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Journal Articles

Structural characterization by X-ray analytical techniques of calcium aluminate cement modified with sodium polyphosphate containing cesium chloride

Takahatake, Yoko; Watanabe, So; Irisawa, Keita; Shiwaku, Hideaki; Watanabe, Masayuki

Journal of Nuclear Materials, 556, p.153170_1 - 153170_7, 2021/12

Journal Articles

Influence of mixing solution on characteristics of calcium aluminate cement modified with sodium polyphosphate

Irisawa, Keita; Garcia-Lodeiro, I.*; Kinoshita, Hajime*

Cement and Concrete Research, 128, p.105951_1 - 105951_7, 2020/02

 Times Cited Count:2 Percentile:42.15(Construction & Building Technology)

This study investigated characteristics of a calcium aluminate cement modified with a phosphate (CAP) by changing an amount and concentration of mixing solution with sodium polyphosphate. When the amount of mixing solution was increased with a constant amount of sodium polyphosphate, an enhanced consumption of monocalcium aluminate was observed compared with gehlenite in calcium aluminate cement (CAC). Formation of gibbsite, Al(OH)$$_{3}$$, was also increased as a hydration product in the CAP and the possible reduction of water in the amorphous gel phase. When the amount of mixing solution was increased with a constant concentration of sodium polyphosphate, the enhanced consumption of monocalcium aluminate was not observed. Neither gibbsite nor any other crystalline hydration products were identified in this series. In addition, unreacted sodium polyphosphate remained in the system. The increased formation of gibbsite and the possible reduction of water from the amorphous gel phase appears to contribute to the improvement of the microstructure in the products.

Journal Articles

Development of phosphate modified CAC cementitious systems with reduced water content for the immobilization of radioactive wastes

Garcia-Lodeiro, I.*; Irisawa, Keita; Meguro, Yoshihiro; Kinoshita, Hajime*

Proceedings of 15th International Congress on the Chemistry of Cement (ICCC 2019) (Internet), 10 Pages, 2019/09

The immobilization of low or intermediate-level radioactive wastes in cements is a common practise. Grout, a mixture of Portland cement and supplemental cementitious materials, is commonly used to encapsulate the wastes. However, the conventional cementing process based on portland cement has the risk of hydrogen gas generation, due to the radiolysis of the water intrinsically present in the cement matrix both in the pore solution and the hydrated products. The addition of phosphates to calcium aluminate cement (CAC) is interesting because this system sets and hardens via the acid-based reaction, between the acid phosphate solution and the basic CAC cement. Due to this different mechanism of reaction, it would be possible to generate a solid cementitious product with a reduced water content, which can be beneficial to minimize the risk of hydrogen gas generation associated with the radiolysis of water by radioactive wastes. The present study investigates the effect of water reduction on a phosphate modified CAC systems at different temperatures (35$$^{circ}$$C, 60$$^{circ}$$C, 95$$^{circ}$$C, 110$$^{circ}$$C,180$$^{circ}$$C) in the initial 7 days of curing. Experimental results indicate that these phosphate-based cements do not form the conventional CAC crystalline hydration products in the condition tested, but provide a structural integrity despite a significant amount of water loss. The results also suggest the formation of hydroxyapatite in samples cured at 95$$^{circ}$$C.

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

Reduction of water content in calcium aluminate cement with/out phosphate modification for alternative cementation technique

Garcia-Lodeiro, I.*; Irisawa, Keita; Jin, F.*; Meguro, Yoshihiro; Kinoshita, Hajime*

Cement and Concrete Research, 109, p.243 - 253, 2018/07

 Times Cited Count:10 Percentile:57.69(Construction & Building Technology)

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.

