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Journal Articles

Hydrogen gas measurements of phosphate cement irradiated during heat treatment

Irisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu

QST-M-16; QST Takasaki Annual Report 2017, P. 63, 2019/03

no abstracts in English

Journal Articles

Micro-PIXE analysis study of ferrite products synthesized from simulated radioactive liquid waste containing chemical hazardous elements

Abe, Tomohisa; Shimazaki, Takejiro; Osugi, Takeshi; Nakazawa, Osamu; Yamada, Naoto*; Yuri, Yosuke*; Sato, Takahiro*

QST-M-16; QST Takasaki Annual Report 2017, P. 140, 2019/03

no abstracts in English

Journal Articles

Application of phosphate modified CAC for incorporation of simulated secondary aqueous wastes in Fukushima Daiichi NPP, 1; Characterization of solidified cementitious systems with reduced water content

Garcia-Lodeiro, I.*; Lebon, R.*; Machoney, D.*; Zhang, B.*; Irisawa, Keita; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Meguro, Yoshihiro; Kinoshita, Hajime*

Proceedings of 3rd International Symposium on Cement-based Materials for Nuclear Wastes (NUWCEM 2018) (USB Flash Drive), 4 Pages, 2018/11

Journal Articles

Characterization of phosphate cement irradiated by $$gamma$$-ray during dehydration

Irisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu

QST-M-8; QST Takasaki Annual Report 2016, P. 63, 2018/03

A solidification technique with minimized water content is being developed using a phosphate cement for safe storage of secondary radioactive wastes in the Fukushima Daiichi Nuclear Power Plant. To understand the applicability of the solidification technique for the actual secondary wastes, phosphate cement during dehydration was irradiated by $$^{60}$$Co $$gamma$$-ray. The G(H$$_{2}$$) for the phosphate cement decreased with time during dehydration, and was not detected after 7 days. Moreover, the $$^{60}$$Co $$gamma$$-ray irradiation during dehydration did not change the crystalline and amorphous phases of the phosphate cement.

Journal Articles

Application of ferrite process to radioactive waste; Study of ferrite product stability by micro-PIXE analysis

Abe, Tomohisa; Shimazaki, Takejiro; Osugi, Takeshi; Yamada, Naoto*; Yuri, Yosuke*; Sato, Takahiro*

QST-M-8; QST Takasaki Annual Report 2016, P. 61, 2018/03

no abstracts in English

Journal Articles

Chemical state analysis of high-temperature molten slag components by using high-energy XAFS

Okamoto, Yoshihiro; Osugi, Takeshi; Akabori, Mitsuo; Kobayashi, Toru; Shiwaku, Hideaki

Journal of Molecular Liquids, 232, p.285 - 289, 2017/04

 Times Cited Count:2 Percentile:76.93(Chemistry, Physical)

High energy XAFS measurement using cerium K-edge was performed to study the chemical state of cerium in high-temperature molten slag (SiO$$_{2}$$-CaO-Fe$$_{2}$$O$$_{3}$$-CeO$$_{2}$$). It was found from the change in the nearest Ce-O distance obtained from EXAFS analysis and the energetic shift of the white line peak observed in XANES analysis that oxidation state of cerium was tetravalent in the molten state and trivalent in solid state. The Debye-Waller factor of the nearest Ce-O pair in solid slag was very large even at room temperature, and the change in its value upon heating and melting was very small. This result suggests that cerium is highly disordered and stable in solid slag.

