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Tochigi, Yoshikatsu; Kogawa, Noritaka*; Mukai, Satoru*; Jintoku, Takashi*; Sasamoto, Hiroshi; Shibata, Masahiro; Yui, Mikazu
JAEA-Research 2007-024, 27 Pages, 2007/03
JAEA-Research-2007-024.pdf:1.83MB
In the safety assessment of high-level radioactive waste (HLW) geological disposal, it is important to understand diffusion behavior of radionuclides for evaluation of retardation capacity in the host rock. In this study, non steady state diffusion experiments with non-sorbing ion ware carried out using several granitic rock samples of different length and the matrix diffusion depth was evaluated. As the results of experiment, it is confirmed that the non-sorbing ion can diffuse into the unaltered zone of granitic rock at least about 200 mm in depth and almost same diffusion coefficient is estimated for all rock samples independent of length. Based on these results, it is expected that matrix diffusion of nuclides is acting on a scale of several dozens of centimeters in the granitic rock.
Tanai, Kenji; Jintoku, Takashi*; Kikuchi, Hirohito*; Nishimura, Mayuka; Matsumoto, Kazuhiro*; Aoyanagi, Shigeo; Yui, Mikazu
JAEA-Research 2006-035, 32 Pages, 2006/06
JAEA-Research-2006-035.pdf:3.46MB
In order to contribute to the safety standards and guidelines which a regulator decides, state-of the art assessment method is investigated and summarized in the table about performance guarantee contents of buffer material related to the mechanical support and protection of the overpack and rock matrix, and the retardation of radionuclide. In addition, examples of the assessment tool are described. In this report, summary of (1) basic properties of bentonite, including swelling properties, mechanical properties and hydraulic properties, (2) long-term behavior of bentonite, including creep deformation, penetration into host rock, erosion and alteration, (3) gas permeability, (4) colloid filtration and (5) mechanical stability of the near-field is described. Check points, assessment methods (based on the data obtained from the experimental results, the estimation value obtained from empirical equations and database, and the modeling calculations) and latest results of these R&D programs were also summarized.
Saji, Shinichi*; Ito, Masakazu*; Shibata, Masahiro; Jintoku, Takashi*; Isogai, Takeshi*
JNC TN8400 2005-017, 86 Pages, 2005/09
Porewater chemistry in Buffer Material is one of the most important information for assessment of corrosion behavior on the overpack, and of solubility and sorption of nuclides in the buffer etc. In the Second Progress Report of HLW in Japan (H12 Report), porewater chemistry is estimated by batch modeling calculation based on the batch experiment. However, it is expected that, in the disposal vault, temporal-spatial evolution of porewater chemistry occurrs. After H12 report, JNC started experimental study and modeling work for further understanding of the chemical evolution. However, modeling for long term evaluation of porewater chemistry is calculated on the basis of the short term laboratory experiment. Thus, the long term reliability of the model needs to be verified by comparing natural analogue.In this study, bentonite deposit under the river bed was sampled as function of depth by boring. At the sampling point, the river improvement was carried out in 1987 and river water contact with bentonite deposit since then. Mineral composition, chemical composition, inter layer cation concentration, CEC and methylene blue adsorption etc. of the sample are measured.As a result, erosion of the smectite, decreasing of pH and leaching out of SO4 are obsereved. However, clear trend of the depth direction is not obtained for the reason of natural inhomogeneous system.
Sasamoto, Hiroshi; Yoshida, Yasushi*; Isogai, Takeshi*; Suyama, Tadahiro*; Jintoku, Takashi*; Shibata, Masahiro; Yui, Mikazu
Saikuru Kiko Giho, (28), p.27 - 33, 2005/09
JNC has developed the databases of nuclides migration for safety assessment of high-level radioactive waste (HLW), and the databases have been used in the second progress report to present the technical reliability of HLW geological disposal in Japan. The technical level and applicability of databases developed by JNC have been evaluated highly not only in Japan but also in overseas. Thus we have performed the followings in order to provide the databases broadly in the word and to promote the use of databases; 1) development of tools to convert the database format from geochemical code PHREEQE to PHREEQC, GWB and EQ3/6, 2) open the web site including the databases to the public. As a result, a down-load system of databases from web site has been applied and the database users have significantly increased. Additionally it has been performed that we consider the useful comments from database user for modification and/or update of databases.
