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Journal Articles

Diffusion and adsorption of uranyl ion in clays; Molecular dynamics study

Arima, Tatsumi*; Idemitsu, Kazuya*; Inagaki, Yaohiro*; Kawamura, Katsuyuki*; Tachi, Yukio; Yotsuji, Kenji

Progress in Nuclear Energy, 92, p.286 - 297, 2016/09

 Times Cited Count:6 Percentile:61.4(Nuclear Science & Technology)

Diffusion and adsorption behavior of uranyl (UO$$_2^{2+}$$) species is important for the performance assessment of radioactive waste disposal. The diffusion behaviors of UO$$_2^{2+}$$, K$$^{+}$$, CO$$_3^{2-}$$ and Cl$$^{-}$$ and H$$_{2}$$O in the aqueous solutions were evaluated by molecular dynamics (MD) calculations. The diffusion coefficient (De) of UO$$_2^{2+}$$ is the smallest and is 26% less than the self-diffusion coefficient of H$$_{2}$$O. For the aqueous solution with high concentration of carbonate ions, uranyl carbonate complexes: UO$$_{2}$$CO$$_{3}$$ and UO$$_{2}$$(CO$$_{3}$$)$$^{2-}$$ can be observed. For the clay (montmorillonite or illite)-aqueous solution systems, the adsorption and diffusion behaviors of UO$$_2^{2+}$$ and K$$^{+}$$ were evaluated by MD calculations. The distribution coefficients (Kd) increase with the layer charge of clay, and Kd of UO$$_2^{2+}$$ might be smaller than that of K$$^{+}$$. Further, their two-dimensional diffusion coefficients were relatively small in the adsorption layer and were extremely small for illite with higher layer charge.

Journal Articles

Oxygen potential measurement of (Pu$$_{0.928}$$Am$$_{0.072}$$)O$$_{2-x}$$ at high temperatures

Matsumoto, Taku; Arima, Tatsumi*; Inagaki, Yaohiro*; Idemitsu, Kazuya*; Kato, Masato; Morimoto, Kyoichi; Sunaoshi, Takeo*

Journal of Nuclear Science and Technology, 52(10), p.1296 - 1302, 2015/10

 Times Cited Count:2 Percentile:22.25(Nuclear Science & Technology)

The oxygen potentials of (Pu$$_{0.928}$$Am$$_{0.072}$$)O$$_{2-x}$$ were measured at 1873K, 1773K and 1473K by gas equilibrium method. It was shown that following the reduction of Am at the O/M ratio above 1.96, Pu was reduced at the O/M ratio below 1.96.

Journal Articles

Corrosion behavior of simulated high-level waste glass in the presence of calcium ion or metallic iron

Maeda, Toshikatsu; Watanabe, Koichi; Omori, Hiroyuki*; Sakamaki, Keiko; Inagaki, Yaohiro*; Idemitsu, Kazuya*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 21(2), p.63 - 74, 2014/12

Static leach tests were conducted for simulated HLW glass in CaCl$$_{2}$$/Ca(OH)$$_{2}$$ solutions to investigate the corrosion behavior of HLW glass under calcium-rich environments induced by cement based materials in geological repositories. Another series of leach tests were conducted in deionized water in the presence of iron to investigate the effects of iron over-pack on the glass corrosion. In Ca solutions, corrosion of the glass was inhibited during the test period compared to that in deionized water, while the corrosion was enhanced at the presence of iron. The enhancement of the glass corrosion was assumed to be accompanied with transformation of silica, a glass network former, into iron silicates.

Journal Articles

An International initiative on long-term behavior of high-level nuclear waste glass

Gin, S.*; Abdelouas, A.*; Criscenti, L.*; Ebert, W.*; Ferrand, K.*; Geisler, T.*; Harrison, M.*; Inagaki, Yaohiro*; Mitsui, Seiichiro; Mueller, K. T.*; et al.

Materials Today, 16(6), p.243 - 248, 2013/06

 Times Cited Count:275 Percentile:99.01(Materials Science, Multidisciplinary)

The nations producing borosilicate glass as a confinement material for high-level waste resulting from spent fuel reprocessing have decided to reinforce scientific collaboration in order to obtain consensus on the mechanisms controlling the long-term dissolution rate of glass. This goal is the most important issue for developing reliable predictive models usable for performance assessment and safety demonstration of geological storage of such materials. This collaboration involves numerous laboratories working either in fundamental or applied research and using all the modern tools available in material science. We present first the situation of the six countries involved in the project regarding their history in nuclear waste vitrification, current policy, and geological disposal project development. This provides an understanding of the common and country specific needs regarding the issue of long-term behavior of glass. Then main proposals and first results are briefly presented.

