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Journal Articles

Comprehensive exposure assessments from the viewpoint of health in a unique high natural background radiation area, Mamuju, Indonesia

Nugraha, E. D.*; Hosoda, Masahiro*; Kusdiana*; Untara*; Mellawati, J.*; Nurokhim*; Tamakuma, Yuki*; Ikram, A.*; Syaifudin, M.*; Yamada, Ryohei; et al.

Scientific Reports (Internet), 11(1), p.14578_1 - 14578_16, 2021/07

 Times Cited Count:1 Percentile:76.35(Multidisciplinary Sciences)

Mamuju is one of the regions in Indonesia which retains natural conditions but has relatively high exposure to natural radiation. The goals of the present study were to characterize exposure of the entire Mamuju region as a high natural background radiation area (HNBRA) and to assess the existing exposure as a means for radiation protection of the public and the environment. A cross-sectional study method was used with cluster sampling areas by measuring all parameters that contribute to external and internal radiation exposures. It was determined that Mamuju was a unique HNBRA with the annual effective dose between 17 and 115 mSv, with an average of 32 mSv. The lifetime cumulative dose calculation suggested that Mamuju residents could receive as much as 2.2 Sv on average which is much higher than the average dose of atomic bomb survivors for which risks of cancer and non-cancer diseases are demonstrated. The study results are new scientific data allowing better understanding of health effects related to chronic low-dose-rate radiation exposure and they can be used as the main input in a future epidemiology study.

Journal Articles

Discriminative measurement of absorbed dose rates in air from natural and artificial radionuclides in Namie Town, Fukushima Prefecture

Ogura, Koya*; Hosoda, Masahiro*; Tamakuma, Yuki*; Suzuki, Takahito*; Yamada, Ryohei; Negemi, Ryoju*; Tsujiguchi, Takakiyo*; Yamaguchi, Masaru*; Shiroma, Yoshitaka*; Iwaoka, Kazuki*; et al.

International Journal of Environmental Research and Public Health, 18(3), p.978_1 - 978_16, 2021/02

 Times Cited Count:1 Percentile:76.35(Environmental Sciences)

Journal Articles

A Unique high natural background radiation area; Dose assessment and perspectives

Hosoda, Masahiro*; Nugraha, E. D.*; Akata, Naofumi*; Yamada, Ryohei; Tamakuma, Yuki*; Sasaki, Michiya*; Kelleher, K.*; Yoshinaga, Shinji*; Suzuki, Takahito*; Rattanapongs, C. P.*; et al.

Science of the Total Environment, 750, p.142346_1 - 142346_11, 2021/01

 Times Cited Count:5 Percentile:96.3(Environmental Sciences)

The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h$$^{-1}$$ and 1109 nGy h$$^{-1}$$. Indoor radon concentrations ranged from 124 Bq m$$^{-3}$$ to 1015 Bq m$$^{-3}$$. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m$$^{-3}$$ recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure.

Journal Articles

Reconstruction of residents' thyroid equivalent doses from internal radionuclides after the Fukushima Daiichi Nuclear Power Station accident

Oba, Takashi*; Ishikawa, Tetsuo*; Nagai, Haruyasu; Tokonami, Shinji*; Hasegawa, Arifumi*; Suzuki, Gen*

Scientific Reports (Internet), 10(1), p.3639_1 - 3639_11, 2020/02

 Times Cited Count:6 Percentile:72.43(Multidisciplinary Sciences)

Internal doses of residents after the Fukushima Daiichi Nuclear Power Station accident have been reconstructed. In total 896 behaviour records in the Fukushima Health Management Survey were analysed to estimate thyroid doses via inhalation, using a spatiotemporal radionuclides concentration database constructed by atmospheric dispersion simulations. After a decontamination factor for sheltering and a modifying factor for the dose coefficient were applied, estimated thyroid doses were close to those estimated on the basis of direct thyroid measurement. The median and 95th percentile of thyroid doses of 1-year-old children ranged from 1.2 to 15 mSv and from 7.5 to 30 mSv, respectively.

