2011 were approximately 84 % after three times wash and 88 % after a once, respectively.   (3) Radioactive Cs remained slightly after the wash and attached a little on clothes dried out of doors. Whenever the public lived in Fukushima prefecture might wear continuously the clothes contaminated by a trace of Cs after the wash and drying outside, the radiation safety was sufficiently confirmed because the estimated effective dose rate would be extremely lower than the annual dose limit.   Consequently, the wash by using a commercial washing machine and detergent was useful and easy for removing the RI from clothes without a special apparatus for the RI decontamination. Furthermore, the wash was effective both for eliminating an anxiety over radiation exposure by wearing the contaminated clothes, and for bringing a feel of relief by wearing the clean washed clothes.

著者

Midori ISOBE Hiroyuki MORI Narufumi OKADA Yuriko MANNAMI Hiroaki TERATO

出版者

Japanese Society of Radiation Safety Management

雑誌

Radiation Safety Management (ISSN:13471511)

巻号頁・発行日

vol.22, pp.1-6, 2023 (Released:2023-12-09)

参考文献数

6

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Radiation shielding is one of the necessary procedures in radiation protection. The lead blocks are commonly used to shield against gamma- and X-rays. However, due to lead's biotoxicity, the development of alternative materials is required. We developed a novel ceramic product as a non-biotoxic shielding material composed mainly of iron (III) oxide. In this study, the radiation shielding performance against gamma-rays was evaluated and its potential as a radiation shielding material was investigated. We measured the gamma-ray amount transmitted through the ceramic specimens using a NaI scintillation counter with three different gamma sources (133Ba, 137Cs, and 60Co). The order of shielding ability of the sample with the same volume was lead > iron > the ceramics. The effects of piling the blocks and the type of jointing agent used in the gaps on the shielding ability were also observed for considering actual use.

著者

Takahira TAKEMOTO Kazutaka OHSAWA Naoki MATSUDA

出版者

Japanese Society of Radiation Safety Management

雑誌

Radiation Safety Management (ISSN:13471511)

巻号頁・発行日

vol.19, pp.49-57, 2020 (Released:2020-06-26)

参考文献数

24

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To support the safe return of residents after the TEPCO Fukushima Daiichi Nuclear Power Plant accident, cleaning methods and materials for the removal of radiocesium (137Cs) from household surfaces were compared. A spot contaminated with 137Cs on a vinyl floor sheet or a glass plate was wiped in different moisture conditions with different cleaning materials, including a paper sheet, cellulose sponge, polyester sheet, and a polyesterpolyamide sheet. Radioactive solid particles on a vinyl sheet were wiped with miniature mops made of cellulose sponge, polyester microfiber, or cotton yarn. There was little difference in the removal of radioactivity among cleaning materials when the contaminated spot was wiped in wet conditions. The removal of contaminated particles depended on the structure of the mop. The use of an abrasive and a detergent worked well for the vinyl sheet and the glass plate, respectively. These observations suggested that, in appropriate conditions, effective decontamination was achievable by regular indoor cleaning with commercially available cleaning devices.

著者

Water Analysis Group

出版者

Japanese Society of Radiation Safety Management

雑誌

Radiation Safety Management (ISSN:13471511)

巻号頁・発行日

vol.12, no.1, pp.22-30, 2013 (Released:2013-04-12)

