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Journal Articles

Study on the relation between the crystal structure and thermal stability of FeUO$$_{4}$$ and CrUO$$_{4}$$

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:2 Percentile:71.05(Materials Science, Multidisciplinary)

FeUO$$_{4}$$, CrUO$$_{4}$$, and Fe$$_{x}$$Cr$$_{1-x}$$UO$$_{4}$$ 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$$_{4}$$ and CrUO$$_{4}$$, their crystal structures were evaluated in detail. A Raman band was observed at 700 cm$$^{-1}$$ in all the samples. This Raman band was derived from the stretching vibration of the O-U-O axis band, indicating that Fe$$_{x}$$Cr$$_{1-x}$$UO$$_{4}$$ was composed of a uranyl-like structure in its lattice regardless of its "x"' value. M$"o$ssbauer measurements indicated that the Fe in FeUO$$_{4}$$ and Fe$$_{x}$$Cr$$_{1-x}$$UO$$_{4}$$ were trivalent. Furthermore, Fe$$_{x}$$Cr$$_{1-x}$$UO$$_{4}$$ lost its symmetry around Fe$$^{mathrm{III}}$$ with increasing electron densities around Fe$$^{mathrm{III}}$$, as the abundance of Cr increased. These results suggested no significant structural differences between FeUO$$_{4}$$ and CrUO$$_{4}$$. Thermogravimetric measurements for UO$$_{2}$$, FeUO$$_{4}$$, and CrUO$$_{4}$$ showed that the temperature at which FeUO$$_{4}$$ decomposed under an oxidizing condition (approximately 800 $$^{circ}$$C) was significantly lower than the temperature at which the decomposition of CrUO$$_{4}$$ started (approximately 1250 $$^{circ}$$C). Based on these results, we concluded that the decomposition of FeUO$$_{4}$$ was triggered by an "in-crystal" redox reaction, i.e., Fe$$^{mathrm{III}}$$ $${+}$$ U$$^{mathrm{V}}$$ $$rightarrow$$ Fe$$^{mathrm{II}}$$ $${+}$$ U$$^{mathrm{VI}}$$, which would not occur in the CrUO$$_{4}$$ lattice because Cr$$^{mathrm{III}}$$ could never be reduced under the investigated condition. Finally, the existence of Cr$$^{mathrm{III}}$$ in FexCr$$_{1-x}$$UO$$_{4}$$ effectively suppressed the decomposition of the Fe$$_{x}$$Cr$$_{1-x}$$UO$$_{4}$$ crystal, even at a very low Cr content.

JAEA Reports

Carrying-out of whole nuclear fuel materials in Plutonium Research Building No.1

Inagawa, Jun; Kitatsuji, Yoshihiro; Otobe, Haruyoshi; Nakada, Masami; Takano, Masahide; Akie, Hiroshi; Shimizu, Osamu; Komuro, Michiyasu; Oura, Hirofumi*; Nagai, Isao*; et al.

JAEA-Technology 2021-001, 144 Pages, 2021/08

JAEA-Technology-2021-001.pdf:12.98MB

Plutonium Research Building No.1 (Pu1) was qualified as a facility to decommission, and preparatory operations for decommission were worked by the research groups users and the facility managers of Pu1. The operation of transportation of whole nuclear materials in Pu1 to Back-end Cycle Key Element Research Facility (BECKY) completed at Dec. 2020. In the operation included evaluation of criticality safety for changing permission of the license for use nuclear fuel materials in BECKY, cask of the transportation, the registration request of the cask at the institute, the test transportation, formulation of plan for whole nuclear materials transportation, and the main transportation. This report circumstantially shows all of those process to help prospective decommission.

JAEA Reports

Preliminary missions for the decommissioning of the laboratory building No.1 for the plutonium research program

Segawa, Yukari; Horita, Takuma; Kitatsuji, Yoshihiro; Kumagai, Yuta; Aoyagi, Noboru; Nakada, Masami; Otobe, Haruyoshi; Tamura, Yukito*; Okamoto, Hisato; Otomo, Takashi; et al.

