Kyoto University
Research Reactor InstituteInternational Symposium on
Environmental monitoring and dose
estimation of residents after accident of
TEPCO's Fukushima Daiichi Nuclear
Power Stations
14 December 2012
The Shiran Hall, Kyoto University
KURRI Research Program for Scientific
Basis of Nuclear Safety

Programme&
Abstracts

Preface
In March 2011, a massive earthquake and the resulting tsunami struck the Tohoku
area in Japan, causing serious damages to TEPCO’s Fukushima Daiichi nuclear plant
and the release of a significant quantity of radionuclides into the surrounding
environment. This accident underlined the necessity of establishing new andcomprehensive scientific research for promoting safety in nuclear technology. With thisaim, the Kyoto University Research Reactor Institute (KURRI) developed a newresearch program called the “KUR Research Program for Scientific Basis of Nuclear
Safety” from this year. In this program, we are planning to hold an annual series ofinternational symposiums along with many other research activities.
The first in this series of symposiums, entitled “The International Symposium on
Environmental Monitoring and Dose Estimation of Residents after Accident of TEPCO's
Fukushima Daiichi Nuclear Power Station,” deals with the radiological effect of the
March 2011 accident in Fukushima Daiichi NPP on the public. The purpose of this
symposium is to collate data on environmental radioactivity and radiation dose inresidents, discuss and verify these data, and clarify the actual situation of environmental
contamination and resultant radiation exposed to the residents. We believe that an
accurate estimation of the radiation dose is quite essential for planning for the healthy
life and mental contentment of the residents, and we hope that many researchers who are
studying the radiological effects of the accident will join us for these purposes. The
environmental monitoring data are important for the dose assessment for residents.
However, the monitoring data in the early stage are not sufficient for dose assessment,
particularly near the NPP site, because of the confusion and blackout caused by theearthquake. However, many researchers and organizations in Japan and other countries
have independently carried out radiation monitoring. We believe that the publication andreviewing of these data is not only essential but our duty toward future generations.
Approximately 10 invited lectures and 50 scientific papers will be presented in the
symposium. Almost all the presentations have been written as original scientific papers,
peer reviewed by specialists of the relevant research fields, and included in theproceedings booklet. On behalf of all the participants of the symposium, I sincerely
hope that this symposium and its proceedings will contribute to the faster recovery ofpeople who have encountered damages from the accident and will promote further
progress in the research on nuclear safety.

Hirotake Moriyama
Director, Kyoto University Research Reactor Institute
Chair of the organizing committeeHost Organization
Kyoto University Research Reactor Institute (KURRI)

Support organization
・Japan Radiation Research Society
・ Atomic Energy Society of Japan・Japan Health Physics Society
・ Japan Society of Nuclear and Radiochemical

Organizing Committee
Chair: Hirotake Moriyama (Director, KURRI)
Dr. Jiro Inaba (REA)
Dr. Kimiaki Saito (JAEA)
Dr. Kazuo Sakai (NIRS)
Prof. Hirofumi Tsukada (Fukushima Univ.)
Dr. Shigeo Uchida (NIRS)
Prof. Itsumasa Urabe (Fukuyama Univ.)
Prof. Hiromi Yamazawa (Nagoya Univ.)
Prof. Akio Koyama (KURRI)
Prof. Ken Nakajima (KURRI)
Prof. Sentaro Takahashi (KURRI)
Prof. Hajimu Yamana (KURRI)

International Advisor
Prof. Hajimu Yamana (KURRI)
Prof. Yoshiharu Yonekura（NIRS)
Prof. Williams Lee, (Department of Materials, Imperial College London)

Program Committee
Chair: Prof. Sentaro Takahashi (KURRI)
Prof. Nobuhiko Ban (Tokyo Healthcare Univ.)
Dr. Takatoshi Hattori (CRIEPI)Prof. Noriyuki Momoshima (Kyushu Univ.)
Prof. Hirokuni Yamanishi (Kinki Univ.)
Dr. Nobuyuki Sugiura (NIRS)
Dr. Satoshi Yoshida (NIRS)
Prof. Koichi Takamiya (KURRI)
Prof. Minoru Tanigaki (KURRI)
Prof. Toshihiro Yamamoto (KURRI)

Conference Secretariat
Chair: Prof. Tomoyuki Takahashi (KURRI)
Prof. Satoshi Fukutani (KURRI)
Prof. Yuko Kinashi (KURRI)
Prof. Nobuhiro Sato (KURRI)
Ms. Maki Nakatani (KURRI)
1

Program
9:00-10:00

Registration、Poster Reception

10:00-10:05

Opening remarks Prof. Hirotake Moriyama, Director of KURRI

10:05-11:05

Accident of Fukushima Daiichi Nuclear Power Plant-Sequences, FP released, Lessons learned–
Speaker: Prof. Jun Sugimoto (Kyoto University)
Chair: Prof. Ken Nakajima (KURRI)

11:05-11:50

IAEA safety standards for radiological protection of the public in post-accident situations
Speaker: Dr.Gerhard Proehl (IAEA)
Chair: Hirofumi Tsukada (Fukushima University)

11:50-13:20

Lunch and poster session

13:20-14:20

UNSCEARs assessment of radiation levels/effects from Fukushima accident
Speaker: Prof. Wolfgang Weiss（Chair for the fifty-eighth and fifty-ninth sessions of UNSCEAR）

Chair: Prof. Hirotake Moriyama (Director of KURRI)
14:20-15:05

Radiation monitoring and mapping around the Fukushima site
Speaker: Dr. Kimiaki Saito (JAEA)
Chair: Prof. Hiromi Yamazawa (Nagoya University)

15:05-15:35

Coffee break and poster session

15:35-15:50

Implication of the isotopic ratios of radionuclides observed in the contaminatedareas surrounding Fukushima-Daiichi NPP
Speaker: Prof. Hajimu Yamana (KURRI)
Chair: Prof. Itsumasa Urabe (Fukuyama University)

15:50-16:10

Development of a car-borne survey system, KURAMA
Speaker: Prof. Minoru Tanigaki (KURRI)
Chair: Prof. Itsumasa Urabe (Fukuyama University)

16:10-16:40

NIRS’s activities for the reconstruction of early internal exposure in the TEPCO
Fukushima Daiichi Nuclear Power Station accident
Speaker: Dr. Osamu Kurihara (NIRS)
Chair: Prof. Nobuhiko Ban (Tokyo Healthcare University)

16:40-17:10

Release of plutonium isotopes from the Fukushima Daiichi Nuclear Power Plant accident
Speaker: Dr.Jian Zheng (NIRS)
Chair: Prof. Nobuhiko Ban (Tokyo Healthcare University)

17:20-17:50

Discussion

17:50-17:55

Closing remarks

18:00-19:30

Reception

Chair: Dr.Kazuo Sakai (NIRS)
Co-chair: Prof. Sentaro Takahashi (KURRI)
Prof. Hajimu Yamana (KURRI)

2

Poster sessions
Topics 1 Radiation survey in environment
1 Kazuhiro Akimoto
Wind-Driven Transport of Resuspended Radioactive Dust in Fukushima Prefecture
2 Takao Ebisawa, Seiichi Hirose, Etsuko Furuta, Keiji Kusama, Takeshi Iimoto
Environmental radiation status in Bunkyo-ku, Tokyo, after the TEPCO Fukushima Dai-ichi NPP
Nuclear Disaster3 Seiichi Someya, Hirofumi Fujii, Takeshi Iimoto
Environmental radiation status in Kashiwa City (Chiba Prefecture) after the TEPCO Fukushima
Dai-ichi NPP Nuclear Disaster4 Sadao Iiizumi, Hirofumi Fujii, Takeshi Iimoto
Environmental radiation status in Nagareyama City (Chiba Prefecture) after the TEPCO
Fukushima Dai-ichi NPP Nuclear Disaster5 Takeshi Iimoto, Norio Nogawa, Hiroshi Mitani, Masao Kamiko, Takahiko Suzuki
Environmental radiation status in The University of Tokyo after the TEPCO Fukushima Dai-ichi
NPP Nuclear Disaster6 Takumi Kubota, Tomoko Ohta
Radiation measurement in the East Japan with a GM-tube detector after the Fukushima nuclear accident
7 Takumi Kubota, Jun-ichi Hori, Nobuhiro Sato, Koichi Takamiya
Measurement of radiation dose by car in Fukushima from 19 to 22 March 2011
8 Nobuhito Ohte, Masashi Murakami, Kohei Iseda, Keitaro Tanoi, Nobuyoshi Ishii
Diffusion and transportation dynamics of 137Cs deposited on the forested area in Fukushima after
the nuclear power plant accident in March 2011
9 Shinji Sugihara, Noriyuki Momoshima, Akihiro Maekawa, Ryohei Ichikawa, Hidehisa Kawamura
Distribution of gamma-ray dose rate in Fukushima Prefecture by a car borne survey method
10 Kazuaki Yajima, Kazuki Iwaoka, So Kamada, Masashi Takada, Hiroyuki Tabe, Hidenori Yonehara,
Sin-ya Hohara, Genichiro Wakabayashi, Hirokuni Yamanishi, Tetsuo Itoh, Michio Furukawa
Dose rate survey inside and outside three types of public buildings located approximately 40 km
northwest from the Fukushima Daiichi Nuclear Power Stations
11 Kazuaki Yajima, Kazuki Iwaoka, Hiroshi Yasuda
Radiation survey along two trails in Mt. Fuji to investigate the influence of the radioactive
contamination due to the Fukushima nuclear accident
12 Tomoaki Yamamoto, Kenzo Muroi, Sumito Maruyama, Takahisa Koike, Marina Matsuda,
Kenichiro Katsumata
Environmental radiation doses due to the accident at the Fukushima Daiichi Nuclear Power Plants313 Tetsuo Itoh , Michio Furukawa, Nobuyuki Sugiura, Hirokuni Yamanishi, Genichiro Wakabayashi
Tetsuo Horiguchi, Shin-ya Hohara, Masayo Inagaki, Hiroshi Noma, Kiyoshi Kojima
Survey of environmental radiation in Kawamata-machi, Fukushima-ken
14 Masahiro Yoshida
Environmental radiation measurements immediately after the accident and dose evaluations bysoil deposition
Topic 2 Environmental Radioactivity
1 Tatsuo Aono, Satoshi Igarashi, Yukari Ito, Jyota Kanda, Takashi Ishimaru
Radioactivity Survey in Marine Environment in the Pacific off Fukushima after Accident of
TEPCO's Fukushima Daiichi Nuclear Power Station
2 Satoru Endo, Tsuyoshi Kajimoto, Kiyoshi Shizuma
Dose rate estimation for northern Miyagi Prefecture area at the early stage of Fukushima accident
3 Naoto Fujinami, Naoto Miyajima, Tetsuya Watanabe, Yoshihiro Tanabe, Hajime Nishiuchi
Influence of the Fukushima Daiichi Nuclear Power Plant Accident observed from results ofenvironmental radiation monitoring in Kyoto
4 Ryuta Hazama, Akihito MatsushimaComparison between fallout with rain from Fukushima, Chernobyl reactor accidents in Japan,and Hiroshima atomic bomb
5 Sin-ya Hohara, Masayo Inagaki, Hirokuni Yamanishi, Genichiro Wakabayashi, Wataru Sugiyama,
Tetsuo Itoh
Survey of radioactive contamination distribution at Naka-Dori area, Tohoku Region, Japan
6 Nobuyoshi Ishii, Hiroyuki Koiso, Keiko Tagami, Shigeo Uchida
Elution of radiocesium from soil
7 Hidesuke Itadzu, Tetsuo Iguchi, Toshikazu Suzuki
Development of rapid self-absorption correction method used for HPGe detector
8 Tsuyoshi Kajimoto, Satoru Endo, Takeshi Naganuma, Kiyoshi Shizuma
Distribution of radioactive 137Cs and 134Cs in river water and bottom sand for major rivers at
Minami-Souma City in Fukushima
9 Akihiro Maekawa, Noriyuki Momoshima, Shinji Sugihara, Toshiya Tamari
Determination of radiostrontium released from Fukushima Daiichi Nuclear Power Plant by
extraction chromatography and liquid scintillation counting
10 N. Momoshima, S. Sugihara, R. Ichikawa, A. Maekawa, R. Ozawa, A. Nakama
Radioactivity in vegetation at Fukushima area contaminated with radionuclides released fromTEPCO's Fukushima Daiichi Nuclear Power Stations
11 Kimihito Nakamura, Tetsuo Yasutaka
Characteristics of radiocesium concentration in stream water from a catchment in hilly andmountainous area at rainfall event

412 Tatsuya Shimazaki, Yoshioki Shiraishi, Kumiko Goto, Akihiro Kojima, Toru Urano, Seiji Okada
Specific activity and time dependence of radionuclides in soils affected by the accident of the
Fukushima Dai-ichi nuclear power plant.
13 Kiyoshi Shizuma, Tsuyoshi Kajimoto, Satoru Endo
Early air sampling in Higashi-Hiroshima after the accident of the Fukushima daiichi nuclear power
plant and subsequent sampling in Minami-Souma City during October 2011 to September 2012.
14 Keiko Tagami, Shigeo Uchida, Nobuyoshi Ishii, Jian Zheng
Estimation of Tellurium-132 distribution in Fukushima prefecture
15 Yoshito Watanabe, San’ei Ichikawa, Masahide Kubota, Masahiko Mizoguchi, Toshiyuki
Takano,Yoshihisa Kubota, Shoichi Fuma, Satoshi Yoshida
Effects of radionuclide contamination on forest trees in 20 km exclusion zone around the
Fukushima Daiichi Nuclear Power Plant
16 Masanobu Ishida, Ryota Nakagawa, Kohei Umetsu, Miyabi Sugimoto, Yuta Yamaguchi, Hideo
YamazakiGeographical distribution of radioactive nuclides released from the Fukushima Daiichi Nuclear
Power Station accident in the metropolitan area, Japan
17 Ryota Nakagawa, Masanobu Ishida, Daisuke Baba, Satomi Tanimoto, Yuichi Okamoto,
Hideo Yamazaki
Spatial and temporal distribution of 134Cs and 137Cs derived from Fukushima Daiichi Nuclear
Power Station in the sediment of Tokyo Bay, Japan
18 Tetsuo Yasutaka, Yoshishige Kawabe, Kimihito Nakamura, Akihiro Kurosawa, Takeshi Komai
Monitoring dissolved radioactive cesium in the Abukuma river water in Fukushima Prefecture
19 Wenting Bu, Jian Zheng, Tatsuo Aono, Keiko Tagami, Shigeo Uchida, Jing Zhang, Makio Honda,
Masatoshi Yamada
Investigating plutonium contamination in marine sediments off Fukushima following the
Fukushima Daiichi Nuclear Power Plant accident
Topics 3 Transfer model and/or parameters
1 Shigeto Fujimura, Takeshi Ohno, Yasuyuki Muramatsu, Hirofumi Tsukada, Kunio Yoshioka, Hiroshi
Saito, Mutsuto Sato, Makoto Sato, Yuuki Sakuma
The use of rice seedlings to estimate the transfer of radiocaesium from soil to plants in Fukushima
Prefecture
2 Jun Hirouchi, Tian Zhang, Yasuhiro Takamura, Shigekazu Hirao, Jun Moriizumi,
Hiromi Yamazawa
Deduction of useful information from dose rate monitoring data in an emergency
3 Nao Ishikawa, Ayumi Ito, Teruyuki Umita
Possibility of removing radionuclides in landfill leachate using advanced wastewater treatment processes

54 Kayoko Iwata, Keiko Tagami, Shigeo Uchida
Estimation of ecological half-lives of radiocesium in marine biota at the offshore of Fukushima, Japan
5 Masanori Kimura, Kazumasa Shimada, Shogo Takahara, Fumihisa Nagase, Toshimitsu Homma
Estimation of accident source terms for the Fukushima Daiichi Nuclear Power Plant using
RAMS/HYPACT
6 Hi-Rocky Ohtani , Xiaoguang Lu, Akira Tsuchiya, Shinichiro Yoshida, Takahiro Hirayama
Sedimentation diffusion of radioactive cesium in a paddy field.
7 Takashi Saito, Satoru Ohkoshi, Shigeto Fujimura, Koji Iwabuchi, Masaaki Saito, Tomoaki Nemoto,
Mutsuto Sato, Makoto Sato, Kunio Yoshioka, Hirofumi Tsukada
Distribution of radiocesium on cultivated field and suppressive effect of radiocesium uptake inbrown rice by potassium
8 Yasukazu Suzuki, Takasi Saito, Hirofumi Tsukada
Phytoremediation of radiocesium in different soil using cultivated plant
9 Guosheng Yang, Jian Zheng, Keiko Tagami, Shigeo UchidaDirect determination of tellurium in soil and plant samples by sector-field inductively coupledplasma mass spectrometry for the study of soil-plant transfer of radioactive tellurium following
the Fukushima Daiichi Nuclear Power Plant accident
Topics 4 Source term estimation
1 Shigekazu Hirao, Hironori Hibino, Takuya Nagae, Jun Moriizumi, Hiromi Yamazawa,
Source term estimation using environmental monitoring data
Topics 5 Dose estimation
1 Hikaru Amano, Yuji Ohta, Shigeru Banba, Takeshi Maeyama, Yoshihiro Ikeuchi, Takao Morimoto
Radiation doses from external and internal by inhalation of atmosphere and ingestion of drinking
water contaminated by the Fukushima Daiichi Nuclear Power Plants Accident for the people
living in the Chiba district.
2 Sakae Kinase, Masanori Kimura, Shinji Hato
Internal dosimetry for continuous chronic intake of caesium-137 in cedar pollen after the
Fukushima Daiichi Nuclear Power Plant accident
3

Kouta Kurihara, Yuko Kinashi, Kenichi Okamoto, Eiko Kakihana, Tomohiro Miyake,Tomoyuki Takahashi, Keiko Fujiwara, Hiroshi Yashima, Hidehito Nakamura, Sentaro Takahashi
Internal radiation dose of KURRI volunteers working at evacuation shelters after TEPCO`s
Fukushima Daiichi nuclear Power Plant accident

4 Shigeru Kumazawa
Distribution of doses to residents evacuated after Fukushima Nuclear Power Station accident

65 Yoshiyasu Nagakawa, Takashi Suzuki, Yasuhito Kinjo, Noboru Sakurai, Takahiro Sotodate,Hiroaki Ise
Measurement of radioactivity in air-borne dust and estimation of public dose in Tokyo after the
Fukushima Daiichi Nuclear Power Plant Accident
6 Shogo Takahara, Masashi Iijima, Kazumasa Shimada, Masanori Kimura,
Sakae KINASE, Toshimitsu HOMMA
Assessment of doses to the public in the contaminated areas resulting from the Fukushima
Daiichi Nuclear Power Station accident
7 Hiroko Yoshida, Noriyasu Hirasawa, Ikuo Kobayashi
Initial substantial reduction in air dose rate of Cs-origin and personal dose to residents due to the
Fukushima nuclear accident

7

Abstracts

Accident of Fukushima Daiichi Nuclear Power Plant-Sequences, FP released, Lessons learned–
Jun Sugimoto
Dep. of Nuclear Engineering, Graduate School of Engineering, Kyoto University

The nuclear accident occurred at the Fukushima Daiichi Nuclear Power Plant on March 11, 2011
was caused by the extremely massive earthquake, Great East Japan Earthquake, and gigantic tsunami
rarely seen in the history and resulted in the severe accident that extended over multiple reactors
simultaneously. Within an hour of the earthquake tsunami disabled the emergency diesel generators(EDGs), due to flooding of the switchgear, or flooding of the EDG rooms. This resulted in a station
blackout event for Units 1 through 4. All station batteries were also lost at Units 1, 2, and 4 due to thetsunami. Although some details of the accident are still not known well, the sequences, causes andconsequences of the accidents have been basically clarified by the efforts of several investigationcommittees. According to these investigations, no serious damage was identified for safety importantcomponents and systems before the attack of the tsunami. Loss of containment function of reactor
pressure vessel (RPV) and containment vessel (CV) was primarily caused by the loss of isolation
condenser (IC) for Unit 1, reactor core isolation cooling (RCIC) system for Unit 2, and RCIC and highpressure coolant injection (HPCI) systems for Unit 3, causing loss of core cooling for several or more
hours. Especially, CV of Unit 2 is estimated to be breeched and most fission products (FPs) released tothe environment will be from Unit 2. Hydrogen generated with zirconium-water reaction is estimated tobe leaked through flanges, hatches or penetrations, and hydrogen explosion occurred at the highest floorof the reactor building of Unit 1, 3 and 4.
The fission products released to the environment were estimated by the severe accident analysis
code, MELCOR, from inside the reactor core, and also by atmospheric dispersion simulations code,
SPEEDI, by coupling with environmental monitoring data in the reverse estimation method from outsideof the plant. The estimated release amount of I-131 is in the order of 120 – 160 PBq, and that of Cs-137
is in the order of 6 – 15 PBq for both estimations.
Lessons learned from the accident identified by investigation committees cover wide spectrum of
insufficient measures, such as for earthquake and tsunami, station blackout, severe accident management,
common cause accident at multiple unit site, education and training, chain of command at the accident,
disaster prevention and safety regulation system. These lessons should be shared all over the world forthe higher level of safety assurance of current reactors, and advanced reactors without the need of
evacuation in principle should be developed for future.

