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Yanagisawa, Hiroshi; Motome, Yuiko
JAEA-Research 2025-010, 197 Pages, 2025/11
JAEA-Research-2025-010.pdf:3.5MB
For understandings of nuclear criticality risks of TRIGA fuel rods and review of safety measures for handling them, nuclear criticality characteristics for infinite and finite heterogeneous lattice systems composed of the NSRR fuel rods were re-evaluated with the use of a detailed computational model for the fuel rod. The MVP version 3 code was used with the JENDL libraries including the latest version, JENDL-5, for the re-evaluation. As the criticality characteristics, variations of neutron multiplication factors of the infinite and water-reflected finite systems were examined in detail with parameters of the lattice pitch and density of moderator water. From the results of the re-evaluated criticality characteristics, the minimum critical number of fuel rods for the water-reflected hexagonal shaped lattice system was obtained to be 46.8 
0.2 using the JENDL-5 library. Moreover, the attainability of criticality without the water as moderator and reflector was examined because the zirconium hydride moderator and graphite reflector are equipped with the TRIGA fuel rod. It was found that the criticality is possible to be attained by 115.7 0.6 of the number of fuel rods, which is the smaller number of fuel rods than loaded in the NSRR standard core, even though no water exists.
Yomogida, Takumi; Scaria, J.*; Fablet, L.*; Tokunaga, Kohei; Dei, Shuntaro; Higashi, Kotaro*; Kawamura, Naomi*; Takahashi, Yoshio*; Marsac, R.*
Chemical Communications, 61(91), p.17926 - 17929, 2025/11
This paper presents insights into the influence of magnetite stoichiometry (0 
R = Fe(II)/Fe(III) 0.5) on the surface reduction of U(VI) to U(V) and U(IV), as a key parameter controlling U redox speciation in natural settings. Although R can readily change due to the oxidation of structural Fe(II) or proton/ligand-promoted dissolution, prior studies have not quantified U(V) when assessing these effects. We employed U L
-edge HERFD-XANES spectroscopy to investigate the electronic structure of U on magnetite with varying stoichiometries and observed a peak splitting of U(V) on magnetite. Our results demonstrate the high stability of U(V) species under a wide range of conditions, and after 10 days on magnetite by the combination of MCR-ALS analysis. A key finding is that structural Fe(II), whose abundance depends on pH and redox conditions, plays a critical role for in the stabilization of U(V) on magnetite.
Tomita, Jumpei; Tomita, Ryohei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
Journal of Nuclear Science and Technology, 12 Pages, 2025/09
Times Cited Count：0 Percentile：0.00Yamamoto, Masahiko; Horigome, Kazushi; Goto, Yuichi; Taguchi, Shigeo; Kuno, Takehiko
Progress in Nuclear Science and Technology (Internet), 8, p.387 - 392, 2025/09
Flush-out of Tokai Reprocessing Plant was completed in February, 2024 for the preparation of process decontamination. Since remaining nuclear materials were contained in main process, purpose of the activities was to recover nuclear materials by transferring them to the highly radioactive liquid waste storage tank and converting uranium solution into uranium trioxide, and to rinse all related processes with nitric acid and water. During this activity, analysis of U and Pu was conducted for nuclear material control and accountancy. Appropriate analytical methods such as isotope dilution mass spectrometry, gravimetric method, spectrophotometry and alpha-ray counting methods were selected depending on the status of flush-out. Also, gamma-ray emitted nuclides in rinsing solution were detected by highly purified germanium detector. This paper describes analysis and its results related to flush-out activities of decommissioning in reprocessing plant.
Ouchi, Kazuki; Ueno, Katsuhiro; Watanabe, Masayuki
Scientific Reports (Internet), 15, p.18515_1 - 18515_7, 2025/05
Times Cited Count：0 Percentile：0.00(Multidisciplinary Sciences)We first demonstrate a nonaqueous rechargeable battery using uranium and iron as active materials. This uranium-iron battery achieves an open-circuit voltage of approximately 1.3 V, exhibits stable cycling performance, and delivers a good Coulombic efficiency of 862%. These characteristics suggest a promising avenue for utilizing depleted uranium in innovative applications.
Tanabe, Kosuke*; Komeda, Masao; Toh, Yosuke; Kitamura, Yasunori*; Misawa, Tsuyoshi*
Nihon Genshiryoku Gakkai-Shi ATOMO
, 67(3), p.198 - 202, 2025/03
no abstracts in English
Maeda, Mizuho*; Matsuda, Tatsuma*; Haga, Yoshinori; Shirasaki, Kenji*; Kimura, Noriaki*
Journal of the Physical Society of Japan, 94(2), p.024707_1 - 024707_6, 2025/01
Times Cited Count：0 Percentile：0.00(Physics, Multidisciplinary)
U/
U isotope ratios in deep groundwater and its potential application as a groundwater mixing indicatorKuribayashi, Chika*; Miyakawa, Kazuya; Ito, Akane*; Tanimizu, Masaharu*
Geochemical Journal, 59(2), p.35 - 44, 2025/00
Times Cited Count：0 Percentile：65.18(Geochemistry & Geophysics)no abstracts in English
Vali
ka, M.*; Haidamak, T.*; Cabala, A.*; Posp
il, J.*; Bastien, G.*; Sechovsk
, V.*; Prokleka, 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：2 Percentile：25.98(Materials Science, Multidisciplinary)
Cf rotation method with a water Cherenkov neutron detectorTanabe, 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：22 Percentile：98.08(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：8 Percentile：84.77(Materials Science, Multidisciplinary)The thermal conductivities of near-stoichiometric (U,Pu,Am)O
doped with NdO
/SmO, 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
.
Eaton, A. G.*; Weinberger, T. I.*; Popiel, N. J. M.*; Wu, Z.*; Hickey, A. J.*; Cabala, A.*; Pospil, J.*; Prokleka, J.*; Haidamak, T.*; Bastien, G.*; et al.
Nature Communications (Internet), 15, p.223_1 - 223_10, 2024/01
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：2 Percentile：33.46(Nuclear Science & Technology) dissolution in bicarbonate solution with HO; The Effect of temperatureMcGrady, J.; Kumagai, Yuta; Kitatsuji, Yoshihiro; Kirishima, Akira*; Akiyama, Daisuke*; Watanabe, Masayuki
RSC Advances (Internet), 13(40), p.28021 - 28029, 2023/09
Times Cited Count：2 Percentile：22.69(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 HO 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 HO 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 HO 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：14.29(Chemistry, Multidisciplinary)We clarified the chemical state transformation of deposits following the reduction of uranyl ion (U
O
) 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.
Te
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：3 Percentile：41.81(Physics, Multidisciplinary)We investigate the physical properties of a single crystal of uranium telluride UTe. We have confirmed that UTe 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
JAEA-Technology-2022-030.pdf:2.57MBJAEA-Technology-2022-030(errata).pdf:0.11MB
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.