JAEA Reports

Coarse break-up of a stream of oxide and steel melt in a water pool (Contract research)

Moriyama, Kiyofumi; Maruyama, Yu; Usami, Tsutomu*; Nakamura, Hideo

JAERI-Research 2005-017, 173 Pages, 2005/08

JAERI-Research-2005-017.pdf:11.17MB

A series of experiments on the break-up of high temperature oxide and steel melt jets in a water pool was conducted. The objective was to obtain data for the jet break-up length and size distribution of the droplets produced by the jet break-up, and information on the influence of material properties. Also, we tried to obtain additional information giving a clue to the mechanism governing the melt jet break-up, such as flow intensity of the steam column surrounding the melt jet, and its relation with the droplet size. In the experiments, zirconia-alumina mixture and stainless steel melt jets with diameter $$sim$$17mm and velocity $$sim$$7.8m/s at the water surface were dropped into a deep (2.1m) or shallow (0.6m) water pool with various subcool. From the results of the present experiments and also by referring other experimental data from literature, we obtained empirical correlation equations for the jet break-up length, the fraction of jet broken-up in a shallow pool where the jet was not completely broken-up, and the droplet size.

JAEA Reports

An Irradiation experiment for qualification of insulating coating

Nakamichi, Masaru*; Kawamura, Hiroshi

JAERI-Research 2005-015, 35 Pages, 2005/06

JAERI-Research-2005-015.pdf:6.48MB

no abstracts in English

Journal Articles

Elastic-plastic FEM analysis on low cycle fatigue behavior for alumina dispersion-strengthened copper/stainless steel joint

Nishi, Hiroshi

Journal of Nuclear Materials, 329-333(Part2), p.1567 - 1570, 2004/08

 Times Cited Count:9 Percentile:54.8(Materials Science, Multidisciplinary)

Elastic-plastic finite element analysis was performed for low cycle fatigue behavior of stainless steel/alumina-dispersion-strengthened copper (DS Cu) joint in order to investigate the fatigue life and the fracture behavior of the joint. As the results, a strain concentration was occurred near the interface of DS Cu for small strain range, however, in the DS Cu for large strain range. The fatigue life and fracture point were evaluated taking account for the strain concentration. The fatigue life and fracture point were consistent with those of the low cycle fatigue test.

Journal Articles

Roundness and straightness measurement of ceramic beam ducts for the 3GeV-synchrotron of Japan-Proton Accelerator Research Complex

Nishizawa, Daiji*; Kinsho, Michikazu; Kanazawa, Kenichiro; Ogiwara, Norio; Saito, Yoshio*; Kubo, Tomio*; Sato, Yoshihiro*

Shinku, 47(4), p.339 - 343, 2004/05

no abstracts in English

Journal Articles

Radiation-induced swelling and softening in magnesium aluminate spinel irradiated with high-flux Cu$$^{-}$$ ions

Lee, C. G.; Omura, Takahito*; Takeda, Yoshihiko*; Matsuoka, Saburo*; Kishimoto, Naoki*

Journal of Nuclear Materials, 326(2-3), p.211 - 216, 2004/03

 Times Cited Count:4 Percentile:30.82(Materials Science, Multidisciplinary)

Magnesium aluminate spinel of single crystal was irradiated with 60 keV Cu$$^{-}$$ at a dose rate up to 100 $$mu$$A/cm$$^{2}$$, to a total dose of 3$$times$$10$$^{16}$$ ions/cm$$^{2}$$, in order to study changes in hardness and step-height swelling by high-flux implantation. Hardness determined by nano-indentation measurements steeply decreased with implantation. There is a strong negative correlation between dose-rate dependences of the hardness and the step-height swelling: the former decreases as the latter increases. The Rutherford Backscattering Spectrometry (RBS)/channeling measurements showed that the spinel is not completely amorphized over the dose-rate range in this study, and the radiation-induced softening observed is not due to amorphization. Results of optical absorbance suggested that radiation-induced point defects and their clusters on the anion sublattices of the spinel played an important role in the radiation-induced swelling under high-flux ion implantation.

Journal Articles

Roundness and straightness measurement of ceramic beam ducts for the 3GeV-synchrotron of Japan-proton accelerator research complex

Nishizawa, Daiji*; Kinsho, Michikazu; Kanazawa, Kenichiro; Ogiwara, Norio; Saito, Yoshio*; Kubo, Tomio*; Sato, Yoshihiro*

Shinku, 47(4), p.339 - 343, 2004/02

Large aperture cylindrical beam ducts consisting of alumina ceramics will be used for the first time in the 3GeV-synchrotron of High Intensity Proton Accelerator Facility. It is necessary to evaluate roundness and straightness of ceramic ducts because we have to compensate contact area of the connected beam duct large as well as we have to compensate large enough beam aperture. We developed an apparatus of measuring roundness and straightness, and we completed data analysis method as well as measuring method. Then we are measuring and evaluating roundness and straightness of ceramic beam ducts. Now, we have newly made an ellipse ceramic duct for the 3GeV-synchrotron BM. This duct has ellipse cross-sections to satisfy with larger aperture that the beam dynamics requires. In this conference, we are going to present taken data and findings regarding form accuracy including roundness and straightness of the ellipse ceramic duct.

