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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.

Journal Articles

Spectroscopic studies of M$"o$ssbauer, infrared, and laser-induced luminescence for classifying rare-earth minerals enriched in iron-rich deposits

Aoyagi, Noboru; Nguyen, T. T.*; Kumagai, Yuta; Nguyen, T. V.*; Nakada, Masami; Segawa, Yukari; Nguyen, H. T.*; Le, B. T.*

ACS Omega (Internet), 5(13), p.7096 - 7105, 2020/04

 Times Cited Count:1 Percentile:21.55(Chemistry, Multidisciplinary)

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:4 Percentile:45.9(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

Self-radiation effects and glassy nature of magnetic transition in AmO$$_2$$ revealed by $$^{17}$$O-NMR

Tokunaga, Yo; Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori*; Sakai, Hironori; Kambe, Shinsaku; Homma, Yoshiya*; Honda, Fuminori*; Aoki, Dai*; Walstedt, R. E.*

Physical Review B, 89(21), p.214416_1 - 214416_8, 2014/06

 Times Cited Count:7 Percentile:36.72(Materials Science, Multidisciplinary)

The magnetic phase transition near $$T_0=8.5$$ K in AmO$$_2$$ has been investigated microscopically by means of $$^{17}$$O NMR. To avoid complexities arising from sample aging associated with the alpha decay of $$^{243}$$Am, all measurements have been performed within 40 days after sample synthesis. Even during such a short period, however, a rapid change of NMR line shape has been observed at 1.5 K, suggesting that the ground state of AmO$$_2$$ is very sensitive to disorder. We have also confirmed the loss of $$^{17}$$O NMR signal intensity over a wide temperature range below $$T_0$$, and more than half of oxygen nuclei are undetectable at 1.5 K. This behavior reveals the persistence of slow and distributed spin fluctuations down to temperatures well below $$T_0$$. In the paramagnetic state, strong NMR line broadening and spatially inhomogeneous spin fluctuations have been observed. The results are all indicative of short-range, spin-glass-like character for the magnetic transition in this system.

JAEA Reports

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2012

Sumiya, Shuichi; Watanabe, Hitoshi; Miyagawa, Naoto; Nakano, Masanao; Nakada, Akira; Fujita, Hiroki; Takeyasu, Masanori; Isozaki, Tokuju; Morisawa, Masato; Mizutani, Tomoko; et al.

JAEA-Review 2013-056, 181 Pages, 2014/03

JAEA-Review-2013-056.pdf:6.22MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2012 to March 2013. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Co. in March 2011.

Journal Articles

DFT study on the electronic structure and chemical state of americium in an (Am,U) mixed oxide

Suzuki, Chikashi; Nishi, Tsuyoshi; Nakada, Masami; Tsuru, Tomohito; Akabori, Mitsuo; Hirata, Masaru; Kaji, Yoshiyuki

Journal of Physics and Chemistry of Solids, 74(12), p.1769 - 1774, 2013/12

 Times Cited Count:12 Percentile:53.54(Chemistry, Multidisciplinary)

We investigated the electronic state of a CaF$$_{2}$$-type (Am,U) mixed oxide using the all-electron full potential linear augmented plane wave method and compared it with those of Am$$_{2}$$O$$_{3}$$, AmO$$_{2}$$, UO$$_{2}$$, and La$$_{0.5}$$U$$_{0.5}$$O$$_{2}$$. The valence of Am in the mixed oxide was close to that of Am$$_{2}$$O$$_{3}$$ and the valence of U in the mixed oxide was pentavalent. The electronic structure of AmO$$_{2}$$ was different from that of Am$$_{2}$$O$$_{3}$$, particularly just above the Fermi level. In addition, the electronic states of Am and U in the mixed oxide were similar to those of trivalent Am and pentavalent U oxides. These electronic states reflected the high oxygen potential of AmO$$_{2}$$ and the heightened oxygen potential resulting from the addition of Am to UO$$_{2}$$ and also suggested the occurrence of charge transfer from Am to U in the solid solution process.

