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Journal Articles

Clogging properties of HEPA filter induced by loading of soot from burned glove-box panel materials

Tashiro, Shinsuke; Ono, Takuya; Amano, Yuki; Yoshida, Ryoichiro; Watanabe, Koji*; Abe, Hitoshi

Nuclear Technology, 208(10), p.1553 - 1561, 2022/10

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

To contribute to the confinement safety evaluation of the radioactive materials in the Glove box (GB) fire accident, combustion tests with the Polymethyl methacrylate (PMMA) and the Polycarbonate (PC) as typical panel materials for the GB have been conducted with a relatively large scale apparatus. As the important data for evaluating confinement safety, the release ratio and the particle size distribution of the soot generated from the burned materials were obtained. Furthermore, the rise of the differential pressure ($$Delta$$P) of the high efficiency particle air (HEPA) filter by the soot loading was also investigated. As results, the release ratio of the soot from the PC was about seven times as large as the PMMA. In addition, it was found that the behavior of the rise of the $$Delta$$P with soot loading could be represented uniformly regardless of kinds of combustion materials by considering effect of the loading volume of the soot particle in the relatively low loading region.

Journal Articles

Differential pressure changes of a high airflow-type HEPA filter during solvent fire in reprocessing facilities

Tashiro, Shinsuke; Uchiyama, Gunzo; Ono, Takuya; Amano, Yuki; Yoshida, Ryoichiro; Abe, Hitoshi

Nuclear Technology, 208(7), p.1205 - 1213, 2022/07

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

A clogging behavior of a high-efficiency particulate air (HEPA) filter at solvent fire accidents for reprocessing facilities has been studied. In this study, the burning rates of 30% tri-butyl phosphate (TBP)/dodecane (DD) mixed solvent and DD solvent and the differential pressure ($$Delta$$P) of a high airflow typed HEPA filter applied in the actual facilities in japan were measured. It was confirmed that the mainly burned was DD at the early stage of the mixed solvent burning and the TBP at the late stage. Furthermore, it was found that the $$Delta$$P rapidly rose at the late stage of the mixed solvent burning. The increase of the release ratio of the unburned particulate composition (TBP, its degraded solvent and inorganic phosphorus (P$$_{2}$$O$$_{5}$$)) was considered to contribute to the rapid rise. The correlating formulas with the $$Delta$$P and the mass of the loading particulates, except for the region of the rapid rise of $$Delta$$P, could be induced.

JAEA Reports

Effect of nitrous acid on migration behavior of gaseous ruthenium tetroxide into liquid phase

Yoshida, Naoki; Ono, Takuya; Yoshida, Ryoichiro; Amano, Yuki; Abe, Hitoshi

JAEA-Research 2021-011, 12 Pages, 2022/01


In boiling and drying accidents involving high-level liquid waste in fuel reprocessing plants, emphasis is placed on the behavior of ruthenium (Ru). Ru would form volatile species, such as ruthenium tetroxide (RuO$$_{4}$$), and could be released to the environment with coexisting gases, including nitric acid, water, or nitrogen oxides. In this study, to contribute toward safety evaluations of these types of accidents, the migration behavior of gaseous Ru into the liquid phase has been experimentally measured by simulating the condensate during an accident. The gas absorption of RuO$$_{4}$$ was enhanced by increasing the nitrous acid (HNO$$_{2}$$) concentration in the liquid phase, indicating the occurrence of chemical absorption. In control experiments without HNO$$_{2}$$, the lower the temperature, the greater was the Ru recovery ratio in the liquid phase. Conversely, in experiments with HNO$$_{2}$$, the higher the temperature, the higher the recovery ratio, suggesting that the reaction involved in chemical absorption was activated at higher temperatures.

Journal Articles

Consistent modelling of material weight loss and gas release due to pyrolysis and conducting benchmark tests of the model; A Case for glovebox panel materials such as polymethyl methacrylate

Ono, Takuya; Tashiro, Shinsuke; Amano, Yuki; Yoshida, Naoki; Yoshida, Ryoichiro; Abe, Hitoshi

PLOS ONE (Internet), 16(1), p.e0245303_1 - e0245303_16, 2021/01

 Times Cited Count:0 Percentile:5.52(Multidisciplinary Sciences)