Yoshihiko, Saito,; Ochs, M.*; Jintoku, Takashi*; Suyama, Tadahiro*; Shibata, Masahiro; Sasamoto, Hiroshi; Yui, Mikazu
JNC TN8410 2005-011, 59 Pages, 2005/08
JNC-TN8410-2005-011.pdf:2.04MB
Japan Nuclear Cycle Development Institute (JNC) has developed the JNC-Sorption Database (JNC-SDB) for bentonite and rocks in order to assess the retardation property of important radioactive elements in natural and engineered barriers in the H12 report. The database includes distribution coefficient (Kd) of important radionuclides. The Kd values in the JNC-SDB are about 20,000 data. And the JNC-SDB includes a great variety of Kd and additional key information from many different experimental conditions. Accordingly, the following classification guideline and classification system were developed in order to evaluate the reliability of each Kd value. (1) Criterion I: Completeness of documentation and type of Kd information (2) Criterion II: Quality of reported data from a technical and scientific point of view (3) Criterion III: Consistency of data with the majority of related reliable studies (4) An overall classification system / The checkpoints in Criterion II evaluate the reliability of each Kd entry in the JNC-SDB ; solid phase, adjustment and control of pH, redox conditions, final solution composition, temperature, solid/water ratio and grain size, sorption value, initial radionuclide concentration, phase separation, reaction time, agitation method, radionuclide loading, reaction vessels, uncertainty estimates, parameter variation
Taniguchi, Naoki; Kawakami, Susumu; Jintoku, Takashi; Yui, Mikazu
JNC TN8400 2005-002, 29 Pages, 2005/03
JNC-TN8400-2005-002.pdf:36.7MB
In order to contribute to the safety standards and guidelines for overpacks on which the administration decides, the tools for performance guarantee on overpacks were studied based on the present research products for overpack corrosion. The corrosion modes that should to be considered in repository environments were extracted, and then the assessment methods and examples for each mode was summarized based on current understandings of corrosion behavior of overpacks.The passivation, general corrosion, localized corrosion (pitting corrosion, crevice corrosion, and stress corrosion cracking) and hydrogen embrittlement were extracted and the experimental methods to evaluate the initiation and propagation behavior were presented. The assessment examples based on research products such as second progress report (H12 report) were given.
Shibata, Masahiro; Sasamoto, Hiroshi; Jintoku, Takashi; Yui, Mikazu
JNC TN8400 2004-010, 46 Pages, 2004/03
JNC-TN8400-2004-010.pdf:14.26MB
This report presents the assessment for long-term stability of buffer material considering the possible alteration scenarios under repository conditions based on the recent research results (i.e., H12) about bentonite alteration. In the assessment, the following three effects have a priority in view points of performance assessment: 1) temperature effect, 2) interaction effect with overpack as a engineered barrier material, 3) interaction effect with cement as support materials of the dritf in soft rock. Four cases were selected in combination with geological environment in the assessment considering the temperature effect and effects with near-field components.
Kurihara, Yuji; Fujita, Tomoo; Kawakami, Susumu; Jintoku, Takashi; Yui, Mikazu; Sugita, Yutaka
JNC TN8400 2003-053, 32 Pages, 2004/03
JNC-TN8400-2003-053.pdf:0.41MB
In previous JNC tequnichal reports, from a view point of long-term safety on geological disposal of high level radioactive waste, the items which should guarantee the performance of each element of the repository were extracted, and it was shown how to guarantee the performance about these items. Furthermore, future R&D requirements were extracted. In this report, the status of each subject in JNC was reported.
