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Valika, M.*; Haidamak, T.*; Cabala, A.*; Posp
il, J.*; Bastien, G.*; Sechovsk
, V.*; Prokle
ka, J.*; Yanagisawa, Tatsuya*; Opletal, P.; Sakai, Hironori; et al.
Physical Review Materials (Internet), 8(9), p.094415_1 - 094415_9, 2024/09
Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)Tanabe, Kosuke*; Komeda, Masao; Toh, Yosuke; Kitamura, Yasunori*; Misawa, Tsuyoshi*; Tsuchiya, Kenichi*; Sagara, Hiroshi*
Scientific Reports (Internet), 14, p.18828_1 - 18828_10, 2024/08
Times Cited Count:0 Percentile:0.00(Multidisciplinary Sciences)Suetsugu, Shota*; Sakai, Hironori; Opletal, P.; Tokiwa, Yoshifumi; Haga, Yoshinori; 12 of others*
Science Advances (Internet), 10(6), p.eadk3772_1 - eadk3772_6, 2024/02
Times Cited Count:7 Percentile:96.82(Multidisciplinary Sciences)Horii, Yuta; Hirooka, Shun; Uno, Hiroki*; Ogasawara, Masahiro*; Tamura, Tetsuya*; Yamada, Tadahisa*; Furusawa, Naoya*; Murakami, Tatsutoshi; Kato, Masato
Journal of Nuclear Materials, 588, p.154799_1 - 154799_20, 2024/01
Times Cited Count:4 Percentile:83.63(Materials Science, Multidisciplinary)The thermal conductivities of near-stoichiometric (U,Pu,Am)O doped with Nd
O
/Sm
O
, which is major fission product (FP) generated by a uranium-plutonium mixed oxides (MOX) fuel irradiation, as simulated fission products are evaluated at 1073-1673 K. The thermal conductivities are calculated from the thermal diffusivities that are measured using the laser flash method. To evaluate the thermal conductivity from a homogeneity viewpoint of Nd/Sm cations in MOX, the specimens with different homogeneity of Nd/Sm are prepared using two kinds of powder made by ball-mill and fusion methods. A homogeneous Nd/Sm distribution decreases the thermal conductivity of MOX with increasing Nd/Sm content, whereas heterogeneous Nd/Sm has no influence. The effect of Nd/Sm on the thermal conductivity is studied using the classical phonon transport model (A+BT)
. The dependences of the coefficients A and B on the Nd/Sm content (C
and C
, respectively) are evaluated as: A(mK/W)=1.70
10
+ 0.93C
+ 1.20C
, B(m/W)=2.39
10
.
McGrady, J.; Kumagai, Yuta; Watanabe, Masayuki; Kirishima, Akira*; Akiyama, Daisuke*; Kimuro, Shingo; Ishidera, Takamitsu
Journal of Nuclear Science and Technology, 60(12), p.1586 - 1594, 2023/12
Times Cited Count:1 Percentile:35.82(Nuclear Science & Technology)McGrady, J.; Kumagai, Yuta; Kitatsuji, Yoshihiro; Kirishima, Akira*; Akiyama, Daisuke*; Watanabe, Masayuki
RSC Advances (Internet), 13(40), p.28021 - 28029, 2023/09
Times Cited Count:1 Percentile:17.05(Chemistry, Multidisciplinary)Upon nuclear waste canister failure and contact of spent nuclear fuel with groundwater, the UO matrix of spent fuel will interact with oxidants in the groundwater generated by water radiolysis. Bicarbonate (HCO
) is often found in groundwater, and the H
O
induced oxidative dissolution of UO
in bicarbonate solution has previously been studied under various conditions. Temperatures in the repository at the time of canister failure will differ depending on the location, yet the effect of temperature on oxidative dissolution is unknown. To investigate, the decomposition rate of H
O
at the UO
surface and dissolution of U
in bicarbonate solution (0.1, 1, 10 and 50 mM) was analysed at various temperatures (10, 25, 45 and 60
C). At [HCO
]
1 mM, the apparent equilibrium concentration of U
decreased with increasing temperature. This was attributed to the formation of U
-bicarbonate species at the surface and a change in the mechanism of H
O
decomposition from oxidative to catalytic. At 0.1 mM, no obvious correlation between temperature and U dissolution was observed, and thermodynamic calculations indicated this was due to a change in the surface species. A pathway to explain the observed dissolution behaviour of UO
in bicarbonate solution as a function of temperature was proposed.
Iwamoto, Toshihiro; Saito, Madoka*; Takahatake, Yoko; Watanabe, So; Watanabe, Masayuki; Naruse, Atsuki*; Tsukahara, Takehiko*
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 4 Pages, 2023/05
Applicability of temperature swing extraction technology employing monoamides was examined for uranium contaminated waste treatment procedure. Separation experiments on simulated target solution with three kinds of monoamides with different structure showed that Ce(IV) in the solution was selectively recovered by the temperature swing extraction operation. Based on the experiments, an appropriate monoamide for the procedure was selected.
