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Umino, Yoshinori; Kato, Keisuke; Tanigawa, Masafumi; Kobayashi, Daisuke; Obu, Tomoyuki; Kimura, Yuichi*; Nemoto, Ryo*; Tajiri, Kazuma*
Nihon Hozen Gakkai Dai-19-Kai Gakujutsu Koenkai Yoshishu, p.33 - 36, 2023/08
In the basic laboratory of the Plutonium Conversion Development Facility in Tokai Reprocessing Plant, tests had been conducted to obtain effective data for manufacturing mixed plutonium and uranium oxide powder by irradiating a mixture of plutonium and uranium solution with microwaves. The test has already been completed, and we are currently dismantling and removing equipment. In this paper, techniques related to equipment renewal, dismantling and removal works inside the glove-box are discussed.
Miyazaki, Hidetoshi*; Akatsuka, Tatsuyoshi*; Kimura, Koji*; Egusa, Daisuke*; Sato, Yohei*; Itakura, Mitsuhiro; Takagi, Yasumasa*; Yasui, Akira*; Ozawa, Kenichi*; Mase, Kazuhiko*; et al.
Materials Transactions, 64(6), p.1194 - 1198, 2023/06
We investigated the electronic structure of the MgZnY alloy using hard and soft X-ray photoemission spectroscopy and electronic band structure calculations to understand the mechanism of the phase stability of this material. Electronic structure of the MgZnY alloy showed a semi-metallic electronic structure with a pseudo-gap at the Fermi level. The observed electronic structure of the MgZnY alloy suggests that the presence of a pseudogap structure is responsible for phase stability.
Sato, Yohei*; Egusa, Daisuke*; Miyazaki, Hidetoshi*; Kimura, Koji*; Itakura, Mitsuhiro; Terauchi, Masami*; Abe, Eiji*
Materials Transactions, 64(5), p.950 - 954, 2023/05
Dilute Mg-Zn-Y alloy with a mille-feuille structure (MFS) exhibits a mechanical strength comparable to Mg-Zn-Y alloy with long period stacking/ordered (LPSO) structure through kink deformation. In order to deepen understanding the thermal stability of the MFS-type Mg alloys, it is required to clarify the solute cluster structures composed of Zn and Y in solute enriched stacking faults (SESFs). In this study, electron energy-loss and energy dispersive X-ray spectroscopy based on scanning transmission electron microscopy (STEM-EELS/EDS) were conducted to investigate the electronic structure and composition of Zn and Y in the SESFs of the MFS-Mg alloy. Zn-L2,3 spectra indicated that the valence charges of Zn in the dilute Mg alloy were different from that of the LPSO-type Mg-Zn-Y alloy. In addition, the intensity ratio of L3/L2 in Y-L2,3 spectrum of the dilute MFS-Mg alloy was larger than that of the LPSO-Mg alloy, reflecting the electron occupancies of 4d3/2 and 4d5/2 orbitals of Y atoms were different from those of the LPSO-Mg alloys. STEM-EELS analysis of the SESF composition in the dilute MFS-Mg alloy indicated that the Zn/Y ratio should be lower than that of the LPSO-Mg alloy, which was confirmed also by STEM-EDS measurements. These results indicate that the cluster structure in the SESFs of the dilute MFS-Mg alloy should be different from the ideal Zn6Y8 cluster in the LPSO-type Mg-Zn-Y alloys.
Go, Shintaro*; Ideguchi, Eiji*; Yokoyama, Rin*; Aoi, Nori*; Azaiez, F.*; Furutaka, Kazuyoshi; Hatsukawa, Yuichi; Kimura, Atsushi; Kisamori, Keiichi*; Kobayashi, Motoki*; et al.