It is necessary to consider how a glove box's confinement function will be lost when evaluating the amount of radioactive material leaking from a nuclear facility during a fire. In this study, we build a model that consistently explains the weight loss of glove box materials because of heat input from a flame and accompanying generation of the pyrolysis gas. The weight loss suggests thinning of the glove box housing, and the generation of pyrolysis gas suggests the possibility of fire spreading. The target was polymethyl methacrylate (PMMA), used as the glove box panel. Thermal gravimetric tests on PMMA determined the parameters to be substituted in the Arrhenius equation for predicting the weight loss in pyrolysis. The pyrolysis process of PMMA was divided into 3 stages with activation energies of 62 kJ/mol, 250 kJ/mol, and 265 kJ/mol. Furthermore, quantifying the gas composition revealed that the composition of the pyrolysis gas released from PMMA can be approximated as 100 percent methyl methacrylate. This result suggests that the released amount of methyl methacrylate can be estimated by the Arrhenius equation. To investigate the validity of such estimation, a sealed vessel test was performed. In this test, we observed increase of the number of gas molecules during the pyrolysis as internal pressure change of the vessel. The number of gas molecules was similar to that estimated from the Arrhenius equation, and indicated the validity of our method. Moreover, we also performed the same tests on bisphenol-A-polycarbonate (PC) for comparison. In case of PC, the number of gas molecules obtained in the vessel test was higher than the estimated value.

JAEA Reports

Effect of nitrogen oxides on decomposition behavior of gaseous ruthenium tetroxide

Yoshida, Naoki; Amano, Yuki; Ono, Takuya; Yoshida, Ryoichiro; Abe, Hitoshi

JAEA-Research 2020-014, 33 Pages, 2020/12


Considering the boiling and drying accident of high-level liquid waste in fuel reprocessing plant, Ruthenium (Ru) is an important element. It is because Ru would form volatile compounds such as ruthenium tetroxide (RuO$$_{4}$$) and could be released into the environment with other coexisting gasses such as nitric oxides (NOx) such as nitric oxide (NO) and nitrogen dioxide (NO$$_{2}$$). To contribute to the safety evaluation of this accident, we experimentally evaluated the effect of NOx on the decomposition and chemical change behavior of the gaseous RuO$$_{4}$$ (RuO$$_{4}$$(g)). As a result, the RuO$$_{4}$$(g) decomposed over time under the atmospheric gasses with NO or NO$$_{2}$$, however, the decomposition rate was slower than the results of experiments without NOx. These results showed that the NOx stabilized RuO$$_{4}$$(g).

Journal Articles

Decomposition behavior of gaseous ruthenium tetroxide under atmospheric conditions assuming evaporation to dryness accident of high-level liquid waste

Yoshida, Naoki; Ono, Takuya; Yoshida, Ryoichiro; Amano, Yuki; Abe, Hitoshi

Journal of Nuclear Science and Technology, 57(11), p.1256 - 1264, 2020/11

 Times Cited Count:5 Percentile:73.58(Nuclear Science & Technology)

Emphasis has been placed on the behavior of ruthenium (Ru) in the evaporation to dryness accident due to the loss of cooling functions (EDLCF) of high-level liquid waste in fuel reprocessing plants. It is because Ru would form volatile compounds such as ruthenium tetroxide (RuO$$_{4}$$) and could be released into the environment with other coexisting gasses such as nitric acid (HNO$$_{3}$$), water (H$$_{2}$$O). To contribute to the safety evaluation of this accident, we experimentally evaluated the decomposition and chemical change behavior of the gaseous RuO$$_{4}$$ (RuO$$_{4}$$(g)) under the various atmospheric conditions: temperature and composition of coexisting gasses. As a result, the behavior of the RuO$$_{4}$$(g) was diverse depending on the atmospheric conditions. In the experiments with the dry air or H$$_{2}$$O vapor, decomposition of RuO$$_{4}$$(g) was observed. In the experiment with the mixed gas which containing HNO$$_{3}$$, almost no decomposition of the RuO$$_{4}$$(g) was observed, and chemical form of the RuO$$_{4}$$(g) was retained.

Journal Articles

Competing spin modulations in the magnetically frustrated semimetal EuCuSb

Takahashi, Hidefumi*; Aono, Kai*; Nambu, Yusuke*; Kiyanagi, Ryoji; Nomoto, Takuya*; Sakano, Masato*; Ishizaka, Kyoko*; Arita, Ryotaro*; Ishiwata, Shintaro*

Physical Review B, 102(17), p.174425_1 - 174425_6, 2020/11

 Times Cited Count:7 Percentile:46.13(Materials Science, Multidisciplinary)

