Technical Report 12-05

Transcription

1 Technical Report -5 Comparison of Sorption Measurements on Argillaceous Rocks and Bentonite with Predictions Using the SGT-E Approach to Derive Sorption Data Bases November B. Baeyens, M. Marques Fernandes, M.H. Bradbury Paul Scherrer Institut, Villigen PSI National Cooperative for the Disposal of Radioactive Waste Hardstrasse 7 CH-5 Wettingen Switzerland Tel

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3 Technical Report -5 Comparison of Sorption Measurements on Argillaceous Rocks and Bentonite with Predictions Using the SGT-E Approach to Derive Sorption Data Bases November B. Baeyens, M. Marques Fernandes, M.H. Bradbury Paul Scherrer Institut, Villigen PSI National Cooperative for the Disposal of Radioactive Waste Hardstrasse 7 CH-5 Wettingen Switzerland Tel

4 ISSN 5-66 "Copyright by Nagra, Wettingen (Switzerland) / All rights reserved. All parts of this work are protected by copyright. Any utilisation outwith the remit of the copyright law is unlawful and liable to prosecution. This applies in particular to translations, storage and processing in electronic systems and programs, microfilms, reproductions etc."

5 I NAGRA NTB -5 Abstract In Stage of the Sectoral Plan for Deep Geological Repositories, four rock types have been identified as being suitable host rocks for a radioactive waste repository, namely, Opalinus Clay for a high-level (HLW) and a low- and intermediate-level (L/ILW) repository, and 'Brauner Dogger', Effingen Member and Helvetic Marls for a L/ILW repository. Sorption bases (SDBs) for all of these host rocks are required for the provisional safety analyses, including all of the bounding porewater and mineralogical composition combinations. In addition, SDBs are needed for the rock formations lying below Opalinus Clay (lower confining units) and for the bentonite backfill in the HLW repository. A detailed procedure was developed for deriving SDBs for argillaceous rocks (and bentonite) based on sorption edge measurements on (and montmorillonite), the hypothesis that : clay minerals are the dominant sorbents and a series of so called conversion factors which take into account the different radionuclide speciations in the different porewaters. Since this methodology for generating SDBs is relatively new, a validation and demonstration of the robustness and reliability of the sorption values derived was required. This report describes an extensive piece of work in which s of sorption values were compared with measured ones. Sorption isotherms were measured for the following metal ions Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) in a range of realistic porewater chemistries for a range of host rock mineralogies. In the end 5 isotherm sets were measured. For each of these isotherms a prediction was made of the sorption at trace concentrations using the SDB derivation methodology. A comparison between measured and predicted values for each case was then made. This validation study shows that the methodology used for the derivation of the sorption bases for argillaceous rocks and bentonite produces reliable sorption values.

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7 III NAGRA NTB -5 Zusammenfassung In der Etappe des Sachplans geologische Tiefenlager wurden vier Wirtgesteine identifiziert, die für ein Lager für radioaktive Abfälle geeignet sind. Diese Gesteine sind: Opalinuston für ein Lager für hochaktive Abfälle (HAA) sowie für schwach- und mittelaktive Abfälle (SMA) sowie 'Brauner Dogger', Effinger Schichten und Helvetische Mergel für ein Lager für SMA. Für die provisorischen Sicherheitsanalysen werden Sorptionsdatenbanken (SDB) für alle diese Wirtgesteine benötigt. Dies schliesst auch die möglichen Varianten der Porenwässer und der mineralogischen Zusammensetzung der Gesteine ein. Ausserdem sind SDB für die unteren Rahmengesteine des Opalinustons und für das Versatzmaterial Bentonit im HAA-Lager erforderlich. Es wurde ein detailliertes Verfahren zur Ableitung von SDB für Tongesteine (und Bentonit) entwickelt. Dieses basiert auf der Messung von Sorptionskanten auf Illit (und Montmorillonit), auf der Hypothese, dass :-Tonminerale das dominierende Sorbens sind sowie einer Reihe von sogenannten Konvertierungsfaktoren, welche die unterschiedliche Speziation der Radionuklide in den einzelnen Porenwässern berücksichtigen. Das Verfahren zur Herleitung von SDB ist relativ neu. Deshalb wurde dessen Validierung und die Demonstration der Robustheit und Zuverlässigkeit der abgeleiteten Sorptionswerte als notwendig erachtet. Im vorliegenden Bericht wird eine umfangreiche Studie vorgestellt, in der blinde Vorhersagen der Sorptionswerte mit gemessenen Werten verglichen werden. Sorptionsisothermen wurden für Metallionen Cs(I), Co(II), Ni(II), Eu(III), Th(IV) und U(VI) in Bereichen realistischer Grundwasserzusammensetzung und Wirtgesteinsmineralogie gemessen. Insgesamt wurden 5 Isothermen aufgenommen. Für jede dieser Isothermen wurde mittels der Methode zur Ableitung von SDB eine Vorhersage über die Sorption bei Spurenkonzentration getroffen. Für jeden dieser Fälle wurde anschliessend ein Vergleich zwischen gemessenen und vorhergesagten Werten durchgeführt. Die Studie zur Validierung zeigt, dass das Verfahren zur Herleitung von Sorptionsdatenbasen für Tongestein und Bentonit zuverlässige Sorptionswerte generiert.

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9 V NAGRA NTB -5 Résumé Au cours de l étape du plan sectoriel «Dépôts en couche géologiques profondes», quatre roches d accueil potentielles ont été identifiées. Il s agit d une part des argiles à Opalinus (pour les dépôts destinés aux déchets de haute activité (DHA) et aux déchets de faible et de moyenne activité (DFMA) et d autre part du 'Dogger brun' ('Brauner Dogger'), des Couches d Effingen et des formations marneuses de l Helvétique (dépôt DFMA seulement).pour les analyses de sûreté préliminaires, des bases de données de sorption sont requises pour chacune de ces roches d accueil potentielles, comprenant toutes les combinaisons possibles des différentes compositions minéralogiques et chimiques des eaux interstitielles. Des bases de données de sorption sont également nécessaires pour les formations rocheuses «encaissantes» situées en dessous de la couche des argiles à Opalinus, ainsi que pour la bentonite compactée utilisée comme remblais dans le dépôt profond pour DHA. Une méthode détaillée a été mise au point pour l élaboration de bases de données de sorption génériques pour les formations argileuses (et la bentonite) à partir de données de sorption expérimentales obtenues pour l (et la montmorillonite), l hypothèse que le degré de sorption est fortement lié à la teneur en phyllosilicates type : et en appliquant une série de facteurs de conversion qui prennent en compte la spéciation des radionucléides dans les différentes eaux interstitielles. Etant donnée la relative nouveauté de cette méthode, il s agissait de trouver un moyen d en démontrer la validité, la robustesse et le degré de fiabilité des valeurs de sorption dérivées. A cet effet, et c est l objet du présent rapport, on a comparé des valeurs de sorption dérivées selon cette procédure à celle obtenues expérimentalement. Des isothermes de sorption ont été mesurées pour des métaux Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI), pour des roches de différentes compositions minéralogiques et dans différentes eaux interstitielles. Au final, 5 isothermes ont été mesurées. Pour chaque isotherme, la valeur de sorption a été calculée à des concentrations traces par le biais de la méthode décrite et comparée à la valeur obtenue expérimentalement. Cette comparaison détaillée montre que la méthode utilisée est applicable aux différentes formations argileuses ainsi qu à la bentonite et que les valeurs obtenues ont un haut degré de fiabilité.

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11 VII NAGRA NTB -5 List of Contents Abstract... I Zusammenfassung... III Résumé... V List of Contents... VII List of Tables... VIII List of Figures... X Introduction... Conversion Factors for Argillaceous Rocks and Bentonite Sorption Data Bases... Illite and Montmorillonite Source Data Sets Summary of source on Summary of source on montmorillonite... 9 General Methodology... 5 Opalinus Clay Sorption measurements on Mont Terri sample BGP--C Sorption measurements on Mont Terri sample DI-A Sorption measurements on Opalinus Clay from Benken Sorption measurements on Opalinus Clay from Schlattingen 'Brauner Dogger' Sorption measurements on 'Brauner Dogger' Clay-rich sequences Sorption measurements on 'Brauner Dogger' Sandy limestone sequences... 7 Effingen Member Sorption measurements on Effingen Member Calcareous marl sequences Sorption measurements on Effingen Member Limestone sequences Helvetic Marls... 9 MX-8 Bentonite... 5 Overview, Summary and Conclusions... 9 References Appendix A Composition of the Calculated Porewaters Used in the Sorption Measurements... A-

12 NAGRA NTB -5 VIII Appendix B Experimental Procedures... B- Appendix C Characteristics of the Used Rock Samples... C- List of Tables Tab..: Tab..: Tab..: Tab..: Tab. 5.: Tab. 5.: Tab. 5.: Tab. 5.: Tab. 5.5: Tab. 5.6: Tab. 5.7: Tab. 5.8: Tab. 5.9: Tab. 5.: Tab. 5.: Uncertainty factors (UF) for the speciation factor (SF) of the argillaceous rocks in the corresponding porewater compositions (taken from Baeyens et al. ).... Overall uncertainty factors for the predicted R d values in the various argillaceous rock/porewater systems.... Cation exchange reactions and corresponding selectivity coefficients (K c ) on the planar sites, type-ii sites and frayed edge sites of (taken from Bradbury & Baeyens ) Cation exchange reactions and corresponding selectivity coefficients (K c ) for montmorillonite (Bradbury & Baeyens a) Mineralogical composition of Opalinus Clay (Mont Terri) sample BGP--C used in the sorption experiments (Lauber et al. ) Composition of the porewater equilibrated with Opalinus Clay sample BGP--C at ph = 6. (Lauber et al. ) Summary of the conversion factors for the sorption measurements on the Opalinus Clay sample BGP--C at ph = Composition of the equilibrated porewater with Opalinus Clay sample BGP--C at ph = Summary of the conversion factors for the sorption measurements on the Opalinus Clay sample BGP--C.... Mineralogical composition of Opalinus Clay from Mont Terri (Nagra b).... Summary of the conversion factors for the sorption measurements on the Opalinus Clay (BDI-A-.).... Mineralogies of Benken Opalinus Clay used in this study and the reference Opalinus Clay (Nagra b).... Composition of the equilibrated porewater with Opalinus Clay sample BEN Mineralogical composition of Opalinus Clay from Schlattingen- borehole, sample SLA Composition of the equilibrated porewater with Opalinus Clay sample SLA

