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Journal Articles

BWR lower head penetration failure test focusing on eutectic melting

Yamashita, Takuya; Sato, Takumi; Madokoro, Hiroshi; Nagae, Yuji

Annals of Nuclear Energy, 173, p.109129_1 - 109129_15, 2022/08

Journal Articles

Temporal variability of $$^{137}$$Cs concentrations in coastal sediments off Fukushima

Suzuki, Shotaro*; Amano, Yosuke*; Enomoto, Masahiro*; Matsumoto, Akira*; Morioka, Yoshiaki*; Sakuma, Kazuyuki; Tsuruta, Tadahiko; Kaeriyama, Hideki*; Miura, Hikaru*; Tsumune, Daisuke*; et al.

Science of the Total Environment, 831, p.154670_1 - 154670_15, 2022/07

Journal Articles

Online solid-phase extraction-inductively coupled plasma-quadrupole mass spectrometric quantification of $$^{90}$$Sr using $$^{88}$$Sr/$$^{86}$$Sr isotope dilution method

Yanagisawa, Kayo*; Odashima, Mizuki*; Matsueda, Makoto; Furukawa, Makoto*; Takagai, Yoshitaka*

Talanta, 244, p.123442_1 - 123442_7, 2022/07

The determination of a low concentration of $$^{90}$$Sr was achieved by the combination of online SPE-ICP-QMS and ID method using $$^{88}$$Sr/$$^{86}$$Sr ratio. No requirement of radioactive standard material and the preparation process of the calibration curve was in the quantification process and data acquisition can be in one-shot sample injection. The proposed method allowed the rapid (within 15 min/sample) quantification of $$^{90}$$Sr in the presence of significant interferences such as isobaric $$^{90}$$Zr and other elements. The LOD for $$^{90}$$Sr was 5.6 Bq/L for a 10 mL injection and this could be improved by simply increasing the sample volume injected.

Journal Articles

Leaching behavior of multiphase solidified melt prepared from stainless steel and Zircaloy

Ikeuchi, Hirotomo

Journal of Nuclear Science and Technology, 59(6), p.768 - 780, 2022/06

JAEA Reports

Annual report for FY2019 on the activities of Naraha Center for Remote Control Technology Development (April 1, 2019 - March 31, 2020)

Naraha Center for Remote Control Technology Development, Fukushima Research Insitute

JAEA-Review 2021-069, 40 Pages, 2022/05

JAEA-Review-2021-069.pdf:2.45MB

Naraha Center for Remote Control Technology Development (NARREC) was established in Japan Atomic Energy Agency to promote a decommissioning work of Fukushima Daiichi Nuclear Power Station (Fukushima Daiichi NPS). NARREC consists of a Full-scale Mock-up Test Building and Research Management Building. Various test facilities are installed in these buildings for the decommissioning work of Fukushima Daiichi NPS. These test facilities are intended to be used for various users, such as companies engaged in the decommissioning work, research and development institutions, educational institutions, etc. The number of NARREC facility users was 64 in FY2019. We participated booth exhibitions and presentations on the decommissioning related events. Moreover, we also contributed to the development of human resources by supporting the 4th Creative Robot Contest for Decommissioning for simulated fuel debris recovery task utilizing a mock-up made of cardboard. This report summarizes the activities of NARREC in FY2019, such as the utilization of facilities and equipment of NARREC, the development of remote control technologies for supporting the decommissioning work, arrangement of the remote control machines for emergency response, and training for operators by using the machines. Incidentally, the site tour of NARREC was called off from March to June 2020 because of the COVID-19.

Journal Articles

Chemical species of iodine during sorption by activated carbon; Effects of original chemical species and fulvic acids

Kato, Tomoaki; Kozai, Naofumi; Tanaka, Kazuya; Kaplan, D. I.*; Utsunomiya, Satoshi*; Onuki, Toshihiko

Journal of Nuclear Science and Technology, 59(5), p.580 - 589, 2022/05

This study reports the effect of fulvic acids, which is a natural organic substance generally contained in groundwater, on the oxidation states of radioactive iodine anions (iodide and iodate). Iodide and iodate are contained in the contaminated water of the Fukushima Daiichi Nuclear Power Plant and supposed to be removed by activated carbon (AC) via adsorption. When fulvic acids does not exist in the experimental system, the adsorption of iodide on AC was less than that of iodate and their oxidation states after the adsorption were not changed. When fulvic acids existed, a fraction of the adsorbed iodate was reduced to iodide. This result indicates that the reduction of the adsorbed iodate progresses during the storage of the spent AC.

