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Journal Articles

Investigation of removal factors of various materials inside houses after Nuclear Power Station Accident

Mori, Airi; Ishizaki, Azusa; Futemma, Akira; Tanabe, Tsutomu; Wada, Takao; Kato, Mitsugu; Munakata, Masahiro

Hoken Butsuri, 54(1), p.45 - 54, 2019/04

Journal Articles

Evaluation of electronic state of Cs-adsorbed clay minerals by NEXAFS analysis using DFT calculations

Suzuki, Chikashi; Yaita, Tsuyoshi; Suzuki, Shinichi; Pacold, J.*; Altman, A. B.*; Minasian, S. G.*; Tyliszczak, T.*; Shuk, D. K.*; Yoshida, Hiroyuki; Osaka, Masahiko

Journal of Physics and Chemistry of Solids, 127, p.169 - 177, 2019/04

A combined method of NEXAFS measurement and DFT-calculation was employed for Cs evaluation in clay minerals. The Cs M$$_{4,5}$$ NEXAFS spectra of Cs halides were analyzed using the DFT-calculations, and were well reproduced by incorporating the core-hole strength. The Cs M$$_{4,5}$$ NEXAFS spectrum of clay minerals was well-reproduced by the DFT-calculations including the major transitions and tail structures with the established method. The further evaluation of this spectrum by charge density suggests that these major transitions and the tail structures likely reflect bonding states and local environments around the Cs atoms. Comparison of electronic states of Cs in the clay mineral with those in the Cs halides by DFT-calculations has shown that the interaction between Cs and the nearest-neighbor atom is largest in the clay mineral, because the energy level of Cs-5s and 5p is closer to that of O-2s and 2p than the s and p orbitals of other alkali metal and alkali earth metal elements.

Journal Articles

7.2.3 Towards implementation of Fukushima environmental remediation

Miyahara, Kaname; Kawase, Keiichi

Genshiryoku No Ima To Ashita, p.159 - 167, 2019/03

This manuscript overviews lessons learned from decontamination pilot projects towards implementation of regional remediation after the environmental contamination due to the Fukushima Daiichi Nuclear Power Plant Accidents.

Journal Articles

3.5.3 Technologies for contaminated water treatment

Uchida, Shunsuke

Genshiryoku No Ima To Ashita, p.63 - 68, 2019/03

The latest situation of contaminated water treatment in Fukushima Daiichi NPP for 8 years after its accident is reviewed. Major subjects, especially tritium treatment, to be solved related to the contaminated water and some proposal for the subjects are introduced.

Journal Articles

Fukushima $$^{137}$$Cs releases dispersion modelling over the Pacific Ocean; Comparisons of models with water, sediment and biota data

Peri$'a$$~n$ez, R.*; Bezhenar, R.*; Brovchenko, I.*; Jung, K. T.*; Kamidaira, Yuki; Kim, K. O.*; Kobayashi, Takuya; Liptak, L.*; Maderich, V.*; Min, B. I.*; et al.

Journal of Environmental Radioactivity, 198, p.50 - 63, 2019/03

 Percentile:100(Environmental Sciences)

A number of marine radionuclide dispersion models were applied to simulate $$^{137}$$Cs releases from Fukushima Daiichi Nuclear Power Plant accident in 2011 over the northwest Pacific. Simulations extended over two years and both direct releases into the ocean and deposition of atmospheric releases on the ocean surface were considered. Dispersion models included an embedded biological uptake model (BUM). Three types of BUMs were used: equilibrium, dynamic and allometric. Model results were compared with $$^{137}$$Cs measurements in water, sediment and biota. A reasonable agreement in model/model and model/data comparisons was obtained.

Journal Articles

Development of the ReaxFF methodology for electrolyte-water systems

Fedkin, M. V.*; Shin, Y. K.*; Dasgupta, N.*; Yeon, J.*; Zhang, W.*; van Duin, D.*; Van Duin, A. C. T.*; Mori, Kento*; Fujiwara, Atsushi*; Machida, Masahiko; et al.