13 IX NAGRA NTB -5 Tab. 5.: Tab. 6.: Tab. 6.: Tab. 6.: Tab. 6.: Tab. 6.5: Tab. 6.6: Tab. 7.: Tab. 7.: Tab. 7.: Tab. 7.: Tab. 7.5: Tab. 7.6: Tab. 8.: Tab. 8.: Tab. 8.: Summary of the conversion factors for the sorption measurements on the Opalinus Clay from the Schlattingen- borehole on sample SLA Mineralogical composition of 'Brauner Dogger' Clay-rich sequences from Benken, sample BEN Composition of the equilibrated porewater with 'Brauner Dogger' Clay-rich sequences, sample BEN Summary of the conversion factors for the sorption measurements on 'Brauner Dogger' Clay-rich sequences, sample BEN Mineralogical composition of 'Brauner Dogger' Sandy limestone sequences, sample SLA Composition of the equilibrated porewater with 'Brauner Dogger' Sandy limestone sequences, sample SLA Summary of the conversion factors for the sorption measurements on 'Brauner Dogger' Sandy limestone sequences, sample SLA Mineralogical composition of Effingen Member Calcareous marl sequences sample, OFT 69.7 m, used in the sorption experiments Composition of equilibrated porewater with Effingen Member Calcareous marl sequences, sample OFT Summary of the conversion factors for the sorption measurements on Effingen Member Calcareous marl sequences, sample OFT Mineralogical composition of Effingen Member Limestone sequences sample, OFT Composition of the equilibrated porewater with Effingen Member Limestone sequences, sample OFT Summary of the conversion factors for the sorption measurements on the Effingen Member Limestone sequences (OFT 9.65) Mineralogical composition of the Helvetic Marls sample, WLB SBa/v Composition of equilibrated porewater with Helvetic Marls WLB SBa/v Summary of the conversion factors for the sorption measurements on Helvetic Marls, sample WLB SBa/v Tab. 9.: Mineralogical composition of MX-8 bentonite (Müller-Vonmoos & Kahr 98) Tab. 9.: Composition of equilibrated porewater with MX-8 bentonite Tab. 9.: Tab..: Summary of the conversion factors for the sorption measurements on MX-8 bentonite Sorption values measured at trace concentrations (< -8 M) for host rocks and MX-8 bentonite, and the predictions from and montmorillonite... 5

14 NAGRA NTB -5 X Tab. A: Tab. A: Tab. A: Tab. A: Tab. A5: Compositions of the calculated Opalinus Clay porewaters used for the sorption measurements on Opalinus Clay Mont Terri sample BGP--C (Lauber et al., Table ).... A- Composition of the calculated Opalinus Clay porewater used in the sorption experiments on Opalinus Clay Mont Terri sample DI-A (Van Loon et al. 9).... A- Compositions of the calculated Opalinus Clay porewaters used for the sorption measurements on the Opalinus Clay Benken sample BEN (Pearson ).... A- Composition of the calculated Opalinus Clay porewater used in the sorption experiments for Schlattingen- Opalinus Clay (Wersin et al. ).... A- Calculated porewater composition for Effingen Member ('low-salinity' in Mäder 9).... A- Tab. A6: Calculated porewater composition for Helvetic Marls ('Na-Cl base-case' in Mäder ).... A- Tab. A7: Calculated MX-8 bentonite porewater (Bradbury & Baeyens a).... A- List of Figures Fig..: Fig..: Fig..: Fig..: Fig..5: Fig..6: Fig..7: Fig..8: Co(II) sorption edge measurements (symbols) and modelling (continuous line) on conditioned Na- in. M NaClO (Bradbury & Baeyens 9a) Ni(II) sorption edge measurements (symbols) and modelling (continuous line) on conditioned Na- in. M NaClO (Bradbury & Baeyens 9a) Eu(III) sorption edge measurements (symbols) and modelling (continuous line) on conditioned Na- in. M NaClO (Bradbury & Baeyens 9a) Th(IV) sorption edge measurements (symbols) and modelling (continuous line) on conditioned Na- in. M NaClO (Bradbury & Baeyens 9b) U(VI) sorption edge measurements (symbols) and modelling (continuous line) on conditioned Na- in. M NaClO (Bradbury & Baeyens 9b) Ni(II) sorption edge measurements (symbols) and modelling (continuous line) on Na-SWy- in.,. and. M NaClO (Bradbury & Baeyens 997b) Eu(III) sorption edge measurements (symbols) and modelling (continuous line) on Na-SWy- in. M NaClO (Bradbury & Baeyens 5).... Th(IV) sorption edge measurements (symbols) and modelling (continuous line) on Na-SWy- in. and. M NaClO (Bradbury & Baeyens 5)....

15 XI NAGRA NTB -5 Fig..9: Fig. 5.: Fig. 5.: Fig. 5.: Fig. 5.: Fig. 5.5: Fig. 6.: Fig. 6.: Fig. 7.: Fig. 7.: Fig. 8.: Fig. 9.: Fig..: Fig..: U(VI) sorption edge measurements (symbols) and modelling (continuous line) on Na-SWy- in. M NaClO (Marques Fernandes et al. ).... Summary of the sorption measurements and predicted sorption values for Cs(I), Ni(II), Eu(III) and Th(IV) on Opalinus Clay from Mont Terri (BGP--C) at ph Summary of the sorption measurements and predicted sorption values for Cs(I), Ni(II), Eu(III), Th(IV) and U(VI) on Opalinus Clay from Mont Terri (BGP--C) at ph Summary of the sorption measurements and predicted sorption values for Cs(I) at ph = 7. and Co(II) at ph = 7., on Opalinus Clay from Mont Terri (DI-A-.).... Cs(I) sorption measurements at ph = 7.9 and predicted sorption value on Opalinus Clay from Benken (BEN 66.75) Summary of the sorption measurements and the sorption values predicted for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on Opalinus Clay from the Schlattingen- borehole (SLA 98.8) Summary of the sorption measurements and the predicted sorption values for Cs(I), Co(II), Ni(II), Eu(III),Th(IV) and U(VI) on 'Brauner Dogger' Clayrich sequences (BEN 8.).... Summary of the sorption measurements and predictions for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on 'Brauner Dogger' Sandy limestone sequences (SLA 795.7).... Summary of the sorption measurements and the predicted sorption values for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on Effingen Member Calcareous marl sequences (OFT 69.7) Summary of the sorption measurements and predictions for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on Effingen Member Limestone sequences (OFT 9.65).... Summary of the sorption measurements and the predicted sorption values for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on Helvetic Marls (WLB SBa/v.6).... Summary of the sorption measurements and the predicted sorption values for Cs(I), Ni(II), Eu(III), Th(IV) and U(VI) on MX-8 bentonite Overview of the comparison of measured and predicted sorption for Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on different rock types and MX-8 bentonite Overview of the Cs(I) sorption results on five different rock types (Opalinus Clay (OPA), 'Brauner Dogger' (BD), Effingen Member (EFF), Helvetic Marls (MGL) and bentonite (MX-8).... 5

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17 NAGRA NTB -5 Introduction As part of Stage of the Sectoral Plan for Deep Geological Repositories, Nagra has proposed six regions which are suitable for hosting a repository for low- and intermediate-level waste (L/ILW) and three regions for high-level waste (HLW; Nagra 8). In the current Stage of the Sectoral Plan, Nagra will propose at least two siting regions each for the L/ILW repository and for the HLW repository for further consideration. Provisional safety analyses for all siting regions are part of the procedure and support the evaluation and selection process. The host rocks to be considered can all be classified as argillaceous rocks (clay rock and marl) in which released radionuclides will migrate mainly by diffusion. The provisional safety analyses need geochemical models and parameters to describe the migration of radionuclides in the geosphere and the bentonite buffer in a quantitative way. A state-of-the-art sorption base (SDB) is one of the key parameter sets needed to quantify the radionuclide retardation in the host rocks. In order to derive SDBs for a wide range of rocks under a wide range of porewater and mineralogical compositions, a detailed procedure was developed (see below, and Bradbury et al. for more details). A fact of central importance in developing this procedure was that the host rocks Opalinus Clay, 'Brauner Dogger', Effingen Member and Helvetic Marls are all argillaceous rocks which contain significant fractions of : clay minerals such as and smectite mixed layers. Since this methodology for generating SDBs is relatively new, a confirmation of the methodology was required. In a first step, it was decided to compare and contrast the sorption values obtained using the newly developed procedures with those in already existing and accepted SDBs for Opalinus Clay and MX-8 which were used in the Entsorgungsnachweis (Nagra a). The latter SDBs (Bradbury & Baeyens a and b) contained derived from different sources: measurements on Opalinus Clay and MX-8 bentonite, on the clay minerals and montmorillonite, and on other systems. This comparative investigation, carried out on a case by case study for each radionuclide/system, is fully documented in Bradbury & Baeyens (). The main conclusion was that for the majority of radionuclides the sorption values in the two cases were within a factor of two of one another. For those radionuclides which lay outside this range, there were good reasons to believe that the application of the new SDB methodology, coupled with up-to-date knowledge, produced SDBs which were superior and better defensible than those produced previously by a different, less systematic approach. In a second step, the site protolysis non electrostatic surface complexation and cation exchange sorption model (SPNE SC/CE) was used to carry out s of sorption isotherms measured on MX-8 bentonite (for Ni(II), Eu(III), Th(IV) and U(VI)) and on Opalinus Clay (for Ni(II), Co(II), Eu(III), Th(IV) and U(VI)) in a realistic porewater composition (Bradbury and Baeyens a). In these calculations a major assumption was that the radionuclide uptake was only occurring on : clay minerals; montmorillonite in the case of MX-8 and + /smectite mixed layers in the case of Opalinus Clay. In the latter case it was assumed that /smectite mixed layers have sorption characteristics which are very similar to. The results of this exercise were very positive in that the correspondence between the measured isotherm and the calculated isotherms values was good to excellent. These results provide important support for the methodology used to generate SDBs for the provisional safety analyses required for Stage of the Sectoral Plan because exactly the same major assumption given above was made for all of the argillaceous host rocks.