8

IAEA safety standards for radiological protection of the public
in post-accident situations
Gerhard Proehl
International Atomic Energy Agency Division of Transport, Environment and Waste Safety

Introduction
Radioactivity is a natural phenomenon and natural sources of radiation are features of theenvironment. Radiation and radioactive material may also be of human origin and have many beneficial
applications, including uses in medicine, industry, agriculture and research as well as for nuclear power
generation. The radiation risks to people and the environment from radionuclides released to, or existingin, the environment have to be assessed and controlled through the application of standards of safety.
Development of Safety Standards
The development of Safety Standards is a key activity of the IAEA. The Safety Standards provide asystem of fundamental safety principles, safety requirements and guidance on its implementation. The
key document for radiation protection is the recently published International Basis Safety Standards(BSS) (IAEA, 2011). Regarding exposures of the public, the BSS clearly distinguish between planned,
existing and emergency exposure situations.
A planned exposure situation arises from the deliberate operation of a source or from the conduct ofactivities that result in, or could result in, exposure. Provision for protection and safety can be madebefore embarking on the activity concerned, the associated exposures and their likelihood of occurrence
can thereby be restricted from the outset. An emergency exposure situation can arise as a result of an
accident, a malicious act or another unexpected event; it requires prompt action in order to avoid or to
reduce adverse consequences.
Usually, post-accident situations are considered as existing exposure situations, i.e. this being asituation that already exists when a decision has to be taken on the need for remedial actions forcontrolling exposures. In implementing remedial actions, the three radiation protection principles of“justification”, “optimization” and ”limitation” apply. Justification ensures that any facility and activity
that gives rise to radiation risks must yield an overall benefit; i.e. it must do more good than harm.
Optimization of protection and safety is to ensure that all exposures are controlled to levels that are as
low as reasonably achievable, economic, societal and environmental factors being taken into account.
For exposures in post-accident situations, BSS recommends reference levels for the effective dose to therepresentative person in the range of 1–20 mSv/year. The actual value chosen for the reference level will
depend upon the prevailing circumstances for the exposures under consideration. The optimized
protection strategies are intended to keep doses below the reference level. Reference levels are not limits,
but all reasonable steps shall be taken to prevent doses remaining above the reference levels.
Assessment of exposures, optimization and environmental monitoring
For the implementation of these Safety Standards, the radiological assessment of exposures to the
public is a fundamental element. Exposures arising from environmental radioactivity are the result of thecomplex interaction of radionuclide properties, environmental conditions, agricultural practices, living
habits as well as the spatial distribution of radionuclides in the environment and their time-dependence.
The paper will illustrate and discuss these dependencies exemplarily, taking into account the dose
assessments for population groups affected by the Chernobyl accident (UNSCEAR, 2011) and by the
Fukushima accident (WHO, 2012).

9

Optimization is a complex process that has to consider public perception of exposures, side-effects ofremedial actions, the life style of the population in the affected areas. To highlight important input
factors, remediation strategies implemented in areas by the Chernobyl accident are discussed withregard to the reduction of exposures, environmental conditions, costs and acceptance by the public.
For the remediation planning, the characterization of the contamination situation is a key element. The
paper summarizes the most important radiological and radioecological quantities to ensure reliable dose
assessments for potentially affected population groups. Monitoring approaches will be discussed thatfacilitate dose assessment, enable transparency and that help to achieve credibility of the results.
IAEA activities
Finally, the paper gives an overview on objectives and aims of main IAEA activities initiated after
the Fukushima accident.
In order to provide support to monitoring, by mid-March 2011 the IAEA agreed to send teams of IAEA
experts to support Japan in the fields of environmental monitoring. Four teams were active from 18
March – 18 April 2011 providing support to assist in the extensive monitoring programme setup by theJapanese authorities.
On the request of the Government of Japan, the IAEA organized a Mission to support theremediation of large contaminated areas off-site of the Fukushima Dai-ichi Nuclear Power Plant. The
mission was organized in order to: (i) provide assistance related to Japan’s plans to remediate large areas
contaminated by the accident; (ii) discuss the identification of the appropriate set of remedial actions to
reduce exposures to the public after contamination of inhabited and agricultural areas; (iii) review
ongoing remediation strategies, plans and activities; and (iv) disseminate Japanese experience gained
during the remediation activities to the international community.
Within the Action Plan on Nuclear Safety – set up by the IAEA – protection of people and theenvironment from ionizing radiation following a nuclear accident is an important point. Focus is given
to facilitate the use of available information, expertise and techniques, assessment decontamination andremediation both on and off nuclear sites, including monitoring of radionuclides in the environment.

INTERNATIONAL ATOMIC ENERGY AGENCY, Radiation Protection and Safety of Radiation
Sources: International Basic Safety Standards; IAEA Safety Standards Series No. GSR Part 3 (Interim),
IAEA, Vienna (2011). (http://www-pub.iaea.org/MTCD/Publications/PDF/p1531interim_web.pdf)
United Nations Scientific Committee on Effects of Atomic Radiation (UNSCEAR): Sources and effectsof ionizing radiation, Volume II, Annex D: Health effects due to radiation from the Chernobyl accident,
United Nations, New York, 2011.
World Health Organization (WHO): Preliminary dose estimation from the nuclear accident after the2011 Great East Japan Earthquake and tsunami, Geneva, 201210

UNSCEARs assessment of radiation levels/effects from Fukushima
accident
Wolfgang Weiss
Chair of UNSCEAR
1. Aims and objective:
The aim of the assessment is to develop a comprehensive report with scientific annexes for the
General Assembly, the scientific community and the public that evaluates information on the levels ofradiation exposure due to the nuclear accident following the Great East-Japan earthquake and tsunami,
and the associated effects and risks.
Specific objectives are to address the following questions:
Source term:What is the amount and nature of radioactive material released to the environment? How much to air?
How much to sea?
What radionuclides were released?
What was the time profile? What events led to releases and the dispersion patterns?
What are the uncertainties on the source term estimates?
Environmental dispersion and deposition:
What was the dispersion pattern (air and sea)? What were the atmospheric concentrations ofradionuclides with respect to time and location? What are the deposition patterns and modes? What
radionuclides were deposited?
Where are the hotspots and how can they be explained?
How did the accident compare with those at Chernobyl, TMI, and Windscale?
Doses to members of the public:What effects due to radiation were observed to date, if any?
Which are the key exposure pathways?
What were the levels and time profiles of contamination in various foodstuffs (farmed and natural), andexpectations of future development based on past experience?
What were the protective actions taken, who was affected and when?
What were the key organ and effective doses to adults, children, infants, and foetus for each prefecture(and some specific settlements/districts) and in other countries and/or regions of the world?
What were the doses for the first year based on measurements?
What is the effect on these dose estimates from the on-going remediation and protective measures?
What doses are projected for beyond the first year?
What are the uncertainties associated with the dose estimates?
What were the populations most at risk?
Doses to occupationally exposed persons:What effects were observed to date, if any?
What were the exposures of operational staff and emergency response personnel (levels, at what times)?
Key organ and effective doses?
What are the uncertainties associated with estimates of their doses?
What were the working conditions that affected exposure?
What groups of workers were most at risk? How can they be characterized?
What medical monitoring was implemented in groups of workers most at risk?
Effects on the natural environment
What effects were observed to date, if any?
In what components of the natural terrestrial and aquatic environments and in which species are there
significant accumulation of radionuclides?
What in general terms were the doses and dose rates to plants and animals

11What are the uncertainties associated with those dose estimates?
How do they compare with normal exposures?
Did any plants or animals receive doses at levels that UNSCEAR would expect effects?
General aspects:
How confident is UNSCEAR in the representativeness and quality of the information, and of theirassessment?
What is the likely impact on human health and environment? For what time period are effects expected
and of what type?
What are the unknowns and needs for future research or follow-up?
2. Timescale
The plan to assess the levels, effects and risks of exposure was decided on 58th session of UNSCEAR in May
2011. The final report/Report to Assembly and publication is due for the 60th session of UNSCEAR in May 2013.
3. Organization of Work
Coordination
Group

Data compilation,
quality assurance

Releases anddispersion

Dose and risk
assessment

Worker doses

Over 80 experts offered as contributions-in-kindAttendance at meetings and work – cost-free to UN
Project Manager and Coordinating Lead Writer engaged
Channels to Japanese experts
Trust Fund contributions provide bufferInternational Organizations contributing: CTBTO, FAO, IAEA, WHO, WMO.
4. The preliminary findings of 59th session of UNSCEAR (May 2012) are included in the Report to theGeneral Assembly (approved November 2012)
The key findings at this stage oft he assessment are:
No radiation health effects observed among public or workers
Six workers received doses above 250 mSv; 170 received doses above 100 mSv; thyroid doses being
estimated
Six workers died in first year – not due to radiation
Thyroid monitoring of 1,080 children: maximum dose reported was 35 mSv
Highest exposures of wildlife in marine environment.
5. Work in progressAn all expert meeting will be convened end of November 2012 to discuss the status of the work and theway forward to complete the report. Key achievements so far are:
The data management procedures have been established and shared with all experts
Gross checks with date from NGOs are under way
The source term analyses have been completed
Atmospheric dispersion simulations have been performed in close co-operation with WMO
The development oft he methodology and marine dispersion simulations are ongoingInhalation and ingestion dose evaluations fort he public are ongoingProgress has been made with the analyses of non-human biota
Date analyses für worker exposures are underway after all relevant data have been provided.
A Health Implication Task (HIT) Group has been established to assess health risks to workers and the public.
The presentation will describe in detail the achievement made in December 2012 as well as the way forward
toward completing the assessment.

12

Radiation monitoring and mapping around the Fukushima site
Kimiaki Saito
JAEA

Soon after the Fukushima Daiichi Nuclear Power Plant Accident, in order to assess the impact andtake appropriate measures, accurate and precise information was necessary on contamination conditions
around the Fukushima site. Though a large number of environmental monitoring was performed after
the accident, the methods, locations, time, accuracy were diverse, and it was difficult to integrate theresults and construct contamination maps. Thus, the Ministry of Education, Sports, Science andTechnology (MEXT) commissioned JAEA to construct detailed contamination maps around the
Fukushima site, and the first mapping project started. So far, three series of mapping projects have been
implemented in collaboration with a number of organizations.
In the first project, the region up to 100 km from the Fukushima site and the rest of Fukushima
prefecture were divided into about 22,000 small areas, and five soil samples were collected at one
selected location in each area. By analyzing the collected soil samples, radionuclide deposition maps
were constructed for Cs-137, Cs-134, I-131, Te-129m, Ag-110m, Pu-238, Pu-239+240, Sr-89, Sr-90.
Further, maps on dose rates in air was constructed according to monitoring data at soil sampling
locations and to car-borne survey data using the KURAMA systems developed at Kyoto University.
From these maps, detailed contamination conditions around the site were clarified.
Accumulated effective doses for 50 years due to external exposures and inhalation due to resuspension were evaluated from the observed radioactivity, and it was confirmed that radiocesium ismost important among the observed radionuclides from a viewpoint of exposures in future. The doses
from plutonium and strontium were found much smaller than other nuclides.
In the second and third campaigns, radionuclides deposited on ground were quantified utilizing insitu measurements instead collecting soil samples; while, dose rate measurements were carried out using
the same methods. Temporal change of contamination conditions was analyzed based on several
different kinds of monitoring data. Both deposited-radionuclide activity and dose rates in air havecertainly reduced in 14 month after the first campaign. Generally, car-borne survey data showed large
dose-rate reduction as elapsed time. Further, decreasing tendency was found to be different according toland use: in urban and water areas, decreasing tendency was large; in ever-green forest it was small. In a
comparison of air dose rates at 1 m height between measurements in June 2011 and August 2012, there
were locations where dose rate reduction was much higher than other locations, which is considered due
to decontamination.
In the projects, migration of radionuclides in various environmental conditions has been investigatedby field studies, and the features have come to be clarified. In soil, most cesium existed in top 5 cm evenin December 2011. In cedar forests, cesium existed both at canopies and litter layers in June 2011; while,in broad-leaved forests, cesium existed mostly at litter layers. Cesium has come down gradually bythroughfalls in the forests; and the distribution of cesium in forests is changing slowly. Migration ofcesium associated with suspended sediments in water was found to be important both in lands and inrivers. Cesium concentrations in air are not high, though they change according to conditions.
A data base was constructed, and all accumulated data have been recorded in the data base. The data
are now open to the public by pictures and by numerical data through the web site of MEXT, so thatvarious people can easily utilize the data. By analyzing the accumulated data, models to predict
contamination conditions in future are now under developing to provide fundamental information for
countermeasures from now on.

13

Implication of the isotopic ratios of radionuclides observed in
the contaminated areas surrounding Fukushima-Daiichi NPP
Hajimu Yamana

Research Reactor Institute, Kyoto University
Enormous amount of analysis data have been reported for the radionuclide concentrations in the soil
samples taken in the areas contaminated by the Fukushima-Daiichi NPP accident. Since the accident,
the concentrations of 137Cs, 134Cs and 131I have been sufficiently reported by enormous monitoring
activities, and those of 90Sr and alpha-nuclides have been reported even with limited frequency. The
observed ratio of these nuclides, such as 137Cs/134Cs, 131I/137Cs, 90Sr/137Cs, as well as 238Pu/239+240Pu
gives various implications about the origin and the progress of the contamination. The ratio 137Cs/134Cs,
which generally represents the burn-up of the reactor core fuel, is expected to give information about thesource-term of the release. The variation of the ratio between 90Sr and Cs nuclides, which wereobserved in the limited period after the accident, is expected to give a hint on the different progress ofthe severe accident, as well as of the different history of the transport in the environment after the
release. In particular, reported wide variety of the Sr/Cs ratio depending on the places along different
direction from NPP deserves elaborate consideration.
In this paper, by using the fuel burn-up calculation results, the implication that are extractable fromthe observed isotopic ratios of radionuclides will be discussed. In addition, the possible application of
the accumulated carborne monitoring data by KURAMA(Kyoto University Radiation Mapping System)
for this purpose will be also discussed.

Keywords: Fukushima-Daiichi NPP accident, 137Cs, 134Cs, 90Sr, Isotopic ratio, KURAMA

14

Development of a car-borne survey system, KURAMA
M. Tanigaki*, R. Okumura, K. Takamiya, N. Sato, H. Yoshino, H. Yoshinaga, Y. Kobayashi
Research Reactor Institute, Kyoto University

We have developed a car-borne survey system named as KURAMA (Kyoto University RAdiation
MApping system) and KURAMA-II for the establishment of air dose rate map in Fukushima andsurrounding area as a response to the nuclear accident at TEPCO Fukushima Daiichi Nuclear Power
Plant on March 11, 2011.
KURAMA is a γ-ray survey system with GPS and up-to-date network technologies developed for a
primary use of car-borne surveys. An in-vehicle part of KURAMA consists of a commercial air dose
rate survey meter, an interface box, a GPS unit, a PC, and a 3G mobile Wi-Fi router. The monitoringdata tagged by GPS location data are simultaneously shared with remote servers over a cloud-based
network, and then processed by servers for a real time plot on Google Earth and other various purposes.
KURAMA has served for several measurement projects for establishing radiation dose maps by
Fukushima prefectural government or by the Ministry of Education, Culture, Sports, Science andTechnology, Japan (MEXT). Fukushima prefectural government now uses KURAMA for precise
surveys in residential areas to find possible hot spots, which are to be authorized for evacuations after
additional precise surveys. MEXT conducted car-borne surveys twice, one in June 2011 for Fukushima
prefecture and the surrounding area, and the other in December 2011 for a wider region in Eastern Japan.
Based on successful applications of KURAMA for the establishment of air dose rate maps,
KURAMA-II is developed for the continuous monitoring on public vehicles moving around in living
areas, such as local buses and delivery trucks. NI CompactRIO is chosen as the platform of the invehicle part in KURAMA-II because of its compactness, ruggedness and the native support ofLabVIEW. KURAMA-II achieves to obtain energy spectra of radiations by introducing C12137, a CsI
detector series manufactured by Hamamatsu. The system was developed in less than 2 months, todramatically improve the handling and ease-of-use, and achieve better ruggedness for long-hour
invehicle logging purposes. Now KURAMA-II extends its applications to various purposes. A
demonstration test using a local bus in Fukushima city has been in progress since Dec. 2011 and proves
the ability of KURAMA-II to serve continuous monitoring for months. The capability of autonomous
operation and the scalability of KURAMA-II allowed MEXT to complete a large scale car-borne survey
in March 2012, in which one hundred KURAMA-II were deployed to municipalities in Eastern Japanand simultaneously operated. Furthermore, the applications to foot-borne and bikeborne surveys inplaygrounds, rice fields and mountainous areas are about to be started.
This work was partly supported by “Japan recovery grant program”, National Instruments Japan
Corporation.
Keywords
car-borne survey, air dose rate

15

NIRS's activities for the reconstruction of early internal exposure in
the TEPCO Fukushima Daiichi Nuclear Power Station accident
Osamu Kurihara*, Keiichi Akahane, Nobuyuki Sugiura
National Institute of Radiological Sciences

The TEPCO Fukushima Daiichi Nuclear Power Station accident triggered by the Great East Japan
Earthquake Disaster of 2011 resulted in an enormous release of radioactive materials into the environment. It
is thus indispensable to perform individual dose estimations of populations in affected areas. However,regarding internal exposure, it is difficult to estimate the resulting dose because of limited information
available on the intake of each radionuclide via inhalation and ingestion, especially in the early stage of theaccident where radioiodine existed as a main contributor to thyroid exposure of concern. To our knowledge,
there are only about 1500 human thyroid measurement data obtained from this accident. An insufficientnumber of air sampling data also makes it difficult to assume a reliable intake scenario via inhalation that is
expected to be dominant rather than ingestion in the present accident, unlike situations in the Chernobyl
accident. National Institute of Radiological Sciences (NIRS) launched a project for the reconstruction ofearly internal exposure to the public this year and is now deploying activities for this project. The first NIRS
symposium was held last June with the following three aims: (1) collecting human/environmental
measurement data available for the reconstruction of the early internal dose, (2) validating the possibility of
atmospheric dispersion simulations as a tool for the reconstruction and (3) discussing a strategy for thereconstruction among experts from Japan and overseas. Our current activities in the project will be presented
in this symposium.
Keywords
Internal exposure, Radioiodine, Thyroid dose, reconstruction

16

Release of plutonium isotopes from the Fukushima Daiichi Nuclear Power
plant accident
Jian Zheng* , Keiko Tagami,, Shigeo Uchida
National Institute of Radiological Sciences, JapanThe Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has caused serious contamination of
the environment from the atmospheric fallout and the direct discharges of highly radioactive liquid
wastes. Besides the massive releases of highly volatile fission products, such as 127mTe, 132Te, 131I, 133Xe,
134Cs, 136Cs and 137Cs, the possible release of non-volatile Pu isotopes attracted great public attention in
the FDNPP accident because Pu isotopes present a large risk for internal radiation exposure via
ingestions of contaminated agricultural crops, in particular for 241Pu (a beta-emitter, T1/2 = 14.4 years),with its decay, the ingrowth of 241Am (alpha and gamma-emitter, T1/2=432.7 years) will present a newradiation risk.
Plutonium is normally produced in reactor fuel as a mixture of isotopes. The predominant isotope,
239Pu is produced by neutron capture in 238U. If a fuel element containing 239Pu is left in a reactor for any
length of time further neutron capture can occur to yield higher isotopes like 240Pu, 241Pu and 242Pu. In
addition, small quantities of two other isotopes, 236Pu and 238Pu, are produced during the irradiation. To
date, information on the release of Pu isotopes from the FDNPP accident in the environment is very
limited.
Several studies on the determination of Pu isotopes in environmental samples, such as soil, litter, andaerosols, confirmed the release of Pu isotopes from the FDNPP accident. Recently, core inventory
calculation results of Pu isotopes within the FDNPP reactors using ORIGEN model simulation havebeen reported. These studies suggested that the damaged reactors were the major contributor of Pu to theenvironment. However, the release of Pu from the spent fuel pools remains unknown. In this work, wesummarize and analyze the published studies related to the release of Pu isotopes from the FDNPP
accident. Our analysis will focus on: (1) distribution of Pu isotopes derived from the FDNPP accident in
the environment; (2) Pu isotopic composition for source identification; (3) sources for Pu release in the
FDNPP-damaged reactors or spent fuel pools; and (4) the amounts of Pu isotopes released from the
FDNPP accident. The paper concludes with future research directions.