Journal Articles

Heat treatment of phosphate-modified cementitious matrices for safe storage of secondary radioactive aqueous wastes in Fukushima Daiichi Nuclear Power Plant

Irisawa, Keita; Taniguchi, Takumi; Namiki, Masahiro; Garc$'i$a-Lodeiro, I.*; Osugi, Takeshi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro; Kinoshita, Hajime*

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 6 Pages, 2017/04

A solidification technique with minimized water content is being developed using phosphate cements for the safe storage of secondary radioactive wastes in the Fukushima Daiichi Nuclear Power Plant. Conventional cement systems become solidified via hydration reactions, and need a certain water content. Phosphate cement systems, however, become solidified via an acid-base reaction, and so they only require water mainly for reasons of workability. A reduced water content of phosphate cement systems is beneficial for the immobilization of the radioactive wastes from mitigating the potential to generate hydrogen gas by the radiolysis of water by radioactive wastes. The current study investigated the water content and mineralogy of calcium aluminate cement (CAC) and phosphate-modified CAC (CAP) cured in open systems at 60, 90 and 120 $$^{circ}$$C and in a closed system at 20 $$^{circ}$$C as a reference case. Water contents in both the CAC and the CAP were seen to decrease as curing progressed. For $$geq$$ 90 $$^{circ}$$C, the CAP contained less water than CAC. Free water in CAC converted to structural water by heat treatment, but this was not the case for CAP. An orthophosphate hydrate salt, a precursor phase of hydroxyapatite, was found in CAP when cured at 20 and 60 $$^{circ}$$C, and a mixture of the orthophosphate hydrate salt and hydroxyapatite, Ca$$_{10}$$(PO$$_{4}$$)$$_{6}$$(OH)$$_{2}$$, were formed in the CAP when cured at 90 $$^{circ}$$C. Phosphate products in CAP cured at 120 $$^{circ}$$C appears to consist of a different phosphate phase compared with the CAP cured at 20, 60 and 90 $$^{circ}$$C.

Journal Articles

Element distribution measurement in incineration ash using micro-PIXE analysis

Abe, Tomohisa; Shimazaki, Takejiro; Nakayama, Takuya; Osone, Osamu; Osugi, Takeshi; Nakazawa, Osamu; Yuri, Yosuke*; Yamada, Naoto*; Sato, Takahiro*

QST-M-2; QST Takasaki Annual Report 2015, P. 83, 2017/03

no abstracts in English

Journal Articles

The Verification tests of the melting conditions for homogenization of metallic LLW at the JAEA

Nakashio, Nobuyuki; Osugi, Takeshi; Iseda, Hirokatsu; Tohei, Toshio; Sudo, Tomoyuki; Ishikawa, Joji; Mitsuda, Motoyuki; Yokobori, Tomohiko; Kozawa, Kazushige; Momma, Toshiyuki; et al.

Journal of Nuclear Science and Technology, 53(1), p.139 - 145, 2016/01

 Times Cited Count:1 Percentile:78.81(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

User's guide of cement solidification test for incinerated ash

Nakayama, Takuya; Kawato, Yoshimi; Osugi, Takeshi; Shimazaki, Takejiro; Hanada, Keiji; Suzuki, Shinji; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro

JAEA-Technology 2014-046, 56 Pages, 2015/03

JAEA-Technology-2014-046.pdf:7.61MB

The combustible and flame-retardant radioactive wastes generated as a result of the research activities in Japan Atomic Energy Agency (JAEA) are incinerating to reduce their volume. The incinerated ash is planned to be solidified using cement for disposal. Since the properties of ashes generated in each institute of JAEA are varied with the type of incinerator and the wastes to be incinerated, it is necessary to do fundamental solidification tests in each institute to decide operating conditions of the planning cement solidification facility. It is important to standardize evaluating methods of cement and solidified waste because some characters depend on measuring method. This user's guide have been prepared how to decide the cement solidifying conditions of ash to design the cement solidification facility in JAEA. Requirements on the regulations of solidified radioactive waste have been examined and seven technical criteria, e.g. compressive strength, fluidity, have been selected as characters to be evaluated. Some empirical notes about selection of cement, admixtures, procedure on making a test piece, evaluation of expanding, compressive strength, solubility have been described. The strategy of tests and tips for finding optimized solidification condition has been summarized. Finally the example of optimized conditions satisfied the requirements and some problems to be solved have been described.

