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Journal Articles

Current status of Geological disposal by "all-Japan" activities, 6; Post-closure safety assessment (2)

Tachi, Yukio; Saito, Takumi*; Kirishima, Akira*

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 64(5), p.290 - 295, 2022/05

no abstracts in English

Journal Articles

Radiocesium-bearing microparticles cause a large variation in $$^{137}$$Cs activity concentration in the aquatic insect ${it Stenopsyche marmorata}$ (Tricoptera: Stenopsychidae) in the Ota River, Fukushima, Japan

Ishii, Yumiko*; Miura, Hikaru*; Jo, J.*; Tsuji, Hideki*; Saito, Rie; Koarai, Kazuma; Hagiwara, Hiroki; Urushidate, Tadayuki*; Nishikiori, Tatsuhiro*; Wada, Toshihiro*; et al.

PLOS ONE (Internet), 17(5), p.e0268629_1 - e0268629_17, 2022/05

We investigated the variability in $$^{137}$$Cs activity concentration in individual aquatic insects in detritivorous caddisfly (${it Stenopsyche marmorata}$) and carnivorous dobsonfly (${it Protohermes grandis}$) larvae from the Ota River, Fukushima. Caddisfly larvae showed sporadically higher radioactivity, whereas no such outliers were observed in dobsonfly larvae. Autoradiography and scanning electron microscopy analyses confirmed that these caddisfly larvae samples contained radiocesium-bearing microparticles (CsMPs), which are insoluble Cs-bearing silicate glass particles. CsMPs were also found in potential food sources of caddisfly larvae, such as periphyton and drifting particulate organic matter, indicating that larvae may ingest CsMPs along with food particles of similar size. Although CsMPs distribution and uptake by organisms in freshwater ecosystems is relatively unknown, our study demonstrates that CsMPs can be taken up by aquatic insects.

Journal Articles

Sorption of Cs$$^{+}$$ and Eu$$^{3+}$$ ions onto sedimentary rock in the presence of gamma-irradiated humic acid

Zhao, Q.*; Saito, Takeshi*; Miyakawa, Kazuya; Sasamoto, Hiroshi; Kobayashi, Taishi*; Sasaki, Takayuki*

Journal of Hazardous Materials, 428, p.128211_1 - 128211_10, 2022/04

The influence of humic acid and its radiological degradation on the sorption of Cs$$^{+}$$ and Eu$$^{3+}$$ by sedimentary rock was investigated to understand the sorption process of metal ions and humic substances. Aldrich humic acid (HA) solution was irradiated with different doses of gamma irradiation using a Co-60 gamma-ray source prior to the contact between the metal ions and the solid sorbent. The HA molecule decomposed to smaller molecules with a lower complexation affinity. Batch sorption experiments were performed to evaluate the effect of gamma-irradiated HA on the sorption of Cs$$^{+}$$ and Eu$$^{3+}$$ ions. The addition of non-irradiated HA weakened the sorption of Eu because of the lower sorption of the neutral or negatively charged Eu-HA complexes compared with free Eu ions. The sorption of monovalent Cs ions was barely affected by the presence of HA and its gamma irradiation. The concentration ratio of HA complexed species and non-complexed species in the solid and liquid phases was evaluated by sequential filtration and chemical equilibrium calculations. The ratios supported the minimal contribution of HA to Cs sorption. However, the concentration ratio for Eu$$^{3+}$$ in the liquid phase was high, indicating that the complexing ability of HA to Eu$$^{3+}$$ was higher than that of HA to Cs$$^{+}$$ ions. Therefore, the sorption of free Eu$$^{3+}$$ would predominate with the gamma irradiation dose applied to the HA solution under a radiation field near the HLW package.

Journal Articles

Volatilization of B$$_{4}$$C control rods in Fukushima Daiichi nuclear reactors during meltdown; B-Li isotopic signatures in cesium-rich microparticles

Fueda, Kazuki*; Takami, Ryu*; Minomo, Kenta*; Morooka, Kazuya*; Horie, Kenji*; Takehara, Mami*; Yamasaki, Shinya*; Saito, Takumi*; Shiotsu, Hiroyuki; Onuki, Toshihiko*; et al.