Keywords
Plutonium, Sources, isotopic composition, FDNPP

17

Poster session

1-1
Wind-Driven Transport of Resuspended Radioactive Dust in
Fukushima Prefecture
Kazuhiro Akimoto*
Graduate School of Science and Engineering, Teikyo University

Winds are known to transport dust particles and/or aerosols with or without radioactive materials
over a long distance. Here the data of air dose rates measured in Fukushima prefecture in 2011 after theaccident at the Fukushima Dai-ichi nuclear power plant that took place in mid-March are analyzed toreveal their temporal as well as positional variations, considering the effects of wind in particular.
First, during late March when the governing radionucleides were iodine -131 and xenon-133 thewind effects turned out to be rather outstanding. For example, when daily dose rates in the city of
Shirakawa located in southern central Fukushima prefecture are compared with local wind speeds
during March 25th ~31st, it appears that increased wind speed resulted in reduced dose rate. Actually,
the correlation coefficient between the dose rate and the local wind speed is negative almost every day.
However, the wind speed is well correlated with local atmospheric temperature also. Thus, it isnecessary to calculate partial correlation coefficients between the dose rates and the wind speed toremove the effects of the temperature. The partial correlation coefficients thus calculated for each day
during March 25th~31st are respectively, － 0.31, － 0.18, 0.25, － 0.34, 0.12, － 0.49, － 0.22,
respectively. Namely, it is possible that strong winds had caused resuspension of deposited radio
materials and carried some radioactive dust away from Shirakawa to eastward. Similar trend isobservable during the same period elsewhere. However, at the village of Iitate locacted in north eastern
Fukushima the partial correlation coefficients between the dose rates and the wind speed on each day are
0.74, 0.61. 0.44, 0.45, 0.62, －0.02, and －0.43, respectively. Therefore, at this place during the first
five days it is likely that strong winds tended to deposit some radionucleids that were carried fromeleswhere. It appears that there exists a general trend of radionucleids being carried from central
Fukushima to the Pacific coast driven by seasonal westward winds.
After mid-June the dominant radionucleides responsible for most of the radiation were and still are
cesium 134 and cesium 137. The data of air dose rates measured at 155 locations in the eastern
Fukushima prefecture by the central and local governments during mainly the period of June throughDecember in 2011 are investigated. It turns out that the mean dose rate in eastern half of Fukushima
prefecture had declined at a rather swift pace with half-life of 1.4 years, showing the significance of
weathering effects. Actually the mean reduction rate is twice as large as that due to nuclear decay ofcesium. Owing to the strong weathering effects driven mainly by rain and wind, the reduction rate tends
to strongly depend on the season; in fact, the mean reduction rate in the summer is twice as large as thatin the fall.
The variation rates of air dose rates at some places during this period are higher than theoreticalvalues or at some other places they become greater than unity. Hence, it is likely that extensive areas in
Fukushima such as Iitate, Namie, Minami-Soma, and Iwaki etc. during this period at least were still
being weakly contaminated via wind. Dose rates tended to increase particularly in the fall whenapproximately westward winds were dominant in consistency with the results of calculations of partial
correlation coefficients. Meanwhile, near the Fukushima Daiichi Nuclear Power Plant located on the
Pacific coast some increase of dose rates is observed during summer when eastward wind from theocean became locally dominant. Some other pieces of supporting evidence of the wind-driven secondary
contamination will be presented.
Keywords
radionucleides, wind, transport, dust, resuspend

18

1-2
Environmental radiation status in Bunkyo-ku, Tokyo, after the
TEPCO Fukushima Dai-ichi NPP Nuclear Disaster
Takao Ebisawa¹, Seiichi Hirose¹, Etsuko Furuta², Keiji Kusama³, Takeshi Iimoto*⁴¹The Bunkyo Ward Office²Ochanomizu University³Japan Radioisotope Association
⁴The University of Tokyo

Bunkyo-ku is located around the east part of the metropolitan of Tokyo, Japan. The distance fromthe TEPCO Fukushima Dai-ichi nuclear power plant is about 220 km, south. The population of the cityis 201,079 as of August 1st, 2012, and its area is 11.31 km2. The local government has officially beensurveyed environmental radiation status after the disaster with responding to a lot of requests from its
citizen. The radiation surveillance in this area has been technically guided by some radiation protection
specialists. Main two targets on the surveillance items are; (1) the ambient radiation dose (µSv h-1) at all
the school yards, public parks and representative measurement points selected by the local government,and (2) the specific radioactivity (Bq kg-1) on the school lunch. These data have been reported to thecitizens timely through the city website in addition to twice a month in the public relations magazine of
the local government. This presentation shows the background status and technical information of therelated activities, and the estimated environmental radiation data.
The ambient radiation dose in the city has been surveyed since July of 2011. In the 1st season of thesurveillance (from July to August of 2012) at the total number of 304 measurement points, the highest
value of the ambient radiation dose was 0.22 µSv h-1 at the height of 1 meter from the ground, thelowest was 0.05µSv h-1, and the average was around 0.09 µSv h-1, whose values were including natural
background dose rate detected by the survey-meters of energy compensation type. In the latest season,
the data were 0.10 for the highest, 0.05 for the lowest and 0.07 µSv h-1 for the average value.
The specific radioactivity of drinking water has been monitored at the local purification plants since
the accident. No water sample supplying to the city has been exceeding the national limitation values tocontrol the intake dose. The specific radioactivity of school lunch has also been surveyed three times (inDecember of 2011, May of 2012 and July of 2012) by the local government. So far, 127 sets of school
lunch in the city have been checked using a Ge spectroscopy system. The highest specific radioactivityof 134+137Cs was detected as 2.5 Bq kg-1 in a set of school lunch and 15.4 Bq kg-1 of milk, which wereshown in December of 2011.
Keywords
ambient radiation dose, specific radioactivity, Tokyo

19

1-3
Environmental radiation status in Kashiwa City (Chiba Prefecture)
after the TEPCO Fukushima Dai-ichi NPP Nuclear DisasterSeiichi Someya¹, Hirofumi Fujii²,Takeshi Iimoto*³¹Kashiwa City Local Government²National Cancer Center Hospital East
³The University of Tokyo

Kashiwa city is located around the north-west part of Chiba prefecture in the metropolitan area ofTokyo, Japan. The distance from the TEPCO Fukushima Dai-ichi nuclear power plant is about 200 km,
south. The population of the city is 404,252 as of April 1st, 2012, and its area is 114.9 km2. The local
government has officially been surveyed environmental radiation status after the disaster withresponding to a lot of requests from its citizen. The radiation surveillance in this area has beentechnically guided by some radiation protection specialists. Main two targets on the surveillance items
are; (1) the ambient radiation dose (µSv h-1) at all the school yards, public parks and representative
measuring points selected by the local government, and (2) the specific radioactivity (Bq kg-1) ofdrinking water and local foodstuffs. These data have been reported timely in the city website in addition
to twice a month in the public relations magazine of the local government. This presentation shows the
background status and technical information of the related activities, and the estimated environmental
radiation data.
The ambient radiation dose in the city has been surveyed since June of 2011. In the 1st season of thesurveillance (from May to August of 2011) at the total number of about 210 points, the highest value ofthe ambient radiation dose was 0.65 micro Sv h-1 at the height of 1 meter from the ground, the lowest
was 0.08µSv h-1 and the average was around 0.25µSv h-1, whose values were including natural
background dose rate detected by the survey-meters of energy compensation type. In the 4th season, thelatest data around school yards were 0.30 for the highest, 0.04 for the lowest and 0.12µSv h-1 for the
average value. The ambient dose at 41 of 61 school yards and 47 of 635 parks has been in greater or lessreduced under the decontamination project by the local government. The net dose reduction rate without
natural background dose has been ranged around between 80 and 30 % in the school yards and the parks.
Decontamination activity around residential area has just started.
The specific radioactivity of drinking water and local foodstuffs has been surveyed since March of2011 and July of 2011 respectively. So far, one sample of service water showed 110 Bq kg-1 of 131I on
March 23th of 2011, however, no water sample other than this has been shown exceeding the limits.
About 800 samples of the local foodstuffs as of the end of August of 2012 have been checked using an
NaI(Tl) scintillation spectroscopy system. The lower detection limit on this measurement system for
134+137Cs was set as about 25 Bq kg-1. An outdoor bamboo shoot sampled in the city on April 9th of 2012
showed 170 Bq kg-1 as the specific radioactivity of 134+137Cs. In addition, a crucian carp sampled in
Teganuma-lake on June 23th of 2012 showed 241 Bq kg-1. Specific radioactivity due to the disaster of allof the surveyed samples other than above these three samples has been below the limits.
Keywords
ambient radiation dose, specific radioactivity, Chiba

20

1-4
Environmental radiation status in Nagareyama City (ChibaPrefecture)
after the TEPCO Fukushima Dai-ichi NPP Nuclear Disaster
Sadao Iiizumi¹, Hirofumi Fujii²,Takeshi Iimoto*³¹Nagareyama City Local Government²National Cancer Center Hospital East
³The University of Tokyo

Nagareyama city is located around the north-west part of Chiba prefecture in the metropolitan area ofTokyo, Japan. The distance from the TEPCO Fukushima Dai-ichi nuclear power plant is about 200 km,
south. The population of the city is 166,493 as of April 1st, 2012, and its area is 35.28 km2. The local
government has officially been surveyed environmental radiation status after the disaster with responding
to a lot of requests from its citizen. The radiation surveillance in this area has been technically guided bysome radiation protection specialists. Main two targets on the surveillance items are; (1) the ambient
radiation dose (µSv h-1) at all the school yards, public parks and representative measuring points selectedby the local government, and (2) the specific radioactivity (Bq kg-1) of drinking water and local foodstuffs.
These data have been reported timely in the city website in addition to three times a month in the public
relations magazine of the local government. This presentation shows the background status and technicalinformation of the related activities, and the estimated environmental radiation data.
The ambient radiation dose in the city has been surveyed since June of 2011. In the 1st season of thesurveillance (from May to September of 2011) at the total number of about 40 points, the highest value ofthe ambient radiation dose was 0.58 µSv h-1 at the height of 1 meter from the ground, the lowest was 0.17
µSv h-1 and the average was around 0.32 µSv h-1, whose values were including natural background dose
rate detected by the survey-meters of energy compensation type. In the latest season, the data aroundschool yards were 0.36 for the highest, 0.08 for the lowest and 0.17 µSv h-1 for the average value. The
ambient dose at all of the 23 school yards and 57 of 275 parks has been in greater or less reduced under thedecontamination project by the local government as of the end of August of 2012. The net dose reduction
rate without natural background dose has been ranged around between 80 and 20 % in the school yards andthe parks. Decontamination activity around residential area has just started.
The specific radioactivity of drinking water and local foodstuffs has been surveyed since March of2011 and April of 2011, respectively. So far, one sample of service water showed 110 Bq kg-1 of 131I on
March 23th of 2011, however, no water sample other than this has been shown exceeding the limits. 205
samples (46 items) of the local foodstuffs have been checked using an NaI(Tl) scintillation spectroscopy
system so far. A flat Japanese mushroom cultivated on Japanese oak logs sampled in the city on November
16th of 2011 showed the highest specific radioactivity as 831 Bq kg-1 of 134+137Cs. Specific radioactivity
due to the disaster of all of the surveyed food stuffs, other than an outdoor bamboo shoot and above two
samples of a water sample and a flat mushroom, has been below the limits for intake dose.
Keywords
ambient radiation dose, specific radioactivity, Chiba

21

1-5
Environmental radiation status in The University of Tokyo after the
TEPCO Fukushima Dai-ichi NPP Nuclear Disaster
Takeshi Iimoto*, Norio Nogawa, Hiroshi Mitani, Masao Kamiko, Takahiko Suzuki
The University of Tokyo

The University of Tokyo is located mainly in the metropolitan area of Tokyo, Japan. This university
owns three main campuses; the Hongo-campus and the Komaba-campus are located around the middleeast of Tokyo prefecture and Kashiwa-campus is around the north-west of Chiba prefecture. The
distance between the Fukushima Dai-ichi nuclear power plant and the three campuses is ranged about
200 to 250 km. The university organized a special corresponding team to survey the environmental
radiation status inside the university’s site immediately after the nuclear disaster. The team consists ofabout 20 members, mainly of the radiation protection specialists or technical experts on radiation
measurement in the university. The purpose of this project is basically not for research, but for providing
the real data on environmental radiation immediately after the accident both to the university members
and to surrounding public, under the situation of lack of relating information.
Main two targets on the surveillance items are; (1) the ambient radiation dose (µSv h-1) and (2) the
specific radioactivity (Bq kg-1) of soil around ground surface to show the contamination level. The
ambient dose data had been reported every day in the web-site in addition to the portal-site magazine of
the university, and soil contamination data were reported occasionally and timely. In addition, the daily
variation of the specific activity on 131I in urine sampled from a male university staff living in Tokyo
had been also monitored. This presentation shows the background status and technical information of
the related activities, and the estimated environmental radiation data.
Time variation of the ambient radiation dose rate had been officially surveyed since the morning onth
15 March in 2011 at the representative points selected in the campus sites. In addition, area distribution
maps on ambient dose rate in three campuses were also drawn. The first peak dose of 0.72 µSv h-1 wasobserved around at 2:30 pm on 15th May of 2011 in the Kashiwa-campus and the second of 0.80 µSv h-1
was also observed around at 11:00 am on 21th May of 2011 at the same place. The continuous
surveillance ended on the end of March in 2012. At that time, the representative ambient dose rates of
the campuses were around 0.11 µSv h-1 for Hongo, 0.23 for Kashiwa (at the height of one meter fromthe ground level) and 0.05 for Komaba (at the height of about 15 meters from the ground level), whose
values were including natural background dose rate detected by the survey-meters of energy
compensation type. Some parts in the Kashiwa-campus site have been decontaminated following thecorresponding plan determined by the Kashiwa local government. The net dose reduction effect wasestimated between about 80 and 50 %.
The specific radioactivity of soil around ground surface in three campuses has been surveyed using
an NaI(Tl) scintillation spectroscopy system or a Ge spectroscopy system. For example, 0.2 to 0.35 kBq
kg-1 of 131I and 1.0 to 1.5 kBq kg-1 of 134+137Cs were measured in the Kashiwa campus site as of the
middle of April of 2011. On the daily variation of the specific activity on 131I in urine, the highest
concentration as 110 Bq L-1 was observed on 16th March of 2011 under the status of average urine
discharge volume of 2.1 L day-1.
Keywords
ambient radiation dose, specific radioactivity, Tokyo, Chiba

22

1-6
Radiation measurement in the East Japan with a GM-tube detector
after the Fukushima nuclear accident
Takumi Kubota* ¹,Tomoko Ohta ²¹Kyoto University Research Reactor Institute²Hokkaido University

A large amount of radioactive materials was released into the environment by the Fukushima Daiichi
nuclear accident. The resulting effect on air dose rate and surface contamination with mainly radioactive
iodine and cesium were measured with a GM-tube detector calibrated with a cesium-137 radioactive
source. The calibrated values were obtained with a quadratic function of readout value of the detector
from 0 to 5μSv/h. The measurements were demonstrated at the Ueno Park in Tokyo, along the Tohoku
Expressway from Tochigi to Miyagi prefecture and in Namie town in Fukushima prefecture inside a car,and along the Tohoku Shinkansen (bullet train) Line from Tochigi to Fukushima prefecture during theperiod from May to August in 2011. The air dose rate at Nezu in the immediate vicinity of the Ueno
Park and at a subway exhaust port of the Nezu subway station showed 0.17 - 0.23 μSv/h and 2.0 - 2.2
μSv/h, respectively. Although the detector showed the dose rates from 0.6 to 2.4 μSv/h for just nearsurface ground of the park, those decreased by a factor of two to three with removing the surface layerof several mm thickness. The dose rates for road gully around the park, however, showed up to 10μSv/h
and higher radioactive contamination. The measurement of air dose rate in a car along the Tohoku
expressway in May 2011 showed from 0.1 to 1.0μSv/h and the maximum value was obtained at
Nihonmatsu city apart from damaged Fukushima Daiichi nuclear power plants by 55 km. The
measurement of air dose rate in a train along the Tohoku Shinkansen Line, mostly parallel to the Tohoku
expressway, in August 2011 showed from 0.1 to 0.3μSv/h and the maximum value was obtained at
Koriyama city. Nihonmatsu and Koriyama is the similar distance from the nuclear power plants, which
location would derive the similar variation of air dose rate. The measurement of air dose rate in a carand out of a car in Northwest Namie town apart from the nuclear power plants by about 25 km showedfrom 0.6 to 5.1μSv/h and from 54 to 175μSv/h, respectively.
Keywords
mobile radiation survey, GM-tube detector, air dose rate, surface contamination

23

1-7
Measurement of radiation dose by car in Fukushima from 19 to 22
March 2011
Takumi Kubota*, Jun-ichi Hori, Nobuhiro Sato, Koichi Takamiya
Kyoto University Research Reactor Institute

The Fukushima nuclear accident required radiation screening and other support activities forrefugees and residents from a very early stage. As one of these activities we traveled from Kumatori
town (Osaka prefecture) to Fukushima city (north Fukushima prefecture) on 19 March 2011, moved todemonstrate the radiation screening from Fukushima city to Iwaki city (southeast Fukushima prefecture)on March 20 and to Shirakawa city (south Fukushima prefecture) on March 21 and 22, and traveledback to Kumatori. The variation of air dose rate in a cargo van was measured with a calibrated ion
chamber detector during the travel in the Fukushima prefecture. The air dose rate in the Tohoku
expressway basically increased toward north and its highest value of 6 μSv/h was obtained at
Nihonmatsu city (next to south Fukushima city). The variation of air dose rate in the Banetsu
expressway from Koriyama to Iwaki and in Iwaki city showed that the dose rate was around 5.5 μSv/h
at Koriyama, dropped to less than 3µSv/h at the point apart from Koriyama by 15 km on the Banetsu
expressway and stayed around 2 μSv/h from the point to Nakoso (sounth Iwaki city). The value of air
dose rate in Shirakawa city and in Samegawa village between Iwaki and Shirakawa was around 2 μSv/h
and 1 μSv/h, respectively. The low dose rate measured in the Banetsu expressway and in Samegawa
village can derive low radioactive deposition in Abukuma highlands, which would be obstacle to ingressof radioactive plume. The value of air dose rate in Fukushima city on March 19 to 22 varied from 2
μSv/h to 9 μSv/h and depended on the time and place. The difference of air dose rate between places
slightly decreased over time. The value of internal exposure from this activity of radiation screening wasmeasured with a whole body counter to be negligible.
Keywords
mobile radiation survey, ion chamber detector, air dose rate