JAEA-Technology 2016-039, 64 Pages, 2017/03

JAEA-Technology-2016-039.pdf:5.24MB

The laboratory building No.1 for the plutonium research program (Bldg. Pu1) was chosen as one of the facilities to decommission by Japan Atomic Energy Agency Reform in September, 2013. The research groups, users of Bldg. Pu1, were driven by necessity to remove used equipment and transport nuclear fuel to other facilities from Bldg. Pu1. Research Group for Radiochemistry proactively established the Used Equipment Removal Team for the smooth operation of the removal in April, 2015. The team classified six types of work into the nature of the operation, removal of used equipment, disposal of chemicals, stabilization of mercury, stabilization of nuclear fuel, transportation of nuclear fuel and radioisotope, and survey of contamination status inside the glove boxes. These works were completed in December, 2015. This report circumstantially shows six works process, with the exception of the approval of the changes on the usage of nuclear fuel in Bldg. Pu1 to help prospective decommission.

Journal Articles

REDOX state analysis of platinoid elements in simulated high-level radioactive waste glass by synchrotron radiation based EXAFS

Okamoto, Yoshihiro; Shiwaku, Hideaki; Nakada, Masami; Komamine, Satoshi*; Ochi, Eiji*; Akabori, Mitsuo

Journal of Nuclear Materials, 471, p.110 - 115, 2016/02

 Times Cited Count:5 Percentile:49.65(Materials Science, Multidisciplinary)

Extended X-ray Absorption Fine Structure (EXAFS) analyses were performed to evaluate REDOX (REDuction and OXidation) state of platinoid elements in simulated high-level nuclear waste glass samples prepared under different conditions of temperature and atmosphere. At first, EXAFS functions were compared with those of standard materials such as RuO$$_2$$. Then structural parameters were obtained from a curve fitting analysis. In addition, a fitting analysis used a linear combination of the two standard EXAFS functions of a given elements metal and oxide was applied to determine ratio of metal/oxide in the simulated glass. The redox state of Ru was successfully evaluated from the linear combination fitting results of EXAFS functions. The ratio of metal increased at more reducing atmosphere and at higher temperatures. Chemical form of rhodium oxide in the simulated glass samples was RhO$$_2$$ unlike expected Rh$$_2$$O$$_3$$. It can be estimated rhodium behaves according with ruthenium when the chemical form is oxide.

Journal Articles

Cabling technology of Nb$$_3$$Sn conductor for ITER central solenoid

Takahashi, Yoshikazu; Nabara, Yoshihiro; Ozeki, Hidemasa; Hemmi, Tsutomu; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Kawano, Katsumi; Oshikiri, Masayuki; Uno, Yasuhiro; et al.

IEEE Transactions on Applied Superconductivity, 24(3), p.4802404_1 - 4802404_4, 2014/06

 Times Cited Count:23 Percentile:73.01(Engineering, Electrical & Electronic)

Japan Atomic Energy Agency (JAEA) is procuring all amounts of Nb$$_3$$Sn conductors for Central Solenoid (CS) in the ITER project. Before start of mass-productions, the conductor should be tested to confirm superconducting performance in the SULTAN facility, Switzerland. The original design of cabling twist pitches is 45-85-145-250-450 mm, called normal twist pitch (NTP). The test results of the conductors with NTP was that current shearing temperature (Tcs) is decreasing due to electro-magnetic (EM) load cycles. On the other hand, the results of the conductors with short twist pitches (STP) of 25-45-80-150-450 mm show that the Tcs is stabilized during EM load cyclic tests. Because the conductors with STP have smaller void fraction, higher compaction ratio during cabling is required and possibility of damage on strands increases. The technology for the cables with STP was developed in Japanese cabling suppliers. The several key technologies will be described in this paper.

