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Journal Articles

Recent improvements of probabilistic fracture mechanics analysis code PASCAL for reactor pressure vessels

Lu, K.; Takamizawa, Hisashi; Katsuyama, Jinya; Li, Y.

International Journal of Pressure Vessels and Piping, 199, p.104706_1 - 104706_13, 2022/10

 Times Cited Count:1 Percentile:0.01(Engineering, Multidisciplinary)

Journal Articles

Measurement of nuclide production cross sections for proton-induced reactions on $$^{rm nat}$$Ni and $$^{rm nat}$$Zr at 0.4, 1.3, 2.2, and 3.0 GeV

Takeshita, Hayato*; Meigo, Shinichiro; Matsuda, Hiroki*; Iwamoto, Hiroki; Nakano, Keita; Watanabe, Yukinobu*; Maekawa, Fujio

Nuclear Instruments and Methods in Physics Research B, 527, p.17 - 27, 2022/09

To improve accuracy of nuclear design of accelerator driven nuclear transmutation systems and so on, nuclide production cross sections on Ni and Zr were measured for GeV energy protons. The measured results were compared with PHITS calculations, JENDL/HE-2007 and so on.

Journal Articles

Structure, stability, and actinide leaching of simulated nuclear fuel debris synthesized from UO$$_{2}$$, Zr, and stainless-steel

Kirishima, Akira*; Akiyama, Daisuke*; Kumagai, Yuta; Kusaka, Ryoji; Nakada, Masami; Watanabe, Masayuki; Sasaki, Takayuki*; Sato, Nobuaki*

Journal of Nuclear Materials, 567, p.153842_1 - 153842_15, 2022/08

 Times Cited Count:0

To understand the chemical structure and stability of nuclear fuel debris consisting of UO$$_{2}$$, Zr, and Stainless Steel (SUS) generated by the Fukushima Daiichi Nuclear Power Plant accident in Japan in 2011, simulated debris of the UO$$_{2}$$-SUS-Zr system and other fundamental component systems were synthesized and characterized. The simulated debris were synthesized by heat treatment for 1 to 12 h at 1600$$^{circ}$$C, in inert (Ar) or oxidative (Ar + 2% O$$_{2}$$) atmospheres. $$^{237}$$Np and $$^{241}$$Am tracers were doped for the leaching tests of these elements and U from the simulated debris. The characterization of the simulated debris was conducted by XRD, SEM-EDX, Raman spectroscopy, and M$"o$ssbauer spectroscopy, which provided the major uranium phase of the UO $$_{2}$$-SUS-Zr debris was the solid solution of U$$^{mathrm{IV}}$$O$$_{2}$$ (s.s.) with Zr(IV) and Fe(II) regardless of the treatment atmosphere. The long-term immersion test of the simulated debris in pure water and that in seawater revealed the macro scale crystal structure of the simulated debris was chemically very stable in the wet condition for a year or more. Furthermore, the leaching test results showed that the actinide leaching ratios of U, Np, Am from the UO$$_{2}$$-SUS-Zr debris were very limited and less than 0.08 % for all the experiments in this study.

JAEA Reports

Development of semantic survey map building system using semi-autonomous mobile robots for surveying of disaster area and gathering of information in nuclear power station (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Polytechnic University*

JAEA-Review 2022-011, 80 Pages, 2022/07

JAEA-Review-2022-011.pdf:5.42MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of semantic survey map building system using semi-autonomous mobile robots for surveying of disaster area and gathering of information in nuclear power station" conducted from FY2018 to FY2021 (this contract was extended to FY2021). Since the final year of this proposal was FY2021, the results for four fiscal years were summarized. The present study aims to research and develop semi-autonomous mobile robot systems (multi-sensor fusion system, semantic simultaneous localization and mapping (SLAM), system for traversable-route learning and safe traversable-route presentation, etc.) that simply, safely, and rapidly make semantic survey maps including multiple information

Journal Articles

Measurements of thermal-neutron capture cross-section of the $$^{237}$$Np(n, $$gamma$$) reaction with TC-Pn in KUR