Journal Articles

Study of exotic uranium compounds using $$^{238}$$U M$"o$ssbauer spectroscopy

Tsutsui, Satoshi; Nakada, Masami

M$"o$ssbauer Spectroscopy; Applications in Chemistry, Biology, and Nanotechnology, p.123 - 140, 2013/10

no abstracts in English

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:5 Percentile:14.87(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.

JAEA Reports

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2011

Sumiya, Shuichi; Watanabe, Hitoshi; Nakano, Masanao; Takeyasu, Masanori; Nakada, Akira; Fujita, Hiroki; Isozaki, Tokuju; Morisawa, Masato; Mizutani, Tomoko; Nagaoka, Mika; et al.

JAEA-Review 2013-009, 195 Pages, 2013/06

JAEA-Review-2013-009.pdf:3.35MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2011 to March 2012. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Plant on Tokyo Electric Power Co. in March 2011.

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$$_2$$.

JAEA Reports

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2010

Sumiya, Shuichi; Watanabe, Hitoshi; Nakano, Masanao; Takeyasu, Masanori; Nakada, Akira; Fujita, Hiroki; Isozaki, Tokuju; Morisawa, Masato; Mizutani, Tomoko; Kokubun, Yuji; et al.

JAEA-Review 2012-015, 166 Pages, 2012/05

JAEA-Review-2012-015.pdf:3.53MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2010 to March 2011. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Plant on Tokyo Electric Power Co. in 2011 March. Appendices present comprehensive information, such as monitoring program, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes. In addition, the data exceeded the normal range of fluctuation by the accidental release was evaluated in the appendices.

Journal Articles

Core-hole effect on XANES and electronic structure of minor actinide dioxides with fluorite structure

Suzuki, Chikashi; Nishi, Tsuyoshi; Nakada, Masami; Akabori, Mitsuo; Hirata, Masaru; Kaji, Yoshiyuki

Journal of Physics and Chemistry of Solids, 73(2), p.209 - 216, 2012/02

 Times Cited Count:21 Percentile:67.53(Chemistry, Multidisciplinary)

The authors investigated theoretically core-hole effects on X-ray absorption near-edge structures (XANES) of Np and Am L$$_{III}$$ in neptunium dioxide (NpO$$_{2}$$) and americium dioxide (AmO$$_{2}$$) with CaF$$_{2}$$-type crystal lattices using the all-electron full-potential linearized augmented plane-wave (FP-LAPW) method. The peak creation mechanism of XANES was shown by examining the electronic structures of these oxides, which indicated that core-hole screening was more marked for AmO$$_{2}$$ than for NpO$$_{2}$$ because of the difference in the charge transfer between these oxides. Furthermore, the results of charge density analysis suggested that the white line was assigned to the quasi-bound state composed of the localized Np d or Am d components and O components, and that the tail structure was created as a result of delocalized standing waves between the Np or Am atoms.

Journal Articles

Solid-state NMR study of actinide dioxides

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Chudo, Hiroyuki; Osaka, Masahiko; Miwa, Shuhei; Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori; Homma, Yoshiya*

Materials Research Society Symposium Proceedings, Vol.1444, p.149 - 158, 2012/00

 Times Cited Count:0 Percentile:0.11

Besides the importance of AnO$$_2$$ series (An; U, Np, Pu, Am) as a nuclear fuel, the magnetic properties of these compounds at low temperatures are particularly interesting. Their surprisingly varied physical properties continue to be of interest for both theory and experiment. In this study, we have performed NMR studies for the series of actinide dioxides. On the basis of $$^{17}$$O-NMR studies, exotic magnetic orderings associated with multipole degrees of freedom on 5$$f$$ electrons have been identified in UO$$_2$$ (dipolar + quadrupolar ordering) and NpO$$_2$$ (octupolar + quadrupolar ordering), in contrast with the non-magnetic ground state of PuO$$_2$$. In AmO$$_2$$, our $$^{17}$$O-NMR data provide the first microscopic evidence for a phase transition as a bulk property in this system.