Journal Articles

High-temperature X-ray imaging study of simulated high-level waste glass melt

Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*

Denki Kagaku Oyobi Kogyo Butsuri Kagaku, 81(7), p.543 - 546, 2013/07

 Times Cited Count:6 Percentile:18.03(Electrochemistry)

The molten state of simulated high-level waste glass and the behavior of ruthenium element in the melt were investigated by using synchrotron radiation based X-ray imaging technique. Melting, generating and moving of bubbles, condensation and sedimentation of ruthenium element were observed dynamically in continuous 12-bit gray-scale images from the CCD camera. X-ray intensity was obtained easily by digitizing gray-scale values in the image. The existence of ruthenium element is emphasized as a black color in the CCD image at X-ray energy higher than the Ru K-absorption edge. Position sensitive imaging X-ray absorption fine structure (XAFS) measurement was also performed to clarify the chemical state of ruthenium element in the melt.

Journal Articles

High-temperature X-ray imaging study of simulated high-level waste glass melt

Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*

Proceedings of 4th Asian Conference on Molten Salt Chemistry and Technology & 44th Symposium on Molten Salt Chemistry, Japan, p.47 - 52, 2012/09

The molten state of the simulated high-level waste glass and the behavior of ruthenium element in the melt were investigated by using synchrotron radiation based X-ray imaging technique. Melting, generating and moving of bubbles, condensation and sedimentation of ruthenium element were observed dynamically in continuous 12-bit gray-scale images from the CCD camera. The existence of ruthenium in the X-ray CCD image was emphasized over the energy of Ru K-absorption edge. X-ray intensity was obtained easily by digitalizing gray-scale values in the image. Position sensitive imaging X-ray absorption fine structure (XAFS) measurement was performed to clarify the chemical state of ruthenium element in the melt.

Journal Articles

Synchrotron radiation-based X-ray imaging study of ruthenium in simulated high-level waste glass

Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Shiwaku, Hideaki; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 11(2), p.127 - 132, 2012/06

Distribution and the chemical state of Ru element in the simulated high-level waste glass were examined by using the synchrotron radiation based X-ray imaging technique. In this technique, a direct X-ray CCD camera is used in place of an ion chamber. Position sensitive X-ray absorption spectra were obtained by analyzing gray scale in images of the X-ray CCD camera. At first, we measured a test sample containing RuO$$_2$$ and Ru metal powder. We successfully obtained information on the Ru distribution in the sample. In addition, the chemical state (oxide or metal ?) of each small Ru-rich spot was evaluated by the corresponding position sensitive XAFS spectrum. The imaging XAFS technique was applied to some simulated high-level waste glass samples. The Ru distribution of the glass sample and their chemical state were confirmed by image analyses. It can be seen that Ru element scattered in the glass sample exists as oxide RuO$$_2$$.

Journal Articles

Valence state of Am in (U$$_{0.95}$$Am$$_{0.05}$$)O$$_{2.0}$$

Nishi, Tsuyoshi; Nakada, Masami; Suzuki, Chikashi; Shibata, Hiroki; Okamoto, Yoshihiro; Akabori, Mitsuo; Hirata, Masaru

Journal of Nuclear Materials, 418(1-3), p.311 - 312, 2011/11

 Times Cited Count:20 Percentile:81.7(Materials Science, Multidisciplinary)

The XAFS measurements at U-L$$_{3}$$ and Am-L$$_{3}$$ absorption edge of (U$$_{0.95}$$Am$$_{0.05}$$)O$$_{2.0}$$ were performed in transmission mode. Moreover, to clarify the valence state of Am in (U,Am)O$$_{2-x}$$, the XANES spectrum of Am-L$$_{3}$$ absorption edge of (U$$_{0.95}$$Am$$_{0.05}$$)O$$_{2.0}$$ was verified using those of Am-L$$_{3}$$ absorption edge of AmO$$_{2}$$ and Am$$_{2}$$O$$_{3}$$. It was found that the XANES spectrum of the Am-L$$_{3}$$ edge of (U$$_{0.95}$$Am$$_{0.05}$$)O$$_{2.0}$$ is in good accordance with that of Am$$_{2}$$O$$_{3}$$. Thus, Am in (U$$_{0.95}$$Am$$_{0.05}$$)O$$_{2.0}$$ is almost trivalent state.

