Sanada, Yukihisa; Misono, Toshiharu; Shiribiki, Takehiko*
Kaiyo Riko Gakkai-Shi, 27(2), p.37 - 44, 2023/12
This paper summarizes the general situation of marine monitoring conducted after the Fukushima Daiichi Nuclear Power Plant accident, the experience of development and operation of USVs, and the possibility of applying unmanned vessels as a tool for nuclear disaster prevention in the future. 0.01 Bq/L or less for seawater and 10 Bq/L or less for seabed soil. Operational tests of three USVs have been continuously conducted for use in such environmental radiation monitoring. Development of these UAVs is underway with a view to utilizing them for seawater sampling, direct measurement of the seafloor soil surface layer, and seafloor soil sampling, depending on their performance. It is necessary to promote the development of USVs for future nuclear power plant accidents.
Sato, Ikken; Yoshikawa, Shinji; Yamashita, Takuya; Shimomura, Kenta; Cibula, M.*; Mizokami, Shinya*
Nuclear Engineering and Design, 414, p.112574_1 - 112574_20, 2023/12
Johansen, M. P.*; Carpenter, J. G.*; Charmasson, S.*; Gwynn, J. P.*; McGinnity, P.*; Mori, Airi; Orr, B.*; Simon-Cornu, M.*; Osvath, I.*
Journal of Environmental Radioactivity, 268-269, p.107243_1 - 107243_10, 2023/11
Watanabe, So; Takahatake, Yoko; Ogi, Hiromichi*; Osugi, Takeshi; Taniguchi, Takumi; Sato, Junya; Arai, Tsuyoshi*; Kajinami, Akihiko*
Journal of Nuclear Materials, 585, p.154610_1 - 154610_6, 2023/11
Iwamoto, Hiroki; Meigo, Shinichiro; Satoh, Daiki; Iwamoto, Yosuke; Ishi, Yoshihiro*; Uesugi, Tomonori*; Yashima, Hiroshi*; Nishio, Katsuhisa; Sugihara, Kenta*; elik, Y.*; et al.
Nuclear Instruments and Methods in Physics Research B, 544, p.165107_1 - 165107_15, 2023/11
The lack of double-differential cross-section (DDX) data for neutron production below the incident proton energy of 200 MeV hinders the validation of spallation models in technical applications, such as research and development of accelerator-driven systems (ADSs). The present study aims to obtain experimental DDX data for ADS spallation target materials in this energy region and identify issues related to the spallation models by comparing them with the analytical predictions. The DDXs for the () reactions of Pb and Bi in the 100-MeV region were measured over an angular range of 30 to 150 using the time-of-flight method. The measurements were conducted at Kyoto University utilizing the FFAG accelerator. The DDXs obtained were compared with calculation results from Monte Carlo-based spallation models and the evaluated nuclear data library, JENDL-5. Comparison between the measured DDX and analytical values based on the spallation models and evaluated nuclear data library indicated that, in general, the CEM03.03 model demonstrated the closest match to the experimental values. Additionally, the comparison highlighted several issues that need to be addressed in order to improve the reproducibility of the proton-induced neutron-production DDX in the 100 MeV region by these spallation models and evaluated nuclear data library.
Yasumiishi, Misa*; Masoudi, P.*; Nishimura, Taku*; Ochi, Kotaro; Ye, X.*; Aldstadt, J.*; Komissarov, M.*
Radiation Measurements, 168, p.106978_1 - 106978_16, 2023/11
In this study, we surveyed air dose rates using hand-held and backpack-type scintillators in a forest of deciduous and evergreen trees in Fukushima Prefecture, Japan. The effects of topographic features on air dose rates were examined using multivariate adaptive regression splines (MARS) against five selected topographic parameters. The air dose rates were distributed unevenly in the forest, and air dose rates varied by more than 1Sv/h as a function of time, likely owing to ground wetness etc. The effect of different topographic parameters varied between survey dates. The MARS model predictions with all topographic parameters yielded an R of 0.54 or higher. To discuss whether the effect of topography on air dose rates and soil contamination levels is consistent, air dose rates measured in the field were compared with those estimated from the depth profile of radiocesium in soil. Most air dose rates estimated from the soil samples were in the range of field measurements.
