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Journal Articles

The Effect and effectiveness of decontaminating a pond in a residential area of Fukushima

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

Health Physics, 121(1), p.48 - 57, 2021/07

 Times Cited Count:0 Percentile:0.02(Environmental Sciences)

Special reconstruction and revitalization bases were designated in Fukushima's difficult-to-return zones by the Japanese government as targets of intensive decontamination to drastically lower air dose rates and enable residents to return. A pond amidst residences of one of these bases was targeted for decontamination and this study aimed at evaluating the effect and effectiveness of the decontamination by decontamination factor, air dose rate reduction factor, and the additional annual effective dose to residents. Air dose rates were measured in-situ with KURAMMA-II while soil core samples were collected and measured for radioactivity in the laboratory by gamma spectrometry. Lower decontamination factors were observed for more deeply distributed radiocesium soil profiles whereas areas covered with gravel demonstrated the largest reduction in air dose rates. Decontamination effectively lowered the radiocesium inventory and air dose rates by 51% and 37-91% respectively. Moreover, the additional annual effective dose to the public changed from 1.7$$pm$$0.79 mSv to 1.2$$pm$$0.57 mSv because of decontamination representing a dose aversion of 29%. These findings demonstrate how decontaminating ponds in residential areas can help to further lower the external exposure.

Journal Articles

The Ecological half-life of radiocesium in surficial bottom sediments of five ponds in Fukushima based on ${it in situ}$ 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

 Times Cited Count:3 Percentile:59.86(Chemistry, Analytical)

Journal Articles

Development of dose estimation system integrating sediment model for recycling radiocesium-contaminated soil to coastal reclamation

Miwa, Kazuji; Takeda, Seiji; Iimoto, Takeshi*

Radiation Protection Dosimetry, 184(3-4), p.372 - 375, 2019/10

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

The Ministry of the Environment has indicated the policy of recycling the contaminated soil generated by decontamination activity after the Fukushima accident. By recycling to coastal reclamation which is one of effective recycling application, dissolved radiocesium and absorbed radiocesium on soil particles will flow out to the ocean by construction, therefore evaluating radiocesium transition in ocean considering the both types of radiocesium is important for safety assessment. In this study, the radiocesium outflow during constructing and after constructing is modeled, and radiocesium transition in ocean is evaluated by Sediment model suggested in OECD/NEA. The adaptability of sediment model is confirmed by reproducing evaluation of the coastal area of Fukushima. We incorporate the sediment model to PASCLR2 code system to evaluate the doses from radiocesium in ocean.

Journal Articles

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

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

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.

Journal Articles

Current situations and discussions in Japan in relation to the new occupational equivalent dose limit for the lens of the eye

Yokoyama, Sumi*; Hamada, Nobuyuki*; Hayashida, Toshiyuki*; Tsujimura, Norio; Tatsuzaki, Hideo*; Kurosawa, Tadahiro*; Nabatame, Kuniaki*; Oguchi, Hiroyuki*; Ono, Kazuko*; Kawaura, Chiyo*; et al.

Journal of Radiological Protection, 37(3), p.659 - 683, 2017/09

 Times Cited Count:11 Percentile:85.4(Environmental Sciences)

Since the International Commission on Radiological Protection recommended reducing the occupational equivalent dose limit for the lens of the eye in 2011, there have been extensive discussions in various countries. This paper reviews the current situations in radiation protection of the ocular lens and the discussions on the potential impact of the new lens dose limit in Japan. Topics include historical changes to the lens dose limit, the current situations in occupational lens exposures (e.g., in medical workers, nuclear workers, and Fukushima nuclear power plant workers) and measurements, and the current status of biological studies and epidemiological studies on radiation cataracts. Our focus is on the situations in Japan, but we believe such information sharing will be useful in many other countries.

Journal Articles

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

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.

Journal Articles

Addendum report of the JHPS expert committee on radiation protection of the lens of the eye, 2; When and how should the dosimetry of beta $$H_{rm p}$$(3) be made?

