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Journal Articles

Corrosion resistance of nickel-based alloy to gaseous hydrogen iodide decomposition environment in thermochemical water-splitting iodine-sulfur process

Kamiji, Yu; Onuki, Kaoru; Kubo, Shinji

Proceedings of 5th International Conference on Chemical and Biological Sciences (ICCBS 2018) (USB Flash Drive), p.51 - 54, 2018/03

As one of the evaluation of corrosion resistance of structural materials for HI decomposition environment in the iodine-sulfur (IS) thermochemical water-splitting process, we fabricated a HI decomposer which produce practical corrosion environment for the corrosion test using test specimens and examined corrosion resistance of test specimens made of Hastelloy C-276. In the corrosion test, dry HI as the feed gas were used to realize practical environment with copresence of no steam. The experiments were carried out at 500$$^{circ}$$C and atmospheric pressure for 100h in total. Corrosion rates were evaluated from the weight change of each specimen after exposure. Test specimens set in the catalyst layer suffered relatively severe corrosion ($$<$$ 0.75 mm/y) in comparison with those set before the catalyst layer ($$<$$ 0.52 mm/y).

Journal Articles

Current R&D status of thermochemical water splitting iodine-sulfur process in Japan Atomic Energy Agency

Kasahara, Seiji; Iwatsuki, Jin; Takegami, Hiroaki; Tanaka, Nobuyuki; Noguchi, Hiroki; Kamiji, Yu; Onuki, Kaoru; Kubo, Shinji

International Journal of Hydrogen Energy, 42(19), p.13477 - 13485, 2017/05

 Times Cited Count:25 Percentile:19.73(Chemistry, Physical)

Current R&D on the thermochemical water splitting iodine-sulfur (IS) process in Japan Atomic Energy Agency is summarized. Reactors were fabricated with industrial materials and verified by test operations: a Bunsen reactor, a H$$_{2}$$SO$$_{2}$$ decomposer, and a HI decomposer. Reactors of industrial materials showed corrosion stability. Demonstration of the test facility verified integrity of process components and stability of hydrogen production. An 8 hours continuous operation of the total IS process was performed in February 2016 with H$$_{2}$$ production rate of 10 L/h.

JAEA Reports

Mizunami Underground Research Laboratory Project annual report for fiscal year 2014

Hama, Katsuhiro; Mikake, Shinichiro; Ishibashi, Masayuki; Sasao, Eiji; Kuwabara, Kazumichi; Ueno, Tetsuro; Onuki, Kenji*; Beppu, Shinji; Onoe, Hironori; Takeuchi, Ryuji; et al.

JAEA-Review 2015-024, 122 Pages, 2015/11

JAEA-Review-2015-024.pdf:80.64MB

Japan Atomic Energy Agency (JAEA) at Tono Geoscience Center (TGC) is pursuing a geoscientific research and development project namely the Mizunami Underground Research Laboratory (MIU) Project in crystalline rock environment in order to construct scientific and technical basis for geological disposal of High-level Radioactive Waste (HLW). The MIU Project has three overlapping phases: Surface-based Investigation phase (Phase I), Construction phase (Phase II), and Operation phase (Phase III). The MIU Project has been ongoing the Phase III, as the Phase II was concluded for a moment with the completion of the excavation of horizontal tunnels at GL-500m level in February 2014. This report presents the results of the investigations, construction and collaboration studies in fiscal year 2014.

JAEA Reports

Research and development on chemical reactors made of industrial structural materials and hydriodic acid concentration technique for thermochemical hydrogen production IS process

Kubo, Shinji; Iwatsuki, Jin; Takegami, Hiroaki; Kasahara, Seiji; Tanaka, Nobuyuki; Noguchi, Hiroki; Kamiji, Yu; Onuki, Kaoru

JAEA-Technology 2015-028, 32 Pages, 2015/10

JAEA-Technology-2015-028.pdf:23.69MB

JAEA has been conducting a study on IS process for thermochemical hydrogen production in order to develop massive hydrogen production technology for hydrogen society. Integrity of the chemical reactors and concentration technology of hydrogen iodide in HIx solution were studied. In the former study, the chemical reactors were trial-fabricated using industrial materials. A test of 30 times of thermal cycle test under circulating condition of the Bunsen reaction solution showed integrity of the Bunsen reactor made of fluororesin lined steel. Also, 100 hours of reaction tests showed integrity of the sulfuric acid decomposer made of silicon carbide and of the hydrogen iodide decomposer made of Hastelloy C-276. In the latter study, concerning electro-electrodialysis using cation-exchange membrane, sulfuric acid in the anolyte had little influence on the concentration performance. These results suggest the purification system of HIx solution can be simplified. Based on the Nernst-Planck equation and the Smoluchowski equation, proton transport number, water permeance, and IR drop of the cation exchange membrane were formulated. The derived equations enable quantitative estimation for the performance indexes of Nafion membrane and, also, of ETFE-St membranes made by radiation-induced graft polymerization method.