Journal Articles

Initial dissolution rate of a Japanese simulated high-level waste glass P0798 as a function of pH and temperature measured by using micro-channel flow-through test method

Inagaki, Yaohiro*; Makigaki, Hikaru; Idemitsu, Kazuya*; Arima, Tatsumi*; Mitsui, Seiichiro; Noshita, Kenji*

Journal of Nuclear Science and Technology, 49(4), p.438 - 449, 2012/04

 Times Cited Count:16 Percentile:79.93(Nuclear Science & Technology)

Dissolution tests were performed for a simulated HLW glass by using a Micro-Channel Flow-Through (MCFT) test to evaluate the initial dissolution rate, $$r$$$$_{0}$$, as a function of pH and temperature. The results indicated that the $$r$$$$_{0}$$ shows a "V-shaped" pH dependence at 25$$^{circ}$$C, which is almost consistent with the previous results measured by using other test methods including Single Pass Flow-Through (SPFT) test. At elevated temperatures, however, the $$r$$$$_{0}$$ shows a "U-shaped" pH dependence with a flat bottom at neutral pH, which differs from the previous results. The results also indicated that the MCFT provided a higher value of the $$r$$$$_{0}$$with a steep slope of pH dependence than the SPFT results at basic pH from 8 to 11 at 90$$^{circ}$$C. With respect to the temperature dependence, the $$r$$$$_{0}$$ increases with temperature according to an Arrhenius law at any pH, and the apparent activation energy increases with pH, which suggests that the dissolution mechanism can change depending on pH.

Journal Articles

Burning of MOX fuels in LWRs; Fuel history effects on thermal properties of hull and end piece wastes and the repository performance

Hirano, Fumio; Sato, Seichi*; Kozaki, Tamotsu*; Inagaki, Yaohiro*; Iwasaki, Tomohiko*; Oe, Toshiaki*; Kato, Kazuyuki*; Kitayama, Kazumi*; Nagasaki, Shinya*; Niibori, Yuichi*

Journal of Nuclear Science and Technology, 49(3), p.310 - 319, 2012/03

AA2011-0278.pdf:0.56MB

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

The thermal impacts of hull and end piece wastes from the reprocessing of MOX spent fuels burned in LWRs on repository performance were investigated. The heat generation rates in MOX spent fuels and the resulting heat generation rates in hull and end piece wastes change depending on the fuel histories including the burn-up of UO$$_{2}$$ spent fuels, the cooling period before reprocessing, the storage period of fresh MOX fuels. The heat generation rates of hull and end piece wastes from the reprocessing of MOX spent fuels with any of those histories are significantly larger than those from UO$$_{2}$$ spent fuels with burn-ups of 45 GWd/THM. If a temperature below 80$$^{circ}$$C is specified for cement-based materials used in waste packages after disposal, the allowable number of canisters containing compacted hull and end pieces in a package for 45 GWd-MOX needs to be limited to a value of 0.7 to 1.6, which is significantly lower than the value of 4.0 for 45 GWd-UO$$_{2}$$.

Journal Articles

Evaluation of HLW glass dissolution/alteration kinetics by using micro-channel flow-through test method; Initial glass dissolution rate as a function of pH and temperature

Inagaki, Yaohiro*; Sakatani, Keiichi*; Yamamura, Yuki*; Mitsui, Seiichiro; Noshita, Kenji*; Miura, Yoshiyuki*; Kanehira, Norio*; Ochi, Eiji*; Mukunoki, Atsushi*; Chiba, Tamotsu*

Dai-7-Kai Saishori, Risaikuru Bukai Semina Tekisuto, p.136 - 137, 2011/01

Conventional static test methods are not appropriate to evaluate glass dissolution behavior at an arbitrarily-fixed condition due to compositional change of the solution with glass dissolution. In this study, we applied a newly-devised micro-channel flow-through test method to measurement of the initial dissolution rates of Japanese simulated waste glasses, JAEA-P0798 and JNFL-KMOC, at arbitrarily-fixed conditions and we evaluated temperature and pH dependence of glass dissolution. The results showed that the initial dissolution rate increased with temperature and had "V-shaped" pH dependence at each temperature.