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:19 Percentile:83.81(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

NMR study on AmO$$_{2}$$; Comparison with UO$$_{2}$$ and NpO$$_{2}$$

Tokunaga, Yo; Nishi, Tsuyoshi; Kambe, Shinsaku; Nakada, Masami; Homma, Yoshiya*; Sakai, Hironori; Chudo, Hiroyuki

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA110_1 - SA110_3, 2011/07

 Times Cited Count:2 Percentile:21.57(Physics, Multidisciplinary)

We have successfully performed an $$^{17}$$O NMR for the first time on Americium dioxide (AmO$$_2$$). We observed a drastic broadening of the NMR spectrum, after a sudden drop of NMR signal intensity below $$T_0$$. These data provide the first microscopic evidence for a phase transition as a bulk property in this system. In the ordered state, we found a spectrum with a triangular line shape, which resembles neither that of UO$$_2$$ nor NpO$$_2$$. It is also suggested that there is considerable damage to the sample induced by self-radiation effects from the alpha decay of $$^{243}$$Am.

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.

Journal Articles

Local and electronic structure of Am$$_{2}$$O$$_{3}$$ and AmO$$_{2}$$ with XAFS spectroscopy

Nishi, Tsuyoshi; Nakada, Masami; Suzuki, Chikashi; Shibata, Hiroki; Ito, Akinori; Akabori, Mitsuo; Hirata, Masaru

Journal of Nuclear Materials, 401(1-3), p.138 - 142, 2010/06

 Times Cited Count:25 Percentile:87.19(Materials Science, Multidisciplinary)

XAFS studies were performed in a study of americium sesquioxide (Am$$_{2}$$O$$_{3}$$) with A-type rare earth oxide structure and americium dioxide (AmO$$_{2}$$) with fluorite structure. EXAFS results for Am-L$$_{3}$$ absorption edge of Am$$_{2}$$O$$_{3}$$ and AmO$$_{2}$$ were good agreement with the crystallographic data from X-ray diffraction analysis. In order to characterize XANES in aspect of the electronic states, the theoretical assignments for the Am$$_{2}$$O$$_{3}$$ and AmO$$_{2}$$ were performed with the all-electron full potential linearized augmented plane wave (FP-LAPW) method. The theoretical XANES spectra of Am$$_{2}$$O$$_{3}$$ and AmO$$_{2}$$ well reproduced the experimental ones. In addition, it was found that the white line peak was created due to the interaction between Am-d and O-p components, and the broad peak and the tail peak were created due to the interaction between Am-d and O-d component.

Journal Articles

NMR evidence for the 8.5 K phase transition in americium dioxide

Tokunaga, Yo; Nishi, Tsuyoshi; Kambe, Shinsaku; Nakada, Masami; Ito, Akinori; Homma, Yoshiya*; Sakai, Hironori; Chudo, Hiroyuki

Journal of the Physical Society of Japan, 79(5), p.053705_1 - 053705_4, 2010/05

 Times Cited Count:14 Percentile:65.65(Physics, Multidisciplinary)

We report here the first NMR study of americium dioxide (AmO$$_2$$). More than 30 years ago, a phase transition was suggested to occur in this compound at 8.5 K based on magnetic susceptibility data, while no evidence had been obtained from microscopic measurements. We have prepared a powder sample of $$^{243}$$AmO$$_2$$ containing 90 at.% $$^{17}$$O and have performed $$^{17}$$O NMR at temperatures ranging from 1.5 K to 200 K. After a sudden drop of the $$^{17}$$O NMR signal intensity below 8.5 K, at 1.5 K we have observed an extremely broad spectrum covering a range of $$sim$$14 kOe in applied field. These data provide the first microscopic evidence for a phase transition as a bulk property in this system. In addition, the $$^{17}$$O NMR spectrum has been found to split into two peaks in the paramagnetic state, an effect which has not been reported for actinide dioxides studied up to now. We suggest that the splitting is induced by self-radiation damage from the alpha decay of $$^{243}$$Am.

107 (Records 1-20 displayed on this page)