24

1-8
Diffusion and transportation dynamics of 137Cs deposited on theforested area in Fukushima after the nuclear power plant accident inMarch 2011
Nobuhito Ohte*¹, Masashi Murakami²,Kohei Iseda¹, Keitaro Tanoi¹,Nobuyoshi Ishii³¹University of Tokyo²Chiba University³National Institute of Radiological Sciences
Introduction
The accident of the Fukushima Daiichi Nuclear Power Stations in March 2011 emitted 1.5×1017Bq of 131I, 1.2×1016Bq of
137Cs into the surrounding environment1). Those radioactive substances including 137Cs deposited onto the forest areas of thenortheastern region of the Honshu Island, Japan. Forests of these regions are especially important for the people not only for theirforest production industry, but also for the source areas of drinking water and for the residential environments. The first phase of
the governmental survey and investigations showed that major portion of deposited 137Cs is trapped on the canopies and litter
layers of soil surface. As 137Cs is easily adsorbed onto clay minerals in soil, major portion of those can be transported by erodedsoils and particulate organic matters through the hydrological pathways. Dissolved 137Cs which is relatively free from soil
adsorption can be taken up by microbes, algae and plants in soil and aquatic systems. Then, those 137Cs are eventually
introduced into soil insects and worms, fishes and birds through the food web.
In order to clarify the mechanisms of diffusion and export of 137Cs from a forested ecosystem, we started to intensive fieldobservations and samplings in the small catchment including forest and farmlands. The study is conducted at the Kami-Oguni
River catchment in the northern part of Fukushima Prefecture. Major land uses of the catchment are forests and paddy fields.
Expected two major pathways of 137Cs diffusion and export are investigated; 1) transportation by water movement with
dissolved and particulate or colloidal forms through the hydrological processes, 2) diffusion through the food web including
both detritus food chains based upon plant litters and grazing food chains based upon living plant leaves in the forest ? stream
ecological continuum.
Material and method
Study site: The study was conducted at the Kami-Oguni River catchment in the northern part of Fukushima Prefecture. Major
land uses of the catchment are forests and paddy fields. The area is located about 50 km from the Fukushima Daiichi Nuclear
Power Stations. Last year, rice produced in several paddies of this area had high 137Cs concentration exceeding the controlling
criteria. Based on this survey, the Japanese Government decided to prohibit to plant rice in 2012. The local Date city
government conducts only the test plantation for investigation of the 137Cs uptake by rice in several selected paddies. The small
catchment was selected and implemented for the intensive observations and samplings.
Survey: As preliminary investigations, 137Cs concentrations of stream waters at several sampling points are monitored. Also,
137Cs concentrations of various organisms. Germanium detectors were used for measurements of 137Cs concentrations of all
samples at the University of Tokyo and the National Institute of Radiological Sciences.
Preliminary findings:
137Cs export by hydrological processes: Major forms of discharged 137Cs are suspended matters. Especially, particulate organic
matters may be most important carrier of 137Cs. High flow generated by a storm event accelerate the transportation of 137Cs bywater flows from forested catchments. Estimation of 137Cs export from the forested catchments requires precise evaluation of
the high flow acceleration during storm events.
137Cs diffusion through the food web: Because the biggest pool of 137Cs in the forested ecosystem may be litter and its detritus,
the 137Cs diffusion is quicker through the detritus food chain than the grazing food chain. Especially in aquatic systems, most
predators have already taken 137Cs. An urgent question is when and how the 137Cs diffuses through the grazing food chains, andhow quick that process will occur. To solve or predict these phenomena, mechanisms of 137Cs releasing from litters and soilorganic matter should be clarified.
Keywords
137Cs deposition, forested ecosystem, hydrological process, food web

25

1-9
Distribution of gamma-ray dose rate in Fukushima Prefecture by a
car borne survey method
Shinji Sugihara*¹, Noriyuki Momoshima¹, Akihiro Maekawa², Ryohei Ichikawa², Hidehisa Kawamura³¹Radioisotope Center, Kyushu University²Graduate school of Sciences, Kyushu University³Kyushu Environmental Evaluation Association

The Tohoku District-off the Pacific Ocean Earthquake and Tsunami caused by the earthquake
attacked the Fukushima Dai-ichi Nuclear Power Plant of TEPCO on March 11, 2011. A nuclear accident
followed at an unprecedented scale and huge amounts of radioactive material were released into theenvironment.
Distributions of gamma-ray dose rate in Fukushima prefecture were measured on April 18-21, June
20-22, October 18-21 (2011) and April 9-11, July 30- August 1st (2012) by a car borne survey method
using a NaI(Tl) scintillation survey meter. The gamma-ray spectrometry by a NaI(Tl) detector was alsodone at several points. Dose rate near Fukushima Dai-ichi NPP and at iitate-mura, fukushima-city washigh ( 1 ～ >30 µSv/h). The gamma-ray peak of I-131, Cs-134 and Cs-137 were mainly detected in
gamma-ray spectrum on April 2011. For a year and a half has passed after the accident, dose rates havedeclined. Reduced percentage is different at each point. In particular, weathering effects reflects larger
at high dose rate point.
Keywords
gamma-ray dose rate, car borne survey

26

1-10
Dose rate survey inside and outside three types of public buildings
located approximately 40 km northwest from the Fukushima
Daiichi Nuclear Power Stations
Kazuaki Yajima*,1, Kazuki Iwaoka1, So Kamada1, Masashi Takada1, Hiroyuki Tabe1,
Hidenori Yonehara1, Sin-ya Hohara2, Genichiro Wakabayashi2, Hirokuni Yamanishi2, Tetsuo Itoh2,
Michio Furukawa3
1National Institute of Radiological Sciences
2Atomic Energy Research Institute, Kinki University
3Mayor of Kawamata-machi

For the purpose of contributing to the dose estimation of the external exposure of inhabitants livingin radioactivity contaminated areas due to the Fukushima Daiichi Nuclear Power Station accident, wesurveyed the reduction of the dose rate inside three types of public buildings compared to outside. The
three buildings were A) a wooden construction district meeting place, B) a steel construction public hall,C) a reinforced concrete school building, and they are located approximately 40 km northwest from the
Fukushima Daiichi Nuclear Power Stations. The measurement was carried out on January 19, 2012. The
dose rates were measured with NaI (Tl) scintillation survey meters (Aloka TCS-171 and 172) at theheight of 1m from the floor inside the buildings and from the ground outside. The measured dose rates
around the buildings did not show uniform distribution. This is because the distribution of theradioactivity accumulated in environment causing the high dose rate in contaminated areas is not
originally uniform affected by various factors such as topography, state of the ground, weather, and soon. The maximum dose rate outside the buildings were A) 3.2 μSv/h obtained on piled-up fallen leaves,B) 4.1 μSv/h obtained on raindrops, C) 6.4 μSv/h obtained on raindrops. These correspond to a rise indose rate by so-called hotspot. In this work, we evaluated the dose rate reduction inside the building
using the reduction factor, which was represented by the ratio of the dose rate inside the building to thedose rate outside the building. The reduction factors at the point of 1m inside from the wall, in fact fromthe glass window, were less than approximately a half for the three buildings. The reduction factors at
the center of the room were 0.48 for A), 0.23 - 0.34 for B), and 0.10 - 0.14 for C). It was C) reinforced
concrete school building that showed the most remarkable reduction effect among the three buildings.
Keywords
dose estimation, external exposure, dose rate, hotspot

27

1-11
Radiation survey along two trails in Mt. Fuji to investigate theinfluence of the radioactive contamination due to the Fukushima
nuclear accident
Kazuaki Yajima*,1, Kazuki Iwaoka1, Hiroshi Yasuda1,2
1National Institute of Radiological Sciences
2United Nations Scientific Committee on the Effects of Atomic Radiation

A large amount of radioactive materials was released in the environment due to the Fukushima
Daiichi Nuclear Power Station accident caused consecutively by the Great East Japan Earthquake
occurred on March 11, 2011. From 2007 we have started measurements of cosmic radiation at the top
and foot of Mt. Fuji, which is 3,776 m above sea level and the highest mountain in Japan, with thesupport of a non-profit organization “Valid Utilization of Mt. Fuji Weather Station” to investigate thecosmic radiation environment at high altitude. Mt. Fuji is located approximately 300 km southwest fromthe Fukushima Daiichi Nuclear Power Stations. We performed the radiation survey along two main Mt.
Fuji’s trails where are crowded with a lot of climbers in the summer because the spread of theradioactive contamination has become a concern just after the Fukushima nuclear accident.
The measurement was carried out from 4:30 to 18:30 on July 9, 2011. We climbed the Yoshida trail
from the Kawaguchiko starting point of a mountain climb (2,300 m in altitude) to the Yoshida-Subashiri
top (3,720 m in altitude) and descended the Subashiri trail from the Yoshida-Subashiri top to theSubashiri starting point of a climb (2,000 m in altitude) on foot while measuring gamma-ray dose rateand energy spectra. The dose rate at the height of 1 m from the ground was measured using a NaI (Tl)scintillation survey meter (Aloka, TCS-172B). The measured dose rates were within the range from 0.03
µSv/h to 0.05 µSv/h throughout our measuring trip. As a result, it was found that the dose rates of thetwo trails in Mt. Fuji were normal background level. We used a NaI (Tl) scintillation spectrometer(EMF Japan, EMF211) for gamma-ray energy spectra measurement. The gamma-ray spectra obtained
under the sixth station both of the Yoshida and Subashiri trail (2,400 m in altitude) showed the peaks of
two radioactive cesium isotopes (Cs-134 and Cs-137) and natural radioactive nuclides. It was confirmedthat a radioactive plume released from the Fukushima Daiichi Nuclear Power Stations had arrived at theplace of 2,400m above sea level of Mt. Fuji.
Keywords
radiation survey, radioactive contamination, dose rate, energy spectra, plume,

28

1-12
Environmental radiation doses due to the accident at the
Fukushima Daiichi Nuclear Power Plants
Tomoaki Yamamoto*, Kenzo Muroi, Sumito Maruyama, Takahisa Koike, Marina Matsuda,
Kenichiro KatsumataInternational University of Health and Welfare, Department of Radiological Sciences
International University of Health and Welfare, Radiation Disaster Prevention Research Center

On March 11, 2011, an undersea megathrust earthquake caused a tsunami that inflicted serious
damage to the Fukushima Daiichi Nuclear Power Plant (FDNPP). On March 12, 2011, we began
measuring environmental radiation doses and identifying fission product radionuclides at theInternational University of Health and Welfare (IUHW). The purpose of this investigation is to estimate
the external exposure dose of fission products from FDNPP. Measurements were performed fromMarch 12 to August 31, 2011. A NaI(Tl) scintillation survey meter was used to measure theenvironmental radiation dose, and air dust samplers and a NaI(Tl) scintillation spectrum analyzer wereused to identify radionuclides in the atmosphere and soil. Three lifestyles were considered to estimate
external doses to students or office workers, to businesspersons, and to farmers or construction workers.
Increasing doses were detected on March 15 around noon, and peaked on March 16. Post-peak, doses
decreased exponentially and became stable after 2 months. Immediately after the accident, some fission
product radionuclides were detected in atmosphere and soil samples. Approximately 1 month after the
first analysis, almost no radionuclides were detected in the atmosphere, but radionuclide decay products
were detected in the soil. External dose varied with supposed lifestyle; assuming that the abundance
ratio of Cs-134 to Cs-137 was 1:1, the annual external doses for the considered lifestyles were 1.069
mSv for students or office workers, 1.672 mSv for businesspersons, and 2.044 mSv for farmers orconstruction workers. These doses are sufficiently small that most residents living near IUHW,
including children, would not be affected. Further investigation of internal exposure is necessary tobetter estimate effective doses. External exposure to fission product radionuclides is within safe levels,
and while further investigation of internal exposure factors such as milk, water, and mushrooms is stillneeded, it appears that radiation around IUHW does not pose a health hazard.
Keywords
radiation survey, radiation dose, external dose, Fukushima, fission product

29

1-13
Survey of environmental radiation in Kawamata-machi,
Fukushima-ken
Tetsuo Itoh ¹, Michio Furukawa², Nobuyuki Sugiura³, Hirokuni Yamanishi *¹, Genichiro Wakabayashi¹
Tetsuo Horiguchi, Shin-ya Hohara, Masayo Inagaki, Hiroshi Noma, Kiyoshi Kojima¹Atomic Energy Research Institute, Kinki University²Mayor of Kawamata-machi³National Institute of Radiological Science

Large amount of radioactive materials had released by the nuclear power plant accident at
Fukushima Dai-ichi site. The level of radiation dose rate has been raised by the radioactive material on
the ground. We measured the dose rates in Kawamata-machi, Fukushima-ken, Japan, which is locatedabout 40 km from the power plant in north -west direction. We measured the Cs-137 concentration insoil samples by the Ge diode detector. The result shows more than 90 % of Cs-137 exists the depth
from the surface to 10 mm. The soil of shallow depth was sieved to 6 series by particle size. The
radioactivity of the parts less than 1 mm diameter account for more than 80 % of the total. The Cs-137
in soil was not solved by water.
Keywords
environment, soil, Cs-137, depth profile, grain diameter

30

1-14
Environmental radiation measurements immediately after theaccident and dose evaluations by soil deposition
Masahiro Yoshida
Nuclear Safety Technology CenterIn the Nuclear Safety Technology Center, we have measured the environmental radiation on
voluntary basis after the accident in parallel with supporting activities to be based on the request of thegovernment. In this paper, we report the results of major voluntary measurement (Immediately after theaccident, after 2-3 weeks and one month). In particular, the radioactive plume that has passed through inthe morning, on March 15 at Bunkyo-ku Tokyo, is reported that was peaked on 10:05 am. In addition, as
the exposure evaluated from soil deposition based on these measurements, inhalation exposure ofradioactive cesium has been rated as less than one-tenth in 10 years.
Keywords
MCNP5, RESRAD6.5

31

2-1
Radioactivity Survey in Marine Environment in the Pacific off Fukushima
after Accident of TEPCO's Fukushima Daiichi Nuclear Power Station
Tatsuo Aono*¹, Satoshi Igarashi²,Yukari Ito³,Jyota Kanda³, Takashi Ishimaru³¹National Institute of Radiological Sciences²Fukushima Prefectural Fisheries Experimental Station³Tokyo University of Marine Science and Technology

Monitoring and survey of radioactivity in seawater and organisms of marine environment in the
Pacific off Fukushima are important to understand the dispersion of artificial radionuclide after accidentof TEPCO's Fukushima Daiichi Nuclear Power Station (F1NPP). The activities of Cs-134+137 inseawater were observed over 10kBq/L around F1NPP in the end of March, 2011 and recently decreased
gradually to 1~2 mBq/L, which are almost same level before this accident, without the close of F1NPP.
On the other hand, the higher activities of these in sediments have been determined in the Pacific off
Fukushima. It is important that the radioactivity in marine organisms, are not only fish and shellfish but
also benthos as feed, have been monitored continuously, because it is well-known that marine organisms
are accumulated and concentrated elements and radionuclide in the body. The activities of radionuclidein marine organisms, are plankton and benthos etc., off Fukushima are determined to make clear thevariation of radioactivity and Concentration ratio (CR) in marine organisms. The observed artificial
radionuclide as gamma emitter are not only Cs-134+137 but also Ag-110m in marine organisms. Almost
organisms without benthos could not be observed Ag-110m after a year in accident. The variation of Cs134+137 activity in organisms was classified two types, and showing tendency to gradually decrease
and considerable variation. The calculated CRs were higher than these value in compare with IAEATRS-422 (2004). It is thought that CRs could be calculated when the concentrations in water andorganisms are assumed in an equilibrium state. It is considered that rapid change of the radioactivity inseawater, resuspension of particles from sediment and food chain were led to high CRs after theaccident.
Keywords
marine organisms, Cs-134+137, Ag-110m, Concentration ratio

32

2-2
Dose rate estimation for northern Miyagi Prefecture area at the early stageof Fukushima accident
Satoru Endo*, Tsuyoshi Kajimoto, Kiyoshi Shizuma
Graduate School of Engineering, Hiroshima University

Due to Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, Tohoku and northern Kanto area
were widely contaminated. Many soil contamination surveys around Fukushima Prefecture and south
Miyagi Prefecture area have been reported. However, there are few data for northern Miyagi Prefecturearea. Moss sample taken from Tome City on 1 May 2011 was measured with a Ge detector. Radioactive
nuclides of 129m, 129Te, 131I, 134,136,137Cs, 110mAg and 140La are clearly identified in the moss sample andalso 132Te and 132I appeared likely to be present in the spectrum, but were accompanied with large errors.
The identified radionuclides are the same as those in Fukushima contaminated plants and soil by
FDNPP accident. It was found that the radionuclide concentration in moss sample was originated from
FDNPP accident. In order to estimate radiation dose rate in northern Miyagi Prefecture area, soil of 30
cm core sampling was performed at ten locations (Tome City, Kurihara City, Osaki City, Daiwa Town
and Sendai City) on 2011.8.19. The soil cores were dried by oven at 120 degrees for overnight. The
dried samples were sieved through a 2-mm mesh to remove pebbles and large pieces of organic content.
Each soil sample (40 g) was packed into a polystyrene container (4.8 cmφ× 3 cm height) after
homogenization in a polyethylene bag. Radioactive concentrations in soil sample were measured andobtained using a Ge detector. The minimum and maximum concentration of the sum of 134Cs and 137Cs
in soil were obtained to be 2.76 and 35.2 kBq/m2 for Michino-eki in Sanbongi Town and the Izu Pond in
Kurihara City, respectively.
Radiation dose rate at early stage of the FDNPP accident in the northern Miyagi prefecture has been
estimated using radionuclide concentrations in moss and soil samples. The estimated radiation dose rate
at the time after radioactive deposition near the Izu Pond in Kurihara City have been estimated to be 1.8µSv/h on 15 March 2011. Cumulative dose by radioactive deposition for one year from 15 March 2011
is estimated to be 1.2 mSv from radionuclide deposition at maximum in case of outdoor.
Keywords
Fukushima, dose, soil contamination, Miyagi

33

2-3
Influence of the Fukushima Daiichi Nuclear Power Plant Accident
observed from results of environmental radiation monitoring in Kyoto
Naoto Fujinami*, Naoto Miyajima, Tetsuya Watanabe, Yoshihiro Tanabe, Hajime Nishiuchi
Kyoto Prefectural Institute of Public Health and Environment

We have been continuously observing absorbed dose rates in air at environmental radiation
monitoring stations and have carried out analyses of radionuclides in various environmental samples
such as deposited materials, soil, plants, and fishes, in order to examine the influence of nuclear power
plants located in the adjoining Fukui Prefecture, and of global radioactive fallout. As a result, cesium137, cesium-134 and iodine-131 were detected in some kinds of vegetables and fish collected in Kyoto
Prefecture after the Fukushima Daiichi Nuclear Power Plant accident (FDNPPA), whose concentrations
were much lower than 100 Bq/kg. In addition, silver-110m was detected in turban-shell. Allconcentrations of these four radionuclides are so low that public exposure from ingestion would bemuch lower than 1 mSv per year. The influence on Kyoto Prefecture from the FDNPPA appears to beless than 10 percent of that from the Chernobyl NPP accident (CNPPA), as indicated by our comparisonof the deposited amount of Cs-137 and the concentration of Cs-137 in environmental samples caused by
the FDNPPA with those caused by the CNPPA.
Keywords
radioactive cesium, radioactive fallout, soil, sea water, foods

34

2-4
Comparison between fallout with rain from Fukushima,
Chernobyl reactor accidents in Japan, and Hiroshima atomic bomb
Ryuta Hazama*¹, Akihito Matsushima²¹Osaka Sangyo Univerity²Hiroshima University

The Fallout with rain from the Fukushima Reactor Accident has been monitored for about twomonths in Higashi-Hiroshima city, Hiroshima, Japan from March 19 to May 23, 2011. Gamma ray
spectra measured by low background HPGe spectrometer show clear evidence of fission products 131I,
137Cs, and 134Cs. The 131I was observed on March 27 and April 8, while 137Cs and 134Cs were observedon March 27, April 18, and April 22. The 131I, 137Cs, and 134Cs activity concentrations in rainwatercollected in Hiroshima reached 0.44 on April 8, 0.17 on April 18, and 0.15 Bq/L on April 18, 2011,
respectively. These activity levels were compared with the results reported in the world, which werecollected in the northern hemisphere. Several samples of rainwater collected in Chiba (Kashiwa) on
March 21, April 11, and May 12, Tokyo (Nerima) on March 21 and April 11, Osaka (Hirano) on April 8,
Nara (Kitakatsuragi) on April 9, and Fukushima (Fukushima) on April 19, were also measured by ourspectrometer and the ratio of activities such as 131I/137Cs and 134Cs/137Cs were compared with the othermeasurements. Our measured results in Japan due to the Fukushima reactor accident were comparedwith that due to the Chernobyl reactor accident and the result in black rain caused by fallout of theHiroshima Atomic Bomb.
Keywords
Radioactive fallout, Fukushima accident, Fission product, Gamma spectrometry

35

2-5
Survey of radioactive contamination distribution at Naka-Doriarea, Tohoku Region, Japan
Sin-ya Hohara,* Masayo Inagaki, Hirokuni Yamanishi, Genichiro Wakabayashi, Wataru Sugiyama,
Tetsuo Itoh
Kinki University Atomic Energy Research InstituteDue to the Tohoku Region Pacific Coast Earthquake and the Tsunami after the earthquake, residual
heat removal systems of Fukushima Daiichi Nuclear Power Station were down at 11th March 2011. The
systems down caused temperature rise and melt down of the nuclear reactor cores. The heat rise of thereactor core had a causal influence on hydrogen explosions of the reactor building and release ofradioactive materials to the general environment. The released radioactive materials moved into a large
area of Tohoku and Kanto regions with winds, and fall down to the ground with rains and snows. Dose
rates in Tohoku and Kanto regions increase after the fall out. The radioactive materials were fixed
several objects, for example surface soils, pave materials, and so on, and position distribution of thedose rate has changed with movement of the radioactive objects.
Kinki University atomic Energy Research Institute (Kinki Univ. - AERI) started a survey ofradioactive contaminations at 3 points of Naka-Dori area, Tohoku regions in early April 2011. The firstsurvey point is Arakawa-Undo Park neighborhood, Fukushima city of Fukushima prefecture. The
second point is Hayama Park neighborhood, Koriyama city of Fukushima prefecture, and the last point
is Kuroiso Park neighborhood, Nasu-Shiobara city of Tochigi prefecture. 2 investigations have been run
in this survey. One investigation is a position distribution measurement of dose rate in urban area. Kinki
Univ. - AERI use a GPS-linked dose rate recorder, that is constructed with a GPS receiver, an NaI(Tl)survey meter, an ADC including microcomputer and a personal computer. The other investigation is
identification of the radio isotopes those came from Fukushima Daiichi Nuclear Power Station and still
remain in ground soils. Surface soils at Naka-Dori region, Tohoku area has been collected and measured
with a high pure germanium counter at Kinki Univ. - AERI.
Some conditions of the radioactive contaminations became clear from the survey results. The firstpoint is that dose rate distribution depends on the condition of the ground surface and alignments ofconstructions. The dose rate of where is under a construction was lower than where nothing exists on theupper side just after the fall out. Furthermore, the dose rate of non-paved area was higher than the dose
rate of neighbor paved area. Though, relative dose rates’ distributions changed after the rainy season of
2011. Dose rates at some part of non-paved area became lower than those of neighbor paved area, andthe dose rates’ difference at paved area has become clear. The dose rate at paved area depends on the
paved material. The second point is that component ratio of the radioisotopes in surface soils at NakaDori region became clear. 95Nb, 129mTe, 129Te, 132Te, 131I, 134Cs, 136Cs, 137Cs were found from the soil
samples collected at Fukushima city, Koriyama city and Nasu-Shiobara city in April 2011. Though,short half life isotopes decayed and almost can’t be detected in early July 2011 except for 134Cs and
137Cs.
The third point is that specific activities of radio isotopes in the surface soils are decreasing fasterthan the physical half life of the radio isotopes. Current specific activities of 137Cs in the surface soils aremuch less than the activities calculated with physical half life and the detected activities in April 2011.
Keywords
Dose rate, distribution, specific activity

36

2-6
Elution of radiocesium from soil
Nobuyoshi Ishii*¹, Hiroyuki Koiso², Keiko Tagami¹,Shigeo Uchida¹¹National Institute of Radiological Sciences
₂Tokyo Nuclear Services Co., Ltd.