Journal Articles

Measurement of HLW glass dissolution/alteration kinetics by using micro-reactor flow-through test method

Inagaki, Yaohiro*; Mitsui, Seiichiro; Makigaki, Hikaru*; Idemitsu, Kazuya*; Arima, Tatsumi*; Bamba, Tsunetaka; Noshita, Kenji*

Materials Research Society Symposium Proceedings, Vol.1193, p.219 - 228, 2009/05

We developed a new flow-through test method using micro-reactor, and applied it to measurement of the dissolution/alteration kinetics for a simulated HLW glass (P0798). In this method, a glass coupon is placed just on a Teflon plate having a micro-channel, and a solution is injected into the inlet of micro-channel by micro-syringe pump at a constant flow rate. The injected solution flows through the micro-channel reacting with the glass to the outlet, and the outlet solution is retrieved at certain intervals to be analyzed for determination of the dissolution/alteration rate. This method has some major features, i.e., simple test apparatus with compact size, high S/V ratio, sensitive/precise measurement of the glass dissolution/alteration rate, adequate glass shape for analysis of reacted glass surface, and so on. By use of this method the dissolution/alteration rate for P0798 was measured as a function of pH, temperature, flow rate, and time, and some available results were obtained to evaluate the dissolution/alteration kinetics.

Journal Articles

Measurement of initial dissolution rate of P0798 simulated HLW glass by using micro-reactor flow-through test method

Makigaki, Hikaru*; Inagaki, Yaohiro*; Idemitsu, Kazuya*; Arima, Tatsumi*; Mitsui, Seiichiro; Bamba, Tsunetaka; Noshita, Kenji*

Materials Research Society Symposium Proceedings, Vol.1193, p.307 - 314, 2009/05

By using micro-reactor flow-through test method we measured the initial dissolution rate of P0798 glass at 25$$^{circ}$$C as a function of pH between 5.6 and 12. The results showed that the initial dissolution rate determined by dissolution rate of Si has "V-shaped" pH dependency similar to R7T7 glass reported by CEA, France. We also measured the initial dissolution rate at pH 5.6 as a function of temperature between 25 and 90$$^{circ}$$C, and the activation energy was evaluated to be 51 kJ/mol, which value is slightly smaller than that of R7T7 glass at pH 9 reported by CEA. On the basis of these results and comparison, we discussed the dissolution kinetics of P0798 glass.

JAEA Reports

Announced document collection of the 1st Information Exchange Meeting on Radioactive Waste Disposal Research Network (Joint research)

Nakayama, Shinichi; Nagasaki, Shinya*; Inagaki, Yaohiro*; Oe, Toshiaki*; Sasaki, Takayuki*; Sato, Seichi*; Sato, Tsutomu*; Tanaka, Satoru*; Tochiyama, Osamu*; Nagao, Seiya*; et al.

JAEA-Conf 2007-003, 120 Pages, 2007/03

JAEA-Conf-2007-003.pdf:53.18MB

The 1st information exchange meeting on Radioactive Waste Disposal Research Network was held in Nuclear Science Research Institute of Japan Atomic Energy Agency on August 4, 2006. Radioactive Waste Disposal Research Network was established by under Interorganization Atomic Energy Research Program of Japan Atomic Energy Agency, and the objective is to bring both research infrastructures and human expertise in Japan to an adequate performance level, thereby contributing to the development of the fundamental research area in the field of radioactive waste disposal. This lecture material is a collection of research presentations and discussions during the information exchange meeting.

JAEA Reports

Fundamental Study on HLW Glass Corrosion and Mineralization (IV)

Inagaki, Yaohiro*

JNC TJ8400 2004-019, 32 Pages, 2005/02

JNC-TJ8400-2004-019.pdf:0.2MB

The purpose of this study(fiscal year 2001-2004) is to understand, qualitatively and quantitatively, the glass corrosion and associated elemetal release under assumed disposal conditions for long-term referring to geochemical mechanism in order to establish the validation for long-term corrosion/leaching model. This report(fiscal year 2004) discusses glass size dependence of the glass corrosion rate and leaching of Se from the glass on the basis of the results of corrosion tests performed with P0798 simulated HLW glass with four different sizes. The conclusions are; (1) the glass corrosion rate for the glass with four different sizes can be analyzed by use of hydration model (water diffusion model), and value of the diffusion coefficient is evaluated to be 10$$^{-21}$$m$$^{2}$$/s at 120$$^{circ}$$C, (2) Se leaches from the glass congruently with Si, and the leached Se cannot precipitate under the present conditions, (3) the experimental results on glass corrosion rate including previous results of the temperature dependence and the rate in the presence of bentonite can be explained by use of the water diffusion model, which indicates that application of this model is available for confirming validity of the long-term corrosion/leaching model.