Taniguchi, Takeshi*; Isobe, Kazuo*; Imada, Shogo*; Eltayeb, M. M.*; Akaji, Yasuaki*; Nakayama, Masataka; Allen, M. F.*; Aronson, E. L.*
Science of the Total Environment, 899, p.165524_1 - 165524_13, 2023/11
Dryland ecosystems experience seasonal cycles of severe drought and moderate precipitation. Desert plants typically have patchy distributions, and many may develop symbiotic relationships with root endophytic microbes to survive under the repeated wet and extremely dry conditions. Although community coalescence has been found in many systems, the colonization by functional microbes and its relationship to seasonal transitions in arid regions are not well understood. Here we examined root endophytic microbial taxa, and their traits in relation to their root colonization, during the dry and wet seasons in a hot desert of the southwestern United States. We used high-throughput DNA sequencing of 16S rRNA and ITS gene profiling of five desert shrubs, and analyzed the seasonal change in endophytic microbial lineages. In summer, Actinobacteria increased, although this was not genus-specific. For fungi, Glomeraceae selectively increased in summer. In winter, Gram-negative bacterial genera, including those capable of nitrogen fixation and plant growth promotion, increased. Neutral model analysis revealed a strong stochastic influence on endophytic bacteria but a weak effect for fungi, especially in summer. The taxa with higher frequency than that predicted by the neutral model shared environmental adaptability and symbiotic traits, whereas the frequency of pathogenic fungi was at or under the predicted value. These results suggest that community assembly of bacteria and fungi is regulated differently. The bacterial community was affected by stochastic and deterministic processes via the bacterial response to drought (response trait) and beneficial effect on plants (effect trait). For fungi, mycorrhizal fungi were selected by plants in summer. The regulation of beneficial microbes by plants in both dry and wet seasons suggests the presence of plant-soil positive feedback in this natural desert ecosystem.
Dannoshita, Hiroyuki*; Hasegawa, Hiroshi*; Higuchi, Sho*; Matsuda, Hiroshi*; Gong, W.; Kawasaki, Takuro; Harjo, S.; Umezawa, Osamu*
Scripta Materialia, 236, p.115648_1 - 115648_5, 2023/11
Sugita, Tsuyoshi; Mori, Masanobu*; Shimoyama, Iwao
Applied Clay Science, 243, p.107074_1 - 107074_8, 2023/10
We have investigated the conversion of biotite, a subgroup of clay minerals, into photocatalysts by heat treatment with CaCl. The reaction products obtained after heat treatment were examined in terms of composition, structure, and photocatalytic activity against Cr and salicylic acid (SA). When mixtures of biotite and CaCl were heated at temperatures up to 600C, the biotite crystal structure was retained, whereas a phase transformation from biotite to octahedral wadalite crystals occurred upon heating to 700C. The photocatalytic reduction rate of Cr per unit surface area and the photocatalytic degradation efficiency of SA increased significantly with increasing treatment temperature. Even the samples that retained the biotite structure after heat treatment displayed some photocatalytic activity, suggesting that this method may also be suitable for preparing photocatalysts from other common natural materials.
Vauchy, R.; Hirooka, Shun; Watanabe, Masashi; Yokoyama, Keisuke; Murakami, Tatsutoshi
Journal of Nuclear Materials, 584, p.154576_1 - 154576_11, 2023/10
Akaishi, Takaya; Hashimoto, Tadashi; Tanida, Kiyoshi; 35 of others*
Physics Letters B, 845(10), p.138128_1 - 138128_4, 2023/10
Chong, Y.*; Gholizadeh, R.*; Guo, B.*; Tsuru, Tomohito; Zhao, G.*; Yoshida, Shuhei*; Mitsuhara, Masatoshi*; Godfrey, A.*; Tsuji, Nobuhiro*
Acta Materialia, 257, p.119165_1 - 119165_14, 2023/09
Metastable titanium alloys possess excellent strain-hardening capability, but suffer from a low yield strength. As a result, numerous attempts have been made to strengthen this important structural material in the last decade. Here, we explore the contributions of grain refinement and interstitial additions in raising the yield strength of a Ti-12Mo (wt.%) metastable titanium alloy. Surprisingly, rather than strengthening the material, grain refinement actually lowers the ultimate tensile strength in this alloy. This unexpected and anomalous behavior is attributed to a significant enhancement in strain-induced martensite phase transformation, where in-situ synchrotron X-ray diffraction analysis reveals, for the first time, that this phase is much softer than the parent phase. Instead, a combination of both oxygen addition and grain refinement is found to realize an unprecedented strength-ductility synergy in a Ti-12Mo-0.3O (wt.%) alloy. The advantageous effect of oxygen solutes in this ternary alloy is twofold. Firstly, solute oxygen largely suppresses strain-induced transformation to the martensite phase, even in a fine-grained microstructure, thus avoiding the softening effect of excessive amounts of martensite. Secondly, oxygen solutes readily segregate to twin boundaries, as revealed by atom probe tomography. This restricts the growth of deformation twins, thereby promoting more extensive twin nucleation, leading to enhanced microstructural refinement. The insights from our work provide a cost-effective rationale for the design of strong yet tough metastable titanium alloys, with significant implications for more widespread use of this high strength-to-weight structural material.