The competing magnetic ground states of the itinerant magnet EuCuSb, which has a hexagonal layered structure, were studied via magnetization, resistivity, and neutron-diffraction measurements on single-crystal samples. EuCuSb has a three-dimensional semimetallic band structure as confirmed by band calculation and angle-resolved photoelectron spectroscopy, consistent with the nearly isotropic metallic conductivity in the paramagnetic state. However, below the antiferromagnetic transition temperature of $$T$$$$_{rm N1}$$ (8.5 K), the resistivity, especially along the hexagonal axis, increases significantly. This implies the emergence of anisotropic magnetic ordering coupled to the conducting electrons. Neutron-diffraction measurements show that the Eu spins, which order ferromagnetically within each layer, are collinearly modulated (up-up-down-down) along the hexagonal axis below $$T$$$$_{rm N1}$$, followed by the partial emergence of helical spin modulation below $$T$$$$_{rm N2}$$ (6 K). Based on the observation of anomalous magnetoresistance with hysteretic behavior, we discuss the competing nature of the ground state inherent in a frustrated Heisenberg-like spin system with a centrosymmetric structure.

Journal Articles

Rapid clogging of high-efficiency particulate air filters during in-cell solvent fires at reprocessing facilities

Ono, Takuya; Tashiro, Shinsuke; Amano, Yuki; Yoshida, Ryoichiro; Abe, Hitoshi

Nuclear Technology, 206(1), p.40 - 47, 2020/01

 Times Cited Count:2 Percentile:25.41(Nuclear Science & Technology)

Recent Japanese nuclear regulations have focused on the hazards of in-cell solvent fires at reprocessing facilities. In this work, a mixture of tributyl phosphate and dodecane-based solvents was burned to generate an aerosol composed of soot and unburned solvent that was then loaded onto a high-efficiency particulate air filter simulating the ventilation system of reprocessing facilities. A radical increase of differential pressure occurred in the filters during these tests after the dodecane burned out from the solvent in a phenomenon we named as rapid clogging, likely caused by the burnout of dodecane. This relationship provides valuable insight into the establishment of new regulations for reprocessing facilities. This work indicates that clogging of ventilation filters during solvent fires may occur more rapidly than previously estimated.

Journal Articles

Degassing behavior of noble gases from groundwater during groundwater sampling

Nakata, Kotaro*; Hasegawa, Takuma*; Solomon, D. K.*; Miyakawa, Kazuya; Tomioka, Yuichi*; Ota, Tomoko*; Matsumoto, Takuya*; Hama, Katsuhiro; Iwatsuki, Teruki; Ono, Masahiko*; et al.

Applied Geochemistry, 104, p.60 - 70, 2019/05

 Times Cited Count:5 Percentile:29.87(Geochemistry & Geophysics)

no abstracts in English

Journal Articles

New precise measurements of muonium hyperfine structure at J-PARC MUSE

Strasser, P.*; Abe, Mitsushi*; Aoki, Masaharu*; Choi, S.*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; et al.

EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01

 Times Cited Count:13 Percentile:99.33

Journal Articles

Migration behavior of gaseous ruthenium tetroxide under boiling and drying accident condition in reprocessing plant

Yoshida, Naoki; Ono, Takuya; Amano, Yuki; Abe, Hitoshi

Journal of Nuclear Science and Technology, 55(6), p.599 - 604, 2018/06

 Times Cited Count:5 Percentile:53.84(Nuclear Science & Technology)

In the boiling and drying accident of high-level liquid waste in the fuel reprocessing plant, behavior of ruthenium (Ru) has attracted much attention because Ru could form volatile compounds such as ruthenium tetroxide (RuO$$_{4}$$) and could be released into the environment. To contribute towards safety evaluation of this accident, the migration behavior and the leak path factor of the gaseous ruthenium compound has been experimentally measured in this study. The experiment was proceeded by using the Ruthenium Migration Evaluating Apparatus, which partially simulates the atmospheric condition (temperature, flow rate, and composition of water vapor and gaseous nitric acid mixture) of migration pathway in the accident. Experiments with dry air and water vapor were also performed as the control experiment to discuss the effect of nitric acid. As a result, the experiment with dry air and the experiment with water vapor demonstrated that the majority of the ruthenium deposited along the migration pathway. On the other hand, the experiment with the water vapor containing gaseous nitric acid demonstrated that almost all of the ruthenium passed through the migration pathway without deposition. These results suggested that the migration behavior of gaseous ruthenium will be affected by the gas-phase composition.

JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima; As a part of dissemination of evidence-based information

Tsuruta, Tadahiko; Niizato, Tadafumi; Nakanishi, Takahiro; Dohi, Terumi; Nakama, Shigeo; Funaki, Hironori; Misono, Toshiharu; Oyama, Takuya; Kurikami, Hiroshi; Hayashi, Seiji*; et al.