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

Hoken Butsuri, 50(4), p.257 - 261, 2015/12

In a mixed field of photon and beta radiations, the same dose assigned to skin is normally assigned to the dose to the lens of the eye as a conservative estimate of H$$_{p}$$(3). In exceptional cases that a very high beta dose might be imparted of the same order with the dose limit, however, the conservatively biased dose must be too limiting, and thereby an accurate estimate of beta $$H_{rm p}$$(3) is desirable. This article presents a practical proposal of when and how the dosimetry of beta $$H_{rm p}$$(3) should be made.

Journal Articles

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

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 $$H_{rm p}$$(10) and $$H_{rm p}$$(0.07), given by the dosemeter, is generally used as a surrogate of $$H_{rm p}$$(3).

Journal Articles

Measurement of radioactive fragment production excitation functions of lead by 400 MeV/u carbon ions

Ogawa, Tatsuhiko; Morev, M.*; Iimoto, Takeshi*; Kosako, Toshiso*

Progress in Nuclear Science and Technology (Internet), 4, p.574 - 577, 2014/04

Depth distributions of radioactive fragments in a thick lead target exposed to 400 MeV/u carbon ions were measured to obtain isotopic production cross-sections of $$^{Nat}$$Pb(C,x) X reactions as excitation functions. The procedure of this experiment was validated by comparing the obtained data with the available thin target experimental data. Energy and mass dependences of the obtained cross-sections give insight into the reaction mechanism and will be useful for radiation transport code benchmarking.

Journal Articles

AESJ-KNS exchange work of students and young researchers; Subcommittee on students and young researchers exchange program

Ishibashi, Kenji*; Uesaka, Mitsuru*; Morita, Koji*; Sato, Yasushi*; Iimoto, Takeshi*; Watanabe, Yukinobu*; Unesaki, Hironobu*; Yamano, Hidemasa

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 55(7), p.403 - 406, 2013/07

Japan-Korea Exchange program has been successful and their joint sessions have been accompanying conferences. With this background, younger generation's communication has been recognized as important role in Japan and Korea's joint cooperation. Thus students and young researchers support program has started. Understanding the achievements and the current status is important, expecting unrelated areas and working groups to show interest and hopefully join this area of work.

Journal Articles

Dose evaluation from multiple detector outputs using convex optimisation

Hashimoto, Makoto; Iimoto, Takeshi*; Kosako, Toshiso*

Radiation Protection Dosimetry, 146(1-3), p.65 - 68, 2011/07

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

A dose evaluation using multiple radiation detector outputs can be improved by the convex optimisation. It enables flexible dose evaluation corresponding to the radiation field. The neutron ambient dose equivalent is evaluated using a mixed-gas proportional counter. The reliability of evaluated dose values are comparable with current dosimeter. An application to neutron individual dose equivalent measurement is also investigated. The combination of dosimeters with high orthogonality of response characteristics tends to show good suitability for dose evaluation.

Journal Articles

Applicability of convex hull in multiple detector response space for neutron dose measurements

Hashimoto, Makoto; Iimoto, Takeshi*; Kosako, Toshiso*

Radiation Protection Dosimetry, 136(1), p.1 - 10, 2009/07

 Times Cited Count:1 Percentile:10.97(Environmental Sciences)

A novel neutron dose measurement method which flexibly responds to variations of neutron field is being developed in JAEA. This is an implementation of the multi-detector method (first introduced in early 1970s) for neutron dose evaluation using convex hull in the response space defined for multiple detectors. The convex hull provides range of possible neutron dose corresponding to the incident neutron spectrum. Feasibility of the method was studied using simulated response of mixed-gas proportional counter. Monochromatic neutrons are shown to be fundamentally suitable for mapping the convex hull. The convex hull can be further reduced taking into consideration ${it a priori}$ information about physically possible incident neutron spectra, for example, theoretically derived moderated neutron spectra originated from a fission neutron source.