Physical Review C, 103(3), p.034327_1 - 034327_8, 2021/03
Times Cited Count:4 Percentile:58.42(Physics, Nuclear)Asai, Shiho; Hanzawa, Yukiko; Konda, Miki; Suzuki, Daisuke; Magara, Masaaki; Kimura, Takaumi; Ishihara, Ryo*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*
Talanta, 185, p.98 - 105, 2018/08
Times Cited Count:7 Percentile:32.37(Chemistry, Analytical)Estimating the risks associated with radiation from long-lived fission products (LLFP) in radioactive waste is essential to ensure the long-term safety of potential disposal sites. In this study, the amount of Zr, a LLFP, was determined by ICP-MS after separating Zr from a spent nuclear fuel solution using a microvolume anion-exchange cartridge (TEDA cartridge). The TEDA cartridge achieved highly selective separation of Zr regardless of its small bed volume of 0.08 cm. The time taken to complete the Zr separation was 1.2 min with a flow rate of 1.5 mL/min, which was 10 times faster than that for a conventional anion-exchange resin column. Almost all the other elements were removed, leading to accurate measurement of Zr. The result connects experimental value to theoretical prediction provided by ORIGEN2, which requires verification. With the measured value, we demonstrated that the theoretical value is reliable enough to estimate radiation risks.
Sugiyama, Daisuke*; Kimura, Hideo; Tachikawa, Hirokazu*; Iimoto, Takeshi*; Kawata, Yosuke*; Ogino, Haruyuki*; Okoshi, Minoru*
Journal of Radiological Protection, 38(1), p.456 - 462, 2018/03
Times Cited Count:0 Percentile:0.01(Environmental Sciences)Experience after the accident at the Fukushima Daiichi Nuclear Power Station has shown that there is a need to establish radiation protection criteria for radioactive waste management consistent with the criteria adopted for the remediation of existing exposure situations. A stepwise approach to setting such criteria is proposed. Initially, a reference level for annual effective dose from waste management activities in the range 1-10 mSv should be set, with the reference level being less than the reference level for ambient dose. Subsequently, the reference level for annual effective dose from waste management activities should be reduced in one or more steps to achieve a final target value of 1 mSv. The dose criteria at each stage should be determined with relevant stakeholder involvement. Illustrative case studies show how this stepwise approach might be applied in practice.
Asai, Shiho; Hanzawa, Yukiko; Konda, Miki; Suzuki, Daisuke; Magara, Masaaki; Kimura, Takaumi; Ishihara, Ryo*; Saito, Kyoichi*; Yamada, Shinsuke*; Hirota, Hideyuki*
Analytical Chemistry, 88(6), p.3149 - 3155, 2016/03
Times Cited Count:8 Percentile:30.06(Chemistry, Analytical)Neptunium-237 (Np) is one of the major long-lived radionuclides found in spent nuclear fuel. To evaluate the long-term safety of a HLW repository, the Np content in spent nuclear fuel must be determined. In this study, micro-volume anion-exchange porous polymer disk-packed cartridges were prepared for Am-Np separation, which is required prior to the measurement of Np with ICP-MS. Disks with a volume of 0.08 cm were cut out from porous sheets having triethylenediamine (TEDA)-containing polymer chains densely attached on the pore surface. The resulting TEDA-introduced disk cartridge was applied to a spent nuclear fuel sample. The chemical yield of Np was 90.4%, which is sufficiently high for ICP-MS measurement of Np. Compared with the conventional separation technique using commercially available anion-exchange resin columns, the time required to adsorb, wash and elute Np using the TEDA-introduced disk cartridge was reduced by 75%.
Go, Shintaro*; Ideguchi, Eiji*; Yokoyama, Rin*; Kobayashi, Motoki*; Kisamori, Keiichi*; Takaki, Motonobu*; Miya, Hiroyuki*; Ota, Shinsuke*; Michimasa, Shinichiro*; Shimoura, Susumu*; et al.
JPS Conference Proceedings (Internet), 6, p.030005_1 - 030005_4, 2015/06
Katsuyama, Chie*; Nashimoto, Hiroaki*; Nagaosa, Kazuyo*; Ishibashi, Tomotaka*; Furuta, Kazuki*; Kinoshita, Takeshi*; Yoshikawa, Hideki; Aoki, Kazuhiro; Asano, Takahiro*; Sasaki, Yoshito; et al.
