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JAEA Reports

Impact assessment for internal flooding in HTTR (High temperature engineering test reactor)

Tochio, Daisuke; Nagasumi, Satoru; Inoi, Hiroyuki; Hamamoto, Shimpei; Ono, Masato; Kobayashi, Shoichi; Uesaka, Takahiro; Watanabe, Shuji; Saito, Kenji

JAEA-Technology 2021-014, 80 Pages, 2021/09


In response to the new regulatory standards established in response to the accident at TEPCO's Fukushima Daiichi Nuclear Power Station in March 2011, measures and impact assessments related to internal flooding at HTTR were carried out. In assessing the impact, considering the characteristics of the high-temperature gas-cooled reactor, flooding due to assumed damage to piping and equipment, flooding due to water discharge from the system installed to prevent the spread of fire, and flooding due to damage to piping and equipment due to an earthquake. The effects of submersion, flooding, and flooding due to steam were evaluated for each of them. The impact of the overflow of liquids containing radioactive materials outside the radiation-controlled area was also evaluated. As a result, it was confirmed that flooding generated at HTTR does not affect the safety function of the reactor facility by taking measures.

Journal Articles

Measurement of liquid metal flows with electro-magnetic probe

Ariyoshi, Gen; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*

JPS Conference Proceedings (Internet), 33, p.011044_1 - 011044_6, 2021/03

Journal Articles

First isolation and analysis of caesium-bearing microparticles from marine samples in the Pacific coastal area near Fukushima Prefecture

Miura, Hikaru*; Ishimaru, Takashi*; Ito, Yukari*; Kuribara, Yuichi; Otosaka, Shigeyoshi*; Sakaguchi, Aya*; Misumi, Kazuhiro*; Tsumune, Daisuke*; Kubo, Atsushi*; Higaki, Shogo*; et al.

Scientific Reports (Internet), 11, p.5664_1 - 5664_11, 2021/03

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

For the first time, we isolated and investigated seven CsMPs (radioactive caesium-bearing microparticles) from marine particulate matter and sediment. From the elemental composition, the $$^{134}$$Cs/$$^{137}$$Cs activity ratio, and the $$^{137}$$Cs activity per unit volume results, we inferred that the five CsMPs collected from particulate matter were emitted from Unit 2 of the FDNPP, whereas the two CsMPs collected from marine sediment were possibly emitted from Unit 3. The presence of CsMPs can cause overestimation of the solid-water distribution coefficient of Cs in marine sediments and particulate matter and a high apparent radiocaesium concentration factor for marine biota. CsMPs emitted from Unit 2, which were collected from the estuary of a river that flowed through a highly contaminated area, may have been deposited on land and then transported by the river. By contrast, CsMPs emitted from Unit 3 were possibly transported eastward by the wind and deposited directly onto the ocean surface.

Journal Articles

Insight into Kondo screening in the intermediate-valence compound SmOs$$_4$$Sb$$_{12}$$ uncovered by soft X-ray magnetic circular dichroism

Saito, Yuji; Fujiwara, Hidenori*; Yasui, Akira*; Kadono, Toshiharu*; Sugawara, Hitoshi*; Kikuchi, Daisuke*; Sato, Hideyuki*; Suga, Shigemasa*; Yamasaki, Atsushi*; Sekiyama, Akira*; et al.

Physical Review B, 102(16), p.165152_1 - 165152_8, 2020/10

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Journal Articles

Image-based view selection for shape comparison of mode water regions in virtual reality spaces

Yano, Midori; Ito, Takayuki*; Tanaka, Yusuke*; Matsuoka, Daisuke*; Araki, Fumiaki*; Czauderna, T.*; Stephens, K.*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.201 - 208, 2020/10

Visual analysis plays an important role in understanding and evaluating the climate models, their variables, and their outputs because complex processes are required for the tuning of the climate models. Virtual Reality (VR) technologies are effective for 3D visualization and have been recently employed for visual analysis of more various scientific data. However, researchers may have some problematic situations while using VR space depending on user operations and target geometries. Here, we propose an image-based view selection method to solve these situations and understand differences in ocean states between simulations and observations based on shapes of mode water regions. This view selection takes evaluation criteria for shape comparison of mode water regions generated from simulations and observations into account. This paper introduces two example cases applying this view selection and discusses on a degree of shape matching of mode water regions of each case.

