Report on “Radiation Disaster Recovery Studies”
Course: Radioactivity Environmental Protection
Name: NGUYEN TAT THANH○Regarding“Radiation Disaster Recovery Studies”（Describe your thoughts, the process you engaged in and your research progress regarding
Recovery from
Radiation Disaster.）
Triggering by the big earthquake and massive tsunami that occurred at offshore of the Pacific Ocean
led to the Fukushima nuclear power plant accident on March 11th, 2011 [1]. The nuclear power plant
accident was known as one of the biggest nuclear disasters in the world following Chernobyl in April
1986 and Three Mile Island in March 1979. By accident, there was a tremendous amount ofradioactive materials released into the air with the radioactivities of 131I, 132Te, 134Cs, and 137Cs wereestimated to be 160, 88, 18 and 15 PBq [2]. When they deposited on the ground soil or felt down on
aquarium medium, they made the vast radioactivity contaminated regions along with the Tohoku
prefectures of Japan [3]. Short half-live radionuclides as 131I, 132Te were decayed out after several
months of the accident. In contrast, 134Cs and 137Cs with long half-live of 2 and 30.1 years,respectively, take several years to a hundred years for decay [4].
The harmful effects of radioactive cesium on the human body have been investigated and reported bymany researchers. The researches were carried out based on laboratory animal organisms by
exposing to 137Cs sources. Besides, surveys on the people living in highly contaminated regions after
the Chernobyl accident were also conducted. The collected data indicated that radioactive cesium ishighly concentrated in kidneys, myocardium, skeletal muscles, spleen, and lungs, testicle, and liver.
Also, by the results, the function and metabolic activity disorders of the cardiovascular system, liver,kidney, immunity system, and haemopoetic system rated with the external exposure and internalexposure [5]. The death cases were noted with the radioactivity concentration of 137Cs amounted to
192.8 Bq/kg with adults and 645.3 Bq/kg with children in kidneys. The impact of 137Cs on the humanbody shows that the protection of exposure to radiation, especially internal exposure, is crucial work.
On the other face of radiation impacts on the ecosystem, recently, researches on the effects ofradiation to pines living in highly contaminated regions surrounding the Fukushima nuclear power
plant showed that morphological effects of the pines are proportional to the exposure dose level ofthe ambient [6]. Besides, the impacts of radiation on the animals have been pointed by the forewing
size reduction, growth retardation, high mortality rates and high abnormality rate in the pale grassblue butterfly [7], the abundance reduction of birds [8], butterflies and cicadas [9], body weight andhead size reduction of monkey babies [10].
With the harmful effects due to radioactive cesium as mentioned above, the environmental dynamics

of them in an ecosystem is necessary to evaluate. Ordinarily, for the radioactive cesium released
from the Fukushima nuclear power plant, the movement directions are considered in two ways suchas migration in the soil and dispersion in the aquarium mediums. My doctoral thesis was chosen
about the investigation of the environmental dynamics of radioactive cesium released from
Fukushima nuclear power plant accident to make the migration process of radioactive cesium in soilclearer.
The thesis results suggested that although physical migration of radioactive cesium in the soil is fast
moved down to deep layers, this process occurred after several months of the accident, then it wasslowed down following time. Later years, the migration process is continued, however it is said thatthe radioactive cesium is mainly concentrated on around 5 cm soil layer from surface soil. The
results from the research on the absorption of young pines indicated that the radioactivity
concentration in plant is rated with that in the contaminated soil and the internal dose in the plants
was estimated approximately 60 percent of total exposure dose. The results have meaning inmonitoring the distribution of radioactive cesium in soil and estimating the absorption of youngplants via root uptake.

○Title of Doctoral Thesis
Investigation on environmental dynamics of radioactive Cs released from Fukushima nuclear power
plant accident（福島原発事故に伴い放出された放射性 Cs の環境動態についての研究）○Summary of Doctoral Thesis（Describe so as to be easily understood, by relating it to“Radiation Disaster Recovery Studies”.）
The radionuclides released from the Fukushima nuclear power plant accident had made the soil
contaminated in a vast region. This research has an aim to investigate the environmental dynamics ofradiocesium in the soil environment to plant by root uptake process. To make the environmental
dynamics clearly, estimation of the movement level in soil, and transfer from soil to plant areconducted.
Chapter I: The background and circumstance of the Fukushima Nuclear Power Plant accident and its
effects on the environment are introduced briefly. Besides, the reason for choosing the Iitate village
as a research location is explained.
Chapter II: Describe a method for soil sampling and young tree sampling in this investigation. These
collected soil and young tree samples are prepared and measured by Imaging plate measurement andgamma measurement systems. The acquired results are used for further analysis in the next Chapters.
Chapter III: Introduce a technique for determining the shape of the depth profile of radiocesium insoil by using an imaging plate combined with the unfolding algorithm and PHITS code simulation.