FEMS Microbiology Ecology, 86(3), p.532 - 543, 2013/12
Times Cited Count:14 Percentile:36.94(Microbiology)Anaerobic microbial activity has a major influence on the subsurface environment, and should be considered in subsurface activities including the construction of radioactive waste repositories. We investigated denitrification and methanogenesis in anoxic groundwater from 140 m depth in two boreholes, where the redox potential fluctuated. The average maximum potential denitrification rates, measured under anaerobic conditions in the two boreholes using an N tracer. Methanogenesis candidates were detected by 16S rRNA gene analysis. Although the stable isotope signatures suggested that some of the dissolved methane was of biogenic origin, no potential for methane production was evident during the incubations. The groundwater at 140 m depth did not contain oxygen, had an Eh ranging from -144 to 6.8 mV, and was found to be a potential field for denitrification.
Esaka, Fumitaka; Magara, Masaaki; Suzuki, Daisuke; Miyamoto, Yutaka; Kimura, Takaumi
Hyomen Kagaku, 34(3), p.125 - 130, 2013/03
Analysis of individual particles containing nuclear materials in environmental samples gives important information on the origins. This paper describes analytical techniques of individual particles containing nuclear materials such as uranium and plutonium. A scanning electron microscope (SEM) combined with an X-ray detector, solid track detectors, and secondary ion mass spectrometry (SIMS) were used to identify particles containing uranium and/or plutonium in environmental samples. Isotope ratios for these particles were successfully determined with SIMS, thermal ionization mass spectrometry (TIMS) or inductively coupled plasma mass spectrometry (ICPMS). The complementary use of these methods is effective to characterize individual particles rapidly, precisely and accurately.
Ogura, Koichi; Shizuma, Toshiyuki; Hayakawa, Takehito; Yogo, Akifumi; Nishiuchi, Mamiko; Orimo, Satoshi; Sagisaka, Akito; Pirozhkov, A. S.; Mori, Michiaki; Kiriyama, Hiromitsu; et al.
Japanese Journal of Applied Physics, 51(4), p.048003_1 - 048003_2, 2012/04
Times Cited Count:2 Percentile:8.97(Physics, Applied)A proton beam driven by a repetitive high-intensity-laser is utilized to induce a Li(p,n)Be nuclear reaction. The total activity of Be are evaluated by two different methods. The activity obtained measuring the decay -rays after 1912 shots at 1 Hz is 1.70.2 Bq. This is in good agreement with 1.60.3 Bq evaluated from the proton energy distribution measured using a time-of-flight detector and the nuclear reaction cross-sections. We conclude that the production of activity can be monitored in real time using the time-of-flight-detector placed inside a diverging proton beam coupled with a high-speed signal processing system.
Lee, C. G.; Suzuki, Daisuke; Kokubu, Yoko; Esaka, Fumitaka; Magara, Masaaki; Kimura, Takaumi
International Journal of Mass Spectrometry, 314, p.57 - 62, 2012/03
Times Cited Count:22 Percentile:75.67(Physics, Atomic, Molecular & Chemical)In this study, we developed a method for the simultaneous measurement of all the plutonium and uranium isotopes without the need for chemical separation, using thermal ionization mass spectrometry (TIMS) with a continuous heating method. The MOX particles with sizes of 0.6-2.3 m used in this study were made from a mixed solution of plutonium (SRM947) and uranium (U500). The isotope ratios of plutonium and uranium obtained for all the MOX particles, including the ones in the sub-micrometer size range, were in good agreement with the certified values within the range of error. In particular, the determination of the Pu/Pu isotope ratio, which is difficult because of the isobaric interference of U, was performed accurately. The Pu/Pu ratios were obtained by using a correction in which the background of U intensity at the Pu peak was estimated from the peak fitting of the U signal profile.