Journal Articles

Thermochemical decomposition of water

Onuki, Kaoru; Noguchi, Hiroki; Tanaka, Nobuyuki; Takegami, Hiroaki; Kubo, Shinji

Hyomen Kagaku, 36(2), p.80 - 85, 2015/02

Thermochemical water-splitting process decomposes water using thermal energy by operating high temperature endothermic reaction(s) and low temperature exothermic reaction(s) cyclically, with which free energy of water decomposition is produced. The so-called sulfur family processes, which utilize thermal decomposition of sulfuric acid as the high temperature endothermic reaction, have attracted lots of interest among the many processes proposed so far. The IS process represents the pure thermochemical sulfur family processes. The continuous hydrogen production by IS process was demonstrated in laboratory, and the materials of construction for the IS process have been screened by corrosion tests performed in the severe process environment. At present, application of membrane technologies and development of catalysts are under study to improve the hydrogen production performance. Also, development is underway of the chemical reactors made of candidate materials such as ceramics.

JAEA Reports

Mizunami Underground Research Laboratory Project annual report for fiscal year 2013

Hama, Katsuhiro; Mikake, Shinichiro; Nishio, Kazuhisa; Kawamoto, Koji; Yamada, Nobuto; Ishibashi, Masayuki; Murakami, Hiroaki; Matsuoka, Toshiyuki; Sasao, Eiji; Sanada, Hiroyuki; et al.

JAEA-Review 2014-038, 137 Pages, 2014/12

JAEA-Review-2014-038.pdf:162.61MB

Japan Atomic Energy Agency (JAEA) at Tono Geoscience Center (TGC) is pursuing a geoscientific research and development project namely the Mizunami Underground Research Laboratory (MIU) Project in crystalline rock environment in order to construct scientific and technological basis for geological disposal of High-level Radioactive Waste (HLW). The MIU Project has three overlapping phases: Surface-based Investigation phase (Phase I), Construction phase (Phase II), and Operation phase (Phase III). The MIU Project has been ongoing the Phase II and the Phase III in fiscal year 2013. This report presents the results of the investigations, construction and collaboration studies in fiscal year 2013, as a part of the Phase II and Phase III based on the MIU Master Plan updated in 2010.

Journal Articles

Boiling heat transfer characteristics of a sulfuric-acid flow in thermochemical iodine-sulfur cycle

Noguchi, Hiroki; Terada, Atsuhiko; Onuki, Kaoru; Hino, Ryutaro

Chemical Engineering Research & Design, 92(9), p.1659 - 1663, 2014/09

 Times Cited Count:3 Percentile:87.87(Engineering, Chemical)

The Japan Atomic Energy Agency has been conducting research and development on the thermo-chemical iodine-sulfur (IS) process, which is one of the most attractive water-splitting hydrogen production methods that uses nuclear thermal energy. The sulfuric acid decomposer is one of the key components of the IS process. The boiling heat transfer coefficients of sulfuric acid solutions are required to design the sulfuric acid decomposer. These coefficients were measured in aqueous solutions where the mole fraction of H$$_{2}$$O ranged from 0.17 to 0.37 (heat flux range from 16.9 kW/m$$^{2}$$ to 5.6 kW/m$$^{2}$$) and compared with the empirical correlations formulated for binary mixtures. A combination of the Stephan-K$"o$rner correlation, using the empirical constant A$$_{0}$$ = 2.00, and the Nishikawa-Fujita correlation was used to predict the experimental results with an accuracy of 10%.

Journal Articles

Components development for sulfuric acid processing in the IS process

Noguchi, Hiroki; Kubo, Shinji; Iwatsuki, Jin; Kasahara, Seiji; Tanaka, Nobuyuki; Imai, Yoshiyuki; Terada, Atsuhiko; Takegami, Hiroaki; Kamiji, Yu; Onuki, Kaoru; et al.