Nakamura, Shoji; Endo, Shunsuke; Kimura, Atsushi; Shibahara, Yuji*

KURNS Progress Report 2021, P. 93, 2022/07

In terms of nuclear transmutation studies of minor actinides in nuclear wastes, the present work selected $$^{237}$$Np among them and aimed to measure the thermal-neutron capture cross-section of $$^{237}$$Np using a well-thermalized neutron field by a neutron activation method because there have been discrepancies among reported cross-section data. A $$^{237}$$Np standard solution was used for irradiation samples. The thermal-neutron flux at an irradiation position was measured with flux monitors: $$^{45}$$Sc, $$^{59}$$Co, $$^{98}$$Mo, $$^{181}$$Ta and $$^{197}$$Au. The $$^{237}$$Np sample was irradiated together with the flux monitors for 30 minutes in the graphite thermal column equipped in the Kyoto University Research Reactor. The similar irradiation was repeated once more to confirm the reproducibility of the results. After irradiation, the $$^{237}$$Np samples were quantified using 312-keV gamma-ray emitted from $$^{233}$$Pa in radiation equilibrium with $$^{237}$$Np. The reaction rates of $$^{237}$$Np were obtained from the peak net counts of gamma-rays emitted from generated $$^{238}$$Np, and then the thermal-neutron capture cross-section of $$^{237}$$Np was found to be 173.8$$pm$$4.7 barn by averaging the results obtained by the two irradiations. The present result was in agreement with the reported data given by a time-of-flight method within a limit of uncertainty.

Journal Articles

Evolution of the reaction and alteration of granite with Ordinary Portland cement leachates; Sequential flow experiments and reactive transport modelling

Bateman, K.*; Murayama, Shota*; Hanamachi, Yuji*; Wilson, J.*; Seta, Takamasa*; Amano, Yuki; Kubota, Mitsuru*; Ouchi, Yuji*; Tachi, Yukio

Minerals (Internet), 12(7), p.883_1 - 883_20, 2022/07

Journal Articles

Accumulation mechanisms of radiocaesium within lichen thallus tissues determined by means of ${it in situ}$ microscale localisation observation

Dohi, Terumi; Iijima, Kazuki; Machida, Masahiko; Suno, Hiroya*; Omura, Yoshihito*; Fujiwara, Kenso; Kimura, Shigeru*; Kanno, Futoshi*

PLOS ONE (Internet), 17(7), p.e0271035_1 - e0271035_21, 2022/07

Journal Articles

Dynamic probabilistic risk assessment of nuclear power plants using multi-fidelity simulations

Zheng, X.; Tamaki, Hitoshi; Sugiyama, Tomoyuki; Maruyama, Yu

Reliability Engineering & System Safety, 223, p.108503_1 - 108503_12, 2022/07

 Times Cited Count:1 Percentile:0.03(Engineering, Industrial)

JAEA Reports

Study on radioactivity evaluation method of research reactors using DORT and MCNP codes

Kochiyama, Mami; Sakai, Akihiro

JAEA-Technology 2022-009, 56 Pages, 2022/06

JAEA-Technology-2022-009.pdf:4.15MB

It is necessary to evaluate radioactivity inventory in wastes before disposal of low-level radioactive wastes generated from dismantling research reactors. It is efficient for owners of each research reactor to use a common radioactive evaluation method in order to comply with the license application for disposal facility. In this report, neutron transport and activation calculations were carried out for the Rikkyo University research reactor in order to examine a common radioactivity evaluation method for burial disposal of radioactive wastes generated by dismantling. We adopted the neutron transport codes DORT and MCNP and the activation code ORIGEN-S with cross-section libraries based on JENDL-4.0 and JENDL/AD-2017. The radioactivity concentrations obtained by the radiochemical analysis and both calculation codes were in agreement by 0.4 to 3 times. Therefore, by appropriately considering this difference, the radioactivity evaluation method by DORT, MCNP and ORIGEN-S can be applied to the radioactivity evaluation for buried disposal. In order to classify wastes from dismantling by clearance or buried disposal method according to their radioactivity levels, we also created radioactivity concentration distributions in the concrete area and graphite thermal column area.