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The removal rate of radioactive materials from contaminated water was experimentally obtained using various materials and commercial water purifiers with the aim of enabling the public to easily remove radioactive materials from rainwater and tap water contaminated by radioactive 131I, 134Cs, and 137Cs released by the Fukushima Daiichi Nuclear Power Plant accident using readily obtainable instruments and materials at home. Since it was difficult to obtain contaminated tap water, contaminated rainwater was used as samples in our experiments. In the rainwater, 131I, 132I, 134Cs, 137Cs, 132Te, 129mTe, and 129Te were detected. The abundance ratio of the isotopes depended on the location and date of collection, and the abundance of 131I was 12 to 26 times higher than that of 137Cs. Most of the radioactivity in the rainwater originated from 131I. The removal rate was obtained in the case of using readily available materials and water purifiers at home and in a university laboratory. The results of model experiments using nonradioactive I3- and radioactive 125I instead of 131I suggested that activated carbon was effective. On the basis of these results, we investigated the removal rates of radioactive iodine and cesium using five different pot-type water purifiers with activated carbon as the basic adsorbent, to which ion-exchange resin, a hollow fiber membrane, or a ceramic was added. Approximately 90 to 99% of 131I and 94 to 100% of 137Cs were removed by consecutive purifications using the pot-type water purifiers. These results indicated that these water purifiers can be easily used to remove 131I and 137Cs at home, although special care is required when boiling using an electric kettle because it causes the concentration of 131I. Faucet-mounted- and countertop-type water purifiers with activated carbon as the basic material are expected to have a similar performance to pot-type water purifiers, although this requires future experimental verification. We found that 1-9% of the radioactive 131I remained in the rainwater samples after repeated treatment with the pot-type commercial water purifiers, depending on the sampling location and time, and that some of the residual isotopes were adsorbed on silica nanoparticles. Furthermore, to improve the removal rate, it is necessary to develop a removal method for the remaining components.

著者

Kazuhiro Shiba Yoji Kitamura Takashi Kozaka Izumi Uno Kikuo Shimizu Masahiro Hirota Shogo Higaki Kazuyoshi Masumoto

出版者

日本放射線安全管理学会

雑誌

Radiation Safety Management (ISSN:13471511)

巻号頁・発行日

vol.11, no.1, pp.19-22, 2012 (Released:2012-12-21)

参考文献数

5

被引用文献数

1

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We examined the characteristics of the radioactive contamination and the physical removal of radioactivity from contaminated cabbage and spinach. In a distribution imaging study, there were two types of contamination, spot type and spread type, of cabbage and spinach. The relative radioactivity (PSL) of the face of the leaf was much higher than that of the back of a leaf of cabbage. The ratio of relative radioactivity (PSL) between spot contamination and spread contamination in a leaf of spinach was 9.4% and 90.6%, respectively. More than 80% of radioactivity attaches to the surface of leaves of spinach. There was no significant difference of radioactivity removal between hand-washing and rinsing with running water. The degree of removal of radioactivity from contaminated spinach depended on the length of time between contamination and rinsing. When contaminated spinach was rinsed within 1 week after contamination, the removal ratio of 131I and 137Cs was high, with 50% and 70%, respectively. When rinsing contaminated spinaches more than 2 weeks after contamination, the removal ratio of 131I and 137Cs was low, approximately 34% and 69%, respectively.

著者

Kazuhiro Shiba

出版者

日本放射線安全管理学会

雑誌

Radiation Safety Management (ISSN:13471511)

巻号頁・発行日

vol.12, no.1, pp.31-36, 2013 (Released:2013-04-12)

参考文献数

2

被引用文献数

1 1

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Huge amounts of radioactivity derived from the Fukushima nuclear accident were scattered in the atmosphere. Various kinds of vegetables in three prefectures in the Tohoku area were contaminated with 131I and 137Cs over the legal limit for shipment. A simple and effective removal method for contaminated farm products was developed to ensure the relief of farmers and the security of consumers. Distribution imaging of radioactivity in the contaminated vegetables, the physical removal of radioactivity from contaminated vegetables and the chemical removal of radioactivity from contaminated vegetables were examined. As a result, there were two types of vegetable contamination, spot type or spread type. The concentration of radioactivity was higher on the outer side than the inner side of a vegetable leaf. More than 80% of radioactivity attaches to the surface of leaves. Radioactivity removal by water washing showed no significant difference between boiling water and cold water. There was no significant difference between hand-washing and running water washing. The radioactivity of vegetables decreased by 70-80% for 131I and more than 80% for 137Cs by reducing agent treatments. In particular, ascorbic acid is promising as a safe and versatile option.