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Journal Articles

Leaching characteristics of $$^{137}$$Cs for forest floor affected by the Fukushima nuclear accident; A Litterbag experiment

Sakuma, Kazuyuki; Yoshimura, Kazuya; Nakanishi, Takahiro

Chemosphere, 264, p.128480_1 - 128480_9, 2021/02

We investigated characteristic of dissolved $$^{137}$$Cs leaching from litters collected at a coniforest needle and a deciduous broadleaf forests using litterbags at upstream area of Ohta River in Fukushima. Each leaf type of litters was collected into 36 litterbags, respectively, and installed each forest floor in June and December, 2017. Triplicate samples were collected at each forest floor and readily transported to the laboratory in August, December, 2017 and March, May, August, December, 2018. Samples were put in buckets and soaked in purified water. We took leaching water samples from the buckets at 20 min, 140 min, 1 day after soaking litter samples in the water. These samples were analysed about $$^{137}$$Cs activity. The main results were that the deciduous broadleaf litter showed much higher leaching ratio of dissolved $$^{137}$$Cs (0.81-6.6%) than that of the coniferous needle litter (0.13-2.0%). A multi-regression analysis of $$^{137}$$Cs leaching ratios were conducted against antecedent mean precipitation and temperature, and accumulated temperature during the litterbag experiments. The model can reproduce observed $$^{137}$$Cs leaching ratios (R$$^{2}$$ = 0.61-0.99).

Journal Articles

Performance of in situ gamma-ray spectrometry in the assessment of radioactive cesium deposition around the Fukushima Daiichi Nuclear Power Plant

Ji, Y.-Y.*; Ochi, Kotaro; Hong, S. B.*; Nakama, Shigeo; Sanada, Yukihisa; Mikami, Satoshi

Radiation Physics and Chemistry, 179, p.109205_1 - 109205_11, 2021/02

In situ gamma-ray spectrometry using diverse survey platforms has been conducted in contaminated areas with several dose rate levels around the Fukushima Daiichi Nuclear Power Plant (FDNPP). Six survey sites, including two evacuation zones around the FDNPP, were selected for ground-based gamma-ray spectrometry using HPGe (high purity Ge) and LaBr$$_{3}$$(Ce) detectors to assess the radioactive cesium deposition in the ground. The diverse levels of radioactivity of $$^{137}$$Cs were then distributed to six survey sites from 30 to 3000 kBq m$$^{-2}$$ in the measurement period of October 2018. A method to directly calculate the depth profile using in situ measurement was introduced so as to have representation over a wide area, and the results were successfully compared with those of sample analysis at one point in the site.

Journal Articles

Solidification and re-melting mechanisms of SUS-B$$_{4}$$C eutectic mixture

Sumita, Takehiro; Kitagaki, Toru; Takano, Masahide; Ikeda, Atsushi

Journal of Nuclear Materials, 543, p.152527_1 - 152527_15, 2021/01

JAEA Reports

Test methods for robots for nuclear emergency response and decommissioning; Tests for running performances of robots (JAEA-TM-0001, JAEA-TM-0002 and JAEA-TM-0003)

Kawabata, Kuniaki; Yamada, Taichi; Abe, Hiroyuki*

JAEA-Technology 2020-015, 37 Pages, 2020/11

JAEA-Technology-2020-015.pdf:3.81MB

This report describes the test procedures for evaluating running performances of remotely operated robot utilized for nuclear emergency responses and decommissioning. After the accident at Fukushima Daiichi Nuclear Power Station of the Tokyo Electric Power Company Holdings Inc. (FDNPS) occurred, remotely operated robots have been deployed and utilized in the response tasks. Such post-accident work experience and lessons learned are very valuable for developing the robots in the future. Therefore, we were motivated to develop the test methods for performance evaluation of the robot by referring with such experiences and lessons. Based on our examinations, in order to execute the response and decommissioning tasks, the robots are required to run through the space without enough margin and avoiding collisions, to move on stairs while avoiding tumbling or falling down and to drag a cable while avoiding problems caused by the cable entwining around objects. This report describes three test procedures for quantitatively evaluating the performances which are for running narrow passage, climbing up/down on the stairs and running with dragging the cable. Typical course layout and the demonstration of test running are also illustrated for the references.