Journal Articles

Cesium concentrations in various environmental media at Namie, Fukushima

Heged$"u$s, M.*; Shiroma, Yoshitaka*; Iwaoka, Kazuki*; Hosoda, Masahiro*; Suzuki, Takahito*; Tamakuma, Yuki*; Yamada, Ryohei; Tsujiguchi, Takakiyo*; Yamaguchi, Masaru*; Ogura, Koya*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 323(1), p.197 - 204, 2020/01

 Times Cited Count:3 Percentile:57.07(Chemistry, Analytical)

The radioactivity of cesium in the water and sediments of two major rivers was measured along with airborne radioactivity in Namie Town, after the recent partial lift on the evacuation order in 2017. The observed concentrations were up to 384 $$pm$$ 11 mBq/L for $$^{137}$$Cs in unfiltered water and 1.28 $$pm$$ 0.09 mBq/m$$^{3}$$ for $$^{137}$$Cs in air, while the sediment had a maximum of 44900 $$pm$$ 23.4 Bq/kg for $$^{137}$$Cs. The $$^{134}$$Cs/$$^{137}$$Cs ratios indicate the main origin of the cesium in the sediment to be Unit 1 in good agreement with previous reports on the accident.

Journal Articles

Comparative study on performance of various environmental radiation monitors

Tamakuma, Yuki*; Yamada, Ryohei; Suzuki, Takahito*; Kuroki, Tomohiro*; Saga, Rikiya*; Mizuno, Hiroyuki*; Sasaki, Hiroyuki*; Iwaoka, Kazuki*; Hosoda, Masahiro*; Tokonami, Shinji*

Radiation Protection Dosimetry, 184(3-4), p.307 - 310, 2019/10

 Times Cited Count:1 Percentile:23.13(Environmental Sciences)

After the Fukushima Daiichi Nuclear Power Plant accident, the radiation dose for first responders was not evaluated accurately due to lack of the monitoring data. It has been important to evaluate a radiation dose for workers in emergency response at a nuclear accident. In this study, a new device which can evaluate both of external and internal exposure doses was developed and the performance of various environmental radiation monitors including commercially available monitors were tested and compared from the viewpoint of an environmental monitoring at emergency situation. Background counts of the monitors and the ambient dose equivalent rate were measured in Fukushima Prefecture. The detection limit for beta particles was evaluated by the method of ISO11929. The sensitivity for gamma-rays of the dust monitor using a ZnS(Ag) and a plastic scintillator was high, but that of the external exposure monitor using a silicon photodiode with CsI(Tl) crystal was relatively low. The detection limit ranged 190-280 Bq m$$^{-3}$$ at 100 $$mu$$Sv h$$^{-1}$$, exceeding the detection limit of 100 Bq m$$^{-3}$$ in the minimum requirement by the National Regulation Authority in Japan. Use of the shielding with lead is necessary to achieve the minimum requirement. These results indicate that the dust monitor using a ZnS(Ag) scintillator and a plastic scintillator is suitable for the external exposure monitor and the developed internal exposure monitor is for the internal exposure monitor at emergency situation among the evaluated monitors. In the future study, the counting efficiency, the relative uncertainty and the performance of the detection for alpha particles will be evaluated, and it will be considered which type of a monitor is suitable after taking the portability into account.

Journal Articles

A Portable radioactive plume monitor using a silicon photodiode

Tamakuma, Yuki*; Yamada, Ryohei; Iwaoka, Kazuki*; Hosoda, Masahiro*; Kuroki, Tomohiro*; Mizuno, Hiroyuki*; Yamada, Koji*; Furukawa, Masahide*; Tokonami, Shinji*

Perspectives in Science (Internet), 12, p.100414_1 - 100414_4, 2019/09

In this study, a portable radioactive plume monitor using a silicon photodiode was developed for the detection of a radioactive plume (e.g. $$^{131}$$I, $$^{134}$$Cs and $$^{137}$$Cs) in an emergency situation. It was found that the background count rate was proportional to ambient dose equivalent rate and the detection limit for the monitor at 20 $$mu$$Sv h$$^{-1}$$ as an ambient dose equivalent rate was evaluated to be 187 Bq m$$^{-3}$$ using the ISO11929 method. These results suggest that the detection limit for the system can be decreased effectively by lead shielding with optimized thickness.

