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Suyama, Tadahiro; Ganter, C.*; Kunze, S.*; Tachi, Yukio; Ochs, M.*
JAEA-Data/Code 2010-026, 72 Pages, 2011/02
JAEA-Data-Code-2010-026.pdf:1.05MB
Sorption of radionuclides in bentonites and rocks is one of the key processes in the safe geological disposal of radioactive waste. JAEA has developed sorption database (JAEA-SDB) which includes extensive compilation of sorption Kd data. JAEA has been continuing to update the SDB in view of potential future data needs, focusing on assuring the quality level and practical applications to Kd-setting for the geological environment. In this report, the QA/classification of selected entries in the JAEA-SDB, focusing on key radionuclides (Th, Np, Am, Se and Cs) sorption on tuff existing widely in geological environment, was done following the approach/guideline defined in our previous report. As a result, the reliability of 560 Kd values was evaluated and classified. This classification scheme is expected to make it possible to obtain quick overview of the available data from the SDB, and to have suitable access to the respective data for Kd-setting in PA.
Ochs, M.*; Suyama, Tadahiro; Kunze, S.*; Tachi, Yukio; Yui, Mikazu
JAEA-Data/Code 2009-021, 144 Pages, 2010/02
JAEA-Data-Code-2009-021.pdf:4.88MB
Sorption of radionuclides in bentonites and rocks is one of the key processes in the safe geological disposal of radioactive waste. Japan Atomic Energy Agency (JAEA) has developed sorption database (JAEA-SDB) which includes extensive compilation of sorption Kd data by batch experiments, extracted from published literatures. In this report, the QA/classification of selected entries in the JAEA-SDB, focusing granite rocks which are related to reference systems in H12 PA and possible applications in the context of URL activities, and Fe-oxide/hydroxide, Al-oxide/hydroxide existing widely in geological environment, was done following the approach/guideline defined in our previous report. As a result, the reliability of 1,373 Kd values was evaluated and classified. This classification scheme is expected to make it possible to obtain quick overview of the available data from the SDB, and to have suitable access to the respective data for Kd-setting in PA.
Saito, Yoshihiko; Ochs, M.*; Kunze, S.*; Kitamura, Akira; Tachi, Yukio; Yui, Mikazu
JAEA-Technology 2008-018, 116 Pages, 2008/03
JAEA-Technology-2008-018.pdf:1.08MB
In this report, the QA/classification of selected entries (1,056 Kd values) in the JNC-SDB, especially of Kd values for mudstone system to use in the Kd-derivation exercise for Horonobe rocks, was done following the approach defined in our previous report. This classification scheme made it possible to obtain quick overview of the available data, and to have suitable access to the respective Kd values.
-setting for Horonobe rocksOchs, M.*; Kunze, S.*; Saito, Yoshihiko; Kitamura, Akira; Tachi, Yukio; Yui, Mikazu
JAEA-Research 2008-017, 89 Pages, 2008/03
JAEA-Research-2008-017.pdf:3.23MB
In the present report, a first test and illustration was performed regarding the applicability of the JNC-SDB to the derivation of K-values for Th, Np, Cs, and Se valid for Horonobe rocks. The original experimental data selected from the JNC-SDB were converted to the application conditions using the semi-quantitative scaling procedures. To illustrate the effect of the scaling procedures, and of related uncertainties, on the magnitude of the derived K-values, scaling procedures taking into account mineralogy as well as surface and solution speciation were applied sequentially, and all results were discussed in detail. This K-setting exercise allowed to predict the magnitude of K values under the in-situ conditions, however the availability of experimental data that closely match the application conditions is limited for some reasons.
Ochs, M.*; Kunze, S.*; Yui, Mikazu; Sasamoto, Hiroshi
no journal, ,
JAEA has been developing generic methodologies using the generic type of underground research laboratory (URL). In order to develop a practical method for mass transport analysis, it is important to evaluate the application of method to an actual geological environment. Kd is the one of important parameter for mass transport analysis, thus the present study discusses the practical method to derive the Kd for some important radionuclides at the environment of Horonobe URL using the sorption database. As a first step, the present study has been conducted (1) to design the experimental program to be conducted in the Horonobe URL, and to (2) test the usefulness of and identify important gaps in the existing database. The sorption database was applied to an initial prediction of the sorption of Cs, Np, Th, and Se under expected URL-conditions. Kd-derivation was done using the estimation methods discussed in Ochs et al, (2006). This preliminary exercise in Kd-setting allowed to estimate the magnitude of sorption under the expected in-situ conditions. More importantly, it also allowed to identify critical gaps in the existing database and process understanding.
Suyama, Tadahiro; Tachi, Yukio; Yui, Mikazu; Ochs, M.*; Kunze, S.*; Dahinden, M.*
no journal, ,
For estimation of sorption phenomenon on radionuclide on bentonite, reaction constants are led by applying sorption model that is considered ion exchange reaction in the interlayer of smectite and surface complex reaction at edge of smectite using sorption data of important radionuclide about geological disposal performance assessment. Modelling result for Np(V) can be simulated well about pH dependence and carbonate effect, it can be showed a change of Kd with electrolytic solution concentration at low pH. However, it is showed different trend with experimental data about electrolytic solution concentration at high pH. It is necessary to investigate problem that is large error of Kd in this area, effect of soluble salt of smectite and method of activity correction at high salt concentration.
Ochs, M.*; Kunze, S.*; Dahinden, M.*; Tachi, Yukio; Yui, Mikazu
no journal, ,
To predict retention of radionuclides in engineered barriers for radioactive waste disposal, a thermodynamic sorption model for key radionuclide, Ni(II), Am(III), Th(IV), Np(V), U(VI) and Se(IV) on clay minerals and bentonite was developed as a function of chemical conditions. The basic premises are to keep model characteristics relatively simple and to consistently use the same basic model design and parameters. For this objectives, a simple 1-site surface complexation/diffuse layer model in combinations with 1-site ion exchange was selected. Basic parameters were evaluated from surface titration data obtained at 0.01/0.1/0.5 molar background electrolyte. The resulting basic model was then parameterized on the basis of selected published original sorption data of radionuclides. The parameterized models were further evaluated against additional independent datasets. The developed sorption models and results of their application to various radionuclide sorption data are presented.