Study on the relation between the crystal structure and thermal stability of FeUO and CrUO

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

Journal of Nuclear Materials, 568, p.153847_1 - 153847_10, 2022/09

https://doi.org/10.1016/j.jnucmat.2022.153847

FeUO, CrUO, and FeCrUO are monouranates containing pentavalent U. Even though these compounds have similar crystal structures, their formation conditions and thermal stability are significantly different. To determine the factors causing the difference in thermal stability between FeUO and CrUO, their crystal structures were evaluated in detail. A Raman band was observed at 700 cm in all the samples. This Raman band was derived from the stretching vibration of the O-U-O axis band, indicating that FeCrUO was composed of a uranyl-like structure in its lattice regardless of its "x"' value. Mssbauer measurements indicated that the Fe in FeUO and FeCrUO were trivalent. Furthermore, FeCrUO lost its symmetry around Fe with increasing electron densities around Fe, as the abundance of Cr increased. These results suggested no significant structural differences between FeUO and CrUO. Thermogravimetric measurements for UO, FeUO, and CrUO showed that the temperature at which FeUO decomposed under an oxidizing condition (approximately 800 C) was significantly lower than the temperature at which the decomposition of CrUO started (approximately 1250 C). Based on these results, we concluded that the decomposition of FeUO was triggered by an "in-crystal" redox reaction, i.e., Fe U Fe U, which would not occur in the CrUO lattice because Cr could never be reduced under the investigated condition. Finally, the existence of Cr in FexCrUO effectively suppressed the decomposition of the FeCrUO crystal, even at a very low Cr content.

Application of an augmentation method to MCR-ALS analysis for XAFS and Raman data matrices in the structural change of isopolymolybdates

Saeki, Morihisa*; Yomogida, Takumi; Matsumura, Daiju; Saito, Takumi*; Nakanishi, Ryuzo*; Tsuji, Takuya; Oba, Hironori*

Analytical Sciences, 36(11), p.1371 - 1378, 2020/11

https://doi.org/10.2116/analsci.20P147

We measured X-ray absorption fine structure (XAFS) and Raman spectra of isopolymolybdates(VI) in HNO solution (0.15- 4.0 M), which change their geometries depending on acid concentration, and performed simultaneous resolution of the XAFS and Raman data using a multivariate curve resolution by alternating least-squares (MCR-ALS) analysis. In iterative ALS optimization, initial data matrices were prepared by two different methods. The MCR-ALS result of single XAFS data matrix shows large dependence on the preparation method of the initial data matrices. The MCR-ALS result of an augmented matrix of Raman and XAFS data has little dependence on the initial data matrices. It indicates that the augmentation method effectively improves the rotation ambiguities in the MCR-ALS analysis of the XAFS data. Based on the model fitting of the pure EXAFS oscillations, we revealed the change of [MoO(HO)] [MoO(HO)] [HMoO(HO)] in the highly concentrated HNO solution.

Characterization of C films polymerized by ion irradiation

Narumi, Kazumasa; Sakai, Seiji; Naramoto, Hiroshi*; Takanashi, Koki

Fullerenes, Nanotubes, and Carbon Nanostructures, 14(2-3), p.429 - 434, 2006/00

no abstracts in English

Study on the stress corrosion cracking of zirconium in nuclear fuel reprocessing environment

Kato, Chiaki

JAERI-Research 2003-013, 143 Pages, 2003/08

JAERI-Research-2003-013.pdf:22.12MB

This study is investigation about stress corrosion cracking (SCC) of zirconium in nuclear fuel reprocessing. Chapter 1 is described background. Chapter 2 is explained experimental apparates. Chapter 3 is described the increased oxidization potential on the heat-transfer surface and suggested the initiation of SCC on a boiling heat-transfer surface. Chapter 4 is described that the SCC susceptibility increased with increasing nitric acid concentration and solution temperature on notched specimen by SSRT. In addition, the SCC susceptibility effected by the crystal anisotropy by the hot rolling direction and increased on a parallel face to the rolling direction. Chapter 5 is described that the SCC susceptibility increased in HAZ/base metal boundary in order to the preferential orientation of cleavage plane (0002). Chapter 6 is described that the increased oxidization potential on the heat-transfer surface is attributed to the reduction of nitrous acid concentration by the thermal decomposition on the surface and the removal of the decomposition product from solution by boiling bubbles.

Mesoscopic patterning induced by co-deposition of C and Ni on the MgO(100) single crystal

Vacik, J.; Naramoto, Hiroshi; Narumi, Kazumasa; Yamamoto, Shunya; Miyashita, Kiyoshi*

Materials Research Society Symposium Proceedings, Vol.648, p.P3.50.1 - P3.50.6, 2001/00

None

Air oxidation behavior of fuel for the High Temperature Engineering Test Reactor(HTTR)

; Hayashi, Kimio; Fukuda, Kosaku

JAERI-M 92-114, 20 Pages, 1992/08

JAERI-M-92-114.pdf:1.06MB

no abstracts in English

Fabrication and physical properties of AlF-BeF based fluoride glasses for IR transmission

Ono, Hideo; Igawa, Naoki; Ishii, Yoshinobu; Umesaki, Norimasa*; *

Journal of Nuclear Materials, 191-194, p.525 - 529, 1992/00

no abstracts in English

Grain size dependence of thermal-shock resistance of yttria-doped tetragonal zirconia polycrystals

*; *; *; *; Ono, Hideo; Igawa, Naoki; Nagasaki, Takanori

Journal of the American Ceramic Society, 73(8), p.2523 - 2525, 1990/00

https://doi.org/10.1111/j.1151-2916.1990.tb07625.x

no abstracts in English

Chemical sputtering of sintered diamond compacts and diamond film

J.Vac.Sci.Technol.,A, 5(4), p.2222 - 2226, 1987/04

no abstracts in English

In situ Raman spectroscopy on nuclear materials in hot cell

Miro, S.*; Peuget, S.*; Tupin, M.*; Fayette, L.*; Nakayoshi, Akira; Perrin, S.*; Jegou, C.*

no journal, ,