Journal Articles

Distribution map of natural gamma-ray dose rates for studies of the additional exposure dose after the Fukushima Dai-ichi Nuclear Power Station accident

Sanada, Yukihisa; Yoshimura, Kazuya; Urabe, Yoshimi*; Iwai, Takeyuki*; Katengeza, E. W.*

Journal of Environmental Radioactivity, 223-224, p.106397_1 - 106397_9, 2020/11

Journal Articles

Development of Short-Term Emergency Assessment system of Marine Environmental Radioactivity

Kobayashi, Takuya; Kawamura, Hideyuki; Kamidaira, Yuki

Nippon Genshiryoku Gakkai-Shi, 62(11), p.635 - 639, 2020/11

It is important to predict the dispersion of radioactive materials released into the ocean due to nuclear accidents in the surrounding ocean of the east Asian countries. The Japan Atomic Energy Agency developed a Short-Term Emergency Assessment system of Marine Environmental Radioactivity (STEAMER) based on an oceanic dispersion model. STEAMER quickly predicts the oceanic dispersion of radioactive materials in the surrounding ocean of the east Asian countries using the online prediction data of oceanic condition. We validated the predictability of the oceanic dispersion and demonstrated the improvement of the predictability using an ensemble prediction method. Moreover, we developed a high resolution model in the coastal region using a Regional Ocean Modeling System (ROMS).

Journal Articles

Measurements of the doses of eye lens for the workers of Fukushima Daiichi Nuclear Power Plant

Yokoyama, Sumi*; Ezaki, Iwao*; Tatsuzaki, Hideo*; Tachiki, Shuichi*; Hirao, Kazushige*; Aoki, Katsunori; Tanimura, Yoshihiko; Hoshi, Katsuya; Yoshitomi, Hiroshi; Tsujimura, Norio

Radiation Measurements, 138, p.106399_1 - 106399_5, 2020/11

Journal Articles

Reservoir sediments as a long-term source of dissolved radiocaesium in water system; a mass balance case study of an artificial reservoir in Fukushima, Japan

Funaki, Hironori; Sakuma, Kazuyuki; Nakanishi, Takahiro; Yoshimura, Kazuya; Katengeza, E. W.*

Science of the Total Environment, 743, p.140668_1 - 140668_9, 2020/11

 Times Cited Count:0

JAEA Reports

Survey on the radioactive substance in the coastal areas near Fukushima Prefecture in FY2019 (Contract research)

Misono, Toshiharu; Tsuruta, Tadahiko; Nakanishi, Takahiro; Sanada, Yukihisa; Shiribiki, Takehiko; Miyamoto, Kenji*; Urabe, Yoshimi*

JAEA-Research 2020-008, 166 Pages, 2020/10

JAEA-Research-2020-008.pdf:13.11MB
JAEA-Research-2020-008(errata).pdf:0.92MB

After the accident at TEPCO Fukushima Daiichi Nuclear Power Station (1F), marine monitoring survey on radioactive substances have been conducted with financially supported by the Nuclear Regulatory Agency from FY2019. Results obtain in the project in FY2019 are presented in this report. Based on scientific grounds, the concept necessary for "progress of sea area monitoring" was arranged for the future medium- to long-term investigation of radiocesium concentrations. As basic information of survey frequency revise, a seabed topography and sediment distribution survey was conducted, and an attempt was made to understand the relationship between the seabed topography and the grain size distribution of bottom sediment. A columnar core sample was collected in the coastal area and analyzed for radioactive cesium concentration. In order to understand the dynamics of radioactive cesium contained in suspended matter flowing in from a river, suspended solids was collected using a sediment trap and the concentration of radioactive cesium was measured. We re-analyzed the towed monitoring data that had been implemented since 2013, and tried to improve the accuracy of the radioactive cesium distribution estimation map in the coastal area.

JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018) (Translated document)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2020-007, 249 Pages, 2020/10

JAEA-Research-2020-007.pdf:15.83MB

The accident of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, Japan Atomic Energy Agency (JAEA) has been conducting "Long-term Assessment of Transport of Radioactive Contaminants in the Environment of Fukushima" concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

JAEA Reports

HAND: A Handy criticality analysis tool for fuel debris

Tada, Kenichi

JAEA-Data/Code 2020-014, 30 Pages, 2020/10

JAEA-Data-Code-2020-014.pdf:2.84MB

The decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Plant accident is one of the most important issues in Japan. In the process of the decommissioning, preventing radiation exposure of workers is imperative originating in nuclear criticality of fuel debris. This study provides the handy tool enabling the analysis on nuclear criticality of fuel debris. The developed analysis tool named as HAND enables estimation of the criticality of fuel debris in short time. HAND deduces the range of parameters such as the size and composition, in which the criticality of fuel debris is specified. By selecting the range of the parameters using HAND in advance, total calculation time of the detail analysis will be reduced. Since the input data of HAND is designed to be simple and the output of HAND is to be user friendly, this tool is expected to be also an intuitive tool to study the criticality of fuel debris. This report explains the outline of the HAND and input instructions for HAND.