Nuclear Engineering and Design, 271, p.201 - 205, 2014/05

 Times Cited Count:6 Percentile:51.92(Nuclear Science & Technology)

The Japan Atomic Energy Agency has been conducting research and development on a thermochemical iodine-sulfur (IS) process. An examination is planned to verify the integrity of the components in the sulfuric acid decomposition section. A bayonet-type sulfuric acid decomposer made of SiC ceramics, a key component in the section, was test-fabricated. In parallel, a direct-contact heat exchanger (DCHX) is contemplated for use in the sulfuric acid decomposition section to simplify the process. Although the concept is very attractive, little is known about the heat and mass transfer behavior in the DCHX. Therefore, a test apparatus was constructed to measure the gas-phase mass transfer coefficients required for the optimal design of the DCHX. These coefficients of water were acquired and compared with an empirical correlation. The experimental data were in good agreement with those obtained from empirical correlation, and thus, the apparatus was confirmed to be reasonable.

Journal Articles

Affinity of ion-exchange membranes for HI-I$$_{2}$$-H$$_{2}$$O mixture

Tanaka, Nobuyuki; Yamaki, Tetsuya; Asano, Masaharu; Terai, Takayuki*; Onuki, Kaoru

Journal of Membrane Science, 456, p.31 - 41, 2014/04

 Times Cited Count:1 Percentile:93.01(Engineering, Chemical)

Electro-electrodialysis (EED) has been applied to thermochemical water-splitting iodine-sulfur process for hydrogen production in order to enhance the HI uptake from a HI-I$$_{2}$$-H$$_{2}$$O mixture (HIx solution). In this paper, the constitution of the HIx solution absorbed in grafted membranes and in Nafion 212 is evaluated. The affinity of the membranes for the HIx solution is discussed based on the measurement results. The behavior of each component in the membrane was as follows: The strong affinity of the ETFE-St membrane for I$$_{2}$$ was shown because of the formation of a charge-transfer complex with electron-donating aromatic groups, whereas I$$_{2}$$ absorption by Nafion 212 was minimal. The difference of affinity for the ions can be attributed to the formation of the I$$_{3}$$- complex from I- and I$$_{2}$$ absorbed in the grafted membranes, which was precluded in Nafion 212.

Journal Articles

Effect of sulfuric acid on electro-electrodialysis of HIx solution

Tanaka, Nobuyuki; Onuki, Kaoru; Kubo, Shinji

International Journal of Hydrogen Energy, 39(1), p.86 - 89, 2014/01

 Times Cited Count:7 Percentile:76.3(Chemistry, Physical)

The effect of sulfuric acid on the concentration of HIx solution by electro-electrodialysis (EED) was examined for the thermochemical water-splitting iodine-sulfur process. Presence of sulfuric acid in the anolyte HIx solution did not affect the concentration behavior. However, sulfuric acid in the catholyte solution caused side reaction(s) producing whitish precipitates, which indicates that the sulfur compound should be removed prior to the EED operation.

JAEA Reports

Safety measures for integrity test apparatus for IS process (Sulfuric acid decomposition section)

Noguchi, Hiroki; Kubo, Shinji; Iwatsuki, Jin; Onuki, Kaoru

JAEA-Technology 2013-020, 38 Pages, 2013/07

JAEA-Technology-2013-020.pdf:3.24MB

Hazardous substances such as sulfuric acid, sulfur dioxide and hydrogen iodide acid are employed in thermochemical Iodine-sulfur (IS) process. It is necessary to take safety measure against workers and external environments to study experimentally on IS process. Presently we have been conducting to verify the soundness of main components made of engineering material in actual corrosive condition. An integrity test apparatus for the components of sulfuric acid decomposition was set up. We will use the hazardous substances such as sulfuric acid and sulfur dioxide and perform the experiment in pressurized condition in this integrity test. Safety measures for test apparatus, operation and abnormal situation were considered prior to starting the test. This report summarized the consideration results for the safety measures on the integrity test apparatus for the components of sulfuric acid decomposition.

