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Journal Articles

Dissolution behavior and aging of iron-uranium oxide

Tonna, Ryutaro*; Sasaki, Takayuki*; Okamoto, Yoshihiro; Kobayashi, Taishi*; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*

Journal of Nuclear Materials, 589, p.154862_1 - 154862_10, 2024/02

https://doi.org/10.1016/j.jnucmat.2023.154862

Times Cited Count：0 Percentile：0.01(Materials Science, Multidisciplinary)

The dissolution behavior of FeUO $_{4}$ compounds formed by a high-temperature reaction of UO $_{2}$ with iron, a stainless-steel component of reactor structural materials, was investigated under atmospheric conditions. The compounds were prepared in an electric furnace using U $_{3}$ O $_{8}$ and Fe $_{3}$ O $_{4}$ as starting materials, and their solid states were analyzed using X-ray diffraction, scanning electron microscopy energy dispersive X-ray spectroscopy, and X-ray absorption fine structure spectroscopy. The concentration of nuclides dissolved in water was examined by performing static leaching tests of FeUO $_{4}$ compounds for up to three months. A redox reaction was proposed to occur between trivalent Fe and pentavalent U ions in the early stage of FeUO $_{4}$ dissolution. It was thermodynamically deduced that the reduced divalent Fe ion was finally oxidized into a trivalent ion in the presence of dissolved oxygen, and iron hydroxide limited the solubility of Fe. Meanwhile, the concentration of hexavalent U (i.e., uranyl ion) was limited owing to the presence of secondary minerals such as metaschoepite and sodium uranate and subsequently decreased, possibly owing to sorption on Fe oxides, for example. The concentrations of multivalent ions of fission products, such as Ru and Ce, also decreased, likely for the reason above. By contrast, the concentration of soluble Cs ions did not decrease. The validity of this interpretation was supported by comparing the results with the dissolution behavior of a reference sample (Fe-free U $_{3}$ O $_{8}$ ).

Journal Articles

Radiation-induced dissolution of uranium oxide materials in water

Kumagai, Yuta

Hoshasen Kagaku (Internet), (115), p.43 - 49, 2023/04

Oxidation and dissolution of uranium oxide materials has been a subject of numerous studies as a basis of the geological disposal technology for spent nuclear fuel. The understandings obtained by these studies provide useful suggestions for research and development regarding the retrieval and storage of nuclear fuel debris generated by a nuclear severe accident. Here, these research backgrounds of oxidative dissolution of uranium oxides are briefly reviewed and some studies relating to radiation-induced reactions will be introduced.

Journal Articles

Homogeneity of (U, )O ( = Th, Np) prepared by supercritical hydrothermal synthesis

Shirasaki, Kenji*; Tabata, Chihiro*; Sunaga, Ayaki*; Sakai, Hironori; Li, D.*; Konaka, Mariko*; Yamamura, Tomoo*

Journal of Nuclear Materials, 563, p.153608_1 - 153608_11, 2022/05

https://doi.org/10.1016/j.jnucmat.2022.153608

Times Cited Count：2 Percentile：50.96(Materials Science, Multidisciplinary)

We focused on the direct synthesis of (U, )O solid solution (=Th, Np) by extending our recent progress in hydrothermal synthesis with additives. The homogeneity of the (U, )O ( = Th, Np) systems prepared by supercritical hydrothermal reactions was investigated through crystallographic analysis based on Vegard's law, and the $^{23}$ Na nuclear magnetic resonance (NMR) measurement of (U, Np, Na)O solid solutions. Our experimental and analytical results revealed that (i) an optimal additive is ammonium carbonate and starting uranium valence is IV in the case of (U, Th)O $_{2+x}$ , and (ii) an optimal additive is ethanol and starting uranium valence is VI in the case of (U, Np)O $_{2+x}$ , for producing the homogeneous solid solutions by hydrothermal synthesis.

Journal Articles

Supercritical hydrothermal synthesis of UO $_{2+x}$ ; Stoichiometry, crystal shape and size, and homogeneity observed using $^{23}$ Na-NMR spectroscopy of (U, Na)O $_{2+x}$

Tabata, Chihiro*; Shirasaki, Kenji*; Sunaga, Ayaki*; Sakai, Hironori; Li, D.*; Konaka, Mariko*; Yamamura, Tomoo*

CrystEngComm (Internet), 23(48), p.8660 - 8672, 2021/12

https://doi.org/10.1039/D1CE00996F

Times Cited Count：5 Percentile：63.38(Chemistry, Multidisciplinary)

The hydrothermal synthesis of pure uranium dioxide under supercritical water (SCW) conditions was investigated. The nonstoichiometry, crystallite size and morphology of the UO $_{2+x}$ particles were investigated. The SCW hydrothermal synthesis may be a promising method for producing homogeneous UO $_{2+x}$ and its solid solutions with well-defined nonstoichiometries (), shapes, and sizes.