A large amount of radiocesium (134Cs and 137Cs) was released into the environment by the
Fukushima Nuclear Accident. These radionuclides have caused serious contamination onto the soil
surface and have emitted gamma rays. Most of the people living in the contaminated areas concerned
about radiation exposure resulting from the accident. Techniques to reduce radiation dose, therefore,
has been desired. Some of local governments tried to remove the surface soil for the reduction ofradiation dose, but this technique has problems that must be considered, such as huge cost, disposal of
the contaminated soil, and the use of heavy machine. We have thought that the downward migration ofradiocesium might be an effective technique, because this technique has the similar effect to deep
plowing which inverts the surface soil to the deep soil. Shielding effects on radiation is expected bycovering the contaminated surface soil with the non-contaminated deep soil. We studied elution ofradiocesium from soil as a first step for the vertical migration of radiocesium into the soil profile. To
elute radiocesium, various solutions such as water, potassium chloride, ammonium sulfate, Good's
buffers, and treating water with ozone were used.
Based on the annual rainfall in Namie-machi where is located inside the evacuation zone, amount ofwater, equivalent to the rainfall of 7 months and of 17 months, was passed through the contaminated soil.
Elution of radiocesium by water, however, was not observed. The contaminated soil which was soakedwith water was bubbled with ozone gas for 30 min, but no elution was also observed. Strong oxidation
power of ozone has no effects on the elution of radiocesium under our experimental conditions.
Although we tried to elute radiocesium with Good's buffers such as MES (pH6.0) and HEPES (pH 7.5),
these radionuclides in Good's buffers were under the detection limit. When the contaminated soil was
soaked with 100 mM KCl and 100 mM (NH4)2SO4, elution ratios were 3.9% and 15.4%, respectively.
The elution ratios for the addition of KCl were constant for 13 weeks, but the ratios for (NH4)2SO4
decreased with time. After 13 weeks from the addition of (NH4)2SO4 the ratio was 11.7%. As one of
the reasons for the decreasing ratio, it is considered that the concentration of ammonium ion decreased.
From these results, (NH4)2SO4 is the most effective chemical agent for the elution of radiocesium.
The downward migration distance and shielding effects by the use of (NH4)2SO4 must be studied toestablish practical techniques for reducing radiation dose to the people in the nest step.
This work was supported by the Agency for Natural Resources and Energy, and the Ministry of
Economy, Trade and Industry (METI), Japan.
Keywords
Elution, radiocesium, ammonium sulfate

37

2-7
Development of rapid self-absorption correction method usedfor HPGe detector
Hidesuke Itadzu*¹², Tetsuo Iguchi¹, Toshikazu Suzuki²¹Department of Quantum Engineering, Graduate School of Engineering, Nagoya University²Department of Radiation Dosimetry, National Institute of Radiological Sciences

Quantitative analysis for food products and natural samples to determine the activity of eachradionuclide is done by using high-purity germanium (HPGe) gamma-ray spectrometer system. An
analysis procedure is based upon the guidelines established by the Nuclear Safety Division of Ministryof Education, Culture, Sports, Science and Technology in Japan (JP MEXT).
In case of gamma-ray spectrum analysis for large volume samples, re-entrant (marinelli) containers
are commonly used. The effect of photon attenuation in large volume sample, so-called “selfabsorption”, should be corrected in order to determine the activity. As for marinelli beakers, twoaccurate geometries are shown in the guideline for 700 milliliters and 2 liters in volume. In the
document, the functions to obtain self-absorption coefficients for these specific shapes are also shown.
Therefore, self-absorption correction has been carried out only for these two containers with practicalmedium.
However, in order to determine the activity in samples, those are filled in the containers, which are
not described in the guideline, functions for self-absorption correction must be obtained by measuring atleast two standard multinuclide volume sources which consist of different media or different linear
attenuation coefficients.
In this work, we developed a method to obtain functions over a wide range of linear attenuation
coefficient for self-absorption in various shapes of marinelli beakers using Monte Carlo simulation. Thismethod was applied to a 1-liter marinelli beaker, which is widely used for quantitative analysis, but its
self-absorption method is not established yet. As a result, validity of this method was shown byprocessing an analysis of natural sample filled in this container, that its activity is pre-verified.
Keywords
HPGe detector, self absorption, marinelli beaker, quantitative radioactive analysis, Monte Carlosimulation, peak efficiency

38

2-8
Distribution of radioactive 137Cs and 134Cs in river water andbottom sand for major rivers at Minami-Souma City in Fukushima
Tsuyoshi Kajimoto*¹, Satoru Endo¹, Takeshi Naganuma², Kiyoshi Shizuma¹¹Graduate School of Engineering, Hiroshima University²Graduate school of Biosphere Science, Hiroshima University

A nuclear accident occurred on March 11, 2011 caused a catastrophic radioactive contamination in
Fukushima. Minami-Souma City locates at 10 km-40 km to the north of the TEPCO’s Fukushima
Daiichi Nuclear Power Plant. The eastern sea coast area of the city was severely damaged by tsunami
and west ern area of the city where Abukuma chain of mountains located were known to be highly
contaminated areas. Most of rivers in Minami-Souma city has its origins at around highly contaminatedareas. We have started environmental radioactive survey along four rivers and branches in MinamiSouma City since October 2011. Sampling points were four to six locations along one river. One-litterof water and bottom sands of about 300 g were collected at the same points for each river. Water sample
of 1 L was dried up on a thin naflon sheet using hot-plate keeping temperature at 100℃. Then the sheet
was folded to 10 mm dia.×30 mm length to measure gamma-rays with a well-type Ge detector. Sand
samples were dried with an drying oven, then mixed well and about 50 g of sand was taken in a
polypropylene container (U9: 50mm dia.×30 mm height) . Gamma-ray measurement was performed
using a low-background coaxial Ge detector. Detection efficiencies for each sample size were
determined by using a reference gamma-ray source.
The Cs concentration (137Cs+134Cs) were 10,000-20,000 Bq/kg in the bottom sand at upper reachesof the river, whereas the concentration at down reaches near the sea coast were about 200 Bq/kg. The Cs
concentration in river water were about 0.8 Bq/L at upper reaches of the river and 0.3 Bq/L at downreaches, indicating the Cs concentration in water is quite low. It is necessary to follow how thecontamination at the upstream of the river will move to the down stream area hereafter.
Keywords
Minami-Souma, river water, bottom sand, Cs concentration

39

2-9
Determination of radiostrontium released from Fukushima Daiichi
Nuclear Power Plant by extraction chromatography and liquid
scintillation counting
Akihiro Maekawa*¹, Noriyuki Momoshima², Shinji Sugihara², Toshiya Tamari³¹Graduate School of Sciences, Kyushu University²Radioisotope Center, Kyushu University³Kyushu Environmental Evaluation Association

Various kinds of radionuclides were released from Fukushima Daiichi Nuclear Power Plant(FDNPP) due to the accident occurred on March 2011. Sr-89 and Sr-90 are hazardous because they
accumulate in bone. However, only a few data of radiostrontium in contaminated soil has been reported
because of time consuming analytical steps for radiostrontium. We adopted extraction chromatographythat utilizes crown ether as the extractant to simplify analysis of radiostrontium. The extraction
chromatography is simpler and faster than classical precipitation methods. The purpose of this study is
to establish the analysis of radiostrontium by extraction chromatography and apply to determination ofradiostrontium in soil at Fukushima. Two soil samples were collected on April 18-20, 2011 at Namie
town and Tomioka town located at 26 km north-west and 11 km south from FDNPP, respectively. The
0-1 cm soil layer was used for experiment. The soil samples were ashed, acid digested, and strontium
was separated from interferences with an extraction chromatography resin (Sr resin, Eichrom
Technologies). The isolation and purification of strontium from matrix components can be completed in
12 hours. After 2 weeks for ingrowth of Y-90, the measurement of beta-ray was conducted with a liquid
scintillation counter for 1200 minutes. The concentration of Sr-90 was 57.4 Bq kg-1 and 10.1 Bq kg-1 forNamie town and Tomioka town, respectively. Sr-89 was not detected from both samples. When 2 g ofsoil was used, the chemical yield of strontium was about 70 % and the detection limit of Sr-90 was 2.7
Bq kg-1. The extraction chromatography method was successfully applied to determination ofradiostrontium in the contaminated soil.
Keywords
Radiostrontium, Soil, Sr resin

40

2-10
Radioactivity in vegetation at Fukushima area contaminated withradionuclides released from TEPCO's Fukushima Daiichi Nuclear
Power Stations
N. Momoshima*, S. Sugihara, R. Ichikawa, A. Maekawa, R. Ozawa, A. Nakama
Kyushu University

The Fukushima Daiichi nuclear power stations lost the reactor cooling functions following theearthquake on March 11, 2011 occurred at Pacific Ocean near Japan and the Tunami that attacked theeast coast of Tohoku area, resulting to the release of radionuclides into the environment and a wide
range contamination by radioactivity at Tohoku area, Japan. At the time of the deposition vegetations inthis area were not well grown on the ground surface because of the end of winter, and we did not see
any green vegetation on the ground surface on middle of April 2011 even one month after the accident
except leaves of ever green trees. The radionuclides deposited on the ground surface would move down
to deep layer and would be taken up by vegetation which comes out this spring. The fate of radionuclide
deposited on the ground surface is crucial information to understand an impact of accident on ecosystem.
We measured radionuclides supplied from the accident in vegetation with an imaging plate and Ge
detector to understand soil-plant interaction in the ecosystem.
Pueraria lobata, Japanese name Kuzu, was collected on June 21, 2011 at Futaba town, Fukushima
prefecture and collected on July 30-31 and August 1, 2012 at several points at Fukushima prefecture. On
March, 2011 at the time of the accidents, the ground surface was not covered by green plants. However,on June 2011, Kuzu grown after the accidents showed considerable activity. 134Cs, 137Cs, 110mAg and
129mTe-129Te were identified by gamma spectrometry. The IP analysis of Kuzu leaves reveals that thecontamination occurred internally and surface deposition. Obviously the radionuclides deposited onlitter and soil surface have taken up through roots. The Kuzu grown in spring 2012 the deposition ofradionuclides on leaf surface was not clearly identify due to low sensitivity of the IP, but Ge
measurements suggest active root uptake. The radiocesium activity in vegetation showed weakcorrelation with radiation dose rate.
Keywords
vegetation, Kuzu, contamination, Imaging plate, Ge detector

41

2-11
Characteristics of radiocesium concentration in stream water froma catchment in hilly and mountainous area at rainfall event
Kimihito Nakamura*¹, Tetsuo Yasutaka²¹Graduate School of Agriculture, Kyoto University²National Institute of Advanced Industrial Science and Tech.

The terrestrial and aquatic systems have been contaminated by the radioactive ingredients since a
nuclei accident at Fukushima Daiichi Nuclear Power Station. Monitoring the concentration ofradiocesium in stream water from a catchment is important because it is used for paddy irrigation anddomestic water, and the soil particles and organic matter in stream water deposit in the river, estuary,
and ocean. Especially, it is predicted that the amount of radioactive cesium by runoff may increase at theintense rainfall event. The some regions of hilly and mountainous areas in Fukushima Prefecture areseriously contaminated and the cultivation in the large area of agricultural field has been abandoned
since the accident.
We have observed the temporal changes in the amount of runoff and the concentration ofradiocesium of stream water from a catchment in hilly and mountainous area in the northwest from thepower plant. The catchment area is about 0.1 km2 and consisted of forest (90 %) and abandoned
agricultural field (10%). Stream water at the end of a catchment was sampled roughly once a month andwas automatically sampled at two hours interval from the time point when water level of the stream
exceeded a certain level at the rainfall event. Concentrations of suspended solid (mg/L) were measured
by filtering sampled water using membrane filters of 0.45 micrometer and the concentrations ofradiocesium (134Cs and 137Cs) of the residue (Bq/kg) were measured using gamma-ray spectrometry
with a Ge semiconductor detector. The concentrations of radioactive Cs absorbed to the residue in thewater (Bq/L) were calculated. The concentrations of the filtrate (dissolved Cs) were below the detection
limit (0.2Bq/L).
The concentration of radioactive Cs in the stream water at low-water stage was 0.2 ? 0.3Bq/L andthe SS was 2 ? 7 mg/L in March and April, 2012. At the heavy rainfall events, we observed the changes
in SS similar to stream water flow rate. The peak time of SS was roughly in accordance with one ofwater flow rate. The maximum of SS was 6894mg/L at the rainfall of 71.0mm (rainfall duration =2.3hours) on July 23, 2012 (event 1) and 36000mg/L at the rainfall of 37.4mm (rainfall duration =4.3hours) on September 4, 2012 (event 2). The radioactive Cs of SS was 20800Bq/kg at the beginningof rainfall runoff at the event 1, decreased to 400Bq/kg along with the increase of runoff and SS, andincreased to 15100Bq/kg gradually along with the decrease of runoff and SS 33.4hours after the start of
rainfall. At the event 2, the concentration of radioactive Cs of SS changed from 15300Bq/kg to
400Bq/kg and increased to 3300Bq/kg 4.7hours after the start of rainfall. The concentration ofradioactive Cs absorbed to SS in water was 23Bq/L at the beginning of the rainfall runoff and decreased
gradually to 0.3Bq/L at the event 1. This concentration at the event 2 decreased from 52Bq/L to 1.1Bq/L.
It is considered that the radioactive Cs of SS in stream water (Bq/kg) depends on the difference ofsuspended solid particle size composition induced by stream water flow rate. The amount of organic
matter in stream water may also influence the radioactive Cs of suspended solid. The concentration ofradioactive Cs of suspended solid is high at the beginning of the rainfall and after the rainfall event. We
may have to pay attention to stream water with such suspended solids for irrigation and domestic water
use for a prolonged period.
Keywords
stream water, radioactive Cs, suspended solid, rainfall runoff, catchment

42

2-12
Specific activity and time dependence of radionuclides in soils affectedby the accident of the Fukushima Dai-ichi nuclear power plant.
Tatsuya Shimasaki*, Yoshioki Shiraishi, Kumiko Goto, Akihiro Kojima, Toru Urano,
Seiji Okada
Institute of Source Development and Analysis, Kumamoto University

The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) lost all electricity due to a huge tsunami
after the Richter-scale magnitude 9 earthquake of March 11, 2011. The water circulation system wasseverely damaged, and the radionuclides were released to the environment, specially for days in the
middle of March. The purpose of this study is to clear the specific activity and the time dependence ofthe radionuclides in soils at Fukushima prefecture and neighborhood area. We performed soil sampling
for six times at several points within 60km from FDNPP and at Tokyo to January 30, 2012 from March
23, 2011. The concentration of 131I, 134Cs, 136Cs, 137Cs and 139mTe were obtained, but only trace amountsof 95Nb, 110mAg and 140La were detected whitch were too low to provide accurate concentrations. The
concentration of radioactivity on March 15, 2011 is 8234 kBq/m2 for 131I and 882 kBq/m2 for 137Cs at
Fukaya, Iitate village. Some radionuclides, such as 103Ru, and 106Ru and 140Ba, observed in the
Chernobyl accident, were not measured in the soil samples. This is estimated that mainly noble gasses
and volantile radionuclides were released from FDNPP. For the time dependence of 137Cs concentration
in soil, it was decreased approximately 10-15% in 10 months at Fukaya, Iitate village. However, at somesampling points, there was not a change at all.
Keywords
Fukushima Dai-ichi N, Cesium-137, specific activity, time dependence, Cesium-134

43

2-13
Early air sampling in Higashi-Hiroshima after the accident of the
Fukushima daiichi nuclear power plant and subsequent sampling in
Minami-Souma City during October 2011 to September 2012.
Kiyoshi Shizuma*, Tsuyoshi Kajimoto, Satoru Endo
Graduate School of Engineering, Hiroshima University

After the accident of TEPCP’s Fukushima Daiichi Nuclear Power Plant on March 11, 2011, we
stared air sampling at Higashi-Hiroshima since March 20. The air sampling was performed with a highvolume air sampler of 500 l/min with a glass fiber filter for three hours in the morning and three hours in
the afternoon. Radioactive 131I was first observed on March 30, thereafter 137Cs, 134Cs, 136Cs, 132Te werealso observed. The concentration in air showed a maximum on April 7 (137Cs: 8×10-3Bq/m3), 2012,
and also April 18 (137Cs: 1×10-3Bq/m3). After April 30, no radionuclides originated to the accident
were observed reflecting no release of radionuclides. Since 137Cs and 134Cs have long half life; 30 y and
2 y, respectively, all air filters were measured again during February-March 2012. The dust filter was
folded to 10 mm dia.×30 mm length for the measurement with the well-type Ge detector. As a result, it
was found 137Cs was already observed on March 26, 2011.
Air sampling was performed at Minami-Souma City, Fukushima since October, 2011 to September
2012. The purpose of this sampling was to investigate the release of radionuclides from the forest andfly up into the air from the ground by the wind in winter and the release with pollen in spring. The
sampling was performed for 30 min with high volume air sampler. The results showed that theradioactive concentration of 137Cs in air was 5×10-4 ～ 2×10-3 Bq/m3. This means that fly up or
release of radioactivity from the forest by the wind or release with pollen were no occurred indicating
radioactivities are strongly attached to leaves of trees or soils on the ground.
Keywords
early dust sampling, radionuclides, Hiroshima, fly up, Minami -Souma

44

2-14
Estimation of Tellurium-132 distribution in Fukushima prefecture
Keiko Tagami*, Shigeo Uchida, Nobuyoshi Ishii, Jian Zheng,
National Institute of Radiological Sciences