Journal Articles

Neutron transmission spectrum of liquid lead bismuth eutectic

Oba, Yojiro; Ito, Daisuke*; Saito, Yasushi*; Onodera, Yohei*; Parker, J. D.*; Shinohara, Takenao; Oikawa, Kenichi

Materials Research Proceedings, Vol.15, p.160 - 164, 2020/02

Lead Bismuth eutectic (LBE) is a promising candidate of the coolant for accelerator driven system (ADS) and fast breeder reactor. Neutron transmission imaging is a powerful technique to investigate the LBE in flow channel. However, previous studies have focused on the analysis of the neutron transmission spectra due to Bragg diffraction (Bragg edge transmission) from the solid phase of the LBE. If the neutron transmission spectra due to the diffraction from a liquid phase can be observed, it is useful to study the behavior of the molten LBE in the flow channel. Therefore, the energy-resolved neutron transmission imaging measurements of the molten LBE was carried out. The observed neutron transmission spectra can be explained by those calculated from the scattering profiles of the molten LBE. This indicates that the structure of the molten LBE can be characterized and mapped using the neutron transmission imaging.

Journal Articles

Guidance for ${it in situ}$ gamma spectrometry intercomparison based on the information obtained through five intercomparisons during the Fukushima mapping project

Mikami, Satoshi; Ishikawa, Daisuke*; Matsuda, Hideo*; Hoshide, Yoshifumi*; Okuda, Naotoshi*; Sakamoto, Ryuichi*; Saito, Kimiaki

Journal of Environmental Radioactivity, 210, p.105938_1 - 105938_7, 2019/12

 Times Cited Count:1 Percentile:10.3(Environmental Sciences)

Five intercomparisons of in situ $$gamma$$ spectrometry by 6-7 participating teams have been conducted between December 2011 and August 2015 at sites in Fukushima prefecture which affected by the fallout of FDNPS accident occurred in March 2011. The evaluated deposition densities agreed within 5-6% in terms of coefficient of variation (CV) for radiocesium ($$^{134}$$Cs and $$^{137}$$Cs), by our best achievement, and the ratio of $$^{134}$$Cs/$$^{137}$$Cs in deposition density agreed within 1-2% in CV, through five intercomparisons. These results guarantee the accuracy of the measurements of the mapping project. Two different methods for intercomparison were conducted: (1) sequential measurements at an identical point; and (2) simultaneous measurements in a narrow area within 3 m radius. In a comparison between the two methods at a site, no significant difference was observed between the results. The standard protocols for the two different intercomparison methods were proposed based on our experience.

Journal Articles

Upgrade of the 3-MeV linac for testing of accelerator components at J-PARC

Kondo, Yasuhiro; Hirano, Koichiro; Ito, Takashi; Kikuzawa, Nobuhiro; Kitamura, Ryo; Morishita, Takatoshi; Oguri, Hidetomo; Okoshi, Kiyonori; Shinozaki, Shinichi; Shinto, Katsuhiro; et al.

Journal of Physics; Conference Series, 1350, p.012077_1 - 012077_7, 2019/12

 Times Cited Count:0 Percentile:0.07

We have upgraded a 3-MeV linac at J-PARC. The ion source is same as the J-PARC linac's, and the old 30-mA RFQ is replaced by a spare 50-mA RFQ, therefore, the beam energy is 3 MeV and the nominal beam current is 50 mA. The main purpose of this system is to test the spare RFQ, but also used for testing of various components required in order to keep the stable operation of the J-PARC accelerator. The accelerator has been already commissioned, and measurement programs have been started. In this paper, present status of this 3-MeV linac is presented.

Journal Articles

Study on evaluation method for entrained gas flow rate by free surface vortex

Ito, Kei*; Ito, Daisuke*; Saito, Yasushi*; Ezure, Toshiki; Matsushita, Kentaro; Tanaka, Masaaki; Imai, Yasutomo*

Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.6632 - 6642, 2019/08

In this paper, a mechanistic model is proposed to calculate the entrained gas flow rate by a free surface vortex. The model contains the theoretical equation of transient gas core elongation and the empirical equation of critical gas core length for gas bubble detachment. Based on those two equations, the entrained gas flow rate is calculated as the portion of the gas core elongated beyond the critical gas core length per unit time. Then, the mechanistic model was applied to the calculation of the entrained gas flow rate in a simple water experiment. As a result, it is confirmed that the entrained gas flow rate grows rapidly when the liquid (water) flow rate, which determine the strength of a free surface vortex, exceeds a certain threshold value.