Journal Articles

Evaluation of a surface collection efficiency and a stability of flow rate for the commercially available filters used for ambient radioactive aerosols

Tamakuma, Yuki*; Yamada, Ryohei; Iwaoka, Kazuki*; Hosoda, Masahiro*; Tokonami, Shinji*

Hoken Butsuri (Internet), 54(1), p.5 - 12, 2019/03

Airborne radioactivity measurements are necessary to know the contamination level and internal doses for residents after a nuclear accident. In addition, measurements of radon progenies in air, which are the risk factor of lung cancer, are also important to evaluate lung dose. In these measurements, a filter sampling is used to collect radioactive aerosols. However, it is well known that results of the measurement using a filter are strongly dependent on characteristics of the used filter. Selection of a suitable filter is important to achieve the high-resolution and long-term measurement. "Surface collection efficiency (SCE)" and "stability of air flow rate" were examined for six types of filter that are commercially available in Japan. In Japan, cellulose-glass fiber filter paper (HE-40T) is used for an environmental monitoring in Japan. In this study, it was found that the SCE of HE-40T was lower than that of mixed cellulose ester type membrane filter by Merck Millipore (DAWP02500). Attenuation ratio of flow rate for DAWP02500 was evaluated to be 2.9% which was lowest in six filters. The results suggest that the DAWP02500 is the most suitable for collecting radioactive aerosols for a long term.

Journal Articles

Study of chemical etching conditions for alpha-particle detection and visualization using solid state nuclear track detectors

Yamada, Ryohei; Odagiri, Taiki*; Iwaoka, Kazuki*; Hosoda, Masahiro*; Tokonami, Shinji*

Radiation Environment and Medicine, 8(1), p.21 - 25, 2019/02

We evaluate radon/thoron and its progeny concentration using passive-type monitors using CR-39 plates. After exposure, it is necessary to do chemical etching for CR-39 plates. In the present study, we considered shortening of chemical etching time for CR-39 and enlargement of the track diameter (i.e. etch pit diameter) aiming for introduction of automatic counting system in the future. Optimum conditions were determined by changing solution concentration, solution temperature and etching time. As a result, the optimized conditions (concentration, temperature and etching time) were determined to be 8 M NaOH solution, 75 degrees Celsius and 10 hours. This result of etching time showed that the chemical etching was completed in less than half of conventional etching time. Furthermore, it was suggested that shorter etching time would be possible if we do not consider the enlargement of conventional track diameter.

Journal Articles

Thoron exhalation rates in areas of Japan

Shimo, Michikuni*; Ishimori, Yuu; Hosoda, Masahiro*; Tokonami, Shinji*

Radiation Protection Dosimetry, 141(4), p.473 - 476, 2010/09

 Times Cited Count:2 Percentile:19.27(Environmental Sciences)

Thoron exhalation rates were measured with a newly made portable instrument at 33 areas in 7 prefectures of Japan. Thoron exhalation rates ranged from 49 to 4890 mBq m$$^{-2}$$ s$$^{-1}$$. Radon exhalation rates were also measured in many of the areas at the same time and ranged from 2.1 to 11 mBq m$$^{-2}$$ s$$^{-1}$$. Thoron exhalation rates showed a rough correlation with radon exhalation rates. Both exhalation rates also showed a rough correlation with geological features.

Journal Articles

Epidemiological studies on indoor radon risk; A Review and current issues

Yonehara, Hidenori*; Ishimori, Yuu; Akiba, Suminori*; Iida, Takao*; Iimoto, Takeshi*; Kai, Michiaki*; Shimo, Michikuni*; Tokonami, Shinji*; Yamada, Yuji*; Yoshinaga, Shinji*; et al.