Tellurium-132 (Te-132, half-life: 3.2 d) is one of the major contributors to the radiation dose fromthe Fukushima Daiichi Nuclear Power Plant (FDNPP) during the early stages of accident, that is, inMarch 2011. The Nuclear and Industrial Safety Agency (2011) estimated total amount of radionuclides
discharged to the air from the FDNPP, and the most released radionuclide was non-reactive Xe-133(1.1x1019 Bq) followed by I-131 (1.6x1017 Bq) and Te-132 (8.8x1016 Bq). Indeed, high-volume air
sampling results in March 2011 carried out by JAEA in Takasaki (2012) and KEK in Tsukuba (2012)
showed that observed Te-132 activity was as high as that of I-131 in both institutes. However, there is
far less available data for Te-132 in soil because of the nuclide’s short half-life. Thus, its distribution has
not yet been adequately described. The Ministry of Education, Culture, Sports, Science and Technology(MEXT) has reported Te-129m (half-life: 33.6 d) distribution in soils of Fukushima, but presents nodata for Te-132 because the soil sampling (May-June 2011) was too late to detect it. In this study,
therefore several reliable data sets were compiled to estimate Te-132 distribution in the soils of
Fukushima Prefecture in March 2011.
The radionuclide activities were collected from published monitoring data reported at homepage of
METI (http://radioactivity.mext.go.jp/ja/list/111/list-1.html, accessed 11 Sept. 2012) as well as research
papers. For many available data, concentrations of radionuclides (I-131, Cs-134, Cs-137, Te-129m, Te132, Cs-136 and La-140) in soil samples were reported in Bq/kg at the time of sampling. Using thesedata sets, comparison of Te-132 with Te-129m and I-131 were carried out; all the data were decaycorrected to 11 March 2012.When Te-132 and Te-129m were compared, high correlation was observedby Student’s t-test with R=0.99 (p<0.001). No distance and direction dependences were also revealed.
Thus Te-129m could be used to estimate Te-132. However, Te would be in the anionic forms (HTeO3or HTeO4-) in soil under oxic conditions; therefore, it was suspected that Te-129m might migrate withwater to other places from its initial deposited sites and/or leach into deeper soil layers. Thus activity
ratios between Te-129m and Cs-137 were analyzed with time, because radiocesium is one of the lessmobile radionulcide in soil. The ratio was almost constant for the 2 month period considered indicating
the relative immobility of Te-129m during the data collection period. The published Te-129m data in
Bq/kg was converted into Bq/m2 using a conversion factor, and finally, Te-132 in soil (Bq/m2) was
roughly calculated. Te-132 concentration was high in the north-west direction from FDNPP, a trend also
seen with radiocesium; however, higher Te-132/Cs-137 was also observed to the south from the FDNPP.
Thus the distributions of Te-132 and radiocesium were not the same.
Concentrations of Te-132 and I-131 were also compared and their correlation was also high (R=0.91,
p<0.001). The results indicated that it would be also roughly possible to estimate Te-132 concentration
using I-131 data.
The authors thank Dr. E. R. Landa (U.S. Geological Survey) for his valuable comments. This work waspartially supported by the Agency for Natural Resources and Energy, the Ministry of Economy, Tradeand Industry (METI), Japan.
Keywords
Tellurium-132, Distribution, Soil, Tellurium-129m, Iodine-131

45

2-15
Effects of radionuclide contamination on forest trees in 20 km
exclusion zone around the Fukushima Daiichi Nuclear Power Plant
Yoshito Watanabe*¹, San’ei Ichikawa², Masahide Kubota², Masahiko Mizoguchi³,Toshiyuki Takano³
Yoshihisa Kubota, Shoichi Fuma, Satoshi Yoshida¹National Institute of Radiological Sciences²Japan Wildlife Research Center³Japan NUS Co., Ltd

During the Fukushima nuclear accident in March 2011, radionuclides released to the atmosphere
contaminated the surrounding environment. The largest radioactive plumes from the power plant flew
west to north-westward, where forest land is widely distributed. In the past nuclear accident in
Chernobyl in 1986, radioactive plumes have contaminated the surrounding forest, which have caused
massive radiation damage in forest trees. The damages became obvious by the first summer after theaccident in the highly contaminated forest area, where have been called the Red Forest from the color ofthe dead tree stands. In this study, a preliminary survey was made in forest areas within the 20 km
exclusion zone around the Fukushima Daiichi Nuclear Power Plant for the distribution of radionuclides
and the radiation effects on trees during the first year after the accident. The collection of the tree
samples was carried out for three native coniferous species, Japanese red pine, Japanese cedar andJapanese cypress at 3 sampling locations differing in distance and direction from the nuclear power
plant during the period from November 2011 to March 2012 as part of a project by the Ministry of theEnvironment, Japan. The external gamma dose rate in each sampling location was measured at 1 m
above the ground with NaI scintillation or ionization chamber type survey meter. Radioactive
contamination in the samples was first analyzed nondestructively with an imaging plate. The separated
and homogenized samples were further analyzed for radionuclides using a Ge semiconductor detector.
One of the sampling locations situated in the highest contaminated area in approximately 3 km in thenorthwest direction from the power plant. Even in the area, no externally visible symptoms of radiation
damages including yellowing, malformation and early withering of leaves were observed in trees,
indicating massive radiation damage like the Red Forest did not occur in the forest after the Fukushima
accident. The external gamma dose rate exceeded 50 µSv/h in the highest contaminated sampling
location, and varied widely among the sampling locations. The levels of radionuclides, 134Cs and 137Cs,
in the tree changed depending on the contamination level of the forest, approximately on externalradiation dose rate. The radionuclides not only adhered to the surface of the old leaves, but also
distributed in the new leaves, flowers, cones and seeds that developed during the spring to autumn after
the accident. This indicates translocation of the radionuclides to newly developing tissues, which shouldhave caused an additional internal exposure of meristematic and reproductive tissues. The exposed dose
rate of trees in the highest contaminated forest was likely to be higher than a criteria dose rate of 4-40
µGy/h selected for pine trees by ICRP (2009), which raises the necessity of more detailed analyses ofcytogenetic and reproductive damages in forest trees in the area.
Keywords
Environmental effect, Forest tree, Biological effects, Exclusion zone

46

2-16
Geographical distribution of radioactive nuclides released from the
Fukushima Daiichi Nuclear Power Station accident in the metropolitanarea, Japan
Masanobu Ishida*¹, Ryota Nakagawa², Kohei Umetsu¹, Miyabi Sugimoto¹, Yuta Yamaguchi¹,
Hideo Yamazaki¹¹Faculty of Science and Engineering, Kinki University²Graduate School of Science and Engendering, Kinki University

The pollution and distribution of 134Cs and 137Cs released from the Fukushima Daiichi Nuclear
Power Station accident in the metropolitan area and the eastern Japan district were investigated in orderto reveal the behavior of the radionuclides in environmental ecosystem. The wide region of the easternJapan was contaminated by radioactivity, after the hydrogen exploded in Fukushima Daiichi Nuclear
Power Station. The radionuclides deposited in the Fukushima area by the rain fall on March 16, and themetropolitan area also contaminated on March 21, 2011. The many radionuclides which deposited in the
ground absorbed on clay minerals in soil by ion exchange.
In this study, the concentrations of radionuclides, such as 131I, 134Cs and 137Cs, in soil and biologicalsamples collected in the metropolitan area and the eastern Japan were analyzed. Soil samples werecollected in Fukushima City and the Imperial Palace of the central Tokyo. Fukushima City and theImperial Palace are 60 km and 200 km distant from Fukushima Daiichi Nuclear Power Station. The
radioactivity of 131I (364 keV), 134Cs (605 keV) and 137Cs (662 keV) in soil and biological samples were
determined byγray spectrometry using HPGe detector connected with 4096 channel MCA. Theγray
spectrum was measured in energy regions from 20 to 800 keV. The detection efficiency of the detector
and geometrical efficiency for the sample volume were corrected using NIST Environmental
Radioactivity Standard SRM 4350B (River Sediment), SRM 4354 (Freshwater Lake Sediment), and
SRM 4357 (a blend of ocean sediment collected off the coast of the Sellafield and Chesapeake Bay).
The detection limits of 134Cs and 137Cs were estimated within 0.6 Bq/kg. The radioactivity of 131I was
corrected to the value on March 16, 2011.
In the soil sample collected from Fukushima City on March 18, 2011, 129Te, 129mTe, 132Te, 131I, 132I,
134Cs, 136Cs, 137Cs and 140Ba were detected. The first data of radioactive contamination in themetropolitan area was measured in the soil collected from the outer garden of the Imperial Palace on
April 10, 2011, and 131I, 134Cs and 137Cs were found. Radioactive equilibrium fission products 95Zr-95Nb
was detected in airborne dust collected from Higashiosaka City (The distance from Fukushima Daiichi
Nuclear Power Station is about 600 km) on April 18, 2011. Trace amounts of 110mAg were also found in
the shellfish samples. The concentrations of 134Cs, 137Cs and 131I in the soil sediment collected from
Fukushima City on March 18 were 11600, 14000, and 72800 Bq/kg. On the other hand, theconcentrations of these nuclides in the soil sediment collected from the outer garden of Imperial Palaceon April 10 were 800, 960, 1520 Bq/kg. The highest concentrations of 134Cs, 137Cs and 131I in the soil
sample collected in Tokyo were 2860, 3590, 30400 Bq/kg. Over 95% of these nuclides existed in thelayer from surface to one cm depth. In Kashiwa City located in 20 km northeast of the Imperial Palace,the concentrations of 134Cs, 137Cs and 131I in the gutter sludge soil collected on June 11 were 26200,
33700 and 101000 Bq/kg. It is considered that the high level contaminated hot spot was formed bymoving the radionuclides in the environmental ecosystem.
Analytical results of biological samples are also reported.
Keywords
Fukushima Daiichi Nuclear Power Station, Radioactivity Pollution, Soil, Ecosystem, Food Chain

47

2-17
Spatial and temporal distribution of 134Cs and 137Cs derived from
Fukushima Daiichi Nuclear Power Station in the sediment of Tokyo
Bay, Japan
Ryota Nakagawa*¹, Masanobu Ishida², Daisuke Baba², Satomi Tanimoto², Yuichi Okamoto²,
Hideo Yamazaki²¹Graduate School of Science and Engineering, Kinki University²Faculty of Science and Engineering, Kinki University

The spatial and temporal distribution of 134Cs and 137Cs released from Fukushima Daiichi Nuclear
Power Station in the sediment of Tokyo Bay were investigated. The metropolitan area and the Kanto
district, Japan, received the radioactive pollution by the Fukushima Daiichi Nuclear Power Station
accident. The radioactive nuclides such as 131I, 134Cs and 137Cs in the atmosphere reached the groundwith rainfall on March 21, 2011. The radioactive nuclides flow through the rivers from the watershed,
and will be deposited on the sediment after flowing into Tokyo Bay. Therefore, the Tokyo Bay sediment
may also receive the radioactive contamination. In this study, the spatial and temporal distribution of theradioactive cesium in the sediment of Tokyo Bay was revealed.
The sediment samples were collected between August 20, 2011 and April 3, 2012. The coresamples were collected by the divers using the acrylic pipes of 10cm-inner diameter and 100cm-length.
The surface sediments were collected by using an Ekman-Birge sampler. The samples were collected at
36 sites in a northern area in Tokyo Bay and 12 sites of the Edogawa River water system. The sediment
samples were dried at 60 °C to constant weight. The radioactivity of 134Cs (605 keV) and 137Cs (662keV) was determined byγray spectrometry using HPGe detector connected with 4096 channel MCA.
The detection efficiency of the detector and geometrical efficiency of the sample volume was correctedusing NIST Environmental Radioactivity Standard SRM 4350B (River Sediment), SRM 4354
(Freshwater Lake Sediment), and SRM 4357 (a blend of ocean sediment collected off the coast of the
Sellafield and Chesapeake Bay). The detection limit of 134Cs and 137Cs in the dry sediment samples wasestimated within 0.6 Bq/kg.
The total radioactivities of 134Cs and 137Cs in the Tokyo Bay sediments were detected from 100 to1000 Bq/kg in the estuary of Arakawa River, but the concentrations of the other sites were 100 Bq/kg or
less. It was indicated that the radioactive cesium rapidly deposits following flow into the river mouth.
The maximum concentration of radioactive cesium (134+137Cs) was 2100 Bq/kg at 14-15 cm depth of thesediment in 200 m offshore from TDR, and its inventory was 120000 Bq/m2. The radioactive cesium inthe sediment seems to have strongly adsorbed on clay minerals by ion exchange. The vertical
distribution of radioactive cesium showed that it invaded deeper than estimated from the accumulation
rate of the sediment. It was estimated that the vertical distribution of radioactive cesium was affected byphysical mixing of sediments by tidal current, flood, and bioturbation of benthos. The radioactive
cesium adsorbed on ultrafine particle may also move by diffusion in interstitial water of the sediment.
Keywords
Fukushima Daiichi Nuclear Power Station, Radioactivity Pollution, Tokyo Bay, Sediment, Radioactive
Cesium48

2-18
Monitoring dissolved radioactive cesium in the Abukuma riverwater in Fukushima Prefecture
Tetsuo Yasutaka, Yoshishige Kawabe, Kimihito Nakamura, Akihiro Kurosawa, Takeshi Komai
National Institute of Advanced Industrial Science and Technology

Radioactive materials were released into the atmosphere and deposited over wide areas of farmland,
forests, and cities in the Kanto district; elevated levels of 131I, 134Cs, and 137Cs have been detected inthese areas by the accident at the Tokyo Power Fukushima Daiichi Nuclear Power Plant accompanying
the April 2011 earthquake in eastern Japan. Due to precipitation, radioactive Cs deposited on farmland,
forests, and organic matter in the bark litter layer in the forest gradually leaches into water bodies suchas mountain streams and rivers adsorbed onto particles or in a dissolved state. It is known that dissolved
radioactive Cs can easily migrate to plants. Therefore, it is important to monitor its concentration in the
Fukushima prefecture over time. In this research, we monitored the concentration of the dissolved
radioactive Cs in Abukuma River using a conventional evaporative concentrate method. As a result ofmonitoring from September in 2012, it was estimated that the concentrations of dissolved radioactive Cs
in main stream and brunches of Abukuma River were in the range 0.010 - 0.128Bq/L. be reported at
poster session.
Keywords
Radioactive Cesium, River water

49

2-19
Investigating plutonium contamination in marine sediments off
Fukushima following the Fukushima Daiichi Nuclear Power Plant
accident
Wenting Bu, Jian Zheng*, Tatsuo Aono, Keiko Tagami, Shigeo Uchida, Jing Zhang, Makio Honda,
Masatoshi Yamada
National Institute of Radiological Sciences, JapanOn March 11, 2011, a catastrophic earthquake occurred in the northwest Pacific about 130 km offnortheastern Japan, followed by a gigantic tsunami, caused serious damage of the electric system of the
Fukushima Dai-ichi Nuclear Power Plant (FDNPP). As a result, the cooling system of nuclear reactors
failed, resulting in hydrogen explosions in the reactors. In addition to the large amount of atmosphericreleases caused by the hydrogen explosions and venting activities, the cooling of the reactors with fresh
water and seawater, and the release of highly contaminated water from the damaged reactor buildings
resulted in the direct discharges of radionuclides into the sea.
To make a quick assessment on the environmental impact of possible Pu contamination from the
FDNPP accident, last year, we analyzed the activities of 239+240Pu and 241Pu, and the isotopic
compositions (240Pu/239Pu and 241Pu/239Pu atom ratios) in surface marine sediments 30 km off the
Fukushima Prefecture coast collected in July-August, 2011. Both the activities of Pu isotopes and theiratom ratios detected in the surface sediments were in the same levels of the baseline data established
before the accident, indicating no immediate Pu contamination in the marine sediments off Fukushimacoast.
In this work, we investigate the vertical distributions of Pu activities and Pu atom ratios (240Pu/239Pu
241
and Pu/239Pu) in sediments collected in July-August, 2011 and in June, 2012, to obtain information on
Pu inventory in the sediment column and temporal variation of Pu activity and isotopic composition, andunderstand the transport of Pu from seawater to sediment column and the sources of deposited in marine
sediments before and after the Fukushima sediments. In addition, a comprehensive review on the Pu
inventory in sediments in the Northwest Pacific and its marginal seas will be made to establish baseline
data for accurate assessment of Pu contamination in the marine environment.

Keywords
Plutonium, marine sediment, SF-ICP-MS, FDNPP

50

3-1
The use of rice seedlings to estimate the transfer of radiocaesium from soil
to plants in Fukushima Prefecture
Shigeto Fujimura*¹, Takeshi Ohno², Yasuyuki Muramatsu², Hirofumi Tsukada³, Kunio Yoshioka¹,
Hiroshi Saito¹, Mutsuto Sato¹, Makoto Sato¹, Yuuki Sakuma¹¹Fukushima Agricultural Technology Centre²Gakushuin University³Institute of Environment Sciences

Large amounts of radionuclides were released into the environment as a consequence of the accident
at Fukushima Daiichi Nuclear Power Plant that was caused by the earthquake and subsequent tsunami
on May 11, 2011. Since two isotopes of radiocaesium (134Cs and 137Cs) have relatively long half-lives
and have high biological availability, concentrations of radiocaesium in agricultural fields have beenmonitored during the 2011 and 2012 growing seasons. Agricultural production continues to be restricted
in parts of Fukushima prefecture in order to avoid food contamination. A working estimate of thetransfer of soil radiocaesium to crops in contaminated fields is necessary before agricultural production
can be resumed in the restricted areas. Although the transfer of radiocaesium to crops from the soil isaffected by many environmental factors such as the concentrations of radiocaesium and extractablepotassium, and the clay content of the soil, the net effect that these factors and interactions is not clear.
In addition, these environmental factors should be investigated independently for each field, a processthat is both labor-intensive and time-consuming. The aim of this study was to develop a practical andsimple method for the estimate of transfer of soil radiocaesium to crops. Rice seedlings were used toestimate the transfer of soil radiocaesium since rice seedlings are able to be cultivated under conditionsof high plant-density and the amount of absorbed radiocaesium by rice seedlings can be relatively easily
measured. To examine the hypothesis that radioocaesium concentrations in rice seedlings are reasonably
similar to those observed in brown rice; the rice seedlings and the brown rice were cultivated underidentical soil conditions. Seven different combinations of soil types, radiocaesium concentrations andextractable potassium concentrations were used. Rice seeds were seeded directly on the soil in small
cups (250 cm3) placed inside a phytotron and were germinated. Rice seedlings were cultivated for aweek from the germination inside the phytotron and the concentrations of 137Cs in rice seedlings above
ground were determined. To produce brown rice, rice was cultivated either in a pot (1 / 5000 a Wagner
pot, 4000 cm3) placed in a glass house or in a paddy field in Fukushima prefecture for about five months.
The concentration of 137Cs in the rice seedlings ranged from 150 to 1900 Bq kg-1, and brown rice ranged
from 2 to 890 Bq kg-1. The correlation between the measured concentration of 137Cs in rice seedlings
and the measured concentration in brown rice was significant, as determined by Spearman's rankcorrelation coefficient. This suggests that the use of rice seedlings in this experiment over a period of
two weeks provides an effective proxy for the transfer of 137Cs from soil to crops over a longer period oftime. The two-week experimental time for the rice seedlings includes the time necessary for preparation,cultivation, post-sampling treatment as well as the measurement of 137Cs concentrations.
Keywords
Rice, Cs -137, uptake, soil

51

3-2
Deduction of useful information from dose rate monitoring data in an
emergency
Jun Hirouchi*, Tian Zhang, Yasuhiro Takamura, Shigekazu Hirao, Jun Moriizumi, Hiromi Yamazawa
Department of Energy Engineering and Science, Nagoya University

After the TEPCO’s FDNPS accident in March, 2011, dose rate monitoring has been enhanced andmany monitoring stations and posts have been deployed not only in the vicinity of the NPPs in Japan but
also at distant locations to reinforce the monitoring capability for emergency situations. Although thisincrease in the number of dose rate monitoring points significantly improve the emergency preparedness,
it still remains as a substantial weakness of the emergency monitoring that the dose rate is only an itemout of many other monitoring items indispensable for emergency decision making. These items include
concentrations and composition of radionuclides in air, soil and environmental media. The purpose ofthis study is to explore possibilities of deducing these data items from the dose rate monitoring data byusing rigorous modeling approach on the relation between the dose rate and the concentrations. Thisapproach was tested for the radon decay products deposition cases and was applied to the dose ratemonitoring data from the FDNPS accident.
The fundamental part of the modeling approach consists of a gamma dose rate model that explicitly
expresses the geometry of source distribution, attenuation and scattering of gamma rays in air, soil andbuilding materials around a monitoring post. This model has been tested for the non-accidental cases toshow that it can reasonably reproduce the background dose rate from the radioactivity in the naturalenvironment and in the building materials. Application of the model to the cases with precipitation
showed that the model can also evaluate the activity concentration of the radon decay products on the
ground surface. It was also pointed out that, by applying this model to the radon decay products
deposition cases, the surface run-off of deposited radionuclides can be analyzed.
The second part of the modeling approach is the use of an atmospheric dispersion model in theanalyses of dose rate data measured in the vicinity of the accidental site. The dispersion model with arandom-walk method was applied to evaluate the release rate of radionuclides from the dose rate datameasured by TEPCO at the site boundary. Reasonable release rates of I-131 and Cs-137 were obtained
for the maximum dose rate of 11.9 mSv/h. However, it is also pointed out by the sensitivity analysis thatthe release rate estimation is very sensitive to the parameters and the wind data used in the analysis suchas radionuclide composition, wind direction/speed, release height and atmospheric stability, and hence
that the estimated release rate has a very large uncertainty.
The last part of the approach is a mathematical representation of temporal trend in the measured
dose rate. It was shown that the cloud-shine and ground-shine components were discernible by carefully
reviewing dose rate trends. It is also pointed out that the fractions of these two components differeddepending on the geometry of the source distribution and obstacles. Although the trend in the groundshine components was found to potentially have information on radionuclide composition, it wasdifficult to evaluate the composition quantitatively singly from the dose rate trend. If the fractional
inventory of radionuclides in the accidental reactor is available, the surface concentrations of nuclidegroups can be inferred.
Keywords
gamma dose rate, radioactivity concentration, release rate, radon decay products