Mao, W.; Gao, S.*; Gong, W.; Bai, Y.*; Harjo, S.; Park, M.-H.*; Shibata, Akinobu*; Tsuji, Nobuhiro*
Acta Materialia, 256, p.119139_1 - 119139_16, 2023/09
Transformation-induced plasticity (TRIP)-assisted steels exhibit an excellent combination of strength and ductility due to enhanced strain hardening rate associated with deformation-induced martensitic transformation (DIMT). Quantitative evaluation on the role of DIMT in strain hardening behavior of TRIP-assisted steels and alloys can provide guidance for designing advanced materials with strength and ductility synergy, which is, however, difficult since the phase composition keeps changing and both stress and plastic strain are dynamically partitioned among constituent phases during deformation. In the present study, tensile deformation with neutron diffraction measurement was performed on an Fe-24Ni-0.3C (wt.%) TRIP-assisted austenitic steel. The analysis method based on stress partitioning and phase fractions measured by neutron diffraction was proposed, by which the tensile flow stress and the strain hardening rate of the specimen were resolved into factors associated with each phase, i.e., the austenite matrix, deformation-induced martensite, and the transformation rate of DIMT after differentiation, and then the role of each factor in the global strain hardening behavior was discussed. In addition, the plastic strain partitioning between austenite and martensite was indirectly estimated using the dislocation density measured by diffraction profile analysis, which constructed the full picture of stress and strain partitioning between austenite and martensite in the material. The results suggested that both the transformation rate and the phase stress borne by the deformation-induced martensite played important roles in the global tensile properties of the material. The proposed decomposition analysis method could be widely applied to investigating mechanical behavior of multi-phase alloys exhibiting the TRIP phenomenon.
Nihei, Naoto*; Yoshimura, Kazuya
Agricultural Implications of Fukushima Nuclear Accident (IV), p.33 - 40, 2023/09
Yanagisawa, Kayo; Matsueda, Makoto; Furukawa, Makoto*; Ishiniwa, Hiroko*; Wada, Toshihiro*; Hirata, Takafumi*; Takagai, Yoshitaka*
Analyst, 148(18), p.4291 - 4299, 2023/09
Quantitative imaging of trace elements was successfully performed by online isotope dilution laser ablation inductively coupled plasma mass spectrometry (online LA-ICP-IDMS). The sample aerosols produced by LA are mixed online with the mist created from an isotopically enriched spike solution via an in-house cyclonic spray chamber, which has a gas port on the top. Quantification was continuously achieved in each spot; subsequently, quantitative imaging was realized. Fe and Sr were selected as the model elements, and their spot quantifications based on online-isotope dilution. The method was applied to actual biological hard tissues, and the results were compared with electron probe microanalyzer data.
Amenomori, Michihiro*; Tsuchiya, Harufumi; Tibet AS Collaboration*; 116 of others*
Astrophysical Journal, 954(2), p.200_1 - 200_7, 2023/09
Wang, Z.; Matsumoto, Toshinori; Duan, G.*; Matsunaga, Takuya*
Computer Methods in Applied Mechanics and Engineering, 414, p.116168_1 - 116168_49, 2023/09
Koarashi, Jun; Atarashi-Andoh, Mariko; Nishimura, Shusaku
Ecotoxicology and Environmental Safety, 262, p.115177_1 - 115177_9, 2023/09
Predicting the fate of radiocesium (Cs) vertical distribution in Japanese forest soils is key to assessing the radioecological consequences of the Fukushima Daiichi Nuclear Power Plant accident. It is well documented that in mineral soil, the Cs behavior is mostly governed by interaction with clay minerals; however, observations have also been accumulated suggesting the role of soil organic matter (SOM) in enhancing the mobility of Cs. Here, we hypothesized that soil organic carbon (SOC) concentration profile determines the ultimate vertical distribution of Cs in Japanese forest soils. To test this hypothesis, we investigated the detailed vertical distributions of Cs in four Japanese forest soils with varying SOC concentration profiles roughly half a century after global fallout in the early 1960s. Results revealed that Cs retention ratios in each of 2-cm thick soil layers were negatively correlated with SOC concentrations of the layers, across all soils and depths. This demonstrates that the long-term fate of Cs vertical distribution is predictable as a function of SOC concentration for Japanese forest soils.
Su, Y. H.; Oikawa, Kenichi; Shinohara, Takenao; Kai, Tetsuya; Horino, Takashi*; Idohara, Osamu*; Misaka, Yoshitaka*; Tomota, Yo*
International Journal of Fatigue, 174, p.107729_1 - 107729_12, 2023/09
Takayama, Yusuke; Yamamoto, Yoichi*; Goto, Takahiro*
Jiban Kogaku Janaru (Internet), 18(3), p.317 - 330, 2023/09
It has been reported that the deformation greatly increased in the secondary consolidation process in the past long-term consolidation test of 1.8 years on Na-type bentonite/sand mixed soil. Therefore, we analyzed potential contributing factors in this behavior. A long-term consolidation test for about 10 years on bentonite and kaolinite was started using the test equipment with countermeasures against these factors. In this paper, the secondary consolidation behavior of bentonite was investigated based on the long-term consolidation test data for 2.7, 3.7 and 4 years. The results were generally consistent with the conventional findings on soil mechanics that the deformation due to secondary consolidation progresses linearly with respect to logarithm of time. This test will be continued for about 10 years and longer-term secondary consolidation behavior will be investigated.