Journal Articles

Development of a laser-driven ultrasonic technology for characterizations of heated and aged concrete samples

Yamada, Tomonori; Daido, Hiroyuki*; Shibata, Takuya

Journal of Nuclear Science and Technology, 59(5), p.614 - 628, 2022/05

Journal Articles

Simulation of the self-propagating hydrogen-air premixed flame in a closed-vessel by an open-source CFD code

Thwe, T. A.; Terada, Atsuhiko; Hino, Ryutaro; Nagaishi, Ryuji; Kadowaki, Satoshi

Journal of Nuclear Science and Technology, 59(5), p.573 - 579, 2022/05

The simulations of the combustion of self-propagating hydrogen-air premixed flame are performed by an open-source CFD code. The flame propagation behavior, flame radius, temperature and pressure are analyzed by varying the initial laminar flame speed and grid size. When the initial laminar speed increases, the thermal expansion effects become strong which leads the increase of flame radius along with the increase of flame surface area, flame temperature and pressure. A new laminar flame speed model derived previously from the results of experiment is also introduced to the code and the obtained flame radii are compared with those from the experiments. The formation of cellular flame fronts is captured by simulation and the cell separation on the flame surface vividly appears when the gird resolution becomes sufficiently higher. The propagation behavior of cellular flame front and the flame radius obtained from the simulations have the reasonable agreement with the previous experiments.

Journal Articles

Migration processes of radioactive cesium in the Fukushima nearshore area; Impacts of riverine input and resuspension

Misono, Toshiharu; Nakanishi, Takahiro; Tsuruta, Tadahiko; Shiribiki, Takehiko; Sanada, Yukihisa

Marine Pollution Bulletin, 178, p.113597_1 - 113597_9, 2022/05

It is essential to evaluate secondary migration caused by riverine input and resuspension from seabed sediments to estimate the future distribution of radioactive cesium ($$^{137}$$Cs) in the coastal area off Fukushima Prefecture. In particular, the inflow from rivers cannot be ignored because most of the $$^{137}$$Cs inflow from rivers is deposited on the coast without elute into seawater. Two mooring systems were installed near the Ukedo River's mouth (Fukushima Prefecture) from February 2017 to February 2018. The first contained a sediment trap system, collecting sinking particles during the period. The second comprised a turbidity sensor and a current sensor. The contribution of resuspension and inflow from the river to the mass flux was quantitatively evaluated using multiple regression equations. The results showed that resuspension caused 79%-83% of secondary $$^{137}$$Cs migration in nearshore areas, whereas the influence of riverine $$^{137}$$Cs input on the sediment was only 7% per year.

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

Post-test analyses of the CMMR-4 test

Yamashita, Takuya; Madokoro, Hiroshi; Sato, Ikken

Journal of Nuclear Engineering and Radiation Science, 8(2), p.021701_1 - 021701_13, 2022/04

Journal Articles

Depletion calculation of subcritical system with consideration of spontaneous fission reaction

Riyana, E. S.; Okumura, Keisuke; Sakamoto, Masahiro; Matsumura, Taichi; Terashima, Kenichi

Journal of Nuclear Science and Technology, 59(4), p.424 - 430, 2022/04

Journal Articles

Distribution, dynamics, and fate of radiocesium derived from FDNPP accident in the ocean

Otosaka, Shigeyoshi*; Kamidaira, Yuki; Ikenoue, Tsubasa; Kawamura, Hideyuki

Journal of Nuclear Science and Technology, 59(4), p.409 - 423, 2022/04

After the accident at Fukushima Daiichi Nuclear Power Plant (FDNPP), many oceanographic observations were carried out from various perspectives. Numerical simulations were also effectively applied to understand the distribution of radionunclides. By integrating these results, the dynamics of the accident-derived radionuclides in the ocean were highlighted. The transport processes of the accident-derived radionuclides to the ocean include (1) direct discharge to the ocean, (2) deposition in the ocean via the atmosphere, and (3) inflow from rivers after deposition to the land surface. In the case of $$^{137}$$Cs, one of major accident-derived radionuclides, most of the supply to the ocean immediately after the accident (8-21 PBq) was estimated to be due to processes (1) and (2). The amount of $$^{137}$$Cs accumulated on the seafloor is only about 1% (0.2PBq) of the amount carried to the ocean, but it remains in the sediments in the coastal area for a long period of time and gradually migrates to the seawater and ecosystems near the seafloor.

