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

https://doi.org/10.1016/j.jnucmat.2021.153170

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 (35C, 60C, 95C, 110C,180C) 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 95C.

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

https://doi.org/10.1016/j.cemconres.2018.04.019

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 17mm and velocity 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.

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

https://doi.org/10.1016/j.jnucmat.2004.04.169

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.

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

https://doi.org/10.1016/j.jnucmat.2004.01.010

Magnesium aluminate spinel of single crystal was irradiated with 60 keV Cu at a dose rate up to 100 A/cm, to a total dose of 310 ions/cm, 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.

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

https://doi.org/10.13182/NT03-A3430

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 Co-contaminated specimens sampled from a pipe of the water clean-up system of the Japan Power Demonstration Reactor.

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

https://doi.org/10.1016/S0376-7388(01)00540-3

no abstracts in English

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

Hydrogen separation in H-HO-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

https://doi.org/10.1016/S0376-7388(99)00125-8

no abstracts in English