52

3-3
Possibility of removing radionuclides in landfill leachate using
advanced wastewater treatment processes
Nao Ishikawa*, Ayumi Ito, Teruyuki Umita
Iwate university

The nuclear accident at the Fukushima Daiichi Nuclear Power Plant that followed the Great East
Japan Earthquake on March 11, 2011 resulted in the significant release of radionuclides to theenvironment. With time the part of the radionuclides has transferred to sewage sludge ash and waste ash.
Japanese government has allowed those ashes in which radiocesium concentration is lower than 8000
Bq/kg to be disposed in a controlled landfill site. The leachate from the landfill site, which possibly
contains radionuclides dissolved from the ash, is treated in a leachate treatment plant before it isdischarged into receiving water. The leachate treatment system is a combination of several treatment
steps to remove alkaline components, organic pollutants, suspended solids, heavy metals, and so on.
However, the extent of removal of radionuclides in the leachate by each step is not clear. In this study,
in place of radionuclides, stable element concentrations in the leachate and treated water at eachtreatment step were measured to estimate the possible extent of radionuclide removal from the leachate
step-by-step. Sample collections were done in July 2012 at a leachate treatment plant in a controlled
landfill site in Iwate Prefecture in which ash (e.g., sewage sludge ash and waste ash) known to becontaining radionuclides is being buried. The treatment process steps consist of: alkali crystallization,
aeration treatment, membrane separation, activated carbon adsorption, and adsorption using chelate
resin and zeolite. Samples of the leachate and treated water were collected at each treatment step.
Concentrations of stable elements (e.g., Cs, Sr) and major elements such as Ca and K in these samples
were determined by inductively-coupled plasma atomic emission spectrometry and inductively-coupledplasma mass spectrometry. Additionally, water characteristics such as suspended solids and total carbon
concentration were determined in each sample.
For Sr, its concentrations were 6.0 mg/L in the leachate, 0.07 mg/L in the sample collected after thealkali crystallization step, 0.34 mg/L in the sample collected after the aeration treatment step, 0.40 mg/L
in the sample collected after the membrane separation process, and 0.52 mg/L in discharged water. The
results indicated the alkali crystallization step was effective for Sr removal. For Cs, its concentrations
were 2.8 μg/L in the leachate, 2.6 μg/L in the sample collected after the alkali crystallization step, 2.7
μg/L in the samples collected after the aeration treatment process, 2.9 μg/L in the samples collected after
the membrane separation step, and 2.7 μg/L in the discharged water. The results indicated no treatment
process, even adsorption using zeolite, was effective for the removal of Cs in the leachate from thelandfill site. Further data for samples collected in September 2012 and relationships between element
removal efficiency and water characteristics will be given in the presentation.
Acknowledgement: This work was partly supported by JSPS KAKENHI Grant Number 12014030.
Keywords
landfill leachate, stable isotopes, cesium, strontium

53

3-4
Estimation of ecological half-lives of radiocesium in marine biota at
the offshore of Fukushima, Japan
Kayoko Iwata*, Keiko Tagami, Shigeo Uchida
National Institute of Radiological Sciences

The TEPCO’s Fukushima Daiichi Nuclear Power Plant (FDNPP) accident of March 11, 2011 was
the result of a magnitude 9.0 earthquake and the resultant tsunami, which severely damaged several
reactors. A large amount of radionuclides released from FDNPP into the environment. One and halfyears after the FDNPP accident, although it is considerably easier to estimate the internal exposure
through inhalation from the concentration of the radioactive materials in the air, estimating the degree of
exposure from ingestion is problematic due to the variety of human diets, the distinct levels of foodcontamination, and the indeterminate chemical dynamics of nuclides. Factors, such as ecological halflife (Teco) estimated in organisms in selected biota, have a significant impact on dose by the ingestion
pathway and the associated bioaccumulation. We focused on cesium-137 (T1/2=30y) which was one of
the major radionuclides released.
This paper aims to provide the field data of radiocesium concentrations in marine biota that are
related to the FDNPP accident, and to compare and contrast the Teco in nature and biological half-life(Tb) in the laboratory setting. The Teco of 137Cs in the oceanic community along the coastline of
Fukushima was calculated based on food monitoring data. The selection of sampled fish species is basedon the typical Japanese diet. The monitoring data is organized by the sampling areas: the southern(Iwaki-shi) and the northern parts (Shinchi-cho, Soma-shi, Minami Soma-shi) with respect to the
FDNPP site. A total of 16 species were investigated: all species were collected in the southern part, as
compared to 11 species in the northern part. Plotting the data on a logarithmic scale and getting an
exponential trend line and a best-fit linear equation are required to calculate each Teco.
The 137Cs contamination in the southern and the northern was compared using the concentration
estimated on the 100th day in each species. Higher 100th-day concentrations were observed in the southarea, as compared to in the north area in all the common species. The range of the concentration ratios ofthe south to the north was from approximately 1.1 to 6.4. This result revealed that the concentration in
the southern region was higher than that in the northern region, which was likely caused by a weaksouthward current along the coastline of Fukushima. Although the degree of contamination was
different between the south and north, the calculated Teco for each species was similar in the southernand northern regions. The range of Teco ratio (south/north) was from 0.80 to 1.33. This result indicatesthat the concentration in the biota does not influence Teco among the same species. Furthermore, Tecoobtained from the field data was compared to Tb of laboratory experiments. The result shows that
seaweed and shellfish have Teco that is similar to Tb obtained in laboratory experiments. On the other
hand, demersal fish, which live near the bottom of the sea, such as flatfish, have longer Teco, comparedto Tb of laboratory experiments. It is conceivable that a reason for the longer Teco of demersal fishobtained in the field may result from the leverage of the diet. However, it cannot be concluded due to theshort-term field data and insufficient number of laboratory data. Thus, it is necessary to collect andanalyze more data.
Keywords
radiocesium, marine environment, biota, ecological half-life, trophic level

54

3-5
Estimation of accident source terms for the Fukushima Daiichi
Nuclear Power Plant using RAMS/HYPACT
Masanori Kimura*, Kazumasa Shimada, Shogo Takahara, Fumihisa Nagase, Toshimitsu Homma
Japan Atomic Energy Agency

The source terms for the Fukushima accident were preliminarily estimated by the reverse calculation
method which used the atmospheric dispersion and deposition model in RAMS/HYPACT. In thecalculation, atmospheric and ground concentrations were obtained assuming the release rate of 1 Bq/hand then, the results were compared with monitoring data of soil samples and atmospheric dust samples.
Furthermore, this study took into account dry and wet deposition processes of aerosols and iodine, andthe decay of radionuclides.
Keywords
source terms, RAMS/HYPACT, iodine, dispersion, deposition

55

3-6
Sedimentation diffusion of radioactive cesium in a paddy field.
Hi-Rocky Ohtani*1 , Xiaoguang Lu¹, Akira Tsuchiya², Shinichiro Yoshida³, Takahiro Hirayama³¹Tokyo Metropolitan University²Odayoko Corporation³Earth Corporation

The purpose of this research is to make the radioactive cesium deposited on a paddy field sediment
to the depths. Radioactive cesium is made to sediment to the depths which the root of a rice does notreach by using chitosan. And it aims at reducing the absorptivity of radioactive cesium. A rice crop
becomes possible in the paddy field of radioactive contamination, and radioactive cesium is not detectedfrom the harvested rice.
The paddy field in Fukushima was made into the actual proof examination site, 40kg ofmacromolecule chitosan powder of 5% of the concentration per 1000 square meters was sprinkled, andsoil improvement was performed. The depths soil of each paddy field was extracted and activity
concentration was measured using the NaI scintillation detector.
In the paddy field which has not processed, most radioactive cesium was detected from the topsoil
which is 0 - 5 cm. When radioactive cesium adhered to the clayey ground, sedimenting to the depths
automatically also by osmosis of water stopped at topsoil few. In the paddy field which sprinkled
chitosan, the relative value of radioactive cesium was 120.40% in 10 - 15 cm, 179.44% from topsoil at 5
- 10 cm. Even if it was the 25cm depths, 32.53% was shown, and the effect that chitosan carried out
sedimentation diffusion of the radioactive cesium to the depths became clear. Although radioactive
cesium had adhered to topsoil, the 30cm depths were reversed by tilling. If chitosan spraying is
performed after tilling, radioactive cesium can be further sedimented to the depths rather than 30cm. By
combining this work, it becomes possible to raise a sedimentation rate and to reduce a cesium
absorptivity.
It was effective to have sprinkled chitosan, in order to make the radioactive cesium deposited on apaddy field sediment to the depths. Radioactive cesium is separated from the ground by using the shapeof chelate, and it can sediment to the depths of a paddy field as water solubility. Radioactive cesium isdiffused to the depths by combining tilling.
Keywords
Sedimentation diffus, Radioactive cesium, Macromolecule chitos

56

3-7
Distribution of radiocesium on cultivated field and suppressive
effect of radiocesium uptake in brown rice by potassium
Takashi Saito*, Satoru Ohkoshi, Shigeto Fujimura, Koji Iwabuchi, Masaaki Saito, Tomoaki Nemoto,
Mutsuto Sato, Makoto Sato, Kunio Yoshioka, Hirofumi Tsukada
Fukushima Agricultural Technology Centre
Objective
After the accident by the Fukushima Daiichi Nuclear Power Plant of Tokyo electric power company (TEPCO),
brown rices were produced, including the highly radiocesium from paddy fields in some areas of Fukushima
Prefecture. For this reason, we examined the distribution of radiocesium on cultivated field and the suppressive
effect on radiocesium uptake in brown rice by potassium in order to suppress the migration of radiocesium intobrown rice.
Materials and Methods
1) Vertical and horizontal distribution of radiocesium in the cultivated field (Experiment 1)
Five samples of soil (at depths of 0-15 cm) were collected after cultivating on five fields horizontally using a
stainless steel soil auger of 30 cm in length and 5cm in diameter. The inside of soil auger was lined with atransparent polyvinyl chloride tube for isolating soil samples immediately and protection against soil contamination.
These samples were divided into three parts（0-5 cm, 5-10 cm, 10-15 cm) in order to investigate the vertical
distribution of cultivated field. After being air-dried, the soils were crushed and sieved through a 2-mm mesh.
2) Relationship between concentration of radiocesium in brown rice and concentration of radiocesium in soil,
exchangeable potassium content in the soil (Experiment 2)
The brown rices, after being harvested from five fields in Experimental 1, were dried 30°C. After threshing andpickpocket, these samples sieved through a 1.85-mm mesh. The concentrations of radiocesium were measured
using a Ge semiconductor detector. Exchangeable potassium was determined using the semimicro Schollenberger
method and an atomic absorption spectrophotometer.
Results and Discussion
1) Experiment1
The concentrations of radiocesium in soil in five fields of depths 0-5.0 cm, 5.0-10 cm, 10-15 cm were 5879 Bq/kg
DW, 3223 Bq/kg DW, 1835 Bq/kg DW, respectively. The results showed that the vertical distribution was not
uniform. Even though there was no difference in the vertical distribution of radioactive cesium after plowing in thesame area of upland, in the paddy was observed concentration gradient. We supposed that a small fraction ofparticles such as clay adsorbed radiocesium emerged on top by puddling.
The concentration of radiocesium in soils in five fields of depths 0-5.0 cm after plowing were in the range of 24657823Bq/kg DW, showing apprpximately three-fold variations. The results showed that the horizontal distribution
was not uniform. Therefore, we suggest that in order to accurately evaluate the radiocesium uptake by brown rice,
it is necessary to use the measurements of radiocesium in soil around the root.
2) Experiment2
The concentrations of radiocesium in brown rice were in the range of 52-485 Bq/kg (convert 15% moisture). The
relationship between concentration of radiocesium in brown rice and concentration of radiocesium in soils, were
not showed a correlation. We found that there is not a variation in transfer factor (TF) even same field. On the other
hand, the radiocesium concentrarion in brown rice showed a tendency to decrease by increase exchangeable
potassium in soil. In addition, the radiocesium concentrarion in brown rice showed a tendency to decrease by topdressing in potassium. From these results, we found that radiocesium in brown rices were little related theconcentration of radiocesium in soils, depended on exchangeable potassium in soils. Therefore, we propose toincrease the potassium fertilizer in order to suppress radiocesium uptake in paddy soil.
Keywords: Radiocesium, Brown rice, Potassium

57

3-8
Phytoremediation of radiocesium in different soil using cultivated plant
Yasukazu Suzuki1*, Takasi Saito1, Hirofumi Tsukada2
1Fukushima Agricultural Technology Centre,
2Institute for Environmental Sciences, bFukushima University

Objective
After the Fukushima Dai-ichi Nuclear Power Plant accident, a huge amount of radionuclides
released into the environment. Radiocesium, which is major radionuclide, was deposited on the soil. It
well known that radiocesium adsorbed onto the soil and strongly bound to clay. Therefore, it is difficult
to reduce the contamination level in the soil. We examine the possibility of decontamination by meansof phytoremediation.
Material and methods
Four species of plants (sunflower, sorghum, amaranth, buckwheat) were sown to grow (cultivated)in three 1.6 m2 (2.0×0.6 m) farming plots of Light-colored Andosol and Gray Lowland soil. The
planting density was 625 plants 100 m-2 for sunflower, sorghum, amaranth. The density for the
buckwheat was 18,000 plants per 100 m-2. The amount of N and P2O5 (Excluding K2O) applied was 6kg per 100 m-2 for sunflower, sorghum, and was 1 kg per 100 m-2 for the amaranth and buckwheat.
When the plants matured, they were removed and separated into the different parts of flower, leaf, stem,
and root to make samples for analysis, except for sorghum (of which only the leaves, stems and roots
were sampled).
The separated samples were rinsed in water, and dried at 80°C for 3 d. The dried samples werepulverized with cutter and filled in compressed into plastic vials (U-8). The soil sample in which theplants were cultivated were collected at the time of sowing, air-dried at room temperature 25°C for 10d, and passed through a 2-mm mesh sieve. The soil samples were also compressed into the plastic vials.
The radioactivity of the samples was measured by a germanium semiconductor detector with amultichannel analyzer, over a period of 3,000-48,000 seconds for the plant and 1,200 seconds for thesoil samples.
Results and discussion
The highest yield among the plants was 2.9 kg dry wt m-2 in the sorghum cultivated in Gray
Lowland soil, and the lowest was 0.57 kg dry wt m-2 in the buckwheat cultivated in the Light-colored
Andosol. The concentration of 137Cs in each plant was from 20.6 to 82.9 Bq kg-1 dry wt, which was 4.0
times differences between the amaranth cultivated in the Light-colored Andosol and the sorghum
cultivated in Gray Lowland soil.
The total content of 137Cs in the four plant biomass was 24.2-153.9 Bq m-2 cultivated in the Lightcolored Andosol, and 19.7-83.9 Bq m-2 cultivated in the Gray Lowland soil. The removal percentage of
137Cs, which was defined as the total content of 137Cs in the plant biomass divided into that in thecultivated soil of 0-15 cm depth, was 0.013-0.100 % for the Light-colored Andosol and 0.008-0.039 %for the Gray Lowland soil. The plants showing the highest value cultivated in the Light-colored Andosol
and Gray Lowland soil was the amaranth (0.10 %) and the sunflower (0.039 %), respectively. It
indicates that the remove of radiocesium from the contaminated soil by means of the phytoremediation
techniques is difficult.
Keywords
phytoremediation, soil, cultivated plant

58

3-9
Direct determination of tellurium in soil and plant samples bysector-field inductively coupled plasma mass spectrometry for the
study of soil-plant transfer of radioactive tellurium following the
Fukushima Daiichi Nuclear Power Plant accident
Guosheng Yang, Jian Zheng*, Keiko Tagami, Shigeo Uchida
National Institute of Radiological Sciences, JapanThe Fukushima Daiichi Nuclear Power Plant (FDNPP) accident caused release of large amounts ofradionuclides, including Te-127m, Te-129m, Te-131 and Te-132, into the environment. Among thereleased Te isotopes, Te-127m has a half-life of 109 days, much longer than those of other Te isotopes.
Therefore, the release of 127mTe may have increased the internal radiation dose due to the crops uptake.
The internal radiation dose estimation, however, was found to be difficult because of the lack ofenvironmental transfer data for Te.
Stable Te, as an analogue, is considered to be useful and important for the estimation of soil-planttransfer of radioactive Te. Due to the low concentrations of Te in the environment, for example, 10-109
ng/g in Japanese soils and 18-33 ng/g in plants, the determination of Te in soils and plants has been agreat analytical challenge. Although many analytical techniques, such as INAA, ICP-AES, HG-AFS,
and quadruple ICP-MS have been developed for Te determination in environmental samples, in mostcase, tedious preconcentration and separation operations are inevitable because of the relatively highdetection limit. These drawbacks made them unsuitable for the determination of Te in soil and plant
samples to study the soil-plant transfer factor.
In this work, we report a sensitive and high sample throughput analytical method for direct
determination of trace Te in soil and plant samples using a sector-field-ICP-MS combined with a highefficiency sample introduction system (APEX-Q). Efforts were made to improve the sensitivity for Te
analysis. We investigated: (1) the addition of ethanol to increase Te ionization in the plasma, and reducethe interferences of Xe-128 and Xe-130 on Te-128 and Te-130 analysis; and (2) increase the ICP-MS
resolution from low mode to medium mode to eliminate the polyatomic interferences for Te-125 and Te126 analysis. We also optimized sample digestion methods using aqua regia and mixture acids (HNO3HF-HClO4). The developed analytical method is characterized by a very low detection limit at sub-ppb
level in soil and plant samples, and has been applied for the study of soil-plant transfer to accumulatetransfer factor data in Japan.