Journal Articles

A Model intercomparison of atmospheric $$^{137}$$Cs concentrations from the Fukushima Daiichi Nuclear Power Plant accident, phase III; Simulation with an identical source term and meteorological field at 1-km resolution

Sato, Yosuke*; Sekiyama, Tsuyoshi*; Fang, S.*; Kajino, Mizuo*; Qu$'e$rel, A.*; Qu$'e$lo, D.*; Kondo, Hiroaki*; Terada, Hiroaki; Kadowaki, Masanao; Takigawa, Masayuki*; et al.

Atmospheric Environment; X (Internet), 7, p.100086_1 - 100086_12, 2020/10

The third model intercomparison project for investigating the atmospheric behavior of $$^{137}$$Cs emitted during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident (FDNPP-MIP) was conducted. A finer horizontal grid spacing (1 km) was used than in the previous FDNPP-MIP. Nine of the models used in the previous FDNPP-MIP were also used, and all models used identical source terms and meteorological fields. Our analyses indicated that most of the observed high atmospheric $$^{137}$$Cs concentrations were well simulated, and the good performance of some models improved the performance of the multi-model ensemble. The analyses also confirmed that the use of a finer grid resolution resulted in the meteorological field near FDNPP being better reproduced. The good representation of the wind field resulted in the reasonable simulation of the narrow distribution of high deposition amount to the northwest of FDNPP and the reduction of the overestimation over the area to the south of FDNPP. In contrast, the performance of the models in simulating plumes observed over the Nakadori area, the northern part of Gunma, and the Tokyo metropolitan area was slightly worse.

Journal Articles

Improvement of adsorption performances of Sr adsorption fiber and investigation for realizing simple $$^{90}$$Sr analysis

Horita, Takuma; Asai, Shiho*; Konda, Miki; Matsueda, Makoto; Hanzawa, Yukiko; Kitatsuji, Yoshihiro

Bunseki Kagaku, 69(10/11), p.619 - 626, 2020/10

We have developed a Sr adsorption fiber for rapid analysis of $$^{90}$$Sr. The prepared Sr adsorption fiber has a Sr-extraction layer that densely retains a Sr-selective extractant, an 18-crown-6 ether derivative, on the fiber surface. Hydrophobic group-containing polymer chains embedded onto the surface of the fiber allow to form a hydrophobic phase, incorporating Sr-selective extractants. This unique surface structure provides high adsorption capacity, leading to rapid and highly efficient adsorption of Sr$$^{2+}$$. The adsorption capacity of the Sr adsorption fiber was 3 times higher than commercially available 18-crown-6 ether derivative-impregnated resin (Sr Resin). The equilibrium adsorption capacity of the Sr adsorption fiber was comparable to the Sr Resin. The retained $$^{90}$$Sr was finally determined by a GM counter. The total analysis time including the Sr adsorption and measurement was about 1 hour.

Journal Articles

Development of a Gd$$_{2}$$Si$$_{2}$$O$$_{7}$$ (GPS) scintillator-based alpha imaging detector for rapid plutonium detection in high-radon environments

Morishita, Yuki; Izaki, Kenji; Kaneko, Junichi*; Yamamoto, Seiichi*; Higuchi, Mikio*; Torii, Tatsuo