Isogai, Takeshi*; Jintoku, Takashi; Sasamoto, Hiroshi
JNC TN8400 2003-050, 74 Pages, 2004/03
JNC-TN8400-2003-050.pdf:5.85MB
We determined the pH and chemical compositions of porewaters in compacted bentonite as a function of time. The experiments were carried out using the low-decolorant pH test papers and high-absorbancy pads embedded in compacted bentonite (Kunigel-V1R=100[%]) having dry densities of 1.6 [g/cm
]. We also measured the chemical composition and exchangeable cation concentrations of the bentonite after the experiments. The experiments were conducted in a controlled-atmosphere glove box (O
(g) content is less than 1[ppm]) using distilled water, synthesized seawater and a low-alkaline cement porewater (i.e., HFSC: High Flyash contained Silica fume Cement) as initial solutions. The pH of the distilled water and synthesized seawater was adjusted to pH=9 by adding NaOH solution. Distilled water was reacted with crushed HFSC to produce a solution representing low-alkaline cement solution (pH= about 11). - Distilled water: The pH of porewaters further away from the interface did not vary significantly (pH = 8.0 to 9.0), but the pH of porewaters near the infiltration interface slightly decreased (pH = 7.5-8.5 
pH = 7.0-8.0). - Synthesized seawater: The pH values were roughly constant at the interface between 6.5 and 7.0, but the pH of porewaters further away from the interface slightly decreased with time (pH = 6.5-7.0 pH = 6.0-6.5). - HFSC solution: Like the experiment with involving distilled water, the pH of porewaters contacted with HFSC solution further away from the interface were roughly constant between 8.5 and 10.0, but the pH of porewaters near the infiltration surface significantly decreased with time from pH = 9.5 to pH = 7.5-8.5. Although the determination of porewater chemistry in compacted bentonite was carried out, it was difficult to obtain the quantitative profile for variation during the experiment except the experiment using synthesized seawater.
Jintoku, Takashi; Shibata, Masahiro; Yoshida, Yasushi*; Suyama, Tadahiro*
JNC TN8400 2003-048, 40 Pages, 2004/03
JNC-TN8400-2003-048.pdf:1.91MB
We attended the OECD/NEA Sorption Project in which sorption modeling study and applicability study for sorption experimental results on minerals was held. In this study, JNC selected the sorption modeling of Ni, Np onto Montmorillonite and U onto Weathered Shist, adopted the surface complexation model and/or ion exchange model, and carried out modeling for the experimental results by using the fitting procedure. In this procedure, PHREEQC geochemical calculation code was used. Based on the modeling results which can explain experimental results, the equilibrium constants were fixed.Following the modeling, the applicability study which applies the modeling results to other sorption experiments presented that the errors of Kd value between them were within approximately one order. For the future, validation procedures for this model are needed.
Yoshida, Yasushi*; Sasamoto, Hiroshi; Jintoku, Takashi
JNC TN8400 2003-043, 36 Pages, 2004/02
JNC-TN8400-2003-043.pdf:0.43MB
The compilation for the Pitzer parameters which enable to correct activity coefficients of high ionic strength solution was done. In this compilation parameters for species of geochemical elements and actinide / lanthanide elements were mainly compiled.Calculation results of activity coefficient correction with these compiled parameters shows that activity coefficients of cationic and anionic ion have different tendencies with ionic strength increasing, and also charge of each ion affects the value of activity coefficient. Although parameters of actinide were compiled, these data could not be used as dominant species for the solubility calculation under the condition of the groundwater/porewater compositon estimated in second progress report on research and development for the geological disposal of HLW in Japan. But it is indicated that at rather higher ionic strength condition parameters compiled in this work could be used for solubility calculation because of change of dominant species due to the effect of high ionic strength. For the solubility calculation of Am with analogue data of Cm the difference of the solubility between Pitzer and Davis model is small for the SRHP porewater composition, but at the ionic strength higher than 1 Am solubility calculated by Pitzer model increases notably but Davis model does not simulate this reaction. These Pitzer parameters were compiled as EQ3/6 ver.7.2c format, and this data base file is attached in appendix of this report.