Journal Articles

Crystal structure of U $_{1-y}$ Ln $_{y}$ O $_{2-x}$ (Ln = Gd, Er) solid solution

Pham, V. M.*; Arima, Tatsumi*; Inagaki, Yaohiro*; Idemitsu, Kazuya*; Akiyama, Daisuke*; Nagai, Takayuki; Okamoto, Yoshihiro

Journal of Nuclear Materials, 556, p.153189_1 - 153189_9, 2021/12

https://doi.org/10.1016/j.jnucmat.2021.153189

Times Cited Count：1 Percentile：15.7(Materials Science, Multidisciplinary)

The crystal structure change was evaluated for (1-x)UO $_{2}$ -xLnO $_{1.5}$ (Ln=Gd or Er; x = 0 to 0.4) samples sintered at 1973 K for 8 h under Ar and Ar-10%H $_{2}$ atmospheres. The effect of LnO $_{1.5}$ doping on the crystal structure of UO $_{2}$ was investigated by X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). LnO $_{1.5}$ doping into UO $_{2}$ reduced the lattice parameter of UO $_{2}$ -LnO $_{1.5}$ solid solutions up to 40mol% LnO $_{1.5}$ . The lattice parameters of these samples were comparable to those of stoichiometric (U,Ln)O $_{2.00}$ solid solutions, that is, the O/M ratios were close to 2.00. The U L $_{3}$ -edge XANES analysis showed that higher U oxidation states of +5 or +6 formed, in addition to + 4. The EXAFS analysis indicated that the interatomic distances of U-O and Gd-O decreased with increasing x, whereas those of Er-O may not decrease monotonically.

Journal Articles

Reaction of hydrogen peroxide with uranium zirconium oxide solid solution; Zirconium hinders oxidative uranium dissolution

Kumagai, Yuta; Takano, Masahide; Watanabe, Masayuki

Journal of Nuclear Materials, 497, p.54 - 59, 2017/12

https://doi.org/10.1016/j.jnucmat.2017.10.050

Times Cited Count：13 Percentile：77.73(Materials Science, Multidisciplinary)

We studied oxidative dissolution of uranium and zirconium oxide [(U,Zr)O $_{2}$ ] in aqueous H $_{2}$ O $_{2}$ solution. The interfacial reaction is essential for anticipating how a (U,Zr)O $_{2}$ -based molten fuel may chemically degrade after a severe accident under influence of ionizing radiation. We conducted our experiments with (U,Zr)O $_{2}$ powder and quantitated the H $_{2}$ O $_{2}$ reaction via dissolved U and H $_{2}$ O $_{2}$ concentrations. The dissolution yield relative to H $_{2}$ O $_{2}$ consumption was far less for (U,Zr)O $_{2}$ compared to that of UO $_{2}$ . The reaction kinetics indicates that most of the H $_{2}$ O $_{2}$ catalytically decomposed to O $_{2}$ at the surface of (U,Zr)O $_{2}$ . We confirmed the H $_{2}$ O $_{2}$ catalytic decomposition via O $_{2}$ production (quantitative stoichiometric agreement). In addition, post-reaction Raman scattering spectra of the undissolved (U,Zr)O $_{2}$ showed no additional peaks (indicating a lack of secondary phase formation). The (U,Zr)O $_{2}$ matrix is much more stable than UO $_{2}$ against H $_{2}$ O $_{2}$ -induced oxidative dissolution.

Journal Articles

Pressure-induced weak ferromagnetism in uranium dioxide, UO $_{2}$

Sakai, Hironori; Kato, Harukazu; Tokunaga, Yo; Kambe, Shinsaku; Walstedt, R. E.; Nakamura, Akio; Tateiwa, Naoyuki*; Kobayashi, Tatsuo*

Journal of Physics; Condensed Matter, 15(28), p.S2035 - S2037, 2003/07

https://doi.org/10.1088/0953-8984/15/28/321

Times Cited Count：3 Percentile：21.31(Physics, Condensed Matter)

The cubic-fluorite type uranium dioxide UO is an ionically bounded insulator with localized magnetic moments of U $^{4+}$ (5 $f^{2}$ ) ions. Under atmospheric pressure, UO exhibits a first order antiferromagnetic transition at $T_{rm N}$ =30.8 K accompanied by a small lattice distortion. In order to clarify the interrelation between QQ and exchange interactions in this system, we performed d.c. magnetization measurement under high pressure up to about 1 GPa by a piston-cylinder-type cramped cell. From the d.c. magnetization measurements under high pressure ( 0.1 GPa), it is found that UO shows a weak-ferromagnetic-like transition at 30 K, where the transition temperature is almost independent of external pressure up to 1 GPa. The ferromagnetic component per uranium atom is very small ( $sim 0.05 mu_{rm B}$ ), although its component is dependent of pressure. This small ferromagnetic component may come from a canted antiferromagnetic ordering.