IEEE Transactions on Nuclear Science, 67(10), p.2203 - 2208, 2020/10

We developed a Gd$$_{2}$$Si$$_{2}$$O$$_{7}$$ (GPS) scintillator-based alpha imaging detector and demonstrated its effectiveness by evaluating actual Pu particle and $$^{222}$$Rn progeny. The GPS scintillator plate was prepared by a sintering method. The outer dimensions of the GPS scintillator plate were 5 $$times$$ 5 cm, and the scintillator layer was approximately 50 $$mu$$m on a 3-mm-thick high-transparency glass. The plate was optically coupled to a position-sensitive photomultiplier tube with silicone grease. The developed imaging detector exhibited good uniformity. Pu particle activities were accurately evaluated at 14 different positions, and the difference in activity was within 6%. Radon-222 ($$^{222}$$Rn) progeny counts were reduced by 65.3% by applying an energy window. Although the Pu/$$^{222}$$Rn progeny activity ratio was 1/51, the Pu particle was successfully identified among $$^{222}$$Rn progeny within the 5 min-measurement time. The imaging detector has an excellent ability for detecting Pu among $$^{222}$$Rn progeny. Thus, this detector is useful for alpha contamination monitoring in high-radon-background environments.

Journal Articles

Construction of virtual reality system for radiation working environment reproduced by gamma-ray imagers combined with SLAM technologies

Sato, Yuki; Minemoto, Kojiro*; Nemoto, Makoto*; Torii, Tatsuo

Nuclear Instruments and Methods in Physics Research A, 976, p.164286_1 - 164286_6, 2020/10

 Times Cited Count:0 Percentile:100(Instruments & Instrumentation)

Journal Articles

Comprehensive analysis and evaluation of Fukushima Daiichi Nuclear Power Station Unit 2

Yamashita, Takuya; Sato, Ikken; Honda, Takeshi*; Nozaki, Kenichiro*; Suzuki, Hiroyuki*; Pellegrini, M.*; Sakai, Takeshi*; Mizokami, Shinya*

Nuclear Technology, 206(10), p.1517 - 1537, 2020/10

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Journal Articles

Applications of radiocesium migration models to Fukushima environmental issues: Numerical analysis of radiocesium transport in temperature-stratified reservoirs by 3D-Sea-SPEC

Yamada, Susumu; Machida, Masahiko; Kurikami, Hiroshi

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.140 - 146, 2020/10

no abstracts in English

Journal Articles

Development of side thruster system for ASV

Kato, Tetsu*; Kawamura, Yamato*; Tahara, Junichiro*; Baba, Shoichiro*; Sanada, Yukihisa

Proceedings of the 30th (2020) International Ocean and Polar Engineering Conference (ISOPE 2020) (USB Flash Drive), p.1255 - 1260, 2020/10

Journal Articles

Non-invasive imaging of radiocesium dynamics in a living animal using a positron-emitting $$^{127}$$Cs tracer

Suzui, Nobuo*; Shibata, Takuya; Yin, Y.-G.*; Funaki, Yoshihito*; Kurita, Keisuke; Hoshina, Hiroyuki*; Yamaguchi, Mitsutaka*; Fujimaki, Shu*; Seko, Noriaki*; Watabe, Hiroshi*; et al.

Scientific Reports (Internet), 10, p.16155_1 - 16155_9, 2020/10

JAEA Reports

Annual report for Nuclear Emergency Assistance and Training Center (April 1, 2019 - March 31, 2020)

Nuclear Emergency Assistance and Training Center

JAEA-Review 2020-016, 67 Pages, 2020/09

JAEA-Review-2020-016.pdf:4.09MB

The Japan Atomic Energy Agency (JAEA) is one of the designated public institutions, which is an agency dealing with an emergency situation in cooperation with the Japanese and local governments under the Disaster Countermeasures Basic Act and under the Armed Attack Situation Response Law. JAEA has, therefore, responsibilities of providing technical assistances to the Japanese and local governments in case of nuclear or radiological emergencies based on these Acts. To fulfill the assistances, the JAEA has prepared the Nuclear Emergency Support Measures Regulation, Disaster Prevention Work Plan and Civil Protection Work Plan. The Nuclear Emergency Assistance and Training Center (NEAT) is the main center of the technical assistance in case of emergency, and dispatches experts of JAEA, supplies equipment and materials and gives technical advice and information, to the Japanese and local governments for emergency based on the regulation and plans. In normal time, the NEAT provides the technical assistances such as the exercises and training courses concerning the nuclear preparedness and response to the JAEA experts and also to emergency responders including the Japanese and local government officers. This report introduces the results of activities in Japanese Fiscal Year 2019, conducted by NEAT in accordance with the third medium and long-term plan for the period from Japanese Fiscal Year 2015 to 2021.

4367 (Records 1-20 displayed on this page)