Journal of Hazardous Materials, 428, p.128214_1 - 128214_10, 2022/04

Journal Articles

Time-resolved 3D visualization of liquid jet breakup and impingement behavior in a shallow liquid pool

Kimura, Fumihito*; Yamamura, Sota*; Fujiwara, Kota*; Yoshida, Hiroyuki; Saito, Shimpei*; Kaneko, Akiko*; Abe, Yutaka*

Nuclear Engineering and Design, 389, p.111660_1 - 111660_11, 2022/04

Journal Articles

Magnetoelastic anisotropy in Heusler-type Mn$$_{2-delta}$$CoGa$$_{1+delta}$$ films

Kubota, Takahide*; Takano, Daichi*; Kota, Yohei*; Mohanty, S.*; Ito, Keita*; Matsuki, Mitsuhiro*; Hayashida, Masahiro*; Sun, M.*; Takeda, Yukiharu; Saito, Yuji; et al.

Physical Review Materials (Internet), 6(4), p.044405_1 - 044405_12, 2022/04

Journal Articles

Dispersive XAFS Study on the Laser-Induced Reduction of a Rh$$^{3+}$$ ion complex; Presence of a Rh$$^{+}$$ Intermediate in Direct Photoreduction

Saeki, Morihisa*; Matsumura, Daiju; Nakanishi, Ryuzo*; Yomogida, Takumi; Tsuji, Takuya; Saito, Hiroyuki*; Oba, Hironori*

Journal of Physical Chemistry C, 126(12), p.5607 - 5616, 2022/03

The reaction mechanism of the direct photoreduction of a Rh$$^{3+}$$ ion complex to a Rh$$^{0}$$ species induced by pulsed ultraviolet laser irradiation was studied using dispersive X-ray absorption fine structure (DXAFS) spectroscopy. The time-resolved X-ray absorption near edge structure (XANES) showed the absence of isosbestic points and suggested that more than two Rh$$^{n+}$$ species contribute toward the direct photoreduction of Rh$$^{3+}$$. Analysis of the time-resolved XANES data by singular value deposition showed that the direct photoreduction involves three Rh$$^{n+}$$ species. Multivariate curve resolution by alternating least-squares analysis (MCR-ALS) of the time-resolved XANES data gave pure spectra and concentration profiles of the three Rh$$^{n+}$$ species. The Rh$$^{n+}$$ species were assigned to Rh$$^{3+}$$, Rh$$^{+}$$, and Rh$$^{0}$$ species based on the features of the pure XANES spectra. The concentration profiles suggested that the direct photoreduction proceeds in the order of Rh$$^{3+}$$ $$rightarrow$$ Rh$$^{+}$$ $$rightarrow$$ Rh$$^{0}$$. A reaction mechanism, which was proposed involving photoreductions of Rh$$^{3+}$$ and Rh$$^{+}$$, photoinduced autocatalytic reductions of Rh$$^{3+}$$ and Rh$$^{+}$$, and photooxidation of Rh$$^{+}$$, well reproduced the concentration profiles of three Rh$$^{n+}$$ species.

Journal Articles

Improving the safety of the high temperature gas-cooled reactor "HTTR" based on Japan's new regulatory requirements

Hamamoto, Shimpei; Shimizu, Atsushi; Inoi, Hiroyuki; Tochio, Daisuke; Homma, Fumitaka; Sawahata, Hiroaki; Sekita, Kenji; Watanabe, Shuji; Furusawa, Takayuki; Iigaki, Kazuhiko; et al.

Nuclear Engineering and Design, 388, p.111642_1 - 111642_11, 2022/03

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, the Japan Atomic Energy Agency adapted High-Temperature engineering Test Reactor (HTTR) to meet the new regulatory requirements that began in December 2013. The safety and seismic classifications of the existing structures, systems, and components were discussed to reflect insights regarding High Temperature Gas-cooled Reactors (HTGRs) that were acquired through various HTTR safety tests. Structures, systems, and components that are subject to protection have been defined, and countermeasures to manage internal and external hazards that affect safety functions have been strengthened. Additionally, measures are in place to control accidents that may cause large amounts of radioactive material to be released, as a beyond design based accident. The Nuclear Regulatory Commission rigorously and appropriately reviewed this approach for compliance with the new regulatory requirements. After nine amendments, the application to modify the HTTR's installation license that was submitted in November 2014 was approved in June 2020. This response shows that facilities can reasonably be designed to meet the enhanced regulatory requirements, if they reflect the characteristics of HTGRs. We believe that we have established a reference for future development of HTGR.