Suzuki, Daisuke; Kokubu, Yoko; Lee, C. G.; Esaka, Fumitaka; Magara, Masaaki; Kimura, Takaumi
Chemistry Letters, 41(1), p.90 - 91, 2012/01
Times Cited Count:6 Percentile:29.19(Chemistry, Multidisciplinary)In conventional isotope ratio analysis of individual plutonium particles, the analytical procedure is complicated, because the particles have to be dissolved prior to the measurement. The chemical treatments may cause contamination of U existing in the environment. This makes it difficult to obtain accurate Pu/Pu isotope ratio. In the present work, an analytical method by a combination of single particle transfer and thermal ionization mass spectrometry with a continuous heating method is examined for individual plutonium particles, namely the particles are measured without any chemical treatments. In addition, the technique is applied to the analysis of individual uranium-plutonium mixed oxide (MOX) particles. The results of analysis of individual particles produced from standard solutions indicate that all isotope ratios are consistent with the certified values. There is no effect of isobaric interference on the results. In conclusion, the proposed analytical method is a useful tool for the isotope ratio analysis of plutonium and MOX particles without any chemical treatments.
Kokubu, Yoko; Suzuki, Daisuke; Lee, C. G.; Inagawa, Jun; Magara, Masaaki; Kimura, Takaumi
International Journal of Mass Spectrometry, 310, p.52 - 56, 2012/01
Times Cited Count:20 Percentile:72.82(Physics, Atomic, Molecular & Chemical)A method for measuring isotope ratios of Pu and U in Pu or Pu/U mixture samples was developed by using a continuous heating method of thermal ionization mass spectrometry (TIMS). In this method, temperature of an evaporation filament is increased sequentially. This leads to measure the ratios of Pu and U at different temperature in which each element is evaporated efficiently. In Pu/U mixture samples with pg-level masses and 0.01-10 Pu/U ratios, isotope ratios of Pu/Pu and U/U were measured simultaneously without chemical separation of samples. The relative standard deviation of the isotope ratios of Pu/Pu and U/U in the sample containing each 1 pg of Pu and U were better than 2% and 4%, respectively. Moreover, Pu/Pu ratios were obtained. The results suggest that the continuous heating method of TIMS will be effective tool as a method for measuring isotope ratios in the Pu/U mixture samples.
Lee, C. G.; Suzuki, Daisuke; Esaka, Fumitaka; Magara, Masaaki; Kimura, Takaumi
Talanta, 85(1), p.644 - 649, 2011/07
Times Cited Count:13 Percentile:42.89(Chemistry, Analytical)In this study, we developed a method for detecting plutonium particles in a sample mixture of plutonium and uranium particles using alpha track and fission track techniques. The specific radioactivity (Bq/g) for alpha decay of plutonium is several orders of magnitude higher than that of uranium, indicating that the formation of the alpha track due to alpha decay of uranium can be disregarded under suitable conditions. While alpha tracks in addition to fission tracks were detected in a plutonium particle, only fission tracks were detected in a uranium particle, thereby making the alpha tracks an indicator for detecting particles containing plutonium. Using this correlation, the accuracy in isotope ratios, signal intensity and measurement errors are presumable from the number of alpha tracks prior to the isotope ratio measurements by thermal ionization mass spectrometry. It is expected that this method will become an effective tool for plutonium particle analysis.
Esaka, Fumitaka; Magara, Masaaki; Suzuki, Daisuke; Miyamoto, Yutaka; Lee, C. G.; Kimura, Takaumi
Mass Spectrometry Letters, 2(4), p.80 - 83, 2011/00
In this study, we applied secondary ion mass spectrometry (SIMS) and inductively coupled plasma mass spectrometry (ICP-MS) to the isotope ratio analysis of individual U-Pu mixed oxide particles. In the analysis of individual U-Pu particles prepared from mixed solution of uranium and plutonium standard reference materials, accurate U/U, Pu/Pu and Pu/Pu isotope ratios were obtained with both methods. However, accurate analysis of Pu/Pu isotope ratio was impossible, due to the interference of the Am peak to the Pu peak. In addition, it was indicated that the interference of the UH peak to the Pu peak has a possibility to prevent accurate analysis of plutonium isotope ratios. These problems would be avoided by a combination of ICP-MS and chemical separation of uranium, plutonium and americium in individual U-Pu particles.