Journal of Physical Chemistry A, 123(10), p.2125 - 2141, 2019/03

no abstracts in English

Journal Articles

Penetration of $$^{129}$$I released from Fukushima Daiichi Nuclear Power Plant accident in the western North Pacific Ocean

Suzuki, Takashi; Otosaka, Shigeyoshi; Kuwabara, Jun; Kawamura, Hideyuki; Kobayashi, Takuya

JAEA-Conf 2018-002, p.103 - 106, 2019/02

To investigate the dynamics of radionuclides in the ocean released by the accident at Fukushima Daiichi Nuclear Power Plant (1F), vertical distributions of $$^{129}$$ I at three stations in the western North Pacific was revealed. The 1F accident-derived $$^{129}$$ I existed within the mixed layer at 3 stations. The maximum layer of the 1F accident-derived $$^{129}$$ I existed at the depth of 370 m - 470 m at the most southern station. Considering the dissolved oxygen concentration and the current velocity arround the station, the maximum layer of the 1F accident-derived $$^{129}$$ I would be fromed that $$^{129}$$I which existed in the surface seawater at other area of observation point was carried to the depth of 370 m - 470 m by the fast downward flow.

Journal Articles

Depth profile and inventory of $$^{36}$$Cl in soil near the Fukushima Dai-ichi Nuclear Power Plant

Ota, Yuki*; Sueki, Keisuke*; Sasa, Kimikazu*; Takahashi, Tsutomu*; Matsunaka, Tetsuya*; Matsumura, Masumi*; Tosaki, Yuki*; Honda, Maki*; Hosoya, Seiji*; Takano, Kenta*; et al.

JAEA-Conf 2018-002, p.99 - 102, 2019/02

no abstracts in English

Journal Articles

Chemical reaction kinetics dataset of Cs-I-B-Mo-O-H system for evaluation of fission product chemistry under LWR severe accident conditions

Miyahara, Naoya; Miwa, Shuhei; Horiguchi, Naoki; Sato, Isamu*; Osaka, Masahiko

Journal of Nuclear Science and Technology, 56(2), p.228 - 240, 2019/02

In order to improve LWR source term under severe accident conditions, the first version of a fission product (FP) chemistry database named "ECUME" was developed. The ECUME is intended to include major chemical reactions and their effective kinetic constants for representative SA sequences. It is expected that the ECUME can serve as a fundamental basis from which FP chemical models in the SA analysis codes can be elaborated. The implemented chemical reactions in the first version were those for representative gas species in Cs-I-B-Mo-O-H system. The chemical reaction kinetic constants were evaluated from either literature data or calculated values using ab-initio calculations. The sample chemical reaction calculation using the presently constructed dataset showed meaningful kinetics effects at 1000 K. Comparison of the chemical equilibrium compositions by using the dataset with those by chemical equilibrium calculations has shown rather good consistency for the representative Cs-I-B-Mo-O-H species. From these results, it was concluded that the present dataset should be useful to evaluate FP chemistry in Cs-I-B-Mo-O-H system under LWA SA conditions.

Journal Articles

Effect of seawater components on corrosion behavior of SUS316L in nitric acid solution containing metal ions

Ambai, Hiromu; Nishizuka, Yusuke*; Sano, Yuichi; Uchida, Naoki; Iijima, Shizuka; Shiwaku, Hideaki; Yaita, Tsuyoshi

Journal of Nuclear Science and Technology, 65(2), p.193 - 200, 2019/02

During the accident that occurred at the Fukushima Daiichi Nuclear Power Plant, a large volume of seawater was introduced as coolant into the storage pools for spent nuclear fuel. If this fuel is reprocessed, some components of seawater will be mixed with the nitric acid solution containing metal ions in the reprocessing process where stainless steels are used as structural material. In this study, we investigated the effect of seawater components in high active liquid waste (HAW) containing nitric acid and metal ions as fission products on the corrosion behavior of SUS316L stainless steel. Corrosion tests were conducted in surrogate HAW containing artificial seawater (ASW). Intergranular corrosion was observed in the HAW with ASW, where Ru increased the corrosion potential to the transpassive region. An increase in the amount of ASW led to a decrease in the corrosion rate and suppression of intergranular corrosion. Interactions between Ru ions and seawater components, such as chloride ions, were indicated by the results of extended Xray absorption fine structure spectroscopy and cyclic voltammetry analyses of the solution containing ASW and HAW.