By the proposed technique, the depth profile of radiocesium can be plotted with millimeter depth-binwidth, which is quite difficult to be obtained by conventional techniques (sliding soil core).
Chapter IV: Migration velocity and diffusion coefficient are ordinarily considered as radiocesium
movement indexes in soil, and they are solutions of the equation which are derived from Bossew andKirchner-model for transportation of radionuclides in soil. The migration velocity by this model isindependent of the time factor. However, observation results from previous researches of otherauthors shown that the migration velocity is a function of time. Therefore, in this study, an equationof migration velocity is assumed as an exponential function of time and applied for fitting the depth
profiles of those obtained by the method in Chapter III.
Chapter V: In this chapter, the study aims to propose a soil-to-plant transfer coefficient formulation
expressed using a soil-to-root transfer factor and root-to-plant translocation factor. The soil-to-root
transfer factor is assumed as a ratio of radioactivity concentration in root to radioactivity
concentration in soil at the same soil layer. The proposed formulation is applied for calculating thesoil-to-plant transfer coefficient of young trees collected at Iitate village.
Chapter VI: Summarize the research results and suggestions for further research○Other theses published in academic research journals
1. Nguyen T. T., Kajimoto T., Tanaka K., Endo S (2018). Determination of radiocesium depth profile
by unfolding method with imaging plate. Applied Radiation and Isotopes, (142):128-134 (IF 1.343 2019)
2. Nguyen T. T., Kajimoto T., Tanaka K., Endo S (2016). Triple ionization chamber method forclinical dose monitoring with a Be-covered Li BNCT field. Medical Physics, 43(11), 6049-6057 (IF2.884 - 2017)
3. Endo. S, Kajimoto. T, Tanaka. K, Nguyen. T. T, Hayashi. G, Imanaka. T (2015). Mapping of thecumulative β-ray dose on the ground surface surrounding the Fukushima area. Journal of Radiation
and Research, 56(1), i48-i55 (IF 1.05 - 2016)
4. Kajimoto. T, Endo. S, Nguyen. T. T, Shizuma. K (2015). Calculation of coincidence summing in
gamma-ray spectrometry with the EGS5 code. Applied Radiation and Isotopes, (95): 53-58 (IF 1.128- 2016)
5. Endo. S, Imanaka. T, Kajimoto T., Tanaka. K, Nguyen. T. T, Otaki. J. M. Estimation of β-ray dosein air and soil from Fukushima Daiichi Power Plant accident. Journal of Radiation and Research,
55(3):476-483 (IF 1.536 - 2015)

References[1]. Ministry of Economy, Trade, and Industry, press release, October 20, 2011,
http://www.meti.go.jp/press/2011/10/20111020001/20111020001/pdf[2]. NISA. Regarding the evaluation of the conditions on reactor cores of units 1, 2 and 3 related tothe accident at Fukushima Dai-ichi nuclear power station, Tokyo Electric Power Co. Inc. 2011
http://www.nisa.meti.go.jp/english/press/2011/06/en20110615-5.pdf , released on 6 June 2011.
[3]. S, Mikami, T. Maeyama, Y. Hoshide et al., 2015. Spatial distributions of radionuclides deposited
onto ground soil around the Fukushima Dai-ichi Nuclear Power Plant and their temporal change until
December 2012. Journal of Environmental Radioactivity. 139: 320-343.
[4]. Endo, S., Kajimoto, T., Shizuma, K., 2013. Paddy-field contamination with 134Cs and 137Cs due
to Fukushima Dai-ichi Nuclear Power Plant accident and soil-to-rice transfer coefficients. J. Environ.
Radiact.116, 59-64.
[5]. Bandazhevsky, Y. I., Medical and Biological Effects of Radiocesium incorporated into theHuman. Organism （Institute of Radiation Safety “BELRAD”, Minsk, 2000. ISBN 985-434-080-5.
[6]. Yoschenko Y, Nanba K, Yoshida S, Watanabe Y et al., 2016 Morphological abnormalities inJapanese red pine (Pinus densiflora) at the territories contaminated as a result of the accident at
Fukushima Dai-Ichi Nuclear Power Plant. J. Environ. Radiact., 165:60-67[7]. Taira W, Nohara C, Himaya A et al., 2014. Fukushima’s Biological Impacts: The Case of thePale Grass Blue Butterfly. Journal of Heredity, 105(5):710-722[8]. Moller A P, Mousseau T A, Nishiumi I et al., 2015. Ecological differences in response of birdspecies to radioactivity from Chernobyl and Fukushima. J Ornithol, 156(1): S287-296[9]. Moller A P, Nishiumi I, Suzuki H et al., 2013. Differences in effects of radiation on abundanceof animals in Fukushima and Chernobyl. Ecological Indicators, 24:75-81[10]. Hayama S, Tsuchiya M, Ochiai K et al., 2017. Small head size and delayed body weight growthin wild Japanese monkey fetuses after the Fukushima Daiichi nuclear disaster. Scientific Reports
volume 7, Article number: 3528