18 NAGRA NTB -5 This report represents a third step in providing evidence that the methodology for deriving SDBs as proposed in Bradbury et al. () is robust and reliable. The aim was to measure sorption isotherms for representative metals with valences from I to VI i.e. Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) in realistic porewater chemistries for the host rocks being considered in Stage of the Sectoral Plan. Co(II) and Ni(II) were chosen as being representative for bivalent transition metals, Eu(III) for trivalent lanthanides and actinides, and Th(IV) for tetravalent actinides. Blind predictions would then be made of the sorption at trace concentrations of the metals listed above for each rock type/water chemistry combination using the SDB derivation methodology. A comparison between measured and predicted values for each rock type would then indicate the quality of the selection procedures. In Chapters to the overall selection methodology is briefly described and the source sorption edge for and montmorillonite are given. Following this, each rock type (and bentonite) is taken in turn and the sorption isotherms for the selected radionuclides measured in the given mineralogy/water chemistry combinations are presented. The R d values obtained using the new methodology are shown on the corresponding isotherms. Finally a comparison between the measured and predicted sorption values, again on a rock-by-rock basis, is given and commented upon in Chapter. This report presents the measurements on the following argillaceous rocks and bentonite: Opalinus Clay 'Brauner Dogger' Clay-rich sequences 'Brauner Dogger' Sandy limestone sequences Effingen Member Calcareous marl sequences Effingen Member Limestone sequences Helvetic Marls MX-8 bentonite

19 NAGRA NTB -5 Conversion Factors for Argillaceous Rocks and Bentonite Sorption Data Bases Sorption bases (SDBs) for safety analyses (SA) have been produced on a number of occasions (e.g. Bradbury & Baeyens 997a, Bradbury & Baeyens a and b). The methodology for producing SDBs is continuously under development and a modified procedure was proposed recently for argillaceous rocks based on sorption edge measurements on (Bradbury et al. ). In the case of bentonite the SDB was developed using source sorption on montmorillonite (Baeyens et al. ). For completeness, a brief outline of the methodology is given below. Regarding argillaceous rock systems, one of the main premises used in developing SDBs is that the : clay mineral fraction is predominantly responsible for the uptake of radionuclides (Bradbury et al. ). It is further assumed that /smectite mixed layers have sorption characteristics which are very similar to. Although this cannot be defended unambiguously, because hardly any sorption exist for the mixed layer clay minerals, this approach is supported by some recent modelling work on Opalinus Clay (OPA) and MX-8 bentonite in realistic porewater compositions (Bradbury & Baeyens a). As discussed in more detail in Bradbury et al. (), the approach taken here will be to use source sorption edge wherever possible and scale this over the wt. % content of the : type clay minerals ( + smectite + /smectite mixed layers) in the argillaceous rock under consideration. In the case of bentonite only the : type smectite mineral is present and sorption values on montmorillonite are used as the source. Simple sets of reference conditions for the /montmorillonite source were chosen;. M NaClO and a ph corresponding to the ph of the reference porewater/argillaceous rock system. The selected /montmorillonite sorption at trace concentrations are converted to sorption values for the argillaceous rock using conversion factors as outlined below. Mineralogy conversion factor: CF MIN The conversion factor which takes into account the differences in mineralogy is given by an equation of the form: where: CF MIN = (MIN ARG ROCK / MIN ILLITE ) (.) CF MIN = mineralogy conversion factor, MIN ARG ROCK = + /smectite mixed layer weight fraction in the argillaceous rock, MIN ILLITE = (% ). Speciation conversion factor, CF SPEC The complexation of radionuclides with inorganic and organic ligands has an influence on sorption and therefore corrections need to be made to reflect the variations in aqueous speciation in the different water chemistries considered. In oxide and clay mineral systems it is widely observed that the formation of positively charged and neutral hydrolysed species do not

20 NAGRA NTB -5 adversely influence sorption behaviour. Indeed, very high metal sorption is often measured in regions where neutral hydroxy species dominate (see e.g. Schultess & Huang 99, Gorgeon 99, Turner et al. 6). Whether or not other neutral and positively charged complexes can also be taken up by sorbents is less clear, but remains a possibility. In order to make a correction to sorption values taking into account the differences in radionuclide speciation in different water chemistries, species which sorb and those which do not sorb have to be distinguished. The proposal put forward for metals is to define free cations and positively charged and neutral hydrolysed species as being sorbing. All other species are treated as being non-sorbing (this assumption errs on the conservative side; see e.g. Bradbury et al. ). One exception is made for U(VI) where sorption modelling on montmorillonite (Bradbury & Baeyens 5, Marques Fernandes et al. ) and on (Bradbury & Baeyens 9b) clearly indicate that the negatively charged UO (OH) - species also is sorbing by surface complexation. The conversion factor used for modifying sorption values according to the speciation in different water chemistries is simply: CF SPEC = SF ARG ROCK / SF ILLITE (.) where: CF SPEC SF ARG ROCK SF ILLITE is the speciation conversion factor, is the fraction of sorbing radionuclide species calculated to be present in the aqueous phase in the argillaceous rock porewaters, is the fraction of sorbing radionuclide species calculated to be present in the aqueous phase in the system. The Nagra/PSI thermodynamic base (Version /7) (Thoenen et al. ) has been used throughout this report. This base contains selected and supplemental. In all cases the selected thermodynamic were used except for U(VI), where also the supplemental were used. In the case of Th(IV) the hydrolyses from Neck & Kim () were used. For the trivalent lanthanides and actinides silicate complexes were selected in the thermodynamic base and these have been included in this work. ph conversion factors, CF ph In the comparison described in this report the or montmorillonite sorption values were selected from the sorption edges at the ph value in the porewater of the particular argillaceous rock (bentonite) under consideration. Hence the ph conversion factors are in all cases unity. Formulation The above procedures can be summarised as follows. Consider that a selected source sorption value for a radionuclide (RN) measured under well-defined conditions needs to be transposed into the corresponding value for an argillaceous rock for which reference conditions are defined. The source are: R d ILLITE, MIN ILLITE, ph ILLITE, SF ILLITE. (Note that where the source were measured in a "pure " system, MIN ILLITE equals unity.)

21 5 NAGRA NTB -5 The distribution ratio, R d, ARG ROCK, is required for an argillaceous rock where the reference mineralogical and water composition conditions yield MIN ARG ROCK, ph ARG ROCK, SF ARG ROCK values. Then: where: R d, ARG ROCK = R d ILLITE. CF MIN. CF ph. CF SPEC (.) CF MIN = (MIN ARG ROCK / MIN ILLITE ) CF SPEC = (SF ARG ROCK / SF ILLITE ) CF ph = In the case of MX-8 bentonite the approach is entirely similar and the following relation is applied: where: R d, MX-8 = R d MONT. CF MIN. CF SPEC. CF ph (.) CF MIN = fraction of montmorillonite in the bentonite CF SPEC = (SF MX-8 / SF MONT ) CF ph =

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23 7 NAGRA NTB -5 Illite and Montmorillonite Source Data Sets. Summary of source on The source sorption edge sets for the elements Co(II), Ni(II), Eu(III), Th(IV) and U(VI) measured in. M NaClO are given in Fig..,.,.,. and.5, respectively and are from Bradbury & Baeyens (9a,b). 6 5 log R d Co [L kg - ] Fig..: ph Co(II) sorption edge measurements (symbols) and modelling (continuous line) on conditioned Na- in. M NaClO (Bradbury & Baeyens 9a). 5 log R d Ni [L kg - ] Fig..: ph Ni(II) sorption edge measurements (symbols) and modelling (continuous line) on conditioned Na- in. M NaClO (Bradbury & Baeyens 9a).

24 NAGRA NTB log R d Eu [L kg - ] 5 Fig..: ph Eu(III) sorption edge measurements (symbols) and modelling (continuous line) on conditioned Na- in. M NaClO (Bradbury & Baeyens 9a). 7 6 log R d Th [L kg - ] 5 Fig..: ph Th(IV) sorption edge measurements (symbols) and modelling (continuous line) on conditioned Na- in. M NaClO (Bradbury & Baeyens 9b).