Journal Articles

Estimation of long-term ex-vessel debris cooling behavior in Fukushima Daiichi Nuclear Power Plant unit 3

Sato, Ikken; Yamaji, Akifumi*; Li, X.*; Madokoro, Hiroshi

Mechanical Engineering Journal (Internet), 9(2), p.21-00436_1 - 21-00436_17, 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

Contamination processes of tree components in Japanese forest ecosystems affected by the Fukushima Daiichi Nuclear Power Plant accident $$^{137}$$Cs fallout

Ota, Masakazu; Koarashi, Jun

Science of the Total Environment, 816, p.151587_1 - 151587_21, 2022/04

In forests affected by the Fukushima Daiichi Nuclear Power Plant accident, trees became contaminated with $$^{137}$$Cs. However, $$^{137}$$Cs transfer processes determining tree contamination (particularly for stem wood, which is a prominent commercial resource in Fukushima) remain insufficiently understood. This study proposes a model for simulating the dynamic behavior of $$^{137}$$Cs in a forest tree-litter-soil system and applied it to two contaminated forests (cedar plantation and natural oak stand) in Fukushima. The model-calculated results and inter-comparison of the results with measurements elucidated the relative impact of distinct $$^{137}$$Cs transfer processes determining tree contamination. The transfer of $$^{137}$$Cs to trees occurred mostly ($$>$$ 99%) through surface uptake of $$^{137}$$Cs directly trapped by leaves or needles and bark during the fallout. By contrast, root uptake of $$^{137}$$Cs from the soil was unsubstantial and several orders of magnitude lower than the surface uptake over a 50-year period following the accident. As a result, the internal contamination of the trees proceeded through an enduring recycling (translocation) of $$^{137}$$Cs absorbed on the tree surface at the time of the accident. A significant surface uptake of $$^{137}$$Cs at the bark was identified, contributing 100% (leafless oak tree) and 30% (foliated cedar tree; the remaining surface uptake occurred at the needles) of the total $$^{137}$$Cs uptake by trees. It was suggested that the trees growing at the study sites are currently (as of 2021) in a decontamination phase; the activity concentration of $$^{137}$$Cs in the stem wood decreases by 3% per year, mainly through radioactive decay of $$^{137}$$Cs and partly through a dilution effect from tree growth.

Journal Articles

Effect of $$^{90}$$Sr dissolved solution on corrosion potential of type 316L stainless steel

Aoyama, Takahito; Kato, Chiaki; Sato, Tomonori; Sano, Naruto; Yamashita, Naoki; Ueno, Fumiyoshi

Zairyo To Kankyo, 71(4), p.110 - 115, 2022/04

no abstracts in English

JAEA Reports

HAIROWorldPlugin operation manual (Revised edition)

Suzuki, Kenta; Yashiro, Hiroshi; Kawabata, Kuniaki

JAEA-Testing 2021-004, 125 Pages, 2022/03

JAEA-Testing-2021-004.pdf:6.1MB

This report is updated HAIROWorldPlugin Operation Manual (JAEA-Testing 2020-009). Our motivation is to develop a robot simulator based on Choreonoid for technological development to contribute the decommissioning work at the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company Holdings, Inc. Choreonoid is an open source simulator which calculates the behavior of robots. We are developing HAIROWorldPlugin which is an extended function of Choreonoid for providing a virtual decommissioning experience. In the latest HAIROWorldPlugin, the several functions were additionally implemented. In particular, we implemented new functionalities: logging a collision status between a robot and an object, showing and logging a status of the joystick input signals, generating an environmental object model (pipe, grating, and slope), bookmarking an often used simulation settings, and recording histories of a simulation settings. In addition, this report describes the installation of the plugin to Choreonoid on Ubuntu20.04-LTS and parameter settings of the plugin by presenting snapshots of operation windows.

JAEA Reports

Test methods for robots for nuclear emergency response and decommissioning; Test for maneuvering robot arm over an obstacle (JAEA-TM-0006)

Yamada, Taichi; Kawabata, Kuniaki; Abe, Hiroyuki*

JAEA-Technology 2021-033, 18 Pages, 2022/03

JAEA-Technology-2021-033.pdf:1.58MB

This report describes the test procedures for evaluating performances involved in robot arm maneuvering of remotely operated robot utilized for nuclear emergency responses and decommissioning. After the accident at Fukushima Daiichi Nuclear Power Station of the Tokyo Electric Power Company Holdings Inc. (FDNPS) occurred, remotely operated robots have been deployed and utilized in the response tasks. Such post-accident work experience and lessons learned are very valuable for developing the robots in the future. Therefore, we were motivated to develop the test methods for performance evaluation of the robot by referring with such experiences and lessons. In the response and the decommissioning tasks, robots with a robot arm were deployed for door opening, removal objects, decontamination and cleanup and so on. Some of these tasks were conducted in an environment with obstacles by robot arms maneuvering. This report describes test procedures for quantitatively evaluating the performances which are for maneuvering involving in robot arm to approach target objects in an environment with obstacles. A typical course layout and the demonstration of test are also illustrated for the references.

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