Ouchi, Kazuki; Matsumura, Daiju; Tsuji, Takuya; Kobayashi, Toru; Otobe, Haruyoshi; Kitatsuji, Yoshihiro
RSC Advances (Internet), 13(24), p.16321 - 16326, 2023/05
Times Cited Count:1 Percentile:17.05(Chemistry, Multidisciplinary)We clarified the chemical state transformation of deposits following the reduction of uranyl ion (UO
) from the results of electrochemical quartz crystal microbalance, impedance spectra and X-ray absorption fine structure measurements. We propose the following deposition mechanism: (1) U
is formed by the disproportionation of U
. (2) U
forms U
hydroxide deposits, and (3) finally, the hydroxide deposits transform into U
oxide, generally having a larger electrical resistance than the former.
Opletal, P.; Sakai, Hironori; Haga, Yoshinori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo
Journal of the Physical Society of Japan, 92(3), p.034704_1 - 034704_5, 2023/03
Times Cited Count:1 Percentile:30.70(Physics, Multidisciplinary)We investigate the physical properties of a single crystal of uranium telluride UTe
. We have confirmed that U
Te
crystallizes in the hexagonal structure with three nonequivalent crystallographic uranium sites. The paramagnetic moments are estimated to be approximately 1
per the uranium site, assuming a uniform moment on all the sites. A ferromagnetic phase transition occurs at
= 48 K, where the in-plane magnetization increases sharply, whereas the out of-plane component does not increase significantly. With decreasing temperature further below
under field-cooling conditions, the out-of-plane component increases rapidly around T
= 26 K. In contrast, the in-plane component hardly changes at T
. Specific heat measurement indicates no
-type anomaly around T
, so this is a cross-over suggesting a reorientation of the ordering moments or successive magnetic ordering on the part of the multiple uranium sites.
Yanagisawa, Hiroshi; Umeda, Miki; Motome, Yuiko; Murao, Hiroyuki
JAEA-Technology 2022-030, 80 Pages, 2023/02
Nuclear criticality benchmark analyses were carried out for TRIGA-type reactor systems in which uranium-zirconium hydride fuel rods are loaded by using the continuous-energy Monte Carlo code MVP with the evaluated nuclear data library JENDL-5. The analyses cover two sorts of benchmark data, the IEU-COMP-THERM-003 and IEU-COMP-THERM-013 in the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Handbook, and effective neutron multiplication factors, reactivity worths for control rods etc. were calculated by JENDL-5 in comparison with those by the previous version of JENDL. As the results, it was confirmed that the effective neutron multiplication factors obtained by JENDL-5 were 0.4 to 0.6% greater than those by JENDL-4.0, and that there were no significant differences in the calculated reactivity worths by between JENDL-5 and JENDL-4.0. Those results are considered to be helpful for the confirmation of calculation accuracy in the analyses on NSRR control rod worths, which are planned in the future.
Sakai, Akihiro
Dai-33-Kai Genshiryoku Shisetsu Dekomisshoningu Gijutsu Koza Tekisuto, p.31 - 63, 2023/02
The Japan Atomic Energy Agency (JAEA) is promoting the project for concrete-vault disposal and landfill-type disposal of radioactive waste generated from research facilities, etc. This report introduces current status of technical development for JAEA's disposal project as following items; (1) kinds of research facilities and characteristics of radioactivity inventory of the waste, (2) the structures of the disposal facilities which JAEA conceptually designed, (3) development of waste acceptance criteria for major radioactive waste for the JAEA disposal facilities, (4) the concept of the criteria for disposal of uranium bearing waste, that has been established in 2021.
Watanabe, Masashi; Kato, Masato
Frontiers in Nuclear Engineering (Internet), 1, p.1082324_1 - 1082324_9, 2023/01
Since the oxygen potential and the oxygen coefficient of UO have a significant impact on fuel performance, many experimental data have been obtained. However, experimental data of the oxygen potential and the oxygen diffusion coefficient in the high temperature region above 1673 K are very limited. In the present study, we aimed to obtain these data and analyze them by defect chemistry. The oxygen potentials and the oxygen chemical diffusion coefficient of UO
were measured by the gas equilibrium method in the near stoichiometric region at temperatures ranging from 1673 to 1873 K. A data set of oxygen potentials was made together with literature data and analyzed by defect chemistry. The oxygen potential of UO
was determined as a function of O/U ratio and temperature, and an equation representing the relationship was derived. The oxygen chemical diffusion coefficient values obtained in this study were reasonably close to the literature values. The oxygen partial pressure dependence of the oxygen chemical diffusion coefficients was predicted from the evaluated results of the oxygen potential data, but no clear dependence was observed.