Kawakami, Susumu; Yui, Mikazu; Kurihara, Yuji; Jintoku, Takashi; Sugita, Yutaka
JNC TN8400 2003-037, 26 Pages, 2004/02
JNC-TN8400-2003-037.pdf:1.33MB
In order to contribute to the safety standards and guidelines upon which a administration decides, examination for clarifying how to reflect the result obtained by future R&D was performed in other reports, as the JNC technical reports. In those reports, from a viewpoint of the long-term safety on geological disposal of high-level radioactive waste, the items which should guarantee the performance of each element of the repository were extracted, and it was shown how to guarantee the performance about these items. Furthermore, future R&D requirements were extracted. In this report, the status of each subject in JNC was reported.
Jintoku, Takashi; Shibata, Masahiro; Yoshida, Yasushi*; Suyama, Tadahiro*
Saikuru Kiko Giho, (21), p.65 - 77, 2003/12
We attended the OECD/NEA Sorption Project in which sorption modeling study and applicability study for other experimental results on minerals was held. In this study, JNC selected the sorption modeling of Ni, Np onto Montmorillonite and U onto Weathered Shist, adopted the surface complexation model and/or ion exchange model, and carried out mainly by using the fitting procedure for the experimental results. In this modeling procedure, PHREEQC geochemical calculation code is used. Based on the analytical results similar to experimental results, the equilibrium constants were fixed.From the applicability study, the trend of the analytical result and experimental one are similar. For the future, validation procedures for this model are needed.
-Species of Radioactive ElementsOchs, M.*; Lothenbach, B.*; Christl, I.*; Yui, Mikazu; Shibata, Masahiro; Jintoku, Takashi
JNC TN8400 2003-012, 28 Pages, 2003/06
JNC-TN8400-2003-012.pdf:1.81MB
In the original list of ligands to be considered in the JNC-TDB, NH had not been included, but NH, complexes were evaluated for Pd due to their importance for such soft acid metals. Presently, NH- complexes are considered to be important for the Japanese TRU disposal program, because nitrate contained in this type of waste could possibly be reduced to NH under repository conditions. This report presents thermodynamic data that are particularly critical for evaluating the safety functions of the repository near field, but are also of general importance for performance analysis. An extensive data search and initial evaluation for the interaction of NH with Pb, Sn, Bi, Nb, and Sb were carried out, but yielded no useful results. Therefore, no thermodynamic data can be recommended for NH-species of these elements. However, the compiled information allowed a rough comparative evaluation of stability constants in the system NH - HO - Metal, which indicates that NH is not likely to be a critical ligand for Sn(IV), Bi, Nb, and Sb(V) in dilute solutions. For Pb, complexation with NH may become relevant at elevated NH concentrations. Our evaluation further indicated that NH could be a relevant ligand for Ni and Co. Their interaction with NH had been studied to some degree. Subsequently, a first, traceable compilation of original experimental data was carried out for Ni and Co. However, in most case, the possible complex formation of Ni with the anions of the electrolyte and OH
has not been considered in the calculations of the different constants. It remains to be studied in detail whether these interactions can be neglected or corrected for in all cases. A brief attempt was made to carry out some calculations for Ni in order to roughly estimate possible effect of the presence of NH on a repository performance. The calculations carried out clearly show that very high NH ...