Journal Articles

Structures of magnetic excitations in the spin-$$frac{1}{2}$$ kagome-lattice antiferromagnets Cs$$_{2}$$Cu$$_{3}$$SnF$$_{12}$$ and Rb$$_{2}$$Cu$$_{3}$$SnF$$_{12}$$

Saito, Mutsuki*; Takagishi, Ryunosuke*; Kurita, Nubuyuki*; Watanabe, Masari*; Tanaka, Hidekazu*; Nomura, Ryuji*; Fukumoto, Yoshiyuki*; Ikeuchi, Kazuhiko*; Kajimoto, Ryoichi

Physical Review B, 105(6), p.064424_1 - 064424_15, 2022/02

Journal Articles

Uranium (VI) sorption on illite under varying carbonate concentrations; Batch experiments, modeling, and cryogenic time-resolved laser fluorescence spectroscopy study

Mei, H.; Aoyagi, Noboru; Saito, Takumi*; Kozai, Naofumi; Sugiura, Yuki; Tachi, Yukio

Applied Geochemistry, 136, p.105178_1 - 105178_8, 2022/01

Journal Articles

Bayesian sparse modeling of extended X-ray absorption fine structure to determine interstitial oxygen positions in yttrium oxyhydride epitaxial thin film

Kumazoe, Hiroyuki*; Igarashi, Yasuhiko*; Iesari, F.*; Shimizu, Ryota*; Komatsu, Yuya*; Hitosugi, Taro*; Matsumura, Daiju; Saito, Hiroyuki*; Iwamitsu, Kazunori*; Okajima, Toshihiko*; et al.

AIP Advances (Internet), 11(12), p.125013_1 - 125013_5, 2021/12

Journal Articles

Space weather benchmarks on Japanese society

Ishii, Mamoru*; Shiota, Daiko*; Tao, Chihiro*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Ishii, Takako*; Ichimoto, Kiyoshi*; Kataoka, Ryuho*; Koga, Kiyokazu*; Kubo, Yuki*; et al.

Earth, Planets and Space (Internet), 73(1), p.108_1 - 108_20, 2021/12

 Times Cited Count:1 Percentile:72.01(Geosciences, Multidisciplinary)

We surveyed the relationship between the scale of space weather events and their occurrence rate in Japan and we discussed the social impact of these phenomena during the Project for Solar-Terrestrial Environment Prediction (PSTEP). The information was compiled for domestic users of space weather forecasts for appropriate preparedness against space weather disasters. This paper gives a comprehensive summary of the survey, focusing on the fields of electricity, satellite operations, communication and broadcasting, satellite positioning usage, aviation, human space activity, and daily life on the Earth's surface, using the cutting-edge knowledge of space weather. Quantitative estimations of the economic impact of space weather events on electricity and aviation are also given.

Journal Articles

${it In situ}$ spectrometry of terrestrial gamma rays using portable germanium detectors in area of 80 km radius around the Fukushima Daiichi Nuclear Power Plant

Mikami, Satoshi; Tanaka, Hiroyuki*; Okuda, Naotoshi*; Sakamoto, Ryuichi*; Ochi, Kotaro; Uno, Kiichiro*; Matsuda, Norihiro; Saito, Kimiaki

Nihon Genshiryoku Gakkai Wabun Rombunshi, 20(4), p.159 - 178, 2021/12

In order to know the background radiation level where the area affected by the Fukushima Daiichi Nuclear Power Plant accident in 2011, terrestrial gamma rays had been measured by using portable germanium detectors repeatedly from 2013 through 2019, at 370 locations within 80 km radius area centered on the Fukushima Daiichi Nuclear Power Plant. Radioactive concentrations of Uranium 238, Thorium 232, Potassium 40 and kerma rates in air due to terrestrial gamma rays were obtained at those locations based on the method of ICRU report 53. Averaged concentrations of $$^{238}$$U, $$^{232}$$Th and $$^{40}$$K were 18.8, 22.7, 428 Bq/kg, respectively, and kerma rate in air over the area was found to be 0.0402 $$mu$$Gy/h. The obtained kerma rates in air were compared to those reported in literatures. It was confirmed that the data were correlated with each other, and were agreed within the range of their uncertainty. This is because the kerma rate in air due to terrestrial gamma rays is depend on geology. The similar trend to previous findings was observed that the kerma rate in air at locations geologically classified as Mesozoic era, Granite and Rhyolite were statistically significantly higher than the others.