Journal Articles

Transfer behavior of cesium adsorbed on clay minerals in aqueous solution

Okamoto, Yoshihiro; Osugi, Takeshi; Shiwaku, Hideaki; Akabori, Mitsuo

Nippon Genshiryoku Gakkai Wabun Rombunshi, 13(3), p.113 - 118, 2014/09

Transfer behavior of cesium adsorbed on some clay minerals in aqueous solution was investigated by X-ray absorption fine structure (XAFS) analysis of Cs K-edge. The sample was prepared by mixing Cs-adsorbed mineral with another different kind of pure clay mineral in water. The XAFS results of the dried mixture powder were compared with those obtained before the mixing. It was recognized from the XAFS analysis for three kinds of clay minerals; Illite, Kaolinite and Vermiculite, that cesium was transferred from Kaolinite to Illite and vermiculite, and from Illite to Vermiculite. It can be concluded that cesium is transferred to and accumulated in Vermiculite.

Journal Articles

C-face interface defects in 4H-SiC MOSFETs studied by electrically detected magnetic resonance

Umeda, Takahide*; Okamoto, Mitsuo*; Arai, Ryo*; Sato, Yoshihiro*; Kosugi, Ryoji*; Harada, Shinsuke*; Okumura, Hajime*; Makino, Takahiro; Oshima, Takeshi

Materials Science Forum, 778-780, p.414 - 417, 2014/02

 Times Cited Count:2 Percentile:15.42

Interface defects of Metal-Oxide-Semiconductors (MOSFETs) fabricated on Carbone (C) face 4H-SiC were investigated by Electrically Detected Magnet Resistance (EDMR). Gate oxide of the MOSFETs was formed by either wet-oxidation and H$$_{2}$$ annealing or dry-oxidation. The values of channel mobility for MOSFETS with wet gate oxide and dry gate oxide are less than 1 and 90 cm$$^{2}$$/Vs, respectively. By EDMR measurement under low temperature (less than 20 K), EDMR signals related to C were detected. The peak height of the signals increased with increasing $$gamma$$-ray doses, and the channel mobility decreased. From this result, it is assumed that hydrogen atoms passivating C dangling bonds are released by $$gamma$$-rays and the channel mobility decreases with increasing the C related defects.

Journal Articles

Effect of oxygen partial pressure on the viscosity of iron-bearing alkaline-earth silicate slags

Sukenaga, Sohei*; Osugi, Takeshi; Inatomi, Yosuke*; Saito, Noritaka*; Nakashima, Kunihiko*

Journal of MMIJ, 129(5), p.203 - 207, 2013/05

Viscosity changes of RO-SiO$$_{2}$$-FexO (R = Ca, Sr, Ba) melts due to changes in the oxidation states of the iron ions by systematically varying the oxygen partial pressure were measured at 1773 K. The initial compositions of the samples were 30RO-60SiO$$_{2}$$-10Fe$$_{2}$$O$$_{3}$$(mol%), and the ratio of Fe$$^{3+}$$ toFe$$^{2+}$$ in the RO-SiO$$_{2}$$-FexO melts increased with increasing oxygen partial pressure in all samples. Meanwhile, the viscosity of all the RO-SiO$$_{2}$$-FexO melts decreased with increasing Fe$$^{2+}$$ to total-Fe ratio (Fe$$^{2+}$$/t-Fe). The data indicate that the increase in the amount of Fe$$^{2+}$$ ions, which behave as network modifiers, would result in depolymerization of the silicate anions. In addition, the viscosity of the melts increased in the order of alkaline-earth cationic radius (Ba $$>$$ Sr $$>$$ Ca) when the Fe$$^{2+}$$/t-Fe values of the melts were comparable. This would be due to the change in the coordination structure of Fe$$^{3+}$$ in the melts.