Lee, C. G.; Suzuki, Daisuke; Esaka, Fumitaka; Magara, Masaaki; Kimura, Takaumi; Shinohara, Nobuo
Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-31-Kai Nenji Taikai Rombunshu (CD-ROM), 9 Pages, 2010/12
A method to selectively detect uranium particles with higher U enrichment has been developed; this method can contribute to improving particle analysis on nuclear safeguards environmental samples. The newly developed method involves three key components, (1) a two-step filtration system for particle recovery from swipe samples, (2) a system for controlling the etching time of fission track (FT) detector, (3) a system for comparing the FT morphologies and particle sizes. In order to verify the effectiveness of the screening method developed, a mixture sample containing uranium particles with natural composition and those with 10% enrichment is used. It was shown that enrichment-based screening of uranium particles is possible by comparing the FT morphologies and particle sizes, in addition to controlling the etching time. The method is expected to serve as an effective tool of the particle analysis on nuclear safeguards environmental samples.
Esaka, Fumitaka; Magara, Masaaki; Suzuki, Daisuke; Miyamoto, Yutaka; Lee, C. G.; Kimura, Takaumi
Talanta, 83(2), p.569 - 573, 2010/12
Times Cited Count:16 Percentile:45.71(Chemistry, Analytical)In the present work, an analytical technique by a combination of chemical separation and inductively coupled plasma mass spectrometry (ICP-MS) is developed and applied to isotope ratio analysis of individual sub-micrometer plutonium particles. The ICP-MS results for individual plutonium particles prepared from a standard reference material (NIST SRM-947) indicate that the use of a desolvation system for sample introduction improves the precision of isotope ratios. In addition, the accuracy of the Pu/Pu isotope ratio is much improved, owing to the chemical separation of plutonium and americium. In conclusion, the performance of the proposed ICP-MS technique is sufficient for the analysis of individual plutonium particles.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki*; Shimomura, Takuya; Sasao, Hajime*; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Kondo, Shuji; Kanazawa, Shuhei; et al.
Reza Kenkyu, 38(9), p.669 - 675, 2010/09
This paper reviews the temporal contrast and spatial beam quality improvement techniques in a high intensity Ti:sapphire laser system that is based on chirped-pulse amplification (CPA). We describe a low gain optical parametric chirped-pulse amplification (OPCPA) preamplifier that uses high energy, clean pulse seeding and is shown to significantly improve the contrast to better than 10-10 relative to the peak of the main femtosecond pulse. We also report the use of a diffractive optical element for beam homogenization of a 100 J level Nd:glass green pump laser, achieving a flat-topped spatial profile with a filling factor near 80 %.
Suzuki, Daisuke; Kokubu, Yoko; Sakurai, Satoshi; Lee, C. G.; Magara, Masaaki; Iguchi, Kazunari*; Kimura, Takaumi
International Journal of Mass Spectrometry, 294(1), p.23 - 27, 2010/06
Times Cited Count:39 Percentile:87.26(Physics, Atomic, Molecular & Chemical)A new method for isotope ratio measurement with thermal ionization mass spectrometry (TIMS), "continuous heating method", was developed in order to determine an accurate isotope ratio of uranium ranging from sub-picograms to several dozen picograms. In this method, signals were measured during evaporation of an entire sample; however, part of the higher detected signals was used for calculation of the isotope ratio. The continuous heating method can measure the ratios with high reproducibility regardless of the sample amount and the skill of operators because procedures of measurement and data calculation were standardized, enabling accurate correction of mass discrimination effect. When U/U ratios in isotopic reference materials measured by the continuous heating method were compared with those measured by the conventional method and the total evaporation method, there was no difference in the case of measurement of a larger amount of samples. However, the continuous heating method showed the most accurate result compared with those measured by the other methods for the measurement of the sample of sub-picograms.