Journal Articles

Corrosion resistance of structural materials in high-temperature aqueous sulfuric acids in thermochemical water-splitting iodine-sulfur process

Kubo, Shinji; Futakawa, Masatoshi; Ioka, Ikuo; Onuki, Kaoru; Yamaguchi, Akihisa*

International Journal of Hydrogen Energy, 38(16), p.6577 - 6585, 2013/05

 Times Cited Count:13 Percentile:58.78(Chemistry, Physical)

Very harsh environments exist in the iodine-sulfur process for hydrogen production. Structural materials for sulfuric acid vaporizers and concentrators are exposed to high-temperature corrosive environments. Immersion tests were carried out to evaluate the corrosion resistance of ceramics and to evaluate corrosion-resistant metals exposed to environments of aqueous sulfuric acids at temperatures of 320, 380, and 460$$^{circ}$$C, and pressure of 2 MPa. The aqueous sulfuric acid concentrations for the temperatures were 75, 85, and 95 wt%, respectively. Ceramic specimens of silicon carbides (SiC), silicon impregnated silicon carbides (Si-SiC), and silicon nitrides (Si$$_{3}$$N$$_{4}$$) showed excellent corrosion resistance from weight loss measurements after exposure to 75, 85, and 95 wt% sulfuric acid. High-silicon irons with silicon content of 20 wt% showed a fair measure of corrosion resistance. However, evidence of crack formation was detected via microscopy. Silicon enriched steels severely suffered from uniform corrosion with a corrosion rate in 95 wt% sulfuric acid of approximately 1 gm$$^{-2}$$h$$^{-2}$$. Among the tested materials, the ceramics SiC, Si-SiC, and Si$$_{3}$$N$$_{4}$$ were found to be suitable candidates for structural materials in direct contact with the considered environments.

Journal Articles

Reduction of heat input to IS (iodine-sulfur) process by removal of HI-I$$_{2}$$-H$$_{2}$$O mixture purification

Kasahara, Seiji; Kubo, Shinji; Tanaka, Nobuyuki; Yan, X.; Onuki, Kaoru

Proceedings of 2013 International Congress on Advances in Nuclear Power Plants (ICAPP 2013) (USB Flash Drive), 10 Pages, 2013/04

In thermochemical hydrogen production IS process, purification of all of the HI-I$$_{2}$$-H$$_{2}$$O (HIx) mixture right after Bunsen reaction has been supposed to prevent negative influences of impurities on operation of following process components. An experimental investigation on electro-electrodialysis (EED) in JAEA suggests possibility of removal of the purification of the HIx fed to anode side of the EED cell. In this study, reduction of heat input to IS process by removal of HIx mixture purification was investigated by process flow calculation. The net heat input to the HI separation subsection was 143.1 kJ/mol-HI with removal of purification of the HIx fed to EED anode side, which was considerably smaller than that of 278.9 kJ/mol-HI in the case of no purification removal. The main factor for the reduction was elimination of the heat input for the anode side feed purification. The removal of the purification lowered EED voltage and reduced electricity input to the EED. The removal also decreased feed rate to the HI distillation column and decreased heat input to the reboiler of the column. These side effects also reduced the net heat input.

Journal Articles

Adaptability of Metallic Structural Materials to gaseous HI decomposition environment in thermochemical water-splitting iodine-sulfur process

Kubo, Shinji; Futakawa, Masatoshi; Onuki, Kaoru; Yamaguchi, Akihisa*

Corrosion Engineering, 62(3), p.104 - 111, 2013/03

The iodine-sulfur thermochemical cycle for hydrogen production takes place in very harsh environments. Structural metallic materials for the hydrogen iodide decomposition are exposed in a high temperature halogen corrosion and hydrogen embrittlement environment. To evaluate adaptability of the materials, the corrosion rates and mechanical properties (the yield strength, the tensile strength, and the elongation) were measured. Prepared test specimens were exposed to ambient gas consisting of HI, I$$_2$$, H$$_2$$O, and H$$_2$$ (molar fraction of 1:1:6:0.16) at 450$$^{circ}$$C for 1000 h at atmospheric pressure. After the exposure, the corrosion rates were obtained by the weight loss of each specimen. Nickel-based alloys (Hastelloy C-276, MAT21, Inconel 625) exhibited appropriate corrosion resistance ($$<$$ 0.03 g m$$^{-2}$$ h$$^{-1}$$. In addition, no degradations of the mechanical properties for the MAT21 and the Inconel 625 were observed. The specimens of tantalum and titanium showed hydrogen embrittlement; the specimens of zirconium and niobium exhibited poor corrosion resistance. The specimens of molybdenum (Mo) exhibited good corrosion resistance; however, the strength degradation of Mo is cause for concern. As the results show, the nickel-based alloys are well suited for the structural materials within this environment from the viewpoint of the corrosion resistance. MAT21 among them is an outstanding material with an eye to its corrosion resistance and mechanical properties.