Journal Articles

Removal of fission products in the spent electrolyte using iron phosphate glass as a sorbent

Amamoto, Ippei; Mitamura, Naoki*; Tsuzuki, Tatsuya*; Takasaki, Yasushi*; Shibayama, Atsushi*; Yano, Tetsuji*; Nakada, Masami; Okamoto, Yoshihiro

Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.503 - 508, 2010/10

The main objective of this development is to recycle the purified eutectic medium of the pyroreprocessing, delaying its disposal for as long as possible. We have introduced the simple filtration method to remove the rare earth element (REE) particles which were formed due to the conversion of REE chlorides to phosphates. Here, the iron phosphate glass is used as a filtration medium for the removal of FP particles. However, some soluble FP such as compounds of alkali-metals, alkaline-earth metals, etc. still remain in the eutectic medium. This time around, on an experimental basis, the iron phosphate glass has been used as a sorbent instead, to remove the soluble FP. We have obtained some positive results and have intention to incorporate it into the spent electrolyte recycle process as a part of the FP separation and immobilization system.

Oral presentation

Imaging XAFS study of actinide oxides at the BL-27B station

Okamoto, Yoshihiro; Shiwaku, Hideaki; Suzuki, Shinichi; Yaita, Tsuyoshi; Nakada, Masami; Nishi, Tsuyoshi; Akabori, Mitsuo

no journal, , 

Imaging XAFS technique using X-ray CCD camera has a remarkable feature of position sensitivity in contrast with the standard XAFS technique using ionic chambers. We have obtained XAFS spectra of nuclear materials at the BL-27B station located in the KEK and maintained by JAEA. In the present work, imaging XAFS measurement of actinide oxides was performed to confirm that it can be useful in researches on nuclear fuel and reprocessing of spent fuels in the future.

Oral presentation

Chemical state analysis of metals in imitative glasses by using Imaging XAFS technique

Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Minato, Kazuo; Shiwaku, Hideaki; Komamine, Satoshi*; Fukui, Toshiki*; Nitani, Hiroaki*; Nomura, Masaharu*

no journal, , 

Chemical state analysis of Ru element scattered in an imitative glass matrix was performed by using the Imaging XAFS technique. Information on distribution of Ru element in the matrix was obtained from contrast values of CCD images before and after the Ru K-absorption edge. It is confirmed that the feature of the distributed element can be examined by getting XAFS spectra from the contrast information. We can get two kinds of XAFS spectra corresponding to Ru metal and oxide separately in the Imaging XAFS analysis.

Oral presentation

XAFS study on americium dioxide, americium sesquioxide and uranium-americium mixed oxide solid solution

Nishi, Tsuyoshi; Nakada, Masami; Suzuki, Chikashi; Shibata, Hiroki; Okamoto, Yoshihiro; Akabori, Mitsuo; Hirata, Masaru

no journal, , 

We performed XAFS studies of americium dioxide (AmO$$_{2}$$), americium sesquioxide (Am$$_{2}$$O$$_{3}$$) and uranium-americium mixed oxide (U$$_{0.95}$$Am$$_{0.05}$$O$$_{2}$$) solid solution. EXAFS results on the Am-L$$_{3}$$ absorption edge of AmO$$_{2}$$ and Am$$_{2}$$O$$_{3}$$ were in good agreement with crystallographic data obtained from XRD analysis. In the results of XANES spectra for AmO$$_{2}$$ and Am$$_{2}$$O$$_{3}$$, an energy shift of a white line peak was observed at 4 eV, which is consistent with the chemical shift between Am$$^{4+}$$ and Am$$^{3+}$$. The XANES result on the Am-L$$_{3}$$ absorption edge of U$$_{0.95}$$Am$$_{0.05}$$O$$_{2}$$ solid solution was almost in agreement with that of Am$$_{2}$$O$$_{3}$$. This result suggested that Am in the uranium-americium mixed oxide was in the trivalent state.

Oral presentation

Synchrotron radiation based X-ray imaging study of simulated high-level waste glass

Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Minato, Kazuo; Shiwaku, Hideaki; Yaita, Tsuyoshi; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; et al.

no journal, , 

Distribution and the chemical state of Ru element in the simulated high-level waste glass were examined by using the synchrotron radiation based X-ray imaging technique. In this technique, a direct X-ray CCD camera is used in place of an ion chamber. Position sensitive X-ray absorption spectra were obtained by analyzing gray scale in images of the X-ray CCD camera. It can be seen that Ru element scattered in the glass sample exists as oxide RuO$$_2$$.