Journal Articles

Effect of oxidation state of iron ions on the viscosity of alkali silicate melts

Osugi, Takeshi; Sukenaga, Sohei*; Inatomi, Yosuke*; Gonda, Yoshiyuki*; Saito, Noritaka*; Nakashima, Kunihiko*

ISIJ International, 53(2), p.185 - 190, 2013/02

 Times Cited Count:5 Percentile:62.48(Metallurgy & Metallurgical Engineering)

Understanding the changes in viscosity due to the different oxidation states of iron ions is important for simulating phenomena related to molten slags and also for understanding the structure of iron-oxidecontainingsilicate melts. However, these viscosity changes are not well understood. Here, we show the viscosity changes of R$$_{2}$$O-SiO$$_{2}$$-FexO (R = Li, Na, or K) melts due to changes in the oxidation states of the iron ions by systematically varying the oxygen partial pressure using several Ar-based gases at 1773 K. Not only the oxidation state of the iron ions but also the coordination structure of Fe$$^{3+}$$ may be important for understanding the viscosity.

Journal Articles

Electrically Detected Magnetic Resonance (EDMR) studies of SiC-SiO$$_{2}$$ interfaces

Umeda, Takahide*; Kosugi, Ryoji*; Fukuda, Kenji*; Morishita, Norio*; Oshima, Takeshi; Ezaki, Kana*; Isoya, Junichi*

Materials Science Forum, 717-720, p.427 - 432, 2012/05

 Times Cited Count:4 Percentile:6.02

Metal-Oxide (SiO$$_{2}$$)-Semiconductor (MOS) structures fabricated on Silicon Carbide (SiC) were studied using Electrically Detected Magnetic Resonance technique (EDMR). The residual Carbons are expected to be near the interface between SiC and SiC-SiO$$_{2}$$SiO$$_{2}$$, which is different from Si-SiO$$_{2}$$ interface. By the EDMR measurements at 50K, a defect center related to C dangling bonds which is called P$$_{H1}$$ center and also a center related to C dangling bonds terminated by hydrogens or nitrogens (Ns) which is called P$$_{H1}$$ were observed. In addition, a center related to N donor which is called Nh exist near the interface from N-treatment samples. This suggests that carrier concentration increases near the interface due to the introduction of donors, and as a result, the channel conductance increases.

Journal Articles

X-ray study of radiation damage in UO$$_{2}$$ irradiated with high-energy heavy ions

Ishikawa, Norito; Sonoda, Takeshi*; Okamoto, Yoshihiro; Sawabe, Takashi*; Takegahara, Keisuke; Kosugi, Shinya*; Iwase, Akihiro*

Journal of Nuclear Materials, 419(1-3), p.392 - 396, 2011/12

 Times Cited Count:7 Percentile:40.84(Materials Science, Multidisciplinary)

In order to characterize the radiation damage due to ion-track formation in UO$$_{2}$$, polycrystalline samples have been irradiated with 210-MeV Xe ions, and measured with XRD (X-ray diffraction) technique using Cu X-ray. We have also tried EXAFS (extended X-ray absorption fine structure) measurement using X-ray near U L$$_{3}$$-edge. The results show that XRD technique detects damage at relatively low fluence of 10$$^{16}$$ ions/m$$^{2}$$ and higher, while the irradiation-induced change of EXAFS spectra is not observed even at highest fluence of 10$$^{19}$$ ions/m$$^{2}$$. The damage detection may be critically influenced by the depth profile of X-ray penetration.