Journal Articles

Adaptability of metallic structural materials to gaseous HI decomposition environment in thermochemical water-splitting iodine-sulfur process

Kubo, Shinji; Futakawa, Masatoshi; Onuki, Kaoru; Yamaguchi, Akihisa*

Zairyo To Kankyo, 62(3), p.122 - 128, 2013/03

The iodine-sulfur thermochemical cycle for hydrogen production takes place in very harsh environments. Structural metallic materials for the hydrogen-iodide decomposition are exposed in the high-temperature halogen corrosion and the hydrogen embrittlement environment. To evaluate adaptability of the materials, corrosion rates and mechanical properties (the yield strength, the tensile strength, and the elongation) were measured. Prepared test specimens were exposed to ambient gas consisting of HI, I$$_{2}$$, H$$_{2}$$O and H$$_{2}$$ (molarfraction, 1:1:6:0.16) at 450$$^{circ}$$C for 1000 hours at the atmospheric pressure. After the exposure, the corrosion rates were obtained by the weight loss of each specimen. Nickel-based alloys (Hastelly C-276, MAT21, Inconel 625) exhibited appropriate corrosion resistance ($$<$$ 0.03 g m$$^{-2}$$ h$$^{-1}$$). In addition, no degradations of the mechanical properties for the MAT21 and the Inconel 625 were observed. The specimens of tantalum and titanium showed the hydrogen embrittlement; the specimens of zirconium and niobium exhibited poor corrosion resistance. The specimens of molybdenum (Mo) exhibited good corrosion resistance, however strength degradation of Mo is causing concern. As the results, the nickel-based alloys are well suited for the structural materials within this environment from the viewpoint of the corrosion resistance. MAT21 among them is the outstanding material with an eye to its corrosion resistance and mechanical properties.

JAEA Reports

Safety measures for integrity test apparatus for IS process (Bunsen section)

Kubo, Shinji; Tanaka, Nobuyuki; Noguchi, Hiroki; Iwatsuki, Jin; Onuki, Kaoru; Inagaki, Yoshiyuki

JAEA-Technology 2012-043, 41 Pages, 2013/02

JAEA-Technology-2012-043.pdf:7.74MB

Providing safety measures for workers and external environments are indispensable in R&D activities of the iodine sulfur water-splitting hydrogen production process, since this process uses toxic chemicals as sulfur dioxide, sulfuric acid, iodine and hydriodic acid. One of the R&D subjects is proof of manufacturability of chemical reactors made of practical structural materials and confirmation of the reactors' sound performance in the harsh process conditions. In order to examine the task, test apparatuses of the process are being constructed; the apparatus for a Bunsen reactor has been built and assembled. Capacities of vessels of the apparatus are about 50-150 liter; normal operating pressure will be 0.5 MPa [abs], and that of temperature will be 90 degrees centigrade. Safety measures for the test apparatus, operations, and in abnormal situations were considered prior to the start of the operation. This report summarizes the results of the considerations.

JAEA Reports

Density of Bunsen reaction solution and viscosity of poly-hydriodic acid

Kubo, Shinji; Yoshino, Koji*; Takemoto, Jumpei*; Kasahara, Seiji; Imai, Yoshiyuki; Onuki, Kaoru

JAEA-Technology 2012-037, 20 Pages, 2013/01

JAEA-Technology-2012-037.pdf:17.29MB

Densities of Bunsen reaction solutions in the iodine-sulfur process were measured with an oscillating U-tube density meter. Two types of the solutions were prepared to simulate sulfuric acid solutions and hydriodic acid solutions of the Bunsen reaction step. The former solution ranged in concentration from 0 to 45 wt% of sulfuric acid containing HI and I$$_{2}$$ of 0-2 mole%; the latter solution contained 0-17 mole% I$$_{2}$$, 1-15 mole% HI and 0-2 mole% H$$_{2}$$SO$$_{4}$$. The temperature of the measured solution were 10-60 $$^{circ}$$C. It was found that, in both solutions, the effect of HI and I$$_{2}$$ concentration on the density could well be represented by using a kind of mole fraction of iodine atom. Based on the finding, a set of correlation equations between the densities and the compositions were derived. Additionally, viscosities of ploy-hydriodic acid were measured using an oscillating viscosity meter in temperature range of 5-40 $$^{circ}$$C, and in the composition range of 0-17 mole% I$$_{2}$$ and 1-15 mole% HI; a empirical equation to calculate viscosity from the composition and the temperature are obtained.