25 9 NAGRA NTB -5 5 log R d U(VI) [L kg - ] Fig..5: ph U(VI) sorption edge measurements (symbols) and modelling (continuous line) on conditioned Na- in. M NaClO (Bradbury & Baeyens 9b).. Summary of source on montmorillonite The sorption edge sets for Ni(II), Eu(III), Th(IV) and U(VI) measured on montmorillonite are presented in Fig..6,.7,.8 and.9, respectively and are from Baeyens & Bradbury (997), Bradbury & Baeyens (5) and Marques Fernandes et al (). 5 log R d Ni [Lkg - ]. M Na. M Na. M Na Fig..6: ph Ni(II) sorption edge measurements (symbols) and modelling (continuous line) on Na-SWy- in.,. and. M NaClO (Bradbury & Baeyens 997b).

26 NAGRA NTB -5 6 log R d Eu [L kg - ] 5 Fig..7: ph Eu(III) sorption edge measurements (symbols) and modelling (continuous line) on Na-SWy- in. M NaClO (Bradbury & Baeyens 5). 7 6 log R d Th [L kg - ] 5 Fig..8:. M Na M Na model ph Th(IV) sorption edge measurements (symbols) and modelling (continuous line) on Na-SWy- in. and. M NaClO (Bradbury & Baeyens 5).

27 NAGRA NTB log R d U(VI) [L kg - ] Fig..9: ph U(VI) sorption edge measurements (symbols) and modelling (continuous line) on Na-SWy- in. M NaClO (Marques Fernandes et al. ).

28

29 NAGRA NTB -5 General Methodology The source sorption edge for and montmorillonite are given in Chapter. The sorption values for / montmorillonite for each radionuclide are taken from these curves at the ph values of the porewaters given for each argillaceous rock system in Chapters 5 (Opalinus Clay), 6 ('Brauner Dogger'), 7 (Effingen Member), 8 (Helvetic Marls) and 9 (MX-8 bentonite). The mineralogical conversion factors are given by the fractional content of : clay minerals in the different argillaceous rocks/bentonite. The mineralogical composition of the rock samples was measured at the Institute of Geological Sciences, University of Bern. The speciation factors for each radionuclide are calculated in. M NaClO and in the appropriate porewaters using the PSI/Nagra TDB (Thoenen et al. ). Activity coefficient corrections were carried out using the Davies approach. The speciation conversion factors were calculated as described in Chapter. The uncertainty on the selected source sorption values (R d,illite and R d,mont ) is taken to be a factor of. In the derivation of sorption values in the SDBs for the provisional safety analysis for SGT-E (Baeyens et al. ) a Monte Carlo procedure was applied to estimate the uncertainties for the speciation factors (UF-SF) for the various argillaceous rock systems (Thoenen ). In this report the same UF-SF values for the different elements in the different porewaters are considered and a summary of these values are given in Tab... Tab..: Uncertainty factors (UF) for the speciation factor (SF) of the argillaceous rocks in the corresponding porewater compositions (taken from Baeyens et al. ). Element UF-SF OPA,BD,MX-8 UF-SF EFF UF-SF MGL Cs(I) Co(II)..5. Ni(II)..5. Eu(III).8..5 Th(IV)..6.8 U(VI) OPA = Opalinus Clay; BD = 'Brauner Dogger'; EFF = Effingen Member; MGL = Helvetic Marls It should be noted that the UF-SF for Th(IV) and U(VI) are strongly depending on the porewater composition. The reason is due to the large uncertainty in the thermodynamic stability constants of the carbonate complexes for these two elements. For example, in the case of Th(IV) if the Th(OH) (CO ) complex is dominant in the porewater the UF-SP is large. However, if this complex is not dominant in the porewater (e.g. Effingen Member) the UF-SF is small. In the case of U(VI) the dominant species in the Helvetic Marls porewater are the UO Ca(CO ) - and UO (CO ) - whose stability constants are again associated with higher uncertainties.

30 NAGRA NTB -5 The formalism used to calculate the overall uncertainty on the predicted R d values is applied in a similar way to that described in Baeyens et al. (). The overall uncertainty factor is calculated from the uncertainties in the R d ILLITE/MONT., SF ILLITE/MONT and SF ARG. ROCK/MX-8 and the results are summarised in Tab... The SF ILLITE/MONT for Eu(III) which forms aqueous silicate complexes is taken to be the same as for SF ARG. ROCK/MX-8 (Baeyens et al. ). Tab..: Overall uncertainty factors for the predicted R d values in the various argillaceous rock/porewater systems. Element UF-overall for OPA, BD, MX-8 UF-overall for EFF UF-overall for MGL Cs(I) Co(II). Ni(II). Eu(III) Th(IV).. 7. U(VI) To a first approximation no uncertainties are associated with the ph and the specific : clay mineral content of the argillaceous rocks. The sorption isotherms measured for each argillaceous rock type in the corresponding porewater compositions are given in the appropriate sections below. The measurements on Opalinus Clay from Mont Terri (section 5.) and on MX-8 (Chapter 9) have already been published by Lauber et al. () and Bradbury & Baeyens () respectively. Detailed descriptions of the experimental procedures are contained in these reports. Newly measured isotherms on the argillaceous rocks have been carried out in a similar way. A summary of the experimental procedures is given in Appendix B. The presentation of the results of the predictions is the same in all of the figures. The blue symbols represent the R d, ILLITE or R d, MONT values, selected from the sorption edges on the pure or montmorillonite, respectively, at the ph of the corresponding porewater. The green symbols are R d values which have been scaled with the mineralogical conversion factor. The red symbols represent the R d values scaled additionally with the speciation conversion factor and are the predicted R d values. The error bars associated with the predicted values are the same as the overall uncertainty factors given in Tab... The results are shown on the plots in the trace radionuclide concentration range (< -7 M) since the method is only applicable for trace concentrations. The one exception to the above is the case of Cs(I). Here, the measured Cs(I) sorption isotherm are presented for each argillaceous rock together with the calculated at trace concentration using the generalised Cs(I) sorption model for (Bradbury & Baeyens ) and scaled to the : type clay content in the argillaceous rock. For completeness, Tab.. summarises the cation exchange reactions and corresponding selectivity coefficients used in the calculations for the sorption of Cs(I) on. It is important to note that the model predictions are not fitted to the but rather calculated with the fixed model parameters associated with this Cs(I) sorption model developed for argillaceous rocks (Bradbury & Baeyens ).

31 5 NAGRA NTB -5 Tab..: Cation exchange reactions and corresponding selectivity coefficients (K c ) on the planar sites, type-ii sites and frayed edge sites of (taken from Bradbury & Baeyens ). Illite CEC = meq kg - Cation exchange reactions log K c Site capacities [meq kg - ] Planar sites (PS) 6 Na-PS + K + <=> K-PS + Na +. Na-PS + Cs + <=> Cs-PS + Na + Na-PS + Me + <=> Me-PS + Na Type II sites (II-S) Na-II-S + K + <=> K-II-S + Na +. Na-II-S + Cs + <=> Cs-II-S + Na +.6 Frayed edge sites (FES).5 Na-FES + K + <=> K-FES + Na +. Na-FES + Cs + <=> Cs-FES + Na + 7. Me + = Mg + or Ca + In the case of montmorillonite the procedure is similar, with the Cs(I) sorption being calculated for montmorillonite. Tab.. summarises the cation exchange reactions and selectivity coefficients used in the calculations. Cs(I) sorbs via a cation exchange mechanism and the R d,mont values were calculated from a cation exchange sorption model for montmorillonite in the MX-8 porewater composition. A CEC value of 87 meq kg - was selected for montmorillonite. This value was taken from a larger number of CEC measurements on SWy- montmorillonite (Baeyens & Bradbury 997). The selectivity coefficients for K-Na, Mg-Na and Ca-Na, Tab.., were taken from the porewater chemistry studies on MX-8 bentonite (Bradbury & Baeyens b). Cs sorption was calculated using a Cs + -Na + selectivity coefficient of 5 for montmorillonite (Bradbury & Baeyens, unpubl. ). This is considered to be valid since montmorillonite is the only clay mineral in MX-8 and constitutes ~ 75 wt.-%. The conversions to sorption values for MX-8 are then carried out over the mineralogical conversion factor which is equal to.75. Tab..: Cation exchange reactions and corresponding selectivity coefficients (K c ) for montmorillonite (Bradbury & Baeyens a). Montmorillonite CEC = 87 meq kg -. Cation exchange reaction log K c Na-mont + K + K-mont + Na +.6 Na-mont + Cs + Cs-mont + Na +.8 Na-mont + Mg + Mg-mont + Na +. Na-mont + Ca + Ca-mont + Na +.