Journal Articles

Two-phase flow structure in a particle bed packed in a confined channel

Ito, Daisuke*; Kurisaki, Tatsuya*; Ito, Kei*; Saito, Yasushi*; Imaizumi, Yuya; Matsuba, Kenichi; Kamiyama, Kenji

Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.6430 - 6439, 2019/08

In core disruptive accident of sodium-cooled fast reactor, cooling of residual fuel debris formed in the reactor core is one of important factors to achieve in-vessel retention of the fuel. To clarify the feasibility of the cooling which is called "in-place cooling", characteristics of gas-liquid two-phase flow in the debris bed must be well understood. Since the debris bed can be formed in a confined flow channel in the core, effect of the channel wall cannot be neglected. Thus, this study aims to clarify the effect of the wall on two-phase flow characteristics in the debris bed, which was simulated as a particle bed packed in a pipe. The pressure drop was measured and compared with results by previous models, and porosity and void fraction distributions were measured by X-ray radiography. Then, the pressure drop evaluation model was modified considering the wall effect, and the applicability of the models was discussed.

Journal Articles

Enhancement of element production by incomplete fusion reaction with weakly bound deuteron

Wang, H.*; Otsu, Hideaki*; Chiga, Nobuyuki*; Kawase, Shoichiro*; Takeuchi, Satoshi*; Sumikama, Toshiyuki*; Koyama, Shumpei*; Sakurai, Hiroyoshi*; Watanabe, Yukinobu*; Nakayama, Shinsuke; et al.

Communications Physics (Internet), 2(1), p.78_1 - 78_6, 2019/07

 Times Cited Count:5 Percentile:62.37(Physics, Multidisciplinary)

Searching for effective pathways for the production of proton- and neutron-rich isotopes through an optimal combination of reaction mechanism and energy is one of the main driving forces behind experimental and theoretical nuclear reaction studies as well as for practical applications in nuclear transmutation of radioactive waste. We report on a study on incomplete fusion induced by deuteron, which contains one proton and one neutron with a weak binding energy and is easily broken up. This reaction study was achieved by measuring directly the cross sections for both proton and deuteron for $$^{107}$$Pd at 50 MeV/u via inverse kinematics technique. The results provide direct experimental evidence for the onset of a cross-section enhancement at high energy, indicating the potential of incomplete fusion induced by loosely-bound nuclei for creating proton-rich isotopes and nuclear transmutation of radioactive waste.

Journal Articles

Effect of porosity distribution on two-phase pressure drop in a packed bed

Kurisaki, Tatsuya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Imaizumi, Yuya; Matsuba, Kenichi; Kamiyama, Kenji

Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 3 Pages, 2018/11

In the evaluation of the in-place cooling which is for the residual core materials in the severe accident of sodium-cooled fast reactors, pressure loss of two-phase flow in debris bed is one of the important factors. Although Lipinski model is already proposed for the pressure loss evaluation, the accuracy would decrease when the porosity is not homogeneous. Thus, experiment to measure the pressure loss in a packed bed of non-homogeneous porosity distribution was conducted, and the Lipinski model was modified dividing the cross section to evaluate the pressure loss in it. As a result, it was confirmed that agreement of the experimental values with the values by modified Lipinski model was better than that with the original Lipinski model.

Journal Articles

Estimation of porosity and void fraction profiles in a packed bed of spheres using X-ray radiography

Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Aoyagi, Mitsuhiro; Matsuba, Kenichi; Kamiyama, Kenji

Nuclear Engineering and Design, 334, p.90 - 95, 2018/08

 Times Cited Count:5 Percentile:64.98(Nuclear Science & Technology)

Two-phase flow through porous media must be well understood to develop a severe accident analysis code not only for light water reactor but also sodium-cooled fast reactor. When a core disruptive accident occurs in sodium-cooled fast reactor, the fuel inside the core become melted and interacts with the coolant. As a result, gas-liquid two-phase flow will be formed in the debris bed, which may have porous nature depending on the cooling process. In such condition, the local porosity and its distribution are very important to characterize two-phase flow field in the porous media. In this study, X-ray radiography was applied to measure the local porosity in the packed bed of spheres. The radial profiles were estimated from the chordal profiles measured by the X-ray method and compared with the previous porosity model. In addition, the void fraction radial profiles were also obtained in air-water two-phase flow.

