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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
Times Cited Count:4 Percentile:51.78(Materials Science, Multidisciplinary)FeUO, CrUO
, and Fe
Cr
UO
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 Fe
Cr
UO
was composed of a uranyl-like structure in its lattice regardless of its "x"' value. M
ssbauer measurements indicated that the Fe in FeUO
and Fe
Cr
UO
were trivalent. Furthermore, Fe
Cr
UO
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 FexCr
UO
effectively suppressed the decomposition of the Fe
Cr
UO
crystal, even at a very low Cr content.
Rizaal, M.; Nakajima, Kunihisa; Saito, Takumi*; Osaka, Masahiko; Okamoto, Koji*
Journal of Nuclear Science and Technology, 57(9), p.1062 - 1073, 2020/09
Times Cited Count:9 Percentile:64.46(Nuclear Science & Technology)The interaction of cesium hydroxide and a calcium silicate insulation material was experimentally investigated at high temperature conditions. A thermogravimetry equipped with differential thermal analysis was used to analyze thermal events in the samples of mixed calcium silicate and cesium hydroxide under Ar-5%H and Ar-4%H
-20%H
0 with maximum temperature of 1100
C. Prior being mixed with cesium hydroxide, a part of calcium silicate was pretreated at high temperature to evaluate the effect of possible structural changes of this material due to a preceding thermal history and also the sake of thermodynamic evaluation to those available ones. Based upon the initial condition (preliminary heat treatment) of calcium silicate, it was found that if the original material consisted of xonotlite (Ca
Si
0
(0H)
), the endothermic reaction with cesium hydroxide occurred over the temperature range 575-730
C meanwhile if the crystal phase of original material was changed to wollastonite (CaSi0
), the interaction occurred over temperature range 700-1100
C. Furthermore, the X-ray diffraction analyses have indicated on both type of pretreated calsils that regardless of Ar-5%H
and Ar-4%H
-20%H
0 atmosphere, cesium aluminum silicate, CsAlSi0
was formed with aluminum in the samples as an impurity or adduct.
Nakajima, Ken; ; Yamamoto, Toshihiro; ; Suzaki, Takenori
Journal of Nuclear Science and Technology, 31(11), p.1160 - 1170, 1994/11
Times Cited Count:7 Percentile:56.04(Nuclear Science & Technology)no abstracts in English
Nakajima, Ken; ; Suzaki, Takenori
Nuclear Science and Engineering, 116, p.138 - 146, 1994/00
Times Cited Count:16 Percentile:78.03(Nuclear Science & Technology)no abstracts in English
Masukawa, Fumihiro; ; Inoue, Osamu*; Hara, Toshiharu*
JAERI-M 93-024, 31 Pages, 1993/02
no abstracts in English
Nakano, Yoshihiro
JAERI-M 92-103, 67 Pages, 1992/07
no abstracts in English
C-S.Gil*; Okumura, Keisuke;
JAERI-M 91-200, 61 Pages, 1991/11
no abstracts in English
Okuno, Hiroshi; Naito, Yoshitaka; Sakurai, Y.*
Journal of Nuclear Science and Technology, 28(10), p.958 - 960, 1991/10
no abstracts in English
Okumura, Keisuke; ; Tanaka, Kenichi*; C-J.Jeong*
JAERI-M 89-201, 150 Pages, 1989/12
no abstracts in English
; ;
Journal of Nuclear Science and Technology, 24(8), p.610 - 620, 1987/08
Times Cited Count:4 Percentile:44.56(Nuclear Science & Technology)no abstracts in English
; ;
JAERI-M 86-190, 52 Pages, 1987/01
no abstracts in English
Nakajima, Hayato; Shimizu, Saburo; ; Ikezoe, Yasumasa;
Nihon Kagakkai-Shi, 8, p.1257 - 1261, 1984/00
no abstracts in English
Ugajin, Mitsuhiro
Journal of Nuclear Science and Technology, 20(3), p.228 - 236, 1983/00
Times Cited Count:20 Percentile:85.98(Nuclear Science & Technology)no abstracts in English
;
Radiochem.Radioanal.Lett., 29(6), p.331 - 340, 1977/06
no abstracts in English