32

33 7 NAGRA NTB -5 5 Opalinus Clay In this chapter all the results obtained on the different rock samples of Opalinus Clay are presented. Sets of isotherms were measured for the Entsorgungsnachweis (Nagra a) by Lauber et al. () on an Opalinus Clay sample from the Mont Terri Underground Rock Laboratory. In support to the field experiments at Mont Terri (DI experiment) sorption measurements for Cs(I) and Co(II) were carried out on a different Opalinus Clay sample. On one sample from the Opalinus Clay borehole at the Benken site, a Cs(I) sorption isotherm was determined and is also included in this chapter. Finally, sorption isotherms were measured on an Opalinus Clay sample originating from a new borehole at Schlattingen (geothermal well Schlattingen-). 5. Sorption measurements on Mont Terri sample BGP--C Sorption isotherm measurements of Cs(I), Ni(II), Eu(III), Th(IV) and U(VI) were carried out on an Opalinus Clay sample denoted as BGP--C from Mont Terri (Lauber et al. ). Data sets were obtained at ph 6. and ph 8. These first measurements on fresh samples were carried out in a glove box to avoid the potential oxidation of pyrite. The calculated porewater compositions used in the sorption experiments are presented in Appendix A, Tab. A (Lauber et al. ). The mineralogy of this sample is given in Tab. 5.. Tab. 5.: Mineralogical composition of Opalinus Clay (Mont Terri) sample BGP--C used in the sorption experiments (Lauber et al. ). Minerals BGP--C [wt.-%] Calcite 9 ± Dolomite/Ankerite ±.5 Siderite ± Quartz ± K-Feldspar. ±.8 Albite/Plagioclase. ±.8 Pyrite < d.l. Illite ± Illite/Smectite ML 8 ± Kaolinite ± Chlorite ± d.l.: detection limit The mineralogical conversion factor is taken from the average and /smectite mixed layer contents ( wt.-%). CF MIN =. (see Tab. 5.).

34 NAGRA NTB -5 8 Sorption measurements at ph = 6. The equilibrated porewater compositions for the sorption measurements carried out at ph = 6. are summarised in Tab. 5.. The speciation factors are calculated with PSI/Nagra Chemical Thermodynamic Database /7 (Thoenen et al. ) in the. M NaClO background electrolyte and in the presence of -5 M dissolved Si and in the porewater compositions as given in Tab. 5.. These factors together with the conversion factors are summarised in Tab. 5.. Tab. 5.: Composition of the porewater equilibrated with Opalinus Clay sample BGP--C at ph = 6. (Lauber et al. ). ICP-OES analyses of major elements for the sorption isotherm measurements of Cs(I), Ni(II), Eu(III) and Th(IV). ph log pco [bar] Ionic strength [M] Cl [M] C inorg. [M] ICP-OES analyses of dissolved constituents [M] Na (.87.6) - K (..) - Mg (..5) - Ca (.8.5) - Sr (.6.6) - SO (.9.7) - Al (.9.87) -6 Si (.96.6) - Fe (.7.) -5 Parameters taken from Tab. A (modelled ). Values in parentheses: average of measurements together with standard deviations. Tab. 5.: Summary of the conversion factors for the sorption measurements on the Opalinus Clay sample BGP--C at ph = 6.. The log R d,opa values are the predicted sorption values. Metal ph log R d,illite [L kg - ] SF ILLITE SF OPA CF MIN CF SPEC log R d,opa [L kg - ] Cs(I) Ni(II) Eu(III) Th(IV)

35 9 NAGRA NTB -5 The sorption measurements and the predicted sorption value following the approach described in Chapter (Tab. 5.) are presented in Fig. 5.. For Cs(I), Ni(II) and Th(IV) the uncertainty limits estimated for the predicted sorption values overlap with those of the measured values. The predicted sorption value for Eu(III) lies below the measured values. However, there is experimental evidence to suggest that trivalent lanthanide and actinide (hydroxy)carbonate complexes sorb on : clay minerals (Marques Fernandes et al. 8). This is not taken into account in the SDB methodology used here. This approach is conservative and tends to result in lower predicted sorption values, especially where the carbonate concentrations in the aqueous phase are high. For example, for the measurements given in Fig. 5. the pco is equal to.5 bar which is considerably greater than in most natural argillaceous rock systems. Cs(I) Ni(II) log R d [L kg - ] log R d [L kg - ] log Cs equilibrium concentration [M] wt.-% IL + ISML log Ni equilibrium concentration [M] 5 Eu(III) 6 Th(IV) 5 log R d [L kg - ] log R d [L kg - ] wt.-% IL +ISML wt.-% IL + ISML log Eu equilibrium concentration [M] log Th equilibrium concentration [M] Fig. 5.: Summary of the sorption measurements and predicted sorption values for Cs(I), Ni(II), Eu(III) and Th(IV) on Opalinus Clay from Mont Terri (BGP--C) at ph 6..

36 NAGRA NTB -5 Sorption measurements at ph = The equilibrated porewater compositions for the sorption measurements carried out at ph 8. are summarised in Tab. 5.. The calculated porewater is given in Appendix A, Tab. A. Tab. 5.: Composition of the equilibrated porewater with Opalinus Clay sample BGP--C at ph = 8.. ICP-OES analyses of major elements for the sorption isotherm measurements of Cs(I), Ni(II), Eu(III), Th(IV) and U(VI). ph log pco [bar] Ionic strength [M] Cl [M] C inorg. [M] ICP-OES analyses of dissolved constituents [M] Na (.9.) - K (5.8.) - Mg (.5.) - Ca (.88.5) - Sr (.67.5) - SO (.8.) - Al (5..7) -6 Si (..) - Fe (.7.) -6 Parameters taken from Tab. A (modelled ). Values in parentheses: average of measurements together with standard deviations. Tab. 5.5: Summary of the conversion factors for the sorption measurements on the Opalinus Clay sample BGP--C. The log R d,opa values are the predicted sorption values. Metal ph log R d,illite [L kg - ] SF ILLITE SF OPA CF MIN CF SPEC log R d,opa [L kg - ] Cs(I) Ni(II) Eu(III) Th(IV) U(VI) The sorption measurements and the predicted sorption values following the approach described in Chapter at ph 8 (Tab. 5.5) are presented in Fig. 5.. For Cs(I), Ni(II), Eu(III), Th(IV) and U(VI) the uncertainty limits estimated for the predicted sorption values overlap with those of the measured values. The predicted value for Ni(II) is at the lower limit although the experimental measurements at Ni equilibrium concentration less than -8 M could be due to an artifact (see Lauber et al. ).

37 NAGRA NTB -5 Cs(I) 5 Ni(II) log R d [L kg - ] log R d [L kg - ] log Cs equilibrium concentration [M] wt.-% IL+ISML log Ni equilibrium concentration [M] 6 Eu(III) 6 Th(IV) 5 5 log R d [L kg - ] wt.-% IL+ISML log Eu equilibrium concentration [M] log R d [L kg - ] wt.-% IL+ISML log Th equilibrium concentration [M] 5 U(VI) log R d [L kg - ] wt.-% IL+ISML log U equilibrium concentration [M] Fig. 5.: Summary of the sorption measurements and predicted sorption values for Cs(I), Ni(II), Eu(III), Th(IV) and U(VI) on Opalinus Clay from Mont Terri (BGP--C) at ph 8. Note that in the case of Th(IV) the green and red symbols overlap.

38 NAGRA NTB Sorption measurements on Mont Terri sample DI-A Sorption isotherm measurements of Cs(I) and Co(II) were carried out on an Opalinus Clay sample originating from the in situ diffusion experiments (DI) at Mont Terri Underground Rock Laboratory (Thury & Bossart 999). These, and all following measurements in this report, were carried out under atmospheric conditions. Since these samples had already been exposed to air any pyrite oxidation had probably occurred already. There was, however, no evidence that additional oxidation of pyrite was taking place (e.g. by an increase in sulphate concentration). The mineralogical composition of the sample denoted as DI-A-. was not determined but the reference mineralogy of Mont Terri was considered to be representative for this sample. Tab. 5.6: Mineralogical composition of Opalinus Clay from Mont Terri (Nagra b). Minerals Mont Terri OPA [wt.-%] Calcite ± 8 Dolomite/Ankerite < d.l. Siderite ±.8 Quartz ± K-Feldspar ±.6 Albite ±. Pyrite. ±.5 Illite ± Illite/Smectite ML ± Kaolinite ± Chlorite ± d.l.: detection limit Taking the given in Tab. 5., the mineralogical conversion factor, CF MIN, for this sample is equal to.. The isotherms were measured in an air equilibrated porewater (Pearson 998) similar to that used in the field diffusion experiments at the Mont Terri Underground Rock Laboratory. The calculated composition of this porewater is given in Appendix A, Tab. A. The ph is given as 7.6, but after completion of the sorption experiments the measured ph values in the supernatant were slightly lower, i.e. 7. and 7. for the Cs(I) and Co(II), respectively. For these sorption measurements the equilibrated porewater was not analyzed, and the speciation calculation for Co(II) was carried out using the porewater composition given in Tab. A at the measured ph values. A summary of the selected source values together with the conversion factors are given in Tab The results of the sorption measurements and the predicted R d values are shown in Fig. 5.. For both elements the agreement between measurement and is good.

39 NAGRA NTB -5 Tab. 5.7: Summary of the conversion factors for the sorption measurements on the Opalinus Clay (BDI-A-.). The log R d,opa values are the predicted sorption values. Metal ph log R d,illite [L kg - ] SF ILLITE SF OPA CF MIN CF SPEC log R d,opa [L kg - ] Cs(I) Co(II) Cs(I) Co(II) log R d [L kg - ] log R d [L kg - ] log Cs equilibrium concentration [M] wt.-% IL+ISML log Co equilibrium concentration [M] Fig. 5.: Summary of the sorption measurements and predicted sorption values for Cs(I) at ph = 7. and Co(II) at ph = 7., on Opalinus Clay from Mont Terri (DI-A-.). 5. Sorption measurements on Opalinus Clay from Benken Cs(I) sorption measurements have been carried out on an Opalinus Clay sample from the Benken borehole (BEN 66.75). The mineralogical composition of this specific sample has been determined and the results are given in Tab. 5.8 and Appendix C. The mineralogy of the sample is in good agreement with the reference Benken Opalinus Clay mineralogy (Nagra b) (also shown in Tab. 5.8 for comparison). The most important minerals with respect to the prediction of Cs(I) sorption are the and /smectite mixed layer content. As described in Chapter, the sorption of Cs(I) at trace concentration is calculated on pure in the equilibrated porewater and then scaled over the mineralogical conversion factor which is in this case equal to.7. The Opalinus Clay sample was conditioned to the Benken Opalinus Clay porewater using the recipe of Pearson (). The analysis of the main components in the equilibrated porewater is given in Tab. 5.9.