JAEA Reports

Basic research on the stability of fuel debris including alloy phase (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2022-009, 73 Pages, 2022/06

JAEA-Review-2022-009.pdf:2.08MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the "Basic research on the stability of fuel debris including alloy phase" conducted from FY2018 to FY2021 (this contract was extended to FY2021). Since the final year of this proposal was FY2021, the results for four fiscal years were summarized. The present study focus on fuel debris consisting of oxide phase and alloy phase generated by the high temperature chemical reaction between structure materials (SUS pipes, pressure vessels, etc.) and fuels (melted fuels, claddings components, etc.). We synthesize the simulated debris of UO$$_{2}$$-SUS system and UO$$_{2}$$-Zr(ZrO$$_{2}$$)-SUS system by high-temperature heat treatment, and measure their chemical property and dissolution behavior in water. Also, we will conduct

JAEA Reports

Development of a new corrosion mitigation technology using nanobubbles toward corrosion mitigation in PCV system under the influence of $$alpha$$/$$beta$$/$$gamma$$-rays radiolysis (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2022-002, 85 Pages, 2022/06

JAEA-Review-2022-002.pdf:3.39MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2020, this report summarizes the research results of the "Development of a new corrosion mitigation technology using nanobubbles toward corrosion mitigation in PCV system under the influence of $$alpha$$/$$beta$$/$$gamma$$-rays radiolysis" conducted in FY2020. In this work, in order to ensure the long-term reliability of steel structures that ensure important confinement functions in the debris removal process, such as existing PCVs and newly constructed negative pressure maintenance systems and piping, corrosion phenomena in wet environments where $$alpha$$- and $$beta$$-ray emitting nuclides come into contact with steel are clarified for the first time. At the same time, we will develop a new corrosion prevention technology that has excellent basic applicability to PCVs and has

JAEA Reports

An Attempt to estimate the migration pathway of slab-derived fluid using shear wave splitting analysis

Hiratsuka, Shinya; Asamori, Koichi; Saiga, Atsushi

JAEA-Research 2022-002, 38 Pages, 2022/06

JAEA-Research-2022-002.pdf:4.49MB

Deep groundwater originates from dehydration of Pacific and Philippine Sea slab subducting beneath Japanese islands, which has characteristics of high temperature and is rich in carbonate species. In this respect, it is very important for geological disposal of high-level radioactive waste to estimate reservoir and migration pathway of deep groundwater. The region where cracks are densely distributed can be regarded as the migration pathway of slab-derived fluid. It is highly probable that the region has strong anisotropy. Shear wave propagating through anisotropic media splits into two mutually orthogonally polarized waves due to shear wave polarization anisotropy. In this report, we applied shear wave splitting analysis to Hongu area of Tanabe City, Wakayama Prefecture and estimated the spatial distribution of leading shear wave polarization direction (LSPD) and arrival time difference between leading and lagging shear waves (dt). Based on comparison with helium isotope ratio of ground water and bubbling gas samples and two-dimensional resistivity structure estimated by previous study, we attempt to estimate migration pathway of slab-derived fluid in Hongu area of Tanabe City, Wakayama Prefecture. The main results are summarized as follows. When helium isotope ratio of groundwater and bubbling gas samples is high, dt value tends to be large. Shear wave propagating through high and low resistivity anomaly zone show small and large dt values, respectively. Previous study suggested that slab-derived fluid migrates from deeper part of western side of Hongu area and wells out in Yunomine and Kawayu hot springs. This is consistent with spatial distribution of dt values estimated by this study.

Journal Articles

Environmental monitoring of trace elements and evaluation of environmental impacts to organisms near a former uranium mining site in Nigyo-toge, Japan

Horai, Sawako*; Murakami, Shoichi*; Sakoda, Akihiro; Nakashita, Rumiko*; Kunisue, Tatsuya*; Ishimori, Yuu

Environmental Monitoring and Assessment, 194(6), p.415_1 - 415_25, 2022/06

 Times Cited Count:1 Percentile:0(Environmental Sciences)

This study conducted an investigation of trace element behavior at a former uranium (U) mining site and evaluated environmental impacts to biota. Concentrations of trace elements were determined in sediments, water, and three organism types (insects, frogs, and newts) from three zones in the former U mining site. Concentrations of As and U in the sediments and water samples were the highest at the mill tailings pond site, where post-U extraction remnants have been accumulated. Additionally, among the organisms analyzed the highest levels of these elements/isotopes were found in newts from MP. Considering data analyses of the whole-body element concentrations, bioaccumulation factors, and $$delta$$$$^{15}$$N values for the organisms, it was concluded that newts might be the most vulnerable species in this location. Further monitoring and more accurate evaluation of the ecological impacts are preferred for this former U mining site.

