Application of USV to marine monitoring after Fukushima Daiichi Nuclear Power Plant Accident and its applicability as a nuclear disaster prevention tool

Sanada, Yukihisa; Misono, Toshiharu; Shiribiki, Takehiko*

Kaiyo Riko Gakkai-Shi, 27(2), p.37 - 44, 2023/12

https://doi.org/10.14928/amstec.27.2_37

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.

Seafood dose parameters; Updating Po retention factors for cooking, decay loss and mariculture

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

https://doi.org/10.1016/j.jenvrad.2023.107243

Neutron-production double-differential cross sections of Pb and Bi in proton-induced reactions near 100 MeV

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

https://doi.org/10.1016/j.nimb.2023.165107

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.

Root endophytic bacterial and fungal communities in a natural hot desert are differentially regulated in dry and wet seasons by stochastic processes and functional traits

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

https://doi.org/10.1016/j.scitotenv.2023.165524

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.

Conversion of clay minerals to photocatalysts for Cr reduction and salicylic acid decomposition

Sugita, Tsuyoshi; Mori, Masanobu*; Shimoyama, Iwao

Applied Clay Science, 243, p.107074_1 - 107074_8, 2023/10

https://doi.org/10.1016/j.clay.2023.107074

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.

Precise lifetime measurement of H hypernucleus using in-flight HeH reaction

Akaishi, Takaya; Hashimoto, Tadashi; Tanida, Kiyoshi; 35 of others*

Physics Letters B, 845(10), p.138128_1 - 138128_4, 2023/10

https://doi.org/10.1016/j.physletb.2023.138128

Oxygen interstitials make metastable titanium alloys strong and ductile

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

https://doi.org/10.1016/j.actamat.2023.119165

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.

Effects of radioactive cesium from suspended matter and fallout on agricultural products

Nihei, Naoto*; Yoshimura, Kazuya

Agricultural Implications of Fukushima Nuclear Accident (IV), p.33 - 40, 2023/09

https://doi.org/10.1007/978-981-19-9361-9_4

Observation of gamma rays up to 320 TeV from the middle-aged TeV pulsar wind nebula HESS J1849-000

Amenomori, Michihiro*; Tsuchiya, Harufumi; Tibet AS Collaboration*; 116 of others*

Astrophysical Journal, 954(2), p.200_1 - 200_7, 2023/09

https://doi.org/10.3847/1538-4357/acebce

Effect of soil organic matter on the fate of Cs vertical distribution in forest soils

Koarashi, Jun; Atarashi-Andoh, Mariko; Nishimura, Shusaku

Ecotoxicology and Environmental Safety, 262, p.115177_1 - 115177_9, 2023/09

https://doi.org/10.1016/j.ecoenv.2023.115177

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.