Journal Articles

Rapid separation of zirconium using microvolume anion-exchange cartridge for $$^{93}$$Zr determination with isotope dilution ICP-MS

Asai, Shiho; Hanzawa, Yukiko; Konda, Miki; Suzuki, Daisuke; Magara, Masaaki; Kimura, Takaumi; Ishihara, Ryo*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*

Talanta, 185, p.98 - 105, 2018/08

 Times Cited Count:7 Percentile:45.32(Chemistry, Analytical)

Estimating the risks associated with radiation from long-lived fission products (LLFP) in radioactive waste is essential to ensure the long-term safety of potential disposal sites. In this study, the amount of $$^{93}$$Zr, a LLFP, was determined by ICP-MS after separating Zr from a spent nuclear fuel solution using a microvolume anion-exchange cartridge (TEDA cartridge). The TEDA cartridge achieved highly selective separation of Zr regardless of its small bed volume of 0.08 cm$$^{3}$$. The time taken to complete the Zr separation was 1.2 min with a flow rate of 1.5 mL/min, which was 10 times faster than that for a conventional anion-exchange resin column. Almost all the other elements were removed, leading to accurate measurement of $$^{93}$$Zr. The result connects experimental value to theoretical prediction provided by ORIGEN2, which requires verification. With the measured value, we demonstrated that the theoretical value is reliable enough to estimate radiation risks.

Journal Articles

Characterization and thermodynamic study of humic acid in deep groundwater at Horonobe, Hokkaido, Japan

Kimuro, Shingo*; Kirishima, Akira*; Nagao, Seiya*; Saito, Takumi*; Amano, Yuki; Miyakawa, Kazuya; Akiyama, Daisuke*; Sato, Nobuaki*

Journal of Nuclear Science and Technology, 55(5), p.503 - 515, 2018/05

 Times Cited Count:3 Percentile:45.99(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Decontamination of radioactive concrete waste and reuse of aggregate using pulsed power technology

Sakamoto, Hiroyuki*; Akagi, Yosuke*; Yamada, Kazuo*; Tachi, Yukio; Fukuda, Daisuke*; Ishimatsu, Koichi*; Matsuda, Mikiya*; Saito, Nozomi*; Uemura, Jitsuya*; Namihira, Takao*; et al.

Nihon Genshiryoku Gakkai Wabun Rombunshi, 17(2), p.57 - 66, 2018/05

Concrete debris contaminated with radioactive cesium and other nuclides have been generated from the accident in the Fukushima Dai-ichi Nuclear Power Plant and there will be generated due to the decommissioning of nuclear power plants in the future. Although conventional decontamination techniques are effective for flat concrete surfaces such as floors and walls, it is not clear what techniques to apply for decontaminating radioactive concrete debris. In this study, focusing on a pulsed power discharge technique, fundamental experimental works were carried out. Decontamination of concrete by applying the aggregate recycling technique using the pulsed power discharge technique was evaluated by measuring radioactivity of aggregate and sludge separated from the contaminated concrete. The results suggest that the separation into aggregate and sludge of the contaminated concrete debris could achieve decontamination and volume reduction of the radioactive concrete debris.

Journal Articles

Ecological and genomic profiling of anaerobic methane-oxidizing archaea in a deep granitic environment

Ino, Kohei*; Hernsdorf, A. W.*; Konno, Yuta*; Kozuka, Mariko*; Yanagawa, Katsunori*; Kato, Shingo*; Sunamura, Michinari*; Hirota, Akinari*; Togo, Yoko*; Ito, Kazumasa*; et al.

ISME Journal, 12(1), p.31 - 47, 2018/01

 Times Cited Count:30 Percentile:93.55(Ecology)

In this study, we found the dominance ofanaerobic methane-oxidizing archaea in groundwater enriched in sulfate and methane from a 300-m deep underground borehole in granitic rock.

Journal Articles

Shell evolution beyond $$Z$$=28 and $$N$$=50; Spectroscopy of $$^{81,82,83,84}$$Zn

Shand, C. M.*; Podoly$'a$k, Zs.*; G$'o$rska, M.*; Doornenbal, P.*; Obertelli, A.*; Nowacki, F.*; Otsuka, T.*; Sieja, K.*; Tostevin, J. A.*; Tsunoda, T.*; et al.

Physics Letters B, 773, p.492 - 497, 2017/10

 Times Cited Count:18 Percentile:88.47(Astronomy & Astrophysics)

Journal Articles

Two-phase flow measurements in a simulated debris bed

Ito, Daisuke*; Rivera, M. N.*; Saito, Yasushi*; Aoyagi, Mitsuhiro; Kamiyama, Kenji; Suzuki, Toru*

Proceedings of 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) (USB Flash Drive), 10 Pages, 2017/09

Journal Articles

Measurements of two-phase pressure drop in a simulated debris bed

Nava, M.*; Ito, Daisuke*; Saito, Yasushi*; Aoyagi, Mitsuhiro; Kamiyama, Kenji; Suzuki, Toru*

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 5 Pages, 2017/07

177 (Records 1-20 displayed on this page)