Oral presentation

XAFS measurement on Am containing oxide

Nishi, Tsuyoshi; Nakada, Masami; Suzuki, Chikashi; Shibata, Hiroki; Okamoto, Yoshihiro; Akabori, Mitsuo; Hirata, Masaru

no journal, , 

no abstracts in English

Oral presentation

XAFS measurement on uranium and americium mixed oxide

Nishi, Tsuyoshi; Nakada, Masami; Suzuki, Chikashi; Shibata, Hiroki; Okamoto, Yoshihiro; Akabori, Mitsuo; Hirata, Masaru

no journal, , 

no abstracts in English

Oral presentation

Synchrotron radiation based imaging XAFS analysis of simulated high-level waste glass

Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*

no journal, , 

Distribution and the chemical state of fission product elements like Zr, Mo and Ru in the simulated high-level waste glass were examined by using the synchrotron radiation based X-ray imaging technique. We used the high resolution imaging system and the high-speed CCD camera for imaging XAFS measurement of the glass sample at molten state. Position sensitive X-ray absorption spectra were obtained by analyzing gray scale in images of the CCD camera.

Oral presentation

Properties and behavior of insoluble residue in the cold cap, 3; Imaging and XAFS analysis of simulated high-level waste glass

Okamoto, Yoshihiro; Shiwaku, Hideaki; Nakada, Masami; Takano, Masahide; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*

no journal, , 

Chemical properties and behavior of insoluble residue in the cold cap of simulated high-level waste glass was examined by using synchrotron radiation based imaging and XAFS analyses. From XAFS analyses of Zr, Mo and Ce, (1) Zr is in a complex oxide like ZrSiO$$_4$$ or Zr(MoO$$_4$$)$$_2$$, (2) The complex MoO$$_4$$$$^{2-}$$ ion is predominant for Mo element, (3) Redox state for cerium element was evaluated from Ce L$$_3$$-edge XAFS, and (4) Chemical state of cerium was determined from Ce K-edge XAFS. Chemical state and bubble growth at molten state was investigated by using X-ray imaging analysis.

Oral presentation

Chemical analysis of simulated high-level waste glass by using imaging XAFS technique

Okamoto, Yoshihiro; Nakada, Masami; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*; Nitani, Hiroaki*; Nomura, Masaharu*

no journal, , 

The high level liquid waste (HLLW) generated in the reprocessing of spent nuclear fuels is disposed of as vitrified waste mixed with borosilicate glass. Chemical state of noble metals like Ru in simulated glasses was investigated by using the synchrotron based X-ray imaging analysis in the present work. The X-ray imaging measurement was performed at the NW10A of PF-AR and the BL-27B of PF, KEK. The imaging system is composed of the beam monitor (AA40 and AA50) and the CCD camera (high-speed type C9300-221 and high resolution type C11440-10C). X-ray absorption fine structure (XAFS) spetcra of Ru K-edge for very small area were obtained from the imaging intensity data. It can be seen by comparing with standard materials that Ru in the small area exists as RuO$$_2$$.

Oral presentation

Properties and behavior of Insoluble Residue in the fused glass, 2; Chemical analysis by synchrotron XAFS technique

Okamoto, Yoshihiro; Shiwaku, Hideaki; Nakada, Masami; Takano, Masahide; Akabori, Mitsuo; Komamine, Satoshi*; Fukui, Toshiki*; Ochi, Eiji*

no journal, , 

Synchrotron based X-ray absorption fine structure analysis of Mn, Ce, Zr, Mo, Ru, Rh and Pd was performed to evaluate chemical state and the local structure in the simulated glass samples. Redox state and chemical state were confirmed from X-ray near edge structure (XANES) analysis. Information on the local structure was obtained from the extended X-ray absorption fine structure (EXAFS) analysis.

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