40 NAGRA NTB -5 Tab. 5.8: Mineralogies of Benken Opalinus Clay used in this study and the reference Opalinus Clay (Nagra b). Minerals BEN [wt.-%] Reference OPA from Benken [wt. %] Calcite 6 ± Dolomite/Ankerite ±. Siderite < d.l. ±. Quartz 5 ± 5 K-Feldspar ± Albite/Plagioclase ±. Pyrite.7. ± Illite 7 8 ± 6 Illite/Smectite ML ± Kaolinite 7 7 ± 6 Chlorite 5 ± d.l.: detection limit Tab. 5.9: Composition of the equilibrated porewater with Opalinus Clay sample BEN ICP-OES analyses of major elements for the Cs(I) sorption isotherm measurements. ph log pco [bar] Ionic strength [M] Cl [M] C inorg. [M] ICP-OES analyses of dissolved constituents [M] Na.6 - K. - Mg Ca Sr.9 - SO.7 - Al < -6 Si.9-5 Parameters taken from Tab. A (modelled ). ICP-OES results are the average of two sample measurements.

41 5 NAGRA NTB -5 The results of the are shown in Fig. 5.. Cs(I) log R d [L kg - ] log Cs equilibrium concentration [M] Fig. 5.: Cs(I) sorption measurements at ph = 7.9 and predicted sorption value on Opalinus Clay from Benken (BEN 66.75). 5. Sorption measurements on Opalinus Clay from Schlattingen- Sorption isotherm measurements of Cs(I), Co(II), Ni(II), Eu(III) and Th(IV) and U(VI) were carried out on an Opalinus Clay sample from the Schlattingen- borehole. The isotherms were measured in a synthetic porewater which was equilibrated with air (ph = 7.9) and is based on the reference Opalinus Clay porewater defined for SGT-E (Wersin et al. ). The mineralogical composition of this sample has been determined at the University of Bern and is given in Tab. 5.. (CF MIN =.7) and Appendix C. The Opalinus Clay sample (SLA 98.8) was conditioned with the new defined reference Opalinus Clay porewater by Wersin et al. (). The chemical composition of this porewater is given in the Appendix A, Tab. A. For each sorption isotherm ICP-OES analyses of the equilibrated porewater were made, and the results in Tab. 5. are the average of all measurements. The speciation calculations were carried out with the values given in Tab. 5.. Cl and C inorg. were not analysed and these were taken from Tab. A.

42 NAGRA NTB -5 6 Tab. 5.: Mineralogical composition of Opalinus Clay from Schlattingen- borehole, sample SLA Minerals SLA 98.8 [wt.-%] Calcite 7 Dolomite/Ankerite Siderite 6 Quartz 9 K-Feldspar Albite/Plagioclase < d.l. Pyrite.9 Illite 7 Illite/Smectite ML Kaolinite Chlorite 6 d.l.: detection limit Tab. 5.: Composition of the equilibrated porewater with Opalinus Clay sample SLA ICP-OES analyses of major elements for the sorption isotherm measurements of Cs(I), Co(II), Ni(II), Eu(III) and Th(IV). ph log pco [bar] Ionic strength [M] Cl [M] C inorg. [M] ICP-OES analyses of dissolved constituents [M] Na (.67.6) - K (.5.) - Mg (8.69.) - Ca (..) - Sr (.75.) -6 SO (..8) - Al. - Si Mn Fe <.8-6 Parameters taken from Tab. A (modelled ). Values in parentheses: average of 5 duplicate measurements together with standard deviations.

43 7 NAGRA NTB -5 The conversion factors are derived as given before. From Tab. 5. a CF MIN of.7 is obtained. The speciation factors for Cs(I), Co(II), Ni(II), Eu(III) and Th(IV) in the. M NaClO and for the equilibrated Opalinus Clay porewaters are given in Tab. 5., together with the measured ph in the sorption experiments. Tab. 5.: Summary of the conversion factors for the sorption measurements on the Opalinus Clay from the Schlattingen- borehole on sample SLA The log R d,opa values are the predicted sorption values. Metal ph log R d,illite [L kg - ] SF ILLITE SF OPA CF MIN CF SPEC log R d,opa [L kg - ] Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI) Fig. 5.5 shows the sorption measurements for the five elements measured on this Opalinus Clay sample and the predicted sorption values. Once again, for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) the uncertainty limits estimated for the predicted sorption values overlap with those of the measured values.

44 NAGRA NTB -5 8 Cs(I) Co(II) log R d [L kg - ] log R d [L kg - ] log Cs equilibrium concentration [M] 7 wt.-% IL+ISML log Co equilibrium concentration [M] Ni(II) 6 5 Eu(III) log R d [L kg - ] log R d [L kg - ] 7 wt.-% IL+ISML 7 wt.-% IL+ISML log Ni equilibrium concentration [M] log Eu equilibrium concentration [M] log R d [L kg - ] wt.-% IL+ISML Th(IV) log R d [L kg - ] 5 U(VI) 7 wt.-% IL+ISML log Th equilibrium concentration [M] log U equilibrium concentration [M] Fig. 5.5: Summary of the sorption measurements and the sorption values predicted for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on Opalinus Clay from the Schlattingen- borehole (SLA 98.8).

45 9 NAGRA NTB -5 6 'Brauner Dogger' 6. Sorption measurements on 'Brauner Dogger' Clay-rich sequences Sorption isotherm measurements of Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) were carried out on a 'Brauner Dogger' Clay-rich sequences sample (BEN 8. m) from the Benken borehole. The isotherms were measured in the same porewater as used for Opalinus Clay measurements on the sample SLA 98.8 (see Section 5. and Tab. A). Its composition is given in Appendix A, Tab. A. The mineralogy of the rock sample is given in Tab. 6. and Appendix C. It is clear from Tab. 6. that the CF MIN is equal to.6. Tab. 6.: Mineralogical composition of 'Brauner Dogger' Clay-rich sequences from Benken, sample BEN 8.. Minerals BEN 8. [wt.-%] Calcite 5 Dolomite/Ankerite Siderite < d.l. Quartz K-Feldspar Albite/Plagioclase Pyrite.5 Illite Illite/Smectite ML 5 Kaolinite 7 Chlorite d.l.: detection limit The ICP-OES analyses of the equilibrated porewater are summarised in Tab. 6.. The elements Cl and C inorg. were not analysed and for the speciation calculations the values in Tab. A were taken. A summary of the conversion factors for Cs(I), Co(II), Ni(II), Eu(III) and Th(IV) are given in Tab. 6.. Fig. 6. shows the results for the five elements measured on 'Brauner Dogger' Clayrich sequences sample. As in the case of the Opalinus clay samples from Schlattingen-, the uncertainty limits estimated for the predicted sorption values for Cs(I), Ni(II), Eu(III) and Th(IV) on the 'Brauner Dogger' samples overlap with those of the measured values, although the predicted value for Eu(III) is at the lower limit.

46 NAGRA NTB -5 Tab. 6.: Composition of the equilibrated porewater with 'Brauner Dogger' Clay-rich sequences, sample BEN 8.. ICP-OES analyses of major elements for the sorption isotherm measurements of Cs(I), Co(II), Ni(II), Eu(III) and Th(IV). ph log pco [bar] Ionic strength [M] Cl [M] C inorg. [M] ICP-OES analyses of dissolved constituents [M] Na (.65.) - K (.77.5) - Mg (9.5.5) - Ca (..) - Sr (..9) -6 SO (..) - Al Si Mn Fe <.8-6 Parameters taken from Tab. A (modelled ). Values in parentheses: average of 5 triplicate measurements together with standard deviations. Tab. 6.: Summary of the conversion factors for the sorption measurements on 'Brauner Dogger' Clay-rich sequences, sample BEN 8.. The log R d,bd values are the predicted sorption values. Metal ph log R d,illite [L kg - ] SF ILLITE SF BD CF MIN CF SPEC log R d,bd [L kg - ] Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI)

47 NAGRA NTB -5 Cs(I) Co(II) log R d [L kg - ] log R d [L kg - ] log Cs equilibrium concentration [M] 6 wt.-% IL+ISML log Co equilibrium concentration [M] Ni(II) 6 Eu(III) 5 log R d [L kg - ] log R d [L kg - ] 6 wt.-% IL+ISML log Ni equilibrium concentration [M] 6 wt.-% IL+ISML log Eu equilibrium concentration [M] log R d [L kg - ] wt.-% IL+ISML Th(IV) log Th equilibrium concentration [M] log R d [L kg - ] 5 U(VI) 6 wt.-% IL+ISML log U equilibrium concentration [M] Fig. 6.: Summary of the sorption measurements and the predicted sorption values for Cs(I), Co(II), Ni(II), Eu(III),Th(IV) and U(VI) on 'Brauner Dogger' Clay-rich sequences (BEN 8.).