Journal Articles

Radiation imaging using an integrated radiation imaging system based on a compact Compton camera under Unit 1/2 exhaust stack of Fukushima Daiichi Nuclear Power Station

Sato, Yuki; Terasaka, Yuta

Journal of Nuclear Science and Technology, 59(6), p.677 - 687, 2022/06

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Journal Articles

Potential bacterial alteration of nuclear fuel debris; A Preliminary study using simulants in powder and pellet forms

Liu, J.; Dotsuta, Yuma; Sumita, Takehiro; Kitagaki, Toru; Onuki, Toshihiko; Kozai, Naofumi

Journal of Radioanalytical and Nuclear Chemistry, 331(6), p.2785 - 2794, 2022/06

 Times Cited Count:0 Percentile:0.02(Chemistry, Analytical)

Remnant nuclear fuel debris in the damaged nuclear reactors at the Fukushima Daiichi Nuclear Power Plant (FDNPP) has contacted the groundwater containing microorganisms for over ten years. Herein, we report the possibility of bacterial alteration of fuel debris. We investigated the physical and chemical changes of fuel debris simulants (FDS) in the powder and pellet forms via exposure to two ubiquitous bacteria, Pseudomonas fluorescens and Bacillus subtilis. In the experiments using FDS composed of the powders of Fe(0), solid solution of CeO$$_{2}$$ and ZrO$$_{2}$$, and SiO$$_{2}$$, Ce, Zr, and Si were hardly dissolved, while Fe was dissolved, a fraction of the dissolved Fe was present in the liquid phase as Fe(II) and Fe(III), and the rest was precipitated as the nano-sized particles of iron (hydr)oxides. In the experiment using P. fluorescens and FDS pellet pieces prepared by melting the Fe(0) particles and solid solution of CeO$$_{2}$$ and ZrO$$_{2}$$, the bacteria selectively gathered on the Fe(0) particle surface and made corrosion pits. These results suggest that bacteria in groundwater corrode the iron in fuel debris at FDNPP, change fuel debris into porous one, releasing the nano-sized iron (hydr)oxide particles into the water.

Journal Articles

Development of an ${it in-situ}$ continuous air monitor for the measurement of highly radioactive alpha-emitting particulates ($$alpha$$-aerosols) under high humidity environment

Tsubota, Yoichi; Honda, Fumiya; Tokonami, Shinji*; Tamakuma, Yuki*; Nakagawa, Takahiro; Ikeda, Atsushi

Nuclear Instruments and Methods in Physics Research A, 1030, p.166475_1 - 166475_7, 2022/05

 Times Cited Count:0 Percentile:0.06(Instruments & Instrumentation)

In the long-lasting decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), the dismantling of nuclear fuel debris (NFD) remaining in the damaged reactors is an unavoidable but significant issue with many technical difficulties. The dismantling is presumed to involve mechanical cutting, generating significant concentrations of particulates containing $$alpha$$-radionuclides ($$alpha$$-aerosols) that pose significant health risk upon inhalation. In order to minimize the radiation exposure of workers with $$alpha$$-aerosols during the dismantling/decommissioning process at 1F, it is essential to monitor the concentration of $$alpha$$-aerosols at the point of initial generation, i.e. inside the primary containment vessels (PCV) of the damaged reactors. Toward this end, an ${it in situ}$ monitoring system for $$alpha$$-aerosols (${it in situ}$ alpha air monitor: IAAM) was developed and its technical performance was investigated under the conditions expected for the actual environments at 1F. IAAM was confirmed to fulfill four technical requirements: (1) steady operation under high humidity, (2) operation without using filters, (3) capability of measuring a high counting rate of $$alpha$$-radiation, and (4) selective measurement of $$alpha$$-radiation even under high radiation background with $$beta$$/$$gamma$$-rays. IAAM is capable of selectively measuring $$alpha$$-aerosols with a concentration of 3.3 $$times$$ 10$$^{2}$$ Bq/cm$$^{3}$$ or higher without saturation under a high humid environment (100%-relative humidity) and under high background with $$beta$$/$$gamma$$-radiation (up to 100 mSv/h of $$gamma$$-radiation). These results demonstrate promising potential of IAAM to be utilized as a reliable monitoring system for $$alpha$$-aerosols during the dismantling of NFD, as well as the whole long-lasting decommissioning of 1F.