JAEA-Review 2017-018, 86 Pages, 2017/10


Since the accidents at Fukushima Daiichi Nuclear Power Plant following the Tohoku Region Pacific Coast Earthquake on March 11th, 2011, Fukushima Environmental Safety Center has carried out research on natural mobilization of radionuclide (especially radiocesium) and future forecast from forest to water system and surrounding residential areas. The report summarizes the latest results that have been accumulated from each study field, of our agency together with the other related research organizations. The contents of the report is to be used as evidence-based information for the QA-styled pages in the website of JAEA Sector of Fukushima Research and Development at the time of next renewal.

Journal Articles

HEPA filter clogging and volatile material release under solvent fire accident in fuel reprocessing facility

Ono, Takuya; Watanabe, Koji; Tashiro, Shinsuke; Amano, Yuki; Abe, Hitoshi

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 7 Pages, 2017/07

After the Fukushima-Daiichi accident, countermeasures against the severe accident are newly required as regulatory items for nuclear facilities. Organic solvent fire in cell was defined as one of the accidents in the fuel reprocessing plant. When the solvent burns, aerosols including soot are released. The substances clog HEPA filters in the ventilation system and their breakthrough may happen because of differential pressure rising. Moreover, the fire can also release volatile radioactive gaseous species, which can pass through HEPA filters. These phenomena are important for evaluation of confinement capability of the facility and public exposure. We have investigated, in relating to the clogging behavior, release behavior of aerosols as well as of volatile materials from burnt solvent. In the presentation, we will report experimental data and evaluation results obtained from recent research.

Journal Articles

New muonium HFS measurements at J-PARC/MUSE

Strasser, P.*; Aoki, Masaharu*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; Ito, Takashi; Iwasaki, Masahiko*; et al.

Hyperfine Interactions, 237(1), p.124_1 - 124_9, 2016/12

 Times Cited Count:7 Percentile:91.43

Journal Articles

Use of fracture filling mineral assemblages for characterizing water-rock interactions during exhumation of an accretionary complex; An Example from the Shimanto Belt, southern Kyushu Japan

Ono, Takuya; Yoshida, Hidekazu*; Metcalfe, R.*

Journal of Structural Geology, 87, p.81 - 94, 2016/06

 Times Cited Count:4 Percentile:14.33(Geosciences, Multidisciplinary)

Fracture filling minerals were formed during the development of an accretionary complex. Each mineral formed under favourable geological conditions and can be used to estimate the conditions of accretion. Geological observations and analyses were made on fracture fillings from boreholes of ca. 140 m depth, in the Shimanto Belt of Kyushu. Results revealed that the minerals were formed in 5 stages distinguished by the textural relationships of the minerals. Filling minerals show that the studied rock formation has been subducted to several km depth and the temperature reached was ca. 200 - 300$$^{circ}$$C. After the subduction, the rock formation uplifted and surface acidic water penetrated up to 80 m beneath the present ground surface. The acid water dissolved calcite fillings to form the present groundwater flow-paths. The results shown here imply that filling minerals can be an effective tool to evaluate the environmental changes during accretionary complex formation.

Journal Articles

Photoelectron diffraction from laser-aligned molecules with X-ray free-electron laser pulses

Nakajima, Kyo*; Teramoto, Takahiro*; Akagi, Hiroshi; Fujikawa, Takashi*; Majima, Takuya*; Minemoto, Shinichiro*; Ogawa, Kanade*; Sakai, Hirofumi*; Togashi, Tadashi*; Tono, Kensuke*; et al.

Scientific Reports (Internet), 5, p.14065_1 - 14065_11, 2015/09

 Times Cited Count:37 Percentile:83.85(Multidisciplinary Sciences)

We report on the measurement of deep inner-shell 2p X-ray photoelectron diffraction (XPD) patterns from laser-aligned I$$_{2}$$ molecules using X-ray free-electron laser (XFEL) pulses. The XPD patterns of the I$$_{2}$$ molecules, aligned parallel to the polarization vector of the XFEL, were well matched with our theoretical calculations. Further, we propose a criterion for applying our molecular-structure-determination methodology to the experimental XPD data. In turn, we have demonstrated that this approach is a significant step toward the time-resolved imaging of molecular structures.

Journal Articles

Fabrication process qualification of TF Insert Coil using real ITER TF conductor

Ozeki, Hidemasa; Isono, Takaaki; Kawano, Katsumi; Saito, Toru; Kawasaki, Tsutomu; Nishino, Katsumi; Okuno, Kiyoshi; Kido, Shuichi*; Semba, Tomoyuki*; Suzuki, Yozo*; et al.