48 NAGRA NTB Sorption measurements on 'Brauner Dogger' Sandy limestone sequences Sorption isotherm measurements of Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) were carried out on a 'Brauner Dogger' Sandy limestone sequences sample (SLA 795.7) from the Schlattingen borehole. The isotherms were measured in the same synthetic porewater as the 'Brauner Dogger' Clay-rich sequences (Section 6.). The ICP-OES analyses of the equilibrated porewater are given in Tab The mineralogy of the rock sample is given in Tab. 6. and Appendix C and the total : type clay content is equal to.5 wt.-%, i.e. CF MIN =.5. Tab. 6.: Mineralogical composition of 'Brauner Dogger' Sandy limestone sequences, sample SLA Minerals SLA [wt.-%] Calcite 85 Dolomite/Ankerite Siderite Quartz 7 K-Feldspar Albite < d.l. Pyrite. Illite.8 Illite/Smectite ML.7 Kaolinite. Chlorite. d.l.: detection limit A summary of the conversion factors for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) are given in Tab Fig. 6. shows the isotherm results for the six elements measured on 'Brauner Dogger' Sandy limestone sequences sample and the predicted sorption values. As can be seen, the agreement between predicted and measured values is generally very good except for U(VI) where the uncertainties of calculation and measurement overlap.

49 NAGRA NTB -5 Tab. 6.5: Composition of the equilibrated porewater with 'Brauner Dogger' Sandy limestone sequences, sample SLA ICP-OES analyses of major elements for the Cs(I) and Ni(II) sorption isotherm measurements. ph log pco [bar] Ionic strength [M] Cl [M] C inorg. [M] ICP-OES analyses of dissolved constituents [M] Na (.69.) - K (.5.) - Mg (8.9.) - Ca (..) - Sr (8.5.6) -7 SO (.55.) - Al. -5 Si <.6-5 Mn < Fe <. -6 Parameters taken from Tab. A (modelled ). Values in parentheses: average of triplicate measurements together with standard deviations. Tab. 6.6: Summary of the conversion factors for the sorption measurements on 'Brauner Dogger' Sandy limestone sequences, sample SLA The log R d,bd values are the predicted sorption values. Metal ph log R d,illite [L kg - ] SF ILLITE SF BD CF MIN CF SPEC log R d,bd [L kg - ] Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI)

50 NAGRA NTB -5 Cs(I) Co(II) log R d [L kg - ] log R d [L kg - ].5 wt.-% Il+ISML log Cs equilibrium concentration [M] log Co equilibrium concentration [M] Ni(II) 6 Eu(III) 5 log R d [L kg - ].5 wt.-% IL+ISML log Ni equilibrium concentration [M] log R d (L kg - ).5 wt.-% IL+ISML log Eu equilibrium concentration [M] log R d (L kg - ) 6 5 Th(IV) wt.%.5 wt.-% IL+ISML log Th equilibrium concentration [M] log R d [L kg - ] 5 U(VI).5 wt.-% IL+ISML log U equilibrium concentration [M] Fig. 6.: Summary of the sorption measurements and predictions for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on 'Brauner Dogger' Sandy limestone sequences (SLA 795.7).

51 5 NAGRA NTB -5 7 Effingen Member 7. Sorption measurements on Effingen Member Calcareous marl sequences Sorption measurements for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) were carried out on an Effingen member Calcareous marl sequences sample, OFT The mineralogy of the sample used is given in Tab. 7. and Appendix C. Tab. 7.: Mineralogical composition of Effingen Member Calcareous marl sequences sample, OFT 69.7 m, used in the sorption experiments. Minerals OFT 69.7 [wt.-%] Calcite Dolomite/Ankerite Siderite < d.l. Quartz K-Feldspar Albite/Plagioclase Pyrite.7 Illite Illite/Smectite ML 9 Kaolinite Chlorite 6 d.l.: detection limit The + /smectite ML content of the sample is 9 wt.-%. The mineralogical conversion factor is thus.9. Sorption isotherms were measured for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) in a synthetic porewater as defined by Mäder (9) and which was in equilibrium with air (ph = 7.7). The chemical composition of the 'low-salinity' porewater (.677 M) used in the isotherm measurements is given in Tab. 7.. The speciation factors, conversion factors and predicted sorption values for each element are given in Tab. 7.. Fig. 7. shows the sorption values for the six elements measured on the Effingen Member sample and the predicted sorption values. Although in all cases the uncertainty limits estimated for the predicted sorption values overlap with those of the measured values, the calculated sorption values for Cs(I), Co(II), Ni(II) and U(VI) are slightly overpredicted.

52 NAGRA NTB -5 6 Tab. 7.: Composition of equilibrated porewater with Effingen Member Calcareous marl sequences, sample OFT ICP-OES analyses of major elements for the sorption isotherm measurements of Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI). ph log pco [bar] Ionic strength [M] Cl [M] C inorg. [M] ICP-OES analyses of dissolved constituents [M] Na (.7.9) - K (..6) - Mg (.8.) - Ca (6.5.5) - Sr (9.5.) - SO (.7.5) - Al <.7-6 Si (..69) -5 Parameters taken from Tab. A5 (modelled ). Values in parentheses: average of 5 triplicate measurements together with standard deviations. Tab. 7.: Summary of the conversion factors for the sorption measurements on Effingen Member Calcareous marl sequences, sample OFT The log R d,eff values are the predicted sorption values. Metal ph log R d,illite [L kg - ] SF ILLITE SF EFF CF MIN CF SPEC log R d,eff [L kg - ] Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI)

53 7 NAGRA NTB -5 Cs(I) Co(II) log R d [L kg - ] log R d [L kg - ] log Cs equilibrium concentration [M] 9 wt.-% IL+ISML log Co equilibrium concentration [M] Ni(II) 6 Eu(III) 5 log R d [L kg - ] 9 wt.-% IL+ISML log Ni equilibrium concentration [M] log R d [L kg - ] 9 wt.-% IL+ISML log Eu equilibrium concentration [M] log R d [L kg - ] 6 5 Th(IV) log R d [L kg - ] 5 U(VI) 9 wt.-% IL+ISML 9 wt.-% IL+ISML log Th equilibrium concentration [M] log U equilibrium concentration [M] Fig. 7.: Summary of the sorption measurements and the predicted sorption values for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on Effingen Member Calcareous marl sequences (OFT 69.7).

54 NAGRA NTB Sorption measurements on Effingen Member Limestone sequences Sorption measurements for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) were carried out on an Effingen Member Limestone sequences sample (OFT 9.65). The mineralogical analysis was not carried out on the specific sample used for the sorption measurements, but on an adjacent sample. The mineralogical composition used for the prediction of the sorption values is given in Tab. 7. and Appendix C. Tab. 7.: Mineralogical composition of Effingen Member Limestone sequences sample, OFT Minerals OFT 9.65 [wt.-%] Calcite 77 Dolomite/Ankerite Siderite < d.l. Quartz 7 K-Feldspar < Albite/Plagioclase < Pyrite. Illite Illite/Smectite ML Kaolinite Chlorite < d.l. detection limit The Effingen Member Limestone sequences sample, OFT-9, was conditioned to the same porewater composition as the Effingen Member Calcareous marl sequences. The mineralogical conversion factor is.7. The speciation conversion factors for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) are summarised in Tab As can be seen from the sorption measurements there is not a large difference between the Effingen Member Calcareous marl sequences (Fig. 7.) and the Effingen Member Limestone sequences (Fig. 7.) because the : clay mineral contents are within a factor of ~. The uncertainty in the measurements is of the same order as this factor.

55 9 NAGRA NTB -5 Tab. 7.5: Composition of the equilibrated porewater with Effingen Member Limestone sequences, sample OFT ICP-OES analyses of major elements for the Cs(I) and Ni(II) sorption isotherm measurements. ph log pco [bar] Ionic strength [M] Cl [M] C inorg. [M] ICP-OES analyses of dissolved constituents [M] Na (.7 ±.) - K (.9 ±.) - Mg (.69 ±.) - Ca (6. ±.5) - Sr (7.9 ±.5) - SO (. ±.) - Al (. ±.9) -5 Si (.9 ±.) - Parameters taken from Tab. A5 (modelled ). Values in parentheses: Average of 6 measurements together with standard deviations. Tab. 7.6: Summary of the conversion factors for the sorption measurements on the Effingen Member Limestone sequences (OFT 9.65). The log R d,eff values are the predicted sorption values. Metal ph log R d,illite [L kg - ] SF ILLITE SF EFF CF MIN CF SPEC log R d,eff [L kg - ] Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI)

56 NAGRA NTB -5 Cs(I) Co(II) log R d [L kg - ] log R d [L kg - ] log Cs equilibrium concentration [M] 7 wt.-% IL+ISML log Co equilibrium concentration [M] Ni(II) 6 Eu(III) 5 log R d [L kg - ] 7 wt.-% IL+ISML log Ni equilibrium concentration [M] log R d [L kg - ] 7 wt.-% IL+ISML log Eu equilibrium concentration [M] 6 Th(IV) 5 U(VI) log R d [L kg - ] 5 S:L = 5. g/l S:L = 5. g/l S:L = 6. g/l 7 wt.-% IL + ISML log Th equilibrium concentration [M] log R d [L kg - ] 7 wt.-% IL+ISML log U equilibrium concentration [M] Fig. 7.: Summary of the sorption measurements and predictions for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on Effingen Member Limestone sequences (OFT 9.65).