Journal Articles

Dose evaluation with closed space in vector space composed of radiation detector outputs

Hashimoto, Makoto; Iimoto, Takeshi*; Kosako, Toshiso*

Proceedings of International Symposium commemorating the First Anniversary of the Foundation of GoNERI "Key to the Future; Energy Security and Nuclear Education & Research", p.247 - 252, 2008/10

Neutron dose evaluation method which flexibly respond to an alteration of neutron field is developing. The mulitidetector method is introduced. The method uses a convex hull in a topological vector space composed of the ratio of multi detector outputs and objective quantities. The convex hull provides range of possible conversion factor to obtain objective quantity based on the circumstance condition. The convex hull is sophisticated with elemental neutron spectra group of respective neutron field. Mixed gas proportional counter is applied to validate the effectively of the dose evaluation method with a convex hull.

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.

JAEA Reports

An Investigation of methods for neutron dose measurement in high temperature irradiation fields

Kosako, Toshiso*; Sugiura, Nobuyuki*; Kudo, Kazuhiko*; Mori, Chizuo*; Iimoto, Takeshi*; Shikama, Tatsuo*; Katagiri, Masaki; Hayashi, Kimio; Aihara, Jun; Shibata, Taiju; et al.

JAERI-Review 2000-017, 78 Pages, 2000/10

JAERI-Review-2000-017.pdf:4.62MB

no abstracts in English

Oral presentation

Study on neural network application for bonner sphere neutron spectrometry

Hashimoto, Makoto; Sohn, S.-K.*; Iimoto, Takeshi*; Kosako, Toshiso*

no journal, , 

While unfolding calculation is widely applied for the neutron spectrum evaluation with multi moderator method, such experiments can configure neural network for neutron spectrum evaluation and it makes quick to evaluate the neutron spectrum. Conformation of the neural network and effects of some condition to the network will be discussed.

Oral presentation

Discussion about the application of neural network technique for neutron dosimetory

Hashimoto, Makoto; Sohn, S.-K.*; Iimoto, Takeshi*; Kosako, Toshiso*

no journal, , 

Application of neural network technique for neutron spectrometry with multi-moderator neutron spectrometer is discussed. It is confirmed that the convergent of neural network estimation is good in a case of high orthogonarity in responses of multi-moderated detectors.

Oral presentation

Dose evaluation with closed space in vector space composed of radiation detector outputs

Hashimoto, Makoto; Sohn, S.-K.*; Iimoto, Takeshi*; Kosako, Toshiso*

no journal, , 

It is known that the ratios of multiple detectors outputs and objective values compose closed convex in vector space forming with these ratios in the case of optimum obcective value evaluation, such as dose evaluation, with multiple radiation detectors. Neutron dose evaluation method with this method is discussed. A neutron detector with high sensitivity for thermal neutrons and fast neutrons combined was applied for dose evaluation experiment with this method. The response of the detector was simulated by calculation and experimentally validated with mono-energy neutron and RI. A vector space with tis detector was calculated. It is confirmed that the simulated outputs of detectors with various types of neutron field and experimental outputs plotted in this vector space are arranged in closed convex.

Oral presentation

Radionuclide migration and related dose around a uranium mining site

Sato, Kazuhiko; Koga, Osamu; Tokizawa, Takayuki; Iimoto, Takeshi*; Kosako, Toshiso*

no journal, , 

Oral presentation

Neutron dose measurement using convex hull data treatment

Hashimoto, Makoto; Morev, M. N.*; Iimoto, Takeshi*; Kosako, Toshiso*

no journal, , 

A neutron dose measurement method with multiple neutron detectors is developed. A vector space composed with ratio of multiple neutron detectors' output derive the neutron dose in particular extent. It was applied to special proportional counter or personal dosimeter and confirmed the vallidity of this method. It improved the credibility of neutron dose measurement from the conventional dose measurement in spite of using conventional detectors.

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