Journal Articles

Supercritical CO $_{2}$ fluid leaching (SFL) of uranium from solid wastes using HNO $_{3}$ -TBP complex as a reactant

Tomioka, Osamu*; Meguro, Yoshihiro; Iso, Shuichi; Yoshida, Zenko; Enokida, Yoichi*; Yamamoto, Ichiro*

Proceedings of International Solvent Extraction Conference 2002 (CD-ROM), p.1143 - 1147, 2002/00

no abstracts in English

Journal Articles

New method for the removal of uranium from solid wastes with supercritical CO $_{2}$ medium containing HNO $_{3}$ -TBP complex

Tomioka, Osamu*; Meguro, Yoshihiro; Iso, Shuichi; Yoshida, Zenko; Enokida, Yoichi*; Yamamoto, Ichiro*

Journal of Nuclear Science and Technology, 38(6), p.461 - 462, 2001/06

https://doi.org/10.3327/jnst.38.461

Times Cited Count：27 Percentile：85.67(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

None

JNC TN1400 2000-006, 68 Pages, 2000/07

JNC-TN1400-2000-006.pdf:2.18MB

no abstracts in English

JAEA Reports

None

JNC TN1400 2000-004, 93 Pages, 2000/07

JNC-TN1400-2000-004.pdf:4.27MB

None

Journal Articles

Vaporization properties of SrUO $_{3}$ and BaUO $_{3}$ in atmospheres simulating accident conditions

Huang, J.*; Yamawaki, Michio*; Yamaguchi, Kenji*; Yasumoto, Masaru*; Sakurai, Hiroshi*; Suzuki, Yasufumi

Journal of Nuclear Materials, 248, p.257 - 261, 1997/09

https://doi.org/10.1016/S0022-3115(97)00202-X

no abstracts in English

Journal Articles

Vaporization properties of SrUO $_{3}$ and BaUO $_{3}$ in atmospheres simulating accident conditions

Huang, J.*; *; Yamaguchi, Kenji*; *; *;

Journal of Nuclear Materials, 248, p.257 - 261, 1997/00

https://doi.org/10.1016/S0022-3115(97)00202-X

Times Cited Count：6 Percentile：47.9(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Investigation of the vaporization of BaUO $_{3}$ by means of mass spectrometry

*; Huang, J.*; Yamaguchi, Kenji*; *; Sakurai, Hiroshi*;

Journal of Nuclear Materials, 231, p.199 - 203, 1996/00

https://doi.org/10.1016/0022-3115(96)00375-3

Times Cited Count：11 Percentile：68.04(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

Preparation of source particles for fabricating pellets through sol-gel microsphere pelletization; Preparation of 50m class microspheres of ThO $_{2}$ and (Th,U)O $_{2}$

; Takahashi, Yoshihisa

JAERI-M 93-122, 18 Pages, 1993/06

JAERI-M-93-122.pdf:1.47MB

no abstracts in English

JAEA Reports

Study on the solid state chemistry of ternary uranium oxides

Yamashita, Toshiyuki

JAERI 1310, 84 Pages, 1988/03

JAERI-1310.pdf:3.12MB

no abstracts in English

Journal Articles

Phase relations and crystal chemistry in the ternary UO $_{2}$ -PrO $_{1}$ $_{.}$ $_{5}$ -O $_{2}$ system

; Fujino, Takeo; Tagawa, Hiroaki

Journal of Nuclear Materials, 132, p.192 - 201, 1985/00

https://doi.org/10.1016/0022-3115(85)90414-3

Times Cited Count：21 Percentile：89.53(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Study on the phase behavior of Ca $_{y}$ U $_{1}$ $_{-}$ $_{y}$ O $_{2}$ $_{+}$ $_{x}$ solid solution

; Fujino, Takeo

Journal of Nuclear Materials, 136, p.117 - 123, 1985/00

https://doi.org/10.1016/0022-3115(85)90037-6

Times Cited Count：14 Percentile：83.03(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Dielectric constants of uranium oxides measured at microwave region

Nihon Genshiryoku Gakkai-Shi, 27(1), p.15 - 20, 1985/00

https://doi.org/10.3327/jaesj.27.15

Times Cited Count：0 Percentile：0.02(Nuclear Science & Technology)

no abstracts in English

Journal Articles

The Dielectric properties at 9.1 GHz and natures of small poralon in nonstoichiometric uranium oxides

Journal of Chemical Physics, 81(12), p.6130 - 6135, 1984/00

https://doi.org/10.1063/1.447566

Times Cited Count：6 Percentile：29(Chemistry, Physical)

no abstracts in English