Journal Articles

Dry flowing abrasive decontamination technique for pipe systems with swirling air flow

Kameo, Yutaka; Nakashima, Mikio; Hirabayashi, Takakuni*

Nuclear Technology, 144(1), p.76 - 82, 2003/10

 Times Cited Count:1 Percentile:11.39(Nuclear Science & Technology)

Erosion behavior of stainless and carbon steel pipes by a swirling air flow containing alumina or cast-iron grit abrasive was investigated. Effects of operating conditions such as an abrasive concentration and a flow rate of air-stream on erosion ability was examined. Erosion depths of the test pipes were approximately proportional to the concentration of abrasives and exponent of flow rate of air-stream. The experimental results indicated that the present method could keep satisfactory erosion ability of abrasives even for a large size pipe. The present method was successfully applied to $$^{60}$$Co-contaminated specimens sampled from a pipe of the water clean-up system of the Japan Power Demonstration Reactor.

JAEA Reports

Roundness and straightness measurement of ceramic beam ducts for the 3GeV-synchrotron

Nishizawa, Daiji*; Kinsho, Michikazu; Kanazawa, Kenichiro; Kubo, Tomio*; Sato, Yoshihiro*; Saito, Yoshio*

JAERI-Tech 2001-081, 117 Pages, 2001/12

JAERI-Tech-2001-081.pdf:6.84MB

no abstracts in English

Journal Articles

Simulation study on the catalytic decomposition of hydrogen iodide in a membrane reactor with a silica membrane for the thermochemical water-splitting IS process

Hwang, G.; Onuki, Kaoru

Journal of Membrane Science, 194(2), p.207 - 215, 2001/12

 Times Cited Count:59 Percentile:88.71(Engineering, Chemical)

no abstracts in English

Journal Articles

Repeated impact test on plasma sprayed alumina insulation film for fusion reactor

Kanari, Moriyasu; Abe, Tetsuya; Kosaku, Yasuo; Tanzawa, Sadamitsu; Hiroki, Seiji

Nihon Genshiryoku Gakkai-Shi, 43(12), p.1228 - 1234, 2001/12

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Preliminary joining experiment of alumina pipes by using ceramics sleeve

Abe, Tetsuya; Hiroki, Seiji; Tanzawa, Sadamitsu; Kosaku, Yasuo; Takauchi, Hisao*; Yamakawa, Akira*

JAERI-Research 2001-029, 13 Pages, 2001/05

JAERI-Research-2001-029.pdf:3.39MB

no abstracts in English

Journal Articles

Separation of hydrogen from H$$_{2}$$-H$$_{2}$$O-HI gaseous mixture using a silica membrane

Hwang, G.; Onuki, Kaoru; Shimizu, Saburo

AIChE Journal, 46(1), p.92 - 98, 2000/01

 Times Cited Count:38 Percentile:79.42(Engineering, Chemical)

no abstracts in English

Journal Articles

Hydrogen separation in H$$_{2}$$-H$$_{2}$$O-HI gaseous mixture using the silica membrance prepared by chemical vapor deposition

Hwang, G.*; Onuki, Kaoru; Shimizu, Saburo; *

J. Membr. Sci., 162(1-2), p.83 - 90, 1999/00

 Times Cited Count:62 Percentile:90.42(Engineering, Chemical)

no abstracts in English

JAEA Reports

Durability of alumina electrical insulation films by plasma spraying coating method under repeated impact loads

Kanari, Moriyasu*; Abe, Tetsuya; Enoeda, Mikio; *; *; Shimizu, Katsusuke*; *; Takatsu, Hideyuki

JAERI-Research 98-029, 23 Pages, 1998/06

JAERI-Research-98-029.pdf:2.51MB

no abstracts in English

37 (Records 1-20 displayed on this page)