Nonferroelectric phase with loss of cycloidal magnetic structure in TbGdMnO

Ishii, Yuta*; Sakakura, Terutoshi*; Ishikawa, Yoshihisa*; Kiyanagi, Ryoji; Lustikova, J.*; Aoyama, Takuya*; Ogushi, Kenya*; Wakabayashi, Yusuke*; Kimura, Hiroyuki*; Noda, Yukio*

Physical Review B, 110(18), p.184404_1 - 184404_7, 2024/11

https://doi.org/10.1103/PhysRevB.110.184404

Records of the riverine discharge of I in riverbank sediment after the Fukushima accident

Nakanishi, Takahiro; Sakuma, Kazuyuki; Oyama, Takuya; Hagiwara, Hiroki; Suzuki, Takashi

Environmental Pollution, 355, p.124213_1 - 124213_7, 2024/08

https://doi.org/10.1016/j.envpol.2024.124213

This study investigated the transport behavior of I by riverbank surveys conducted from 2013 to 2015 in a watershed where the I/Cs activity ratio is low in the mountainous area and high in the plain as of 2011. Until 2015, the I/Cs activity ratio of the levee crown in the studied watershed was similar to that of the surrounding area in 2011. However, the I/Cs ratios of the surface riverbank sediments were all low, indicating that radionuclides transported from the mountainous area were deposited on the riverbank in the plain. The vertical distribution of the I/Cs ratio in the riverbank sediments indicated that some I and Cs deposited during the accident remained in the lower layers, but most were eroded immediately after the accident. Based on the I/Cs ratios of sediments deposited on the riverbank, which remained constant until 2015 after the accident, the amount of I discharged to the ocean was determined from the previously evaluated Cs discharge. It was calculated that 1.810 Bq and 1.210 Bq of I were discharged with sediment from the studied watershed and the contaminated river watersheds (Abukuma River and Fukushima coastal rivers, including the study river), respectively. The results of this study indicate that the continuous I discharge from the river contribute little to their amount in the seafloor sediments along the Fukushima coast.

Summary results of subsidy program for the "Project of Decommissioning, Contaminated Water and Treated Water Management (Development of Analysis and Estimation Technologies for Characterization of Fuel Debris (Development of Estimation Technologies of RPV Damaged Condition, etc.) in 2022JFY

Yamashita, Takuya; Shimomura, Kenta; Nagae, Yuji; Yamaji, Akifumi*; Mizokami, Shinya; Mitsugi, Takeshi; Koyama, Shinichi

Hairo, Osensui, Shorisui Taisaku Jigyo Jimukyoku Homu Peji (Internet), 53 Pages, 2023/10

https://dccc-program.jp/5835

JAEA performed the subsidy program for the "Project of Decommissioning, Contaminated Water and Treated Water Management (Development of Analysis and Estimation Technologies for Characterization of Fuel Debris (Development of Estimation Technologies of RPV Damaged Condition, etc.) in 2022JFY. This presentation summarized briefly the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning, Contaminated Water and Treated Water Management.

Impact of extreme typhoon events on the fluvial discharge of particulate radiocesium in Fukushima Prefecture

Nakanishi, Takahiro; Oyama, Takuya; Hagiwara, Hiroki; Sakuma, Kazuyuki

Journal of Coastal Research, 114(SI), p.310 - 314, 2021/10

https://doi.org/10.2112/JCR-SI114-063.1

The two huge typhoons in 2019, Hagibis and Bualoi, caused enormous flood damage to Fukushima. On the basis of field observations over 6 years in Ukedo River near the Fukushima Nuclear Power Plant, sediment and Cs discharges from the river catchment were quantitatively evaluated. Approximately 90% of annual sediment and Cs discharges in 2019 was occupied during the typhoons Hagibis and Bualoi events. This sediment discharge was almost twice than the discharge during the largest ever flood event since the Fukushima nuclear accident, caused by typhoon Etau in September 2015. However, Cs discharge during Hagibis and Bualoi events was two-thirds that of Etau event, because the particulate Cs concentration in river water decreased during the observation period. Moreover, Cs discharge during two typhoon events in 2019 accounted for only 0.1% of the catchment Cs deposition and the impact of radiocesium to the coastal area was extremely limited.

Quantum paramagnet near spin-state transition

Tomiyasu, Keisuke*; Ito, Naoko*; Okazaki, Ryuji*; Takahashi, Yuki*; Onodera, Mitsugi*; Iwasa, Kazuaki*; Nojima, Tsutomu*; Aoyama, Takuya*; Ogushi, Kenya*; Ishikawa, Yoshihisa*; et al.