Keywords
Tellurium, Analytical method, SF-ICP-MS, soil-plant, transfer factor

59

4-1
Source term estimation using environmental monitoring data
Shigekazu Hirao*, Hironori Hibino, Takuya Nagae, Jun Moriizumi, Hiromi Yamazawa,
Department of Energy Engineering and Science, Nagoya University

The purpose of this study is to estimate atmospheric release rates of the radionuclides discharged
from FDNPS by using environmental monitoring data and an atmospheric dispersion model and toinvestigate the uncertainty of the estimated release rates. Environmental monitoring in emergency has
played an important role to estimate source term inversely as well as to assess internal and external dose.
Inverse source term estimations have been carried out by several researchers (e.g. Chino et al. 2011,
Stohl et al. 2012, Terada et al. 2012, Hirao et al. 2012), after the accident. All studies indicated similar
temporal variations in the atmospheric release rate of radionuclides despite of the use of different
monitoring data and atmospheric dispersion models. According to these studies, the release started in themorning of 12 March 2011, the largest release occurred on 15 March and during other periods thereleases were one to two orders of magnitude smaller than that on 15 March. Although this similarity
implies the reliability of the release rate estimated by inverse methods, the uncertainty in the estimatedrelease rate has not been discussed well. Since the main source of the uncertainty is errors in themodeling of deposition processes for regional scale model calculations, we focused on the analysis of
the influence of these errors on release rate estimation.
Release rates of I-131 and Cs-137 in March 2011 were estimated by comparing the calculated
deposition rates with an atmospheric dispersion model and the measured ones in regional area. The
deposition rates used in this study were the daily data sampled at Chiba, Gunma, Ibaraki, Kanagawa,Tochigi, Tokyo, Saitama and Yamagata with a 24-hour sampling time from 18 March. A Lagrangianparticle random-walk model coupled with the atmospheric meteorological model MM5 was used to
calculate dispersion and deposition of radionuclides in plume. The dry and wet depositions were simply
parameterized by a deposition velocity and a scavenging coefficient, respectively. The model domain
was a 600 km square and 6 km depth above the ground in the vertical direction to cover most of the
Tohoku and Kanto regions.
The release rates of I-131 and Cs-137 were estimated to be in the range of 0.6−4 × 102 TBq h-1 forI-131 and 0.3−5 × 101 TBq h-1 for Cs-137 for the period of 20−30 March. The temporal change in theestimated release rates were similar to that reported by others. It was pointed out that, by the sensitivity
analysis to deposition parameters, the estimated release rates varied by a factor of about 10 when the
scavenging coefficient varied by a factor of three. The sensitivity to the deposition velocity was smaller
than that to the scavenging coefficient. In addition, the ratio of the estimated release rate of I-131 to thatof Cs-137 was obtained to be about 10 on 20−21 March and about 80 on 22 March that was the
maximum value. The increase in the ratio similar to our result was obtained in the ratio of measured air
concentrations near FDNPS. According to the sensitivity analysis, the increases in the ratio of theestimated release rate by the different deposition parameters were also obtained during 21−22 March. It
implied that the ratio of I-131 to Cs-137 was large in the time when the nuclides were released.
The release rate estimated by the inverse method still has a large uncertainty if the radioactive plume
passed through rainfall areas. The uncertainty in the estimated release rates affected by the plumetransported in rainfall areas will be further discussed.
Keywords
release rate estimation, deposition rate, atmospheric dispersion model

60

5-1
Radiation doses from external and internal by inhalation of
atmosphere and ingestion of drinking water contaminated by the
Fukushima Daiichi Nuclear Power Plants Accident for the people
living in the Chiba district.
Hikaru Amano*, Yuji Ohta, Shigeru Banba, Takeshi Maeyama, Yoshihiro Ikeuchi, Takao Morimoto
Japan Chemical Analysis Center
Large amounts of radioactive substances were released into the environment from the damaged
Fukushima Daiichi Nuclear Power Plants. Radioactive substances discharged into the atmosphere firstreached the Chiba Metropolitan Area on 15 March, 2011. Atmosphere and fallout deposition samples
were collected from 14 March, 2011, and tap water samples were collected from 19 March, 2011 at
Japan Chemical Analysis Center (JCAC) in Chiba city, located about 220 km SSE of the Fukushima
NPPs. Neighboring downtown Tokyo is 216 km SSE of the Fukushima NPPs. Sampling of airborne
particles and gaseous chemical species was carried out at a height of 1.5 m above ground level at JCAC.
Airborne particles and gaseous iodine were collected continuously using a cellulose glass-fiber filter(Toyo HE 40T) in combination with an activated charcoal cartridge containing 10% triethylenediamine(TEDA) (Toyo CHC-50). The filter and cartridge were changed every day until 17th June, 2011, thenonce a week. Air sampling was performed using a low-volume air sampler, and the air flow rate wasregulated at around 90 L/min. Wet and dry deposition samples were collected continuously in a tray
(0.0283 m2) on the roof of the laboratory. Samples were collected every day in the first 3 months, thenseven days sampling has been performed. Tap water was collected in a 2 L Marinelli beaker typecontainer every day in the first 3 months, then once for one week has been performed from the faucet ina laboratory room at JCAC.
Radioactivity of the samples was directly measured by gamma-ray spectrometry with a Ge detector.
The coincidence summing was corrected in activity of 134Cs. The counting efficiency of the Ge detector
was calibrated using agar standard samples of the same shape and volume prepared from standard
sources. The counting times were usually 3600 s and longer directly after the accident.
Total external gamma-radiation doses were continuously monitored at JCAC using a NaI(Tl)scintillation detector at a height of 1.5 m above ground level located at the center of a 10 m × 10 m
lawn. The dose levels peaked three times (15, 16, and 21 March), and the maximum dose rate was 0.5
μGy h-1. The rises on 15 and 16 March were caused mainly by 133Xe, 131I, and 132I. The rises on 21
March were caused mainly by 131I, 132I, 134Cs, and 137Cs delivered by rainfall. Radiation doses were
estimated from external radiation and internal radiation by inhalation and ingestion of tap water for
people living in the Chiba Area following the accident.
External exposure was estimated to be 135 μSv in the first month (15 March to 14 April) and 101
μSv in the second month (15 April to 14 May), including the exposure from natural backgroundradiation. These doses are calculated for people standing outside on the lawn for the whole day. During
the first three months maximum daily concentrations of airborne radionuclides observed at the Japan
Chemical Analysis Center in the Chiba Metropolitan Area were 4.7 × 101 Bq m-3 of 131I, 7.5 Bq m-3 of137Cs, and 6.1 Bq m-3 of 134Cs, respectively.
The inhalation committed effective dose was dominated by 131I in the first month, but in the second
month the doses from 134Cs and 137Cs were only a little lower than the dose from 131I. The ingestion dose
was dominated by 131I throughout the study period.
Keywords
Fukushima accident, Atmosphere, Fallout, Tap water, Dose estimation

61

5-2
Internal dosimetry for continuous chronic intake of caesium-137 incedar pollen after the Fukushima Daiichi Nuclear Power Plant accident
Sakae Kinase*1,3 Masanori Kimura1 Shinji Hato2,3
1Japan Atomic Energy Agency 2VIC

3Ibaraki University

The Fukushima Daiichi nuclear power plant accident that occurred in March 2011 resulted inwidespread contamination of caesium in the eastern region of Japan. It is predicted that caesium
deposited in cedar forests would be released as cedar pollen after caesium uptake by cedar trees. Internal
exposure from chronic intakes of caesium in cedar pollen is of considerable concern from the standpointof public exposure. In the present study, internal dose assessments for chronic intake of caesium-137 incedar pollen were carried out for members of the public –adult residents in Fukushima, Ibaraki andTokyo– on the basis of data on cedar pollen from a pollen observation system in the Ministry of theEnvironment (MOE) of Japan. Committed effective doses, retention and excretion functions for
caesium-137 in whole-body were evaluated using DSYS-chronic code that was developed at the Japan
Atomic Energy Agency (JAEA). The DSYS-chronic code can treat internal dosimetry for chronic
intakes using the International Commission on Radiological Protection’s (ICRP’s) respiratory tract,
gastrointestinal tract, biokinetic and bioassay models for ICRP Publ.71. The Activity Median
Aerodynamic Diameter (AMAD) and particle density for cedar pollen were assumed to be 32 μm, 0.699
g·cm-3, respectively. The observation period was from early February to the end of May 2012.
Consequently, it was found that the committed effective doses for adults in Fukushima, Ibaraki andTokyo were 1.6-1.8×10-3μSv, 4.5×10-4μSv and 3.0×10-4μSv, respectively. Hence, it can be stated thatinternal doses from chronic intakes of caesium-137 in cedar pollen are small and insignificant in 2012.
In addition, retention and excretion functions for caesium-137 in whole-body were found to be
dependence on the times of intakes. Retention and excretion functions for continuous chronic intakes,
which are evaluated by the DSYS-chronic code, may be useful since they may provide reassurance that
intakes are indeed low.

Keywords
chronic, internal dose, Cs, cedar pollen, DSYS-chronic

62

5-3
Internal radiation dose of KURRI volunteers working at evacuation
shelters after TEPCO`s Fukushima Daiichi nuclear Power Plant accident
Kouta Kurihara, Yuko Kinashi*, Kenichi Okamoto, Eiko Kakihana, Tomohiro Miyake,Tomoyuki Takahashi, Keiko Fujiwara, Hiroshi Yashima, Hidehito Nakamura, Sentaro Takahashi
Research Reactor Institute, Kyoto University

We report the radiation doses encountered by 59 KURRI ( Kyoto University Research Reactor
Institute ) staff members who had been dispatched to screen refugees for radiation at the emergency
evacuation sites 45-80 km from the TEPCO’s Fukushima daiichi nuclear power plant.From 20th March
to 30th April in 2011, 42 members as teams consisting of 2-4 staff were dispatched 15 times to 7
emergency evacuation sites located 45-80 km from the power plant to examine the radioactive
contamination affecting refugees. Continuously, from 10th to 23th May in 2011, 17 members as teams
consisting of 2-5 staff were dispatched 6 times to Fukushima prefecture to establish the KURAMA(Kyoto University Radiation Mapping) system. Internal burden of radioactive nuclides were estimatedusing a whole-body counter consisting of an iron room, four NaI (Tl) scintillation detectors, and a digital
multichannel analyzer (MCA7600; Seiko EG&G). The calibration of the whole-body counter and theconversion of the measured body burden to the committed effective dose by internal exposure werecarried out in accordance with the Nuclear Safety Research Association (NSRA) technical manual. The
external radiation dose to each staff member was measured with a personal dosimeter (ADM-112;
Hitachi-Aloka Medical K. K.). The first dispatched team showed 1300-1929 Bq of the internal radiation
activity of the cesium (including cesium137 and cesium134), and 48-118 Bq of the iodine131. Theinternal doses of four members of the first team were estimated 26-39μSv. The doses from internal
exposure were almost similar to the cumulative external doses for the dispatch period (20th to 22th
March in 2011), when the radiation plumes following the explosion of Unit1 and 3 in TEPCO’s
Fukushima Daiichi nuclear plant had diffused around the Fukushima city. The external radiation dosesof dispatched members after the second team had fallen one third to lower than one tenth of the external
doses of the first dispatched team. The internal radiation doses of 55 members after the second teamshowed that 51 cases were undetectable and 4 cases showed 1-15μSv. These fallen down of the internalradiation doses after the second team owe to the warning statement for the protection of the internalradiation to the dispatched staff of KURRI.
Keywords
internal radiation, cesium137, cesium134, whole-body counter, iodine131

63

5-4
Distribution of doses to residents evacuated after Fukushima Nuclear
Power Station accident
Shigeru Kumazawa
Former, Japan Nuclear Energy Safety Organization

The statistical analysis is essentially useful not only for an adequate interpretation of radiological data measured
in environmental space-time fields but also for the comprehensive dose assessment in such space-time exposure
situations because there are many sources of uncertainty leading to biased conclusion. Radiological data are often
analyzed by lognormal (LN) distribution because of quantities varied in several orders of magnitude. Doses toresidents evacuated are reduced largely for those in higher exposure fields but the doses are reduced insignificantly
for those in low exposure fields. Such countermeasures might distort the lognormality of doses to residents
evaluated or protected to avoid higher doses. This paper presents an interpretation of the distortion in terms ofstatistical variation and shows the skewed lognormal distributions of doses to evacuated residents and other data
relevant to the accident of TEPCO's Fukushima Daiichi Nuclear Power Station.
The hybrid lognormal (HLN) distribution proposed by Kumazawa and Numakunai (1981) was cited byparagraph 20, ANNEX H “Occupational exposures” of UNSCEAR 1982 Report: the control of doses approaching
the dose limits leads to a normal distribution in the higher dose range; this presumption can be used to carry out
analysis as a hybrid normal/lognormal distribution. Therefore the control of doses approaching some reference
levels in emergency exposure situations or existing exposure situations may lead to a normal distribution in thehigher dose range and then this presumption can be used to carry out the HLN analysis.
The HLN distribution is defined for positive variate X so that the transformation Y=ρX+ln(ρX) should be
distributed normally with mean μ and variance σ^2 of Y. The parameter ρ>0 represents the degree of reasonable
feedback efforts for reducing unnecessary controllable radiological risk. When residents, however, are selected toprotect those to be exposed above dose a (to limit the number of evacuees practically) and to be strongly reduced
below dose b (to be seldom beyond reference levels), the HLN distribution of doses to the residents selected can be
defined as ρW+ln(ρW)~N(μ,σ^2) by putting W=X－a or W=(X－a)/(b－X). The former is called the 4-parameter
HLN distribution, and the latter is called the hybrid SB distribution that is corresponding to the Johnson's SB
distribution defined as ln[(X-a)/(b-X)]~N(μ,σ^2).
The Fukushima Health Management Survey presents the tentative dose statistics of residents in Namie, Iidate
and Kawamata for the period of March 12 to July 11, 2011. The MEXT (Ministry of education, culture, sports,science and technology) reports periodically the integrated doses at a point of monitoring in planned evacuationarea, restriction area and others. By matching the area (Namie, Iidate and Kawamata) and the period (3/12/20117/11/2011), the results of analyzing dose distributions based on these data are given to interpret the effectiveness ofevacuation or protection to avoid the higher doses to residents after the accident.
The paper also shows that the statistical distribution analysis is essential to confirm the homogeneity of data
monitored in space and time against possible bias due to the degree of difficulty to obtain data. The environmental
data likely to follow the extreme value distribution (maximum) can be well modeled by using the transformation of
X+ln(X) or W+ln(W). Thus in this paper the linear-plus-logarithm type of hybrid function is also shown to provide
the better estimation for radiological data analysis relating to the Fukushima nuclear accident.
In conclusion, the feasible distributions of doses to residents evacuated after the accident are presented based ondata tentatively reported in the Fukushima Health Management Survey, including some methods for confirming
the statistical homogeneity of relevant data obtained against biased estimation.
Keywords
dose distribution, residents evacuated, protection feedback, hybrid lognormal, homogeneity of data

64

5-5
Measurement of radioactivity in air-borne dust and estimation of publicdose in Tokyo after the Fukushima Daiichi Nuclear Power Plant Accident
Yoshiyasu Nagakawa*,Takashi Suzuki, YasuhitoKinjo, Noboru Sakurai, Takahiro Sotodate, Hiroaki Ise
Tokyo Metroplolitan Industrial Technology Research InstituteWe report the results of emergency monitoring of environmental radiation in Tokyo in response to
the severe accident at Fukushima Daiichi Nuclear Power Plant (NPP). Tokyo Metropolitan Industrial
Technology Research Institute (TIRI) has been in charge of environmental radiation monitoring since1975. The monitoring is based on 'Regional Disaster Prevention Plan' formulated by Tokyo
Metropolitan Government. After the Great East Japan Earthquake occurred on 11 March 2011, we havealso started the emergency monitoring of the environmental radiation from March 13 to detect gammaemitting nuclides in air-borne dust. Based on the results, the public internal doses due to inhalation were
estimated during the period 13 March 2011–12 March 2012.
Air-borne dusts were collected at TIRI in Setagaya (13 March–12 October 2011) and Koto districts(13 October 2011–present date) in Tokyo which are located at distances of 220 km and 230 km from the
Fukushima Daiichi NPP, respectively. Air-borne dusts were collected with a glass-fiber filter using ahigh-volume air sampler which was set at a height of 1 m above ground level. Air flow rate was set tobe 0.6 m3/min. The radioactivity of the collected samples was measured by a Ge semiconductor detector
with measuring times ranging from 1,000 s to 20,000 s. The Coincidence summing was corrected. The
measurement of each sample was carried out immediately after the sampling, and the decay correctionsof radionuclides were not considered. To determine the concentration of 134Cs and 137Cs per weight(Bq/mg), air-borne dusts adsorbed on the filter (April 19–October 20) were weighed.
Gamma-emitting nuclides were detected for the first time in the sample collected in 0:00–7:12 a.m.
of 15 March 2011 at Setagaya district, and we started to collect samples in an interval of 1 h. The second
peak that showed the highest concentration of major fission products was detected in 10:00–11:00 a.m.
of March 15. The concentrations were as follows: 2.4×102 Bq/m3 of 131I, 6.4×101 Bq/m3 of 134Cs,
6.0×101 Bq/m3 of 137Cs. The third peak was observed in 2:00–10:00 a.m. of March 16, then theconcentrations decreased and leveled off to almost undetectable levels. The concentration increased
again in 21–23 March, probably due to rainfall. The concentration of 131I reached undetectable level inJune 2011. On the other hand, 134Cs and 137Cs had been detected intermittently for a year. There was nocorrelation between yield of air-borne dusts and the concentrations of 134Cs and 137Cs.
The internal effective dose due to inhalation was estimated from the concentrations of all radionuclides
that were detected by the detector (Bq/m3) according to the effective dose coefficients listed in ICRP
Publication 72, where it was assumed that people stayed outdoors continuously. The dose to the adultwas estimated to be 25μSv. We must note that the contribution of gaseous radionuclides such as 131I was
not considered in the estimation. These data can be used to understand the potential risk of stochastic
effects for the people in Tokyo.
Keywords
Fukushima Daiichi NPP, Radiation monitoring, Effective dose

65

5-6
Assessment of doses to the public in the contaminated areas resulting fromthe Fukushima Daiichi Nuclear Power Station accident

Shogo Takahara*, Masashi Iijima, Kazumasa Shimada, Masanori Kimura, Sakae Kinase,Toshimitsu Homma
Japan Atomic Energy Agency

The present study provides, in order to reconstruct the doses received by the public, the preliminary
results from the assessment of the effective doses for one year since the accident. The assessment took
into account all major pathways of external exposures and internal exposures. As far as possible, theassessment was based on the measured levels of radioactive materials in the environment. In addition,
an atmospheric dispersion modeling was used to estimate the time of radioactive plumes passing andradionuclides depositing on the ground.
Keywords
Dose assessment, measurement data, exposure pathways

66

5-7
Initial substantial reduction in air dose rate of Cs-origin and personal doseto residents due to the Fukushima nuclear accident
Hiroko Yoshida*¹, Noriyasu Hirasawa¹, Ikuo Kobayashi²¹Tohoku University²Nagase Landauer Ltd.

The earthquake of magnitude 9.0 and tsunami on 11 March 2011 in Japan resulted in severe damage to the
Fukushima Daiichi nuclear power plant (NPP), causing a month-long release of radioactive materials into the atmosphere.
Aerial measurements carried out by the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)
survey showed that the radioactive plumes spread towards the northwest from the NPP, causing radionuclide deposition.
Marumori and Kosugo in Miyagi, a neighboring Fukushima prefecture, is located 46 km northwest of the NPP at theclosest approach. A distribution map of the radioactivity concentration in the soil by the MEXT revealed that this area
was strongly affected by the radioactive plumes and the 137Cs deposition level ranged from 100 to 300 kBq/m2. After 131I
(with a half-life of 8 d) decayed, Cs nuclei predominantly have been responsible for radiation doses since June. In thisstudy, the personal dose equivalent [Hp(10)] for residents in Marumori and Kosugo regions was evaluated using opticallystimulated luminescent (OSL) dosemeters from 1 September 2011. The data of air dose rates in those regions acquired
from the local governments through the period of July 2011 and September 2012 were analysed to investigate theirtemporal variation of Cs-origin. The initial substantial reduction in air dose rate and personal dose to residents werecompared.
The Hp(10) for 54 Marumori and 71 Kosugo residents (125 in total) was evaluated. The measurements were carriedout using OSL personal dosemeters and the OSL reader (InLight badge and microStar system, Nagase Landauer, Ltd).
The dosemeters are small devices worn on a neck strap. Worn close to the torso, they measure the radiation coming to thebody as a whole. Each dosemeter was replaced every 1.5-2 months for reading. During the time the dosemeters were
worn, the residents were instructed to record their daily activity history and whether they followed the dosemeter wearing
instructions correctly. The data on individuals who did not follow the instructions were excluded in the analysis. The dataof air dose rates were analysed by comparing them with the calculated rate attributed to the radioactive decay of 134Cs and
137Cs, obtained using Equation (1).
E (t) =E(0)/3.7x{ 2.7 x exp (-λ1t) + exp (-λ2t) } (1)where λ1 and λ2 are the decay constants of 134Cs and 137Cs, respectively.
The data of air dose rates in both regions showed the similar tendency. The rapid reduction appeared until around theend of July, followed the long-term decrease in accordance with the radioactive decay process of 134Cs and 137Cs from
August to December. During the heavy snow season, air dose rates dropped down and remained low through January to
the beginning of March 2012. The air dose rates returned after the snow thawed then followed the relatively faster
reduction than the radioactive decay of 134Cs and 137Cs. This reduction is considered to be caused by weathering and/or
migration of radionuclides down the soil column. It might be accelelated by snow melting. The half-lives of this reduction
were estimated 450 and 300 days in Marumori and Kosugo, respectively when it is expressed using Equation (2)E (t) =E(0) x exp (-λ3t)(2)
The decrease in Hp(10) of residents in two regions seemed quite differently. The result in Hp(10) of Marumori
residents showed the similar tendency with that obtained from the data of air dose rates before and after the snow season,
however, no faster reduction due to weathering and/or migration of radionuclides was obserbed in Hp(10) of Kosugo
residents. This difference can be explained by dose contributions from contamination on roof pavings and typically to alesser extent, walls in the urban environment of Kosugo.
Keywords
personal dose to residents, weathering, air dose rate67