Journal Articles

Boundary condition free homogenization and evaluation of its performance in fast reactor core analysis

Maruyama, Shuhei

Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) (Internet), 10 Pages, 2022/05

This paper proposes a new homogenization method, "Boundary Condition Free Homogenization (BCFH)". The traditional homogenization method separates the core calculation and the cell (assembly) calculation by assuming a specific boundary condition or a peripheral region in the cell calculation. Nevertheless, there are ambiguities and approximation in these assumptions, and they can also cause a decline in accuracy. BCFH aims to avoid these problems and improve the accuracy in the cell calculation such as homogenization. We imposed the conditions that the physical quantities in the cell related to the reaction rate preservation is preserved for any incoming partial current, during the homogenization. That is, the response matrices of cell average (or total) flux and outgoing partial current, to be the same form between heterogeneous and homogeneous system. As a result, homogenized parameters, such as cross-sections, superhomgenization factors, and discontinuity factors, are no longer dependent on a specific boundary condition. The new homogenized parameters obtained in this way are extended from the conventional vector form to the matrix form in BCFH. To investigate the performance of BCFH, numerical tests are done for the simplified models which originates in 750MW-class sodium-cooled fast reactor with MOX fuel core in Japan. It is found that BCFH is particularly effective in evaluating control rod reactivity worth and reaction rate distribution, compared to the traditional method. We conclude that the BCFH can be a promising homogenization concept for core neutronic analysis.

Journal Articles

R&D on Accelerator Driven Nuclear Transmutation System (ADS) at J-PARC, 1; Accelerator Driven Nuclear Transmutation System (ADS)

Maekawa, Fujio

Purazuma, Kaku Yugo Gakkai-Shi, 98(5), p.201 - 205, 2022/05

The nuclear transmutation technology is a powerful solution to the "nuclear waste" problem that accompanies nuclear power generation. The Accelerator Driven System (ADS), which combines a high-intensity accelerator and a subcritical core, is a promising tool for nuclear transmutation. In this paper, we will explain the significance and principle of nuclear transmutation by ADS, design examples of ADS, partitioning and transmutation technology and its effects, required performance of high-intensity accelerators, overseas trends, etc.

Journal Articles

R&D on Accelerator Driven Nuclear Transmutation System (ADS) at J-PARC, 4; Proton beam technology and neutronics

Meigo, Shinichiro; Nakano, Keita; Iwamoto, Hiroki

Purazuma, Kaku Yugo Gakkai-Shi, 98(5), p.216 - 221, 2022/05

For the realization of accelerator-driven transmutation systems (ADS) and the construction of the ADS target test facility (TEF-T) at J-PARC, it is necessary to study the proton beam handling technology and neutronics for protons in the GeV energy region. Accordingly, the Nuclear Transmutation Division of J-PARC has studied these issues with using J-PARC's accelerator facilities, and so on. This paper introduces these topics.

Journal Articles

Marking actinides for separation; Resonance-enhanced multiphoton charge transfer in actinide complexes

Matsuda, Shohei; Yokoyama, Keiichi; Yaita, Tsuyoshi; Kobayashi, Toru; Kaneta, Yui; Simonnet, M.; Sekiguchi, Tetsuhiro; Honda, Mitsunori; Shimojo, Kojiro; Doi, Reisuke; et al.

Science Advances (Internet), 8(20), p.eabn1991_1 - eabn1991_11, 2022/05

 Times Cited Count:0 Percentile:0(Multidisciplinary Sciences)

no abstracts in English

4261 (Records 1-20 displayed on this page)