Hoken Butsuri, 42(3), p.201 - 213, 2007/09

The pooled analysis recently carried out in European countries and North American countries showed the excess relative risk of lung cancer increased by 10-20% per 100 Bqm$$^{-3}$$ increase in indoor radon concentration. The Scientific Committee on Indoor Radon Risk and Response to the Issue established by the Japan Health Physic Society reviewed the scientific evidence on the indoor radon risk obtained so far and evaluated the pooled analysis results from the viewpoint of estimating the risk coefficient in Japan. The committee concludes that the risk shown by the pooled analysis results has the consistency from miners risk analysis, and that it is probably not low in the reliability and validity, although the value may include the uncertainties caused from the correction of radon concentration measured, from the effect of thoron on measurement results, from the differences of environmental parameters in exposure, and so on.

Oral presentation

Ultra fine particle generation and induced radioactivity in electron linear accelerator

Yamasaki, Keizo*; Oki, Yuichi*; Osada, Naoyuki*; Yokoyama, Sumi; Yamada, Yuji*; Tokonami, Shinji*; Fukutsu, Kumiko*; Iida, Takao*; Rahman, N. M.*; Shimo, Michikuni*

no journal, , 

no abstracts in English

Oral presentation

Generation of natural and artificial radioactive aerosol in electron linear accelerator

Yamasaki, Keizo*; Oki, Yuichi*; Osada, Naoyuki*; Iida, Takao*; Shimo, Michikuni*; Yamada, Yuji*; Tokonami, Shinji*; Fukutsu, Kumiko*; Yokoyama, Sumi

no journal, , 

The physicochemical properties of radioactive aerosols are important factors to assess internal dose at high energy accelerator facilities. In Kyoto University Research Reactor Institute, a generation of radioactive aerosols in ADSR (Accelerator-Driven Subcritical Reactor) facilities was studied as part of the research project of ADSR. The generation of radioactive aerosols in high intensity irradiation fields of ADSR was simulated by irradiation of the target room air at LINAC. We measured the particle size of radioactive aerosols in the target room during the acceleration period. Natural radon aerosols in the target room grew to the larger size because of an attachment of radon daughters to non-radioactive aerosols. The particle size of the produced radioactive aerosols was also larger with time. This would mean that a formation mechanism of the radioactive aerosols produced at high energy accelerator facilities is the same as radon one.

Oral presentation

The Evaluation of the radon dose of radioactivity in high-level radioactive waste geological disposal facility

Yoshizawa, Yuji*; Kai, Michiaki*; Okoshi, Minoru; Kato, Tomoko; Yamaguchi, Tetsuji; Sasaki, Takayuki*; Hattori, Takatoshi*; Miyazaki, Shinichiro*; Higuchi, Natsuko*; Tokonami, Shinji*; et al.

no journal, , 

no abstracts in English

Oral presentation

Dose variation measurement at the high background radiation area in Indonesia

Sasaki, Michiya*; Yamada, Ryohei; Akata, Naofumi*; Tokonami, Shinji*; Hosoda, Masahiro*; Iwaoka, Kazuki*; Chanis, P.*; Kudo, Hiromi*; Sahoo, K.*; Iskandar, D.*; et al.

no journal, , 

Recently, Mamuju city in Sulawesi Island, Indonesia and its surrounding area is known as the high background radiation area, and is regarded as a possible area for an epidemiological study. In this study we have measured the hourly dose rates of individuals and the environment with the D-shuttle dosimeter, which has been developed by the Chiyoda Technol Corporation. With the aid of local residents living at Botteng village, which is located south of Mamuju city, short term and long term measurements were conducted for three days and nine months, respectively. Two volunteers have equipped the D-shuttle for the short term measurement, and seven families supported the short and long term measurements of the environmental dose rate, for both inside and outside the house. From our results, since some variation was observed regarding with day or night, correlation with radon concentration was suggested.