Journal Articles

CLADS for Fukushima Daiichi decommissioning

Okamoto, Koji

Hozengaku, 17(4), P. 1, 2019/01

no abstracts in English

Journal Articles

Development of remote sensing technique using radiation resistant optical fibers under high-radiation environment

Ito, Chikara; Naito, Hiroyuki; Ishikawa, Takashi; Ito, Keisuke; Wakaida, Ikuo

JPS Conference Proceedings (Internet), 24, p.011038_1 - 011038_6, 2019/01

A high-radiation resistant optical fiber has been developed in order to investigate the interiors of the reactor pressure vessels and the primary containment vessels at the Fukushima Daiichi Nuclear Power Station. The tentative dose rate in the reactor pressure vessels is assumed to be up to 1 kGy/h. We developed a radiation resistant optical fiber consisting of a 1000 ppm hydroxyl doped pure silica core and 4 % fluorine doped pure silica cladding. We attempted to apply the optical fiber to remote imaging technique by means of fiberscope. The number of core image fibers was increased from 2000 to 22000 for practical use. The transmissive rate of infrared images was not affected after irradiation of 1 MGy. No change in the spatial resolution of the view scope by means of image fiber was noted between pre- and post-irradiation. We confirmed the applicability of the probing system, which consists of a view scope using radiation-resistant optical fibers.

Journal Articles

Laser-induced breakdown spectroscopy and related resonance spectroscopy for nuclear fuel cycle management and for decommissioning of "Fukushima Daiichi Nuclear Power Station"

Wakaida, Ikuo; Oba, Hironori; Miyabe, Masabumi; Akaoka, Katsuaki; Oba, Masaki; Tamura, Koji; Saeki, Morihisa

Kogaku, 48(1), p.13 - 20, 2019/01

By Laser Induced Breakdown Spectroscopy and by related resonance spectroscopy, elemental and isotope analysis of Uranium and Plutonium for nuclear fuel materials and in-situ remote analysis under strong radiation condition for melt downed nuclear fuel debris at damaged core in "Fukushima Daiichi Nuclear Power Station", are introduced and performed as one of the application in atomic energy research field.

Journal Articles

Radiocarbon variations in tree rings since 1960 near the Tokai nuclear facility, Japan

Matsunaka, Tetsuya*; Sasa, Kimikazu*; Takahashi, Tsutomu*; Hosoya, Seiji*; Matsumura, Masumi*; Satou, Yukihiko; Shen, H.*; Sueki, Keisuke*

Nuclear Instruments and Methods in Physics Research B, 439, p.64 - 69, 2019/01

no abstracts in English

Journal Articles

Development of a multi-copter simulator and a projection system for virtual operation experience

Suzuki, Kenta; Kawabata, Kuniaki

Proceedings of 2019 IEEE/SICE International Symposium on System Integration (SII 2019) (USB Flash Drive), 6 Pages, 2019/01

Journal Articles

Comparison of airborne and ground-based tools used for radiation measurement in the environment

Ochi, Kotaro; Sasaki, Miyuki; Ishida, Mutsushi*; Sanada, Yukihisa

Progress in Nuclear Science and Technology (Internet), 6, p.103 - 107, 2019/01

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, a large amount of radionuclides was spread out all over the world. In our previous study, we developed the aerial radiation monitoring technique using unmanned helicopter for investigating the dose rate derived deposited radionuclides over wide area. In addition, many monitoring techniques were developed for investigating the local distribution of radionuclides using unmanned aerial vehicle, handheld instrument and car within small area. Distinction of these methods depends on desirable position resolution of dose rate. However, the comparison method of the measurement result between different methods is not established. In this study, we attempted to evaluate the some methods of airborne and ground radiation measurement in same extended farm.