Journal Articles

Status of studies on HLW glass performance for confirming its validity in assessment

Inagaki, Yaohiro*; Mitsui, Seiichiro*; Makino, Hitoshi*; Ishiguro, Katsuhiko*; Kamei, Gento*; Kawamura, Kazuhiro*; Maeda, Toshikatsu; Ueno, Kenichi*; Bamba, Tsunetaka*; Yui, Mikazu*

Genshiryoku Bakkuendo Kenkyu, 10(1-2), p.69 - 83, 2004/03

no abstracts in English

JAEA Reports

Fundamental Study on HLW Glass Corrosion and Mineralization(III)

Inagaki, Yaohiro*

JNC TJ8400 2003-055, 24 Pages, 2004/02

JNC-TJ8400-2003-055.pdf:1.46MB

A large number of studies on aqueous corrosion of HLW glass have shown that the glass reacts with water to form more stable solid phases (alteration-phases or secondary phases). The process of alteration-phase formation is expected to play an important role in the radionuclide release from the glass, because it can affect both the glass dissolution rate and the retention of radionuclides in the phases. However, these processes of alteration and diffusion have not been evaluated in details. Therefore, a sound understanding of the glass corrosion mechanism under disposal conditions for long-term is expected to be essential for validation of the long-term performance. The purpose of this study (fiscal year 2001-2003) is to understand, qualitatively and quantitatively, the glass corrosion and associated elemetal release under assumed disposal conditions for long-term referring to geochemical mechanism in order to establish the validation for long-term corrosion/leaching model. This report (fiscal year 2003) discusses temperature dependence of the glass corrosion rate, effects of bentonite on the glass corrosion, and application of the results to the long-term corrosion model, on the basis of the results of corrosion tests performed with a simulated HLW galss, P0798, under various inditions. The conclusions are; 1) the glass corrosion rate can be analyzed by use of hydration(water diffusion) model, and values of the diffusion coefficient are evaluated to be 2$$times$$10$$^{-21}$$ m$$^{2}$$/s (60$$^{circ}$$C) to 5$$times$$10$$^{-20}$$ m$$^{2}$$/s (120$$^{circ}$$C) with the activation energy of 52kJ/mol, 2) the presence of bentonite cannot affect the glass corrosion rate, but most of Cs released from the glass are sorbed on bentonite by ion-exchange, 3) application of the hydration (water diffusion) model to the long-term glass corrosion analysis indicates that the glass has higher potential than that evaluated in H12 report and the glass size is one of key parameters.

JAEA Reports

Status of Studies on HLW Glass Performance for Increasing Its Validity in Assessment

Inagaki, Yaohiro*; Mitsui, Seiichiro; Makino, Hitoshi; Ishiguro, Katsuhiko; Kamei, Gento; Kawamura, Kazuhiro; Maeda, Toshikatsu*

JNC TN8400 2003-036, 53 Pages, 2003/12

JNC-TN8400-2003-036.pdf:0.51MB

Obtain of sufficient data for the performance of high-level radioactive waste(HLW) glass and verification of a model for the radionuclide release from the HLW glass in the disposal condition are required in order to show the objective reliability. In this paper, some reports about performance assessment of HLW glass are reviewed and we clarify the problems to raise reliability comparing these reports.

JAEA Reports

Fundamental study on HLW glass corrosion and mineralization, II; Document prepared by other organization, based on the trust contract

Inagaki, Yaohiro*

JNC TJ8400 2003-014, 45 Pages, 2003/03

JNC-TJ8400-2003-014.pdf:4.76MB

The purpose of this study is to understand, qualitatively and quantitatively, the alteration-phase formation and associated elemetal release during aqueous corrosion of HLW glass in order to establish the validation for long-term corrosion/leaching model. Static corrosion tests were performed with a simulated HLW glass, P0798 glass, in alkalline solutions (NaOH, KOH, DIW) at elevated temperatures, in order to accelerate the reaction, as a function of temperatute, time and alkalline concentration. Crystalline alteration-phases formed in the corroded glass were analyzed by use of XRD and electron microscopies, and the solution concentrations of dissolved elements were measured by use of ICP-MS. The results indicated that; (1)Analcime or Na-beidellite or both of them form during the corrosion depending on the conditions, (2)In addition to solution pH, temperature, solution concentrations of alkalline elements and silicic acid sensitively affect formation of analcime and Na-beidellite, (3)Thermodynamic calculation based on the published data of equilibrium constant cannot evaluate the empirical alteration phase formation, (4)At the conditions where only Na-beidellite forms, the glass dissolution rate is slow, while at the conditions where analcime forms the glass dissolution rate is extremely fast, (5)At the conditions where only Na-beidellite forms, the glass dissolution proceeds in proportion to square root of time, which suggests the process is diffusion-controlled, (6)Most of Cs in the glass is retained in the alteration-phases by sorption onto Na-beidellite or incorporation into analcime.