Journal Articles

Behavior of nitrogen atoms in SiC-SiO$$_{2}$$ interfaces studied by electrically detected magnetic resonance

Umeda, Takahide*; Ezaki, Kana*; Kosugi, Ryoji*; Fukuda, Kenji*; Oshima, Takeshi; Morishita, Norio*; Isoya, Junichi*

Applied Physics Letters, 99(14), p.142105_1 - 142105_3, 2011/10

 Times Cited Count:41 Percentile:13.23(Physics, Applied)

JAEA Reports

Evaluation of void ratio of the solidified wastes containing supercompacted wastes

Sudo, Tomoyuki; Nakashio, Nobuyuki; Osugi, Takeshi; Mimura, Ryuji; Ishihara, Keisuke; Satomi, Shinichi; Myodo, Masato; Momma, Toshiyuki; Kozawa, Kazushige

JAEA-Technology 2010-041, 38 Pages, 2011/01

JAEA-Technology-2010-041.pdf:4.73MB

The super compactor in the AVRF treats compactible metal wastes mainly generated from research reactors in the Nuclear Science Research Institute of JAEA. Those wastes are compacted with the maximum about 2,000-ton force. The supercompacted wastes are packed into the container and then immobilized with cementitious materials. The solidified wastes (containing supercompacted wastes) become an object for near surface disposal with artificial barrier. For disposal, the solidified wastes must be satisfied the technical criteria. One of the important indicators is the void ratio in the solidified wastes. In this report, we manufactured the supercompacted wastes with the ordinary treatment method for actual wastes treated in the AVRF and immobilized with a mortar grout. The void ratio of the solidified wastes were evaluated in consideration for concrete vault disposal. As a result, We confirmed the integrity of the solidified wastes from a point of view of void ratio.

JAEA Reports

Verification of improvement of the casting process in metal melting system

Tohei, Toshio; Nakashio, Nobuyuki; Osugi, Takeshi; Ishikawa, Joji; Mizoguchi, Takafumi; Hanawa, Ritsu; Someya, Keita*; Takahashi, Kenji*; Iseda, Hirokatsu; Kozawa, Kazushige; et al.

JAEA-Technology 2010-008, 28 Pages, 2010/06

JAEA-Technology-2010-008.pdf:5.0MB

The Waste Volume Reduction Facility (WVRF) was constructed for volume reduction and the chemical stabilization of the low level radioactive waste in the Nuclear Science Research Institute of JAEA. The metal melting system in the WVRF treats radioactive metal waste. From the experience of trial operations, the improvement has conducted on the casting process in the metal melting system. The performance of the improved casting process was verified through the trial operations from Oct. 2008. In this report, we describe the reduction of the processing time, of the utilities consumption, of the load of maintenance on the improved casting process.

JAEA Reports

Construction, management and operation on advanced volume reduction facilities

Higuchi, Hidekazu; Osugi, Takeshi; Nakashio, Nobuyuki; Momma, Toshiyuki; Tohei, Toshio; Ishikawa, Joji; Iseda, Hirokatsu; Mitsuda, Motoyuki; Ishihara, Keisuke; Sudo, Tomoyuki; et al.

JAEA-Technology 2007-038, 189 Pages, 2007/07

JAEA-Technology-2007-038-01.pdf:15.13MB
JAEA-Technology-2007-038-02.pdf:38.95MB
JAEA-Technology-2007-038-03.pdf:48.42MB
JAEA-Technology-2007-038-04.pdf:20.53MB
JAEA-Technology-2007-038-05.pdf:10.44MB

The Advanced Volume Reduction Facilities (AVRF) is constructed to manufacture the waste packages of radioactive waste for disposal in the Nuclear Science Research Institute of the Japan Atomic Energy Agency. The AVRF is constituted from two facilities. The one is the Waste Size Reduction and Storage Facility (WSRSF) which is for reducing waste size, sorting into each material and storing the waste package. The other is the Waste Volume Reduction Facility (WVRF) which is for manufacturing the waste package by volume reducing treatment and stabilizing treatment. WVRF has an induction melting furnace, a plasma melting furnace, an incinerator, and a super compactor for treatment. In this report, we summarized about the basic concept of constructing AVRF, the constitution of facilities, the specifications of machineries and the state of trial operation until March of 2006.

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