Saito, Tatsuo; Yamazawa, Hiromi*; Mochizuki, Akihito
Journal of Environmental Radioactivity, 255, p.107035_1 - 107035_14, 2022/12
Times Cited Count:0 Percentile:0.00(Environmental Sciences)The seasonal variation of dissolved U (DU) in Lake Biwa was reproduced by the following model and parameter research. The introduced models are the water-DU mass balance, and the ion exchange between UO and H
on the lakeshore soil. The optimized parameters were the CEC of the lakeshore, TU as the sum of DU and AU (soil adsorbed U), kads and kdes as the first order reaction rate coefficients during rapid soil adsorption and desorption of U, respectively. Tabulated by the chemical equilibria constituting DU and analyzed the contribution of each chemical species, it is shown that the seasonal variation of DU is caused by the seasonal variation of pH. A correction to the ion-exchange equilibrium to shift to first order rate reaction only when the daily AU ratio increased above kads or decreased below kdes, improved the reproducibility of DU measurements and reproduced the delay of the DU peak from the pH peak.
Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*
JAEA-Review 2022-028, 54 Pages, 2022/11
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 FY2021. 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 FY2019, this report summarizes the research results of the "Development of Tailor-made Adsorbents for Uranium Recovery from Seawater on the Basis of Uranyl Coordination Chemistry" conducted from FY2019 to FY2021. Since the final year of this proposal was FY2021, the results for three fiscal years were summarized. The present study aims to develop a new ligand class for efficient and selective capture of uranium from seawater. On the basis of deep understanding on uranyl coordination chemistry, we design molecular structures of pentadentate ligands as functional moieties for uranium adsorption from seawater and study fundamental coordination chemistry of uranyl ion with those ligands in order to resolve current problems in uranium recovery technology …
Nauchi, Yasushi*; Nomi, Takayoshi; Suzuki, Risa; Kosuge, Yoshihiro*; Shiba, Tomooki; Takada, Akira*; Kaburagi, Masaaki; Okumura, Keisuke
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 4 Pages, 2022/10
Porcheron, E.*; Leblois, Y.*; Journeau, C.*; Delacroix, J.*; Molina, D.*; Suteau, C.*; Berlemont, R.*; Bouland, A.*; Lallot, Y.*; Roulet, D.*; et al.
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 5 Pages, 2022/10
One of the important challenges for the decommissioning of the damaged reactors of the Fukushima Daiichi Nuclear Power Station (1F) is the fuel debris retrieval. The URASOL project, which is undertaken by a French consortium consisting of ONET Technologies, CEA, and IRSN for JAEA/CLADS, is dedicated to acquiring basic scientific data on the generation and characteristics of radioactive aerosols from the thermal or mechanical processing of fuel debris simulant. Heating process undertaken in the VITAE facility simulates some representative conditions of thermal cutting by LASER. For mechanical cutting, the core boring technique is implemented in the FUJISAN facility. Fuel debris simulants have been developed for inactive and active trials. The aerosols are characterized in terms of mass concentration, real time number concentration, mass size distribution, morphology, and chemical properties. The chemical characterization aims at identifying potential radioactive particles released and the associated size distribution, both of which are important information for assessing possible safety and radioprotection measures during the fuel debris retrieval operations at 1F.
Aoki, Dai*; Sakai, Hironori; Opletal, P.; Tokiwa, Yoshifumi; Ishizuka, Jun*; Yanase, Yoichi*; Harima, Hisatomo*; Nakamura, Ai*; Li, D.*; Homma, Yoshiya*; et al.
Journal of the Physical Society of Japan, 91(8), p.083704_1 - 083704_5, 2022/08
Times Cited Count:47 Percentile:98.21(Physics, Multidisciplinary)Haga, Yoshinori; Opletal, P.; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Tokunaga, Yo; Kambe, Shinsaku; Sakai, Hironori
Journal of Physics; Condensed Matter, 34(17), p.175601_1 - 175601_7, 2022/04
Times Cited Count:22 Percentile:85.94(Physics, Condensed Matter)Fujimori, Shinichi; Takeda, Yukiharu; Yamagami, Hiroshi; Pospil, J.*; Yamamoto, Etsuji; Haga, Yoshinori
Physical Review B, 105(11), p.115128_1 - 115128_6, 2022/03
Times Cited Count:1 Percentile:9.28(Materials Science, Multidisciplinary)Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*
JAEA-Review 2021-041, 42 Pages, 2022/01
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 FY2019, this report summarizes the research results of the "Development of tailor-made adsorbents for uranium recovery from seawater on the basis of uranyl coordination chemistry" conducted in FY2020. On the basis of deep understanding on uranyl coordination chemistry, we design molecular structures of pentadentate ligands as functional moieties for uranium adsorption from seawater and study coordination chemistry of uranyl ion with those ligands in order to resolve current problems in uranium recovery technology from seawater and to develop novel selective and efficient adsorbents for this purpose.