Journal Articles

Corrosion of Carbon Steel in Compacted Bentonite and its Effect on Neptunium Diffusion under Reducing Condition

Xia, X.; Ishidera, Takamitsu; Arima, Tatsumi*; Inagaki, Yaohiro*

P.290-291(2003), p.290 - 291, 2003/00

None

JAEA Reports

Fundamental study on HLW glass corrosion and minera]ization

Inagaki, Yaohiro*

JNC TJ8400 2002-052, 42 Pages, 2002/02

JNC-TJ8400-2002-052.pdf:1.38MB

A large number of studies on aqueous corrosion of HLW glass have shown that the glass react with water to form more stable solid phases (alteration-phases or secondary phases). The process of alteration-phase formation is expected to play an important role in the radionuclide release from the glass, because it can affect both the glass dissolution rate and the retention of radio nuclides in the phases. Recent studies have indicated that analcime (zeolite) forms during aqueous corrosion of the glass in certain conditions, and the analcime formation can accelerate the glass corrosion by consuming orthosilicic acid (H$$_{4}$$SiO$$_{4}$$) from the solution. On the other hand, the alteration-phases such as zeolite and smectite are expected to have a retention capacity for some radio nuclides by sorption or incorporation. Therefore, a sound understanding of the alteration phase formation is expected to be essential for validation of the long-term performance. The purpose of this study is to understand, qualitatively and quantitatively, the alteration-phase formation and associated elemental release during aqueous corrosion of HLW glass. Static corrosion tests were performed with a simulated HLW glass, P0798 glass, in NaOH solutions at elevated temperatures, in order to accelerate the reaction, as a function of temperature, time and NaOH concentration. Crystalline alteration-phases formed in the corroded glass were analyzed by use of XRD, and the solution concentrations of dissolved elements were measured by use of ICP-MS. The results indicated that; (1)Analcime or Na-beidellite or both of them form during the corrosion depending on the conditions, (2)Si rich amorphous phases are contained in the alteration-phases, (3)In addition to solution pH, solution concentrations of Na and K sensitively affect formation of analcime and Na-beidellite, (4)Analcime formation accelerates the glass corrosion, (5)Most of Cs in the glass is retained in the alteration-phases by sorption ...

Journal Articles

Oxidation Behavior of Modified SUS(PNC316) under Low Oxygen Partial Pressure

Sato, Isamu; Namekawa, Takushi; *; Idemitsu, Kazuya*; *; Inagaki, Yaohiro*

Journal of Nuclear Materials, (304), p.21 - 28, 2002/00

 Times Cited Count:14 Percentile:67.53(Materials Science, Multidisciplinary)

None

Journal Articles

Alteration-phase formation and associated cesium release during alteration of R7T7 waste glass

Inagaki, Yaohiro*; Idemitsu, Kazuya*; Arima, Tatsumi*; Maeda, Toshikatsu; Ogawa, Hiromichi; Itonaga, Fumio

Materials Research Society Symposium Proceedings, Vol.713, p.589 - 596, 2002/00

A large number of studies on HLW glass corrosion have shown that the glass reacts with water to form more stable mineral phases (alteration phases) during the long-term geological disposal. The phase formation is essential to evaluate the radionuclide release from the glass during the long-term disposal. The purpose of this study is to evaluate, experimentally, the mineral phase formation from HLW glass and the associated cesium release. Static corrosion tests were performed on powdered R7T7 glass in alkalline solutions at elevated temperatures to accelerate the reaction, and mineral phases formed were analyzed by XRD. The results showed that analcime (zeolite) is formed as the dominant phase coexisting with SiO$$_{2}$$(am), and beidellite(smectite) or gibbsite coexists dependiting on the conditions. The solution analysis indicated that most of the cesium is retained in the phases of beidellite and analcime by sorption.

45 (Records 1-20 displayed on this page)