IEEE Transactions on Applied Superconductivity, 25(3), p.4200804_1 - 4200804_4, 2015/06

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

Journal Articles

Factors controlling the spatiotemporal variation of $$^{137}$$Cs in seabed sediment off the Fukushima coast; Implications from numerical simulations

Misumi, Kazuhiro*; Tsumune, Daisuke*; Tsubono, Takaki*; Tateda, Yutaka*; Aoyama, Michio*; Kobayashi, Takuya; Hirose, Katsumi*

Journal of Environmental Radioactivity, 136, p.218 - 228, 2014/10

 Times Cited Count:22 Percentile:54.64(Environmental Sciences)

Major controls on spatiotemporal variations of $$^{137}$$Cs activity in seabed sediments derived from the Fukushima Dai-ichi Nuclear Power Plant accident during the first year after the accident were investigated by using numerical simulations. The model successfully reproduced major features of the observed spatiotemporal variations of $$^{137}$$Cs activity in sediments. The spatial pattern of $$^{137}$$Cs in sediments, which mainly reflected the history of $$^{137}$$Cs activity in the bottom water overlying the sediment and the sediment particle size distribution, became established during the first several months after the accident. Taking $$^{137}$$Cs activities in sediments in the coastal area and in the vicinity of the power plant into account, increased the simulated total inventory of $$^{137}$$Cs in sediments off the Fukushima coast to a value on the order of 10$$^{14}$$ Bq.

Journal Articles

Proton-exchange mechanism of specific Cs$$^{+}$$ adsorption $$via$$ lattice defect sites of Prussian blue filled with coordination and crystallization water molecules

Ishizaki, Manabu*; Akiba, Sae*; Otani, Asako*; Hoshi, Yuji*; Ono, Kenta*; Matsuba, Mayu*; Togashi, Takanari*; Kanaizuka, Katsuhiko*; Sakamoto, Masatomi*; Takahashi, Akira*; et al.

Dalton Transactions, 42(45), p.16049 - 16055, 2013/12

 Times Cited Count:165 Percentile:99.56(Chemistry, Inorganic & Nuclear)

We have revealed the fundamental mechanism of specific Cs$$^{+}$$ adsorption into Prussian blue (PB) in order to develop high-performance PB-based Cs$$^{+}$$ adsorbents in the wake of the Fukushima nuclear accident. We compared two types of PB nanoparticles with formulae of Fe$$^{III}$$$$_{4}$$[Fe$$^{II}$$(CN)$$_{6}$$]3$$cdot$$xH$$_{2}$$O (x = 10-15) (PB-1) and (NH$$_{4}$$)0.70Fe$$^{III}$$1.10[Fe$$^{II}$$(CN)$$_{6}$$]$$cdot$$1.7H$$_{2}$$O (PB-2) with respect to the Cs$$^{+}$$ adsorption ability. The synthesised PB-1, by a common stoichiometric aqueous reaction between 4Fe$$^{3+}$$ and 3[Fe$$^{II}$$(CN)$$_{6}$$]$$^{4-}$$, showed much more efficient Cs$$^{+}$$ adsorption ability than did the commercially available PB-2.

Journal Articles

Oceanic dispersion simulations of $$^{137}$$Cs released from the Fukushima Daiichi Nuclear Power Plant

Masumoto, Yukio*; Miyazawa, Yasumasa*; Tsumune, Daisuke*; Tsubono, Takaki*; Kobayashi, Takuya; Kawamura, Hideyuki; Estournel, C.*; Marsaleix, P.*; Lanerolle, L.*; Mehra, A.*; et al.

Elements, 8(3), p.207 - 212, 2012/06

 Times Cited Count:79 Percentile:91.98(Geochemistry & Geophysics)

Present status of oceanic dispersion simulations of cesium 137 ($$^{137}$$Cs) directly discharged from Fukushima Daiichi Nuclear Power Plant are reviewed using five model outputs and other available informations, focusing on estimations of discharged amount of $$^{137}$$Cs and subsequent dispersion in a region off Fukushima during March and April, 2011. Common aspects and discrepancies among the simulated results are described. While the discharged amount spreads from about 1 to 27 P Bq of $$^{137}$$Cs among the estimates, the values obtained from the five models indicate 2 to 4 P Bq. With these total amounts and time evolutions of the discharge rate, mimicking observed $$^{137}$$Cs concentration near FDNPP, as a source for the dispersion calculation, all the five models simulated the $$^{137}$$Cs dispersion in the ocean reasonably well corresponding to the observed distributions.

52 (Records 1-20 displayed on this page)