Sugita, Yutaka; Kurihara, Yuji; Kawakami, Susumu; Jintoku, Takashi; Yui, Mikazu
JNC TN8400 2003-015, 34 Pages, 2003/05
JNC-TN8400-2003-015.pdf:2.65MB
In order to contribute to the safety standards and guidelines upon which a governmental administration decide, examination for clarifying how to reflect the result obtained by future R&D was performed. From a view point of long-term safety on geological disposal, the items which should guarantee the performance of each element which constitutes disposal institutions (by this report, they are the backfill, the plug, the tunnel, and the pit) were extracted, and it was shown what a performance guarantee is concretely offered about these items. Furthermore, based on H12 report as a situation of present R&D for a method of a performance guarantee, the subjects considered that a future R&D is required were extracted.
Kawakami, Susumu; Sugita, Yutaka; Kurihara, Yuji; Jintoku, Takashi; Taniguchi, Naoki; Yui, Mikazu
JNC TN8400 2002-026, 42 Pages, 2003/03
JNC-TN8400-2002-026.pdf:12.1MB
In order to contribute to the safety standards and guidelines upon which a administration decides, examination for clarifying how to reflect the result obtained by future R%D was performed. From a viewpoint of the long-term safety on geological disposal, the items which should guarantee the performance of each element which constitutes disposal institutions (by this report, they are the overpack and the buffer material) were extracted, and it was shown what a performance guarantee is concretely offered about these items. Furthermore, based on the H12 report as a situation of present R&D for a method of a performance guarantee, the subjects considered that a future R&D is required were extracted. Moreover, the items of a safety standard and guideline were assumed, and the relation between these items and a performance guarantee items was arranged. One arrangement for clarifying whether to be reflected in the safety regulations and guidelines whose R%D subjects extracted from the performance guarantee items was shown.
Fukunaga, Sakae*; Nakayama, Mamoru*; Jintoku, Takashi*; *; Kudo, Akira*
JNC TJ8400 2002-037, 68 Pages, 2002/02
JNC-TJ8400-2002-037.pdf:0.28MB
We conducted the following four investigations concerned with microbial influence in geological disposal facilities. (1)Improvement of the FEP dictionary and investigation on chemical evolution of nitrate by microbes. (2)Experimental estimation of microbial mobility in compacted Na bentonite saturated by synthetic seawater with 30wt% silica sand and Ca bentonite with 30wt% silica sand. (Both dry densities are 1.6 g/cm.) (3)Habitation of microbes in Na rich bentonite deposit and Ca rich one. (4)Interaction between SRB (sulfate reducing bacteria) and Np in a reducing environment at Eh=-85mV. As the result, it was revealed that (1)microbial activity in near field rock and microbial denitrification of nitrate under the existence of electron donor are important, (2)microbes didn't move in Na bentonite in 3 weeks and moved to the distance of 20mm in Ca bentonite, and (3)microoragnisms existed at the inside of the deposits. (4) The difference between distribution coefficient of Eh=-85mV and Eh=-500mV was evaluated.
Fukunaga, Sakae*; Nakayama, Mamoru*; Jintoku, Takashi*; *; Kudo, Akira*
JNC TJ8400 2002-036, 186 Pages, 2002/02
JNC-TJ8400-2002-036.pdf:1.34MB
We conducted the following four investigations concerned with microbial influence in geological disposal facilities. (1)Improvement of the FEP dictionary and investigation on chemical evolution of nitrate by microbes. (2)Experimental estimation of microbial mobility in compacted Na bentonite saturated by synthetic seawater with 30wt% silica sand and Ca bentonite with 30wt% silica sand. (Both dry densities are 1.6 g/cm.) (3)Habitation of microbes in Na rich bentonite deposit and Ca rich one. (4)Interaction between SRB (sulfate reducing bacteria) and Np in a reducing environment at Eh=-85mV. As the result, it was revealed that (1)microbial activity in near field rock and microbial denitrification of nitrate under the existence of electron donor are important, (2)microbes didn't move in Na bentonite in 3 weeks and moved to the distance of 20mm in Ca bentonite, and (3)microoragnisms existed at the inside of the deposits. (4)The difference between distribution coefficient of Eh=-85mV and Eh=-500mV was evaluated.