Journal Articles

Development of analysis method for airborne radiation monitoring using the inverse problem solutions

Sasaki, Miyuki; Ishizaki, Azusa; Sanada, Yukihisa

Progress in Nuclear Science and Technology (Internet), 6, p.63 - 67, 2019/01

Since the accident at Fukushima Daiichi Nuclear Power Station (FDNPS), some unmanned vehicles (UAVs) are applied to airborne radiation measurement in around FDNPS. In conventional analysis methods, count rate that is obtained in the sky is converted to air dose rate at 1 m above the ground (agl.) under following premises. (1) Topography under the UAV is a plane (plane source model). (2) The air dose rate at 1 m agl. under the UAV is constant inside approximately 10 m radius. (3) Relationship of altitude and count rate is exponential correlation. Therefore, it is difficult that dose rate by airborne radiation measurement is precisely measured at the mountains and uneven place of dose rate by the conventional method. In this study, Maximum Likelihood-Expectation Maximization (ML-EM) method which is used in the medical radiation such as Positron Emission Tomography (PET) is attempted to apply to environmental radiation measurement using UAV.

Journal Articles

A Method for the prediction of the dose rate distribution in a primary containment vessel of the Fukushima Daiichi Nuclear Power Station

Okumura, Keisuke; Riyana, E. S.; Sato, Wakaei*; Maeda, Hirobumi*; Katakura, Junichi*; Kamada, So*; Joyce, J. M.*; Lennox, B.*

Progress in Nuclear Science and Technology (Internet), 6, p.108 - 112, 2019/01

In order to establish the prediction method of the dose rate distribution in the primary containment vessel (PCV) of the Fukushima Daiichi Nuclear Power Station, a series of calculations were carried out in the following way; (1) burnup calculation to obtain fuel composition at the time of accident, (2) activation calculation for the structural materials including impurities, (3) estimation of Cs contamination in PCV based on the result of severe accident analysis by IRID, (4) decay calculation of radioactive nuclides, (5) photon transport calculation to obtain dose rate distribution. After that, Cs concentration around the dry-well of 1F was modified to be consistent with locally measured dose rates in the PCV-investigation by IRID.

Journal Articles

Development of ROV system to explore fuel debris in the Fukushima Daiichi Nuclear Power Plant

Kamada, So*; Kato, Michio*; Nishimura, Kazuya*; Nancekievill, M.*; Watson, S.*; Lennox, B.*; Jones, A.*; Joyce, M. J.*; Okumura, Keisuke; Katakura, Junichi*

Progress in Nuclear Science and Technology (Internet), 6, p.199 - 202, 2019/01

As a technology development to investigate the distribution of submerged fuel debris in the primary containment vessel (PCV) of the Fukushima Daiichi Nuclear Power Station, we are conducting development experiments of sonar system to be mounted in a compact ROV. The experiments were conducted in two types of water tanks with different depths, simulating the PCV, using sonar with different sizes, ultrasonic frequencies, and beam scanning method, and simulated fuel debris. As a result, we characterized the shape discrimination performance of the simulated debris, and the noise due to multi-path in narrow closed space.

Journal Articles

Study on restricted use of contaminated rubble on Fukushima Daiichi NPS site, 2; Validation of reference radiocesium concentration for recycling materials

Miwa, Kazuji; Shimada, Taro; Takeda, Seiji

Progress in Nuclear Science and Technology (Internet), 6, p.166 - 170, 2019/01

In this study, in order to validate the restricted use of recycling material at the reference radiocesium concentration (determined in series report (1)), we evaluated worker annual doses, air dose rate at the site boundary and impact of migrated radiocesium into groundwater. Firstly, we evaluated the additional annual dose for workers, on the assumption that typical workers coming in contact with the source after construction (Road: 1.2 mSv/y, Building: 1.3 mSv/y). Secondly, we evaluated the air dose rates by distance from road and building including recycling material, and investigated the distance for not exceeding 1 mSv/y (including additional dose rate by recycling and background dose rate of 0.6 mSv/y) at the site boundary (Road: 25 m, Building: 1 m). Thirdly, we evaluated the Cs migration in groundwater, and investigated the distance required for satisfying the operation target value ($$^{134}$$Cs: 1 Bq/L, $$^{137}$$Cs: 1 Bq/L) at the boundary (coastal line) (Road: 10 m, Building: 10 m).

925 (Records 1-20 displayed on this page)