Journal Articles

Distinct variation of electronic states due to annealing in $$T'$$-type La$$_{1.8}$$Eu$$_{0.2}$$CuO$$_{4}$$ and Nd$$_{2}$$CuO$$_{4}$$

Asano, Shun*; Ishii, Kenji*; Matsumura, Daiju; Tsuji, Takuya; Kudo, Kota*; Taniguchi, Takanori*; Saito, Shin*; Sunohara, Toshiki*; Kawamata, Takayuki*; Koike, Yoji*; et al.

Physical Review B, 104(21), p.214504_1 - 214504_7, 2021/12

JAEA Reports

Impact assessment for internal flooding in HTTR (High temperature engineering test reactor)

Tochio, Daisuke; Nagasumi, Satoru; Inoi, Hiroyuki; Hamamoto, Shimpei; Ono, Masato; Kobayashi, Shoichi; Uesaka, Takahiro; Watanabe, Shuji; Saito, Kenji

JAEA-Technology 2021-014, 80 Pages, 2021/09

JAEA-Technology-2021-014.pdf:5.87MB

In response to the new regulatory standards established in response to the accident at TEPCO's Fukushima Daiichi Nuclear Power Station in March 2011, measures and impact assessments related to internal flooding at HTTR were carried out. In assessing the impact, considering the characteristics of the high-temperature gas-cooled reactor, flooding due to assumed damage to piping and equipment, flooding due to water discharge from the system installed to prevent the spread of fire, and flooding due to damage to piping and equipment due to an earthquake. The effects of submersion, flooding, and flooding due to steam were evaluated for each of them. The impact of the overflow of liquids containing radioactive materials outside the radiation-controlled area was also evaluated. As a result, it was confirmed that flooding generated at HTTR does not affect the safety function of the reactor facility by taking measures.

Journal Articles

Present status and future perspective of R&D for 3D-ADRES (3-Dimensional Air Dose Rate Evaluation System); Evaluation scheme for air dose rate distributions in city and forest areas towards Fukushima's revitalization

Kim, M.; Malins, A.; Machida, Masahiko; Yoshimura, Kazuya; Saito, Kimiaki; Yoshida, Hiroko*; Yanagi, Hideaki*; Yoshida, Toru*; Hasegawa, Yukihiro*

RIST News, (67), p.3 - 15, 2021/09

no abstracts in English

Journal Articles

Detecting halfmetallic electronic structures of spintronic materials in a magnetic field

Fujiwara, Hidenori*; Umetsu, Rie*; Kuroda, Fumiaki*; Miyawaki, Jun*; Kashiuchi, Toshiyuki*; Nishimoto, Kohei*; Nagai, Kodai*; Sekiyama, Akira*; Irizawa, Akinori*; Takeda, Yukiharu; et al.

Scientific Reports (Internet), 11(1), p.18654_1 - 18654_9, 2021/09

 Times Cited Count:0

Journal Articles

Observation of the angular momentum compensation by Barnett effect and NMR

Chudo, Hiroyuki; Imai, Masaki; Matsuo, Mamoru; Maekawa, Sadamichi; Saito, Eiji

Journal of the Physical Society of Japan, 90(8), p.081003_1 - 081003_11, 2021/08

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

Journal Articles

Rabi-oscillation spectroscopy of the hyperfine structure of muonium atoms

Nishimura, Shoichiro*; Torii, Hiroyuki*; Fukao, Yoshinori*; Ito, Takashi; Iwasaki, Masahiko*; Kanda, Sotaro*; Kawagoe, Kiyotomo*; Kawall, D.*; Kawamura, Naritoshi*; Kurosawa, Noriyuki*; et al.

Physical Review A, 104(2), p.L020801_1 - L020801_6, 2021/08

 Times Cited Count:0 Percentile:0.01(Optics)

Journal Articles

Correction to Transport and redistribution of radiocesium in Fukushima fallout through rivers

Taniguchi, Keisuke*; Onda, Yuichi*; Smith, H. G.*; Blake, W.*; Yoshimura, Kazuya; Yamashiki, Yosuke*; Kuramoto, Takayuki*; Saito, Kimiaki

Environmental Science & Technology, 55(13), P. 9394, 2021/07

 Times Cited Count:0 Percentile:0.53(Engineering, Environmental)

no abstracts in English

1217 (Records 1-20 displayed on this page)