Advanced Quantum Technologies (Internet), 1(3), p.1800057_1 - 1800057_7, 2018/12

https://doi.org/10.1002/qute.201800057

Spin-state transition, also known as spin crossover, plays a key role in diverse systems. In theory, the boundary range between the low- and high-spin states is expected to enrich the transition and give rise to unusual physical states. However, no compound that realizes a nearly degenerate critical range as the ground state without requiring special external conditions has yet been experimentally identified. This study reports that the Sc substitution in LaCoO3 destabilizes its nonmagnetic low-spin state and generates an anomalous paramagnetic state accompanied by the enhancement of transport gap and magneto-lattice-expansion as well as the contraction of Co-O distance with the increase of electron site transfer. These phenomena are not well described by the mixture of conventional low- and high-spin states, but by their quantum superposition occurring on the verge of a spin-state transition.

Dose rate distributions across the flood plains in eastern Fukushima

Nakanishi, Takahiro; Oyama, Takuya; Hagiwara, Hiroki

KEK Proceedings 2017-6, p.107 - 111, 2017/11

https://lib-extopc.kek.jp/preprints/PDF/2017/1725/1725006.pdf

At riverbanks in six rivers (Odaka, Ukedo, Takase, Kuma, Tomioka and Kido rivers) of eastern Fukushima, dose rate distribution in the cross section had been observed from January 2013 to December 2016. Dose rates in the flood plain which were flooded periodically were different from the surroundings. In rivers without reservoirs (Odaka, Takase and Kuma rivers), dose rates in the flood plain were affected by average radiocesium inventory in the whole catchments. By contrast, in rivers with reservoirs (Ukedo, Tomioka and Kido rivers), dose rates in the flood plain were affected by those in the downstream area of reservoirs and the erosion effect.

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

JAEA-Review-2017-018.pdf:17.58MB

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.

Deposition of radiocesium on the river flood plains around Fukushima

Saegusa, Hiromitsu; Oyama, Takuya; Iijima, Kazuki; Onoe, Hironori; Takeuchi, Ryuji; Hagiwara, Hiroki

Journal of Environmental Radioactivity, 164, p.36 - 46, 2016/11

https://doi.org/10.1016/j.jenvrad.2016.04.020

The environments of Fukushima have been contaminated due to the Fukushima Daiichi Nuclear Power Plant accidents caused by the Great East Japan Earthquake on March 11, 2011. Released radio-cesium mainly affects radiation dose in the environment of Fukushima. It is concerned that redistribution of the radiation dose due to water discharge will be occurred due to the transportation of radio-cesium. Especially, deposition of the transferred soil particle with radio-cesium at flood plain with downstream area is possible cause of increasing radiation dose. Therefore, it is important to understand the influence of deposition behavior of radio-cesium on radiation dose. The paper discusses the deposition behaviors of radio-cesium at river based on the data obtained from the river investigations.

Synthesized research report in the second mid-term research phase; Mizunami Underground Research Laboratory Project, Horonobe Underground Research Laboratory Project and Geo-stability Project

Hama, Katsuhiro; Mizuno, Takashi; Sasao, Eiji; Iwatsuki, Teruki; Saegusa, Hiromitsu; Sato, Toshinori; Fujita, Tomoo; Sasamoto, Hiroshi; Matsuoka, Toshiyuki; Yokota, Hideharu; et al.

JAEA-Research 2015-007, 269 Pages, 2015/08

JAEA-Research-2015-007.pdf:68.65MB
JAEA-Research-2015-007(errata).pdf:0.07MB

We have synthesised the research results from Mizunami/Horonobe URLs and geo-stability projects in the second mid-term research phase. It could be used as technical bases for NUMO/Regulator in each decision point from sitting to beginning of disposal (Principal Investigation to Detailed Investigation Phase). High quality construction techniques and field investigation methods have been developed and implemented and these will be directly applicable to the National Disposal Program (along with general assessments of hazardous natural events and processes). It will be crucial to acquire technical knowledge on decisions of partial backfilling and final closure by actual field experiments in Mizunami/Horonobe URLs as main themes for the next phases.

Colossal thermomagnetic response in the exotic superconductor URuSi

Yamashita, Takuya*; Shimoyama, Yusuke*; Haga, Yoshinori; Matsuda, Tatsuma*; Yamamoto, Etsuji; Onuki, Yoshichika; Sumiyoshi, Hiroaki*; Fujimoto, Satoshi*; Levchenko, A.*; Shibauchi, Takasada*; et al.

Nature Physics, 11(1), p.17 - 20, 2015/01

https://doi.org/10.1038/nphys3170