Oral presentation

Radiation dose estimation at the high background radiation area in Indonesia; Dose rate measurement at different height

Sasaki, Michiya*; Yamada, Ryohei; Nugraha, E.*; Akata, Naofumi*; Tokonami, Shinji*; Hosoda, Masahiro*; Iwaoka, Kazuki*; Pornnumpa, C.*; Kudo, Hiromi*; Sahoo, K.*; et al.

no journal, , 

The area around Mamuju city in West Sulawesi, Indonesia has high possibility of being a target of epidemiological research as a high natural radiation area. We would like to report the difference in radiation dose at different heights from the ground measured by the D-Shuttle.

Oral presentation

Development of direct-type alpha dust monitor for in-situ measurement of airborne concentration during fuel debris retrieval and decommissioning of nuclear fuel cycle facilities

Tsubota, Yoichi; Honda, Fumiya; Nakagawa, Takahiro; Kawasaki, Takashi; Ikeda, Atsushi; Tamakuma, Yuki*; Tokonami, Shinji*; Momose, Takumaro

no journal, , 

A large number of radioactive aerosols, especially alpha particles, are expected to be generated during fuel debris retrieval on Fukushima - Daiichi (1F) site and decommissioning of nuclear fuel cycle facilities. For conventional alpha dust monitor, 1-channel of silicon surface barrier detector (SSBD) is often used as a detector which has not so high limit of count rates. Moreover, since radioactive aerosol collected on a filter paper are measured by a detector, it is difficult to calculate an airborne concentration at the sampling site because a conventional dust monitor measures an integrated radioactivity on a filter paper. In this work, we developed a prototype of alpha dust monitor aiming at an in-situ measurement of high concentration airborne alpha particles. The efficiency for U$$_{3}$$O$$_{8}$$ checking source was 80.8%. For high count rate test using 3 MBq of $$^{241}$$Am checking source, 2.1 $$times$$ 10$$^{7}$$ cpm was achieved which was more than 10 times higher compared to an conventional alpha dust monitor using SSBD. For follow-up test to the airborne concentration of alpha particles using radon chamber, counting rate of prototype alpha dust monitor was smoothly followed with respect to the radon concentration in a radon chamber.

Oral presentation

Re-assessment of evacuation patterns and thyroid equivalent doses for children via inhalation after the Fukushima Daiichi Nuclear Power Station accident

Oba, Takashi*; Ishikawa, Tetsuo*; Nagai, Haruyasu; Tokonami, Shinji*; Hasegawa, Arifumi*; Suzuki, Gen*

no journal, , 

no abstracts in English

Oral presentation

Development of elemental technology for alpha-ray dust monitor for in-situ measurement of radioactive aerosol in dismantling and decommissioning

Tsubota, Yoichi; Honda, Fumiya; Nakagawa, Takahiro; Kawasaki, Takashi; Tamakuma, Yuki*; Tokonami, Shinji*; Momose, Takumaro

no journal, , 

A large number of radioactive aerosols, especially alpha particles, are expected to be generated during fuel debris retrieval on Fukushima - Daiichi (1F) site and decommissioning of nuclear fuel cycle facilities. In the case of conventional alpha dust monitor, silicon surface barrier detector (SSBD) is often used as a detector which has not so high limit of count rates. Moreover, SSBD is not suitable for high humidity environment. In this work, we developed a prototype of alpha dust monitor aiming at an in-situ measurement of high concentration of airborne alpha particles. Approx. 20M cpm of counting rate was achieved which was more than 10 times higher compared to a conventional alpha dust monitor using SSBD. For follow-up test, counting rate of prototype alpha dust monitor was smoothly followed with respect to the airborne concentration of alpha particles.

Oral presentation

Development of elemental technologies for "in-situ" alpha dust monitors for fuel debris retrieval and decommissioning

Tsubota, Yoichi; Yoshida, Masato; Honda, Fumiya; Tokonami, Shinji*; Nakagawa, Takahiro; Kawasaki, Takashi

no journal, , 

In order to measure the airborne concentration in air in real time, a dust monitor to measure directly the alpha-particle concentration in a flat-type flow path was developed and its performance was evaluated. The performance of the prototype dust monitor was evaluated in a high-humidity environment, and its counting rate was more than ten times higher than that of a conventional dust monitor.

24 (Records 1-20 displayed on this page)