Journal Articles

Energy requirement of HI separation from HI-I$$_{2}$$-H$$_{2}$$O mixture using electro-electrodialysis and distillation

Guo, H.*; Kasahara, Seiji; Tanaka, Nobuyuki; Onuki, Kaoru

International Journal of Hydrogen Energy, 37(19), p.13971 - 13982, 2012/10

 Times Cited Count:9 Percentile:69.93(Chemistry, Physical)

Separation of HI from HI-I$$_{2}$$-H$$_{2}$$O mixture determines the efficiency of the IS process for thermochemical hydrogen production. Energy requirement of HI separation from HI-I$$_{2}$$-H$$_{2}$$O mixture using electro-electrodialysis (EED) and distillation was evaluated by a process simulation. For EED, ideal membrane properties and properties of the reported EED experiments using Nafion membrane were evaluated. Effects of the operating parameters on heat duty were estimated, which comprised column pressure, HI molality in the column feed, and the flow rate ratio of the input from the Bunsen section to distillate rate. Low column pressure and high HI molality in the column feed were preferable for the ideal-membrane case; column pressure of 1.0 MPa and optimized HI molality in the column feed were desired for the Nafion-membrane case. The flow rate ratio had little effect on the minimum heat duty in the ideal-membrane case; a value in the vicinity of the lower limit of the flow rate ratio was optimal for the Nafion-membrane case. Optimization of these parameters was also carried out. The minimum heat duty of the Nafion-membrane case was 3.07$$times$$10$$^{5}$$ J/mol-HI, and that of the ideal-membrane case was 12.5% of the value.

Journal Articles

Membrane performance on electro-electrodialysis of HI-I$$_{2}$$-H$$_{2}$$O mixture for IS process

Tanaka, Nobuyuki; Yamaki, Tetsuya; Asano, Masaharu; Terai, Takayuki*; Onuki, Kaoru

Proceedings of 6th International Topical Meeting on High Temperature Reactor Technology (HTR 2012) (USB Flash Drive), 6 Pages, 2012/10

Research and development of a water-splitting hydrogen-production method, called iodine-sulfur (IS) process, has been conducting as one of the heat applications of high temperature gas-cooled reactor. Among the unit operations in this IS process, we have investigated electro-electrodialysis (EED) using an ion-exchange membrane to concentrate HI in an HI-I$$_{2}$$-H$$_{2}$$O mixture. Aiming at maximizing EED performance, new membrane materials were prepared by the radiation-induced graft polymerization and were examined in terms of their proton permeability through the membrane, i.e., transport number and conductivity at different iodine (I$$_{2}$$) concentrations in the HI-I$$_{2}$$-H$$_{2}$$O mixture. The transport number increased and the conductivity decreased with an increase in the feed I$$_{2}$$ molality. The EED model derived by the Nernst-Planck theory suggested that this trend could be explained exclusively by the variation of diffusion coefficient of I$$^{-}$$.

Journal Articles

Components for sulfuric acid processing in the IS process

Noguchi, Hiroki; Kubo, Shinji; Iwatsuki, Jin; Kasahara, Seiji; Tanaka, Nobuyuki; Imai, Yoshiyuki; Terada, Atsuhiko; Takegami, Hiroaki; Kamiji, Yu; Onuki, Kaoru; et al.

Proceedings of 6th International Topical Meeting on High Temperature Reactor Technology (HTR 2012) (USB Flash Drive), 6 Pages, 2012/10

The Japan Atomic Energy Agency (JAEA) has been conducting research and development on a thermochemical iodine-sulfur (IS) process. An examination is planned to verify the integrity of the components in the sulfuric acid decomposition section. A bayonet-type sulfuric acid decomposer made of SiC ceramics, a key component in the section, was test-fabricated. In parallel, a direct-contact heat exchanger (DCHX) is contemplated for use in the sulfuric acid decomposition section to simplify the process. Although the concept is very attractive, little is known about the heat and mass transfer behavior in the DCHX. Therefore, a test apparatus was constructed to measure the gas-phase mass transfer coefficients required for the optimal design of the DCHX. These coefficients of water were acquired and compared with an empirical correlation. The experimental data were in good agreement with those obtained from empirical correlation, and thus, the apparatus was confirmed to be reasonable.

199 (Records 1-20 displayed on this page)