57 NAGRA NTB -5 8 Helvetic Marls Sorption isotherm measurements of Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) were carried out on a Helvetic Marls sample from the Wellenberg SB borehole (WLB SBa/v.6). The mineralogical analysis was not carried out on the specific sample used for the sorption measurements, but rather on an adjacent sample. The mineralogical composition used for the prediction of the sorption values is given in Tab. 8. and Appendix C. The isotherms for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) were measured in a synthetic porewater (see Tab. A6) which was equilibrated with air (ph 8.) and is based on the marl reference porewater defined for SGT-E ('Na-Cl base-case' in Mäder ). The composition of the marl sample equilibrated porewater is given in Tab. 8.. Tab. 8.: Mineralogical composition of the Helvetic Marls sample, WLB SBa/v.6. Minerals WLB SBa/v.6 [wt.-%] Calcite 5 Dolomite/Ankerite Siderite - Quartz K-Feldspar Albite/Plagioclase Pyrite. Illite Illite/Smectite ML Kaolinite Chlorite 6 The + /smectite ML content of the sample is 6 wt.-%. The mineralogical conversion factor is thus.6. The speciation factors, conversion factors and predicted sorption values for each element are given in Tab. 8.. Fig. 8. shows the sorption values for the six elements measured on the Helvetic Marls sample and the predicted sorption values. For Cs(I), Co(II), Ni(II), Eu(III) and Th(IV) the uncertainty bands estimated for the predicted sorption values overlap with those of the measured values. However, in the case of U(VI) the predicted value lies below the measured. As can be seen from Tab. 8., the speciation factor of U(VI) in the porewater is extremely small due to the formation of mainly UO Ca(CO ) - and UO (CO ) - aqueous complexes at the high inorganic carbon concentrations and the high ph values associated with the marl porewater (Tab. 8.). It should be noted that the - UO Ca(CO ) complex, which was taken into account in predicting sorption values in the

58 NAGRA NTB -5 present report (and which is considered to be non sorbing), was also required to describe previous uranyl sorption measurements on Opalinus Clay and MX-8 bentonite (Bradbury & Baeyens a). If this complex had not been considered in the speciation calculations, the model predictions would have largely overestimated the experimental. In the case of Helvetic Marls the reasons why the measured R d value is underpredicted are not currently understood. Tab. 8.: Composition of equilibrated porewater with Helvetic Marls WLB SBa/v.6. ICP-OES analyses of major elements for the sorption isotherm measurements of Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI). ph log pco [bar] Ionic strength Cl [M] C inorg. [M] ICP-OES analyses of dissolved constituents [M] Na (.98 ±.7) - K (. ±.) - Mg (7.8 ±.) - Ca (. ±.) - Sr (.9 ±.) - SO (. ±.) - Si (.6 ±.) -5 Al (. ±.) -5 Parameters taken from Tab. A6 (modelled ). Values in parentheses: average of 6 duplicate measurements together with standard deviations. Tab. 8.: Summary of the conversion factors for the sorption measurements on Helvetic Marls, sample WLB SBa/v.6. The log R d,mgl values are the predicted sorption values. Metal ph log R d,illite [L kg - ] SF ILLITE SF MGL CF MIN CF SPEC log R d,mgl [L kg - ] Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI)

59 NAGRA NTB -5 Cs(I) 5 Co(II) log R d [L kg - ] log Cs equilibrium concentration [M] log R d [L kg - ] 6 wt.-% IL+ISML log Co equilibrium concentration [M] 5 Ni(II) 6 Eu(III) 5 log R d [L kg - ] 6 wt.-% IL+ISML log Ni(II) equil. concentration [M] log R d [L kg - ] 6 wt.-% IL+ISML log Eu equilibrium concentration [M] 6 Th(IV) 5 U(VI) log R d (L kg - ) 5 6 wt.% IL+ISML log Th equilibrium concentration [M] log R d (L kg - ) 6 wt.-% Il-ISML log U equilibrium concentration [M] Fig. 8.: Summary of the sorption measurements and the predicted sorption values for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on Helvetic Marls (WLB SBa/v.6).

60

61 5 NAGRA NTB -5 9 MX-8 Bentonite The MX-8 Na-Bentonite (Wyoming, USA) was obtained from Bentonit International GmbH, Duisburg (Germany). Müller-Vonmoos & Kahr (98, 98) have characterised the MX-8 bentonite and carried out a mineralogical analysis which is reproduced in Tab. 9.. In this analysis ~ wt.-% of the material remained as "unidentified". Tab. 9.: Mineralogical composition of MX-8 bentonite (Müller-Vonmoos & Kahr 98). The compositions are expressed in wt.-% of oven-dried MX-8. Minerals MX-8 Bentonite [wt.-%] Montmorillonite 75 Illite < d.l. Kaolinite < Calcite.7 Gypsum < d.l. K-feldspar 5 8 Plagioclase < d.l. Pyrite. Siderite.7 Quartz 5. d.l.: detection limit The montmorillonite content is 75 wt.-% yielding a mineralogical conversion factor of.75. The sorption isotherm measurements for Cs(I), Ni(II), Eu(III), Th(IV) and U(VI) were carried out before the year as important inputs to the sorption base for MX-8 required for the Entsorgungsnachweis (Nagra a). This was well before a conceptual model for calculating the porewater in compacted bentonite was fully developed, and also before the necessary for such calculations were available. However, in order to carry out the sorption experiments, a bentonite porewater had to be defined. This was done on the basis of the incomplete information and knowledge available at the time (Bradbury & Baeyens unpubl. results). The calculated porewater composition is given in Appendix A, Tab. A7. Tab. 9. summarises the equilibrated porewater compositions. The speciation factors are calculated for each element with the experimentally measured concentrations (Tab. 9.) and fixing the concentrations for C inorg and Cl as given in Tab. A7. The results are given in Tab. 9.. Fig. 9. shows the results of the sorption and predictions. The correspondence between predicted and measured sorption values for Cs(I) and U(VI) is good whereas the sorption values for Ni(II), Eu(III) and Th(IV) are somewhat overpredicted.

62 NAGRA NTB -5 6 Tab. 9.: Composition of equilibrated porewater with MX-8 bentonite. ph log pco [bar] Ionic strength [M] Cl [M] C inorg. [M] ICP-OES analyses of dissolved constituents [M] Na (5.7.7) - K (.79.5) - Mg (..) - Ca (..) - Sr (.85.8) - SO (.9.) - Al (.66.) -6 Si (..6) - Mn. -6 Fe (.8.) -7 Parameters taken from Tab. A7 (modelled ). Values in parentheses: average of 5 duplicate measurements together with standard deviations. Tab. 9.: Summary of the conversion factors for the sorption measurements on MX-8 bentonite. The log R d,mx-8 values are the predicted sorption values. Metal ph log R d,mont [L kg - ] SF MONT SF MX-8 CF MIN CF SPEC log R d,mx-8 [L kg - ] Cs(I) Ni(II) Eu(III) Th(IV) U(VI)

63 7 NAGRA NTB -5 Cs(I) Ni(II). log R d [L kg - ].8. log R d [L kg - ].6 montmorillonite log Cs equilibrium concentration [M] montmorillonite 75 wt.-% mont log Ni equilibrium concentration [M] 6 5 Eu(III) 7 6 Th(IV) log R d [L kg - ] montmorillonite 75 wt.-% mont log Eu equilibrium concentration [M] log R d [L kg - ] 5 montmorillonite 75 wt.-% mont log Th equilibrium concentration [M] log R d [L kg - ] 6 5 U(VI) montmorillonite 75 wt.-% mont log U equilibrium concentration [M] Fig. 9.: Summary of the sorption measurements and the predicted sorption values for Cs(I), Ni(II), Eu(III), Th(IV) and U(VI) on MX-8 bentonite.

64

65 9 NAGRA NTB -5 Overview, Summary and Conclusions In this report a vast amount of sorption on various argillaceous host rocks and MX-8 bentonite has been presented and compared with s. In all, a total of 5 isotherm sets comprising of the elements Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on Opalinus Clay, 'Brauner Dogger', Effingen Member, Helvetic Marls and MX-8 bentonite have been measured. Tab.. summarises all of the measured (column 5) and predicted (column 6) log R d values. If the results are expressed as the ratio of the predicted values to the measured values, i.e. R d,pred /R d,meas (Tab.., column 7) it can be readily seen that about 8 % of the s lie within a factor of ± of the measured values i.e. > R d,pred / R d,meas >., and can be considered as being essentially the same. The factor of ± is the uncertainty factor associated with the source measurements on : type clay minerals and the cation exchange modelling approach for Cs(I) (see Chapter ). The results given in Tab.. can be visualised by plotting the measured R d values (x-axis) against the predicted values (y-axis) for all those metals exhibiting surface complexation as the major sorption mechanism, Fig... The continuous line represents a : correspondence between the measured and predicted. Data points falling below this line indicate underpredicted values whereas those above the line indicate overpredicted values. The dashed lines encompass almost all the measured and illustrate that the maximum difference between the predicted R d value and measured R d values is a factor of ± 6, i.e..8 log units. Based on this result, it is concluded that the methodology applied to derive sorption values, within the uncertainty bounds given, is strongly supported by this study on argillaceous rocks and bentonite. Fig.. presents an overview of the measured and predicted sorption values for Cs(I) on the argillaceous host rocks and bentonite. Cs(I) is shown separately because the sorption mechanism for this element is cation exchange and the predicted values were calculated with the generalised Cs(I) sorption model (Bradbury & Baeyens ) for the argillaceous rocks and with a simple cation exchange model for bentonite. The uncertainty in these model calculations was estimated to be a factor of, i.e..5 log units (Bradbury & Baeyens ). Similar to Fig.., the continuous line represents a : correspondence between the measured and predicted. The maximum difference between the predicted and measured R d values for the sorption of Cs(I) is a factor of ± (dashed lines). Clearly, these results provide convincing support for the methodology used to derive sorption values for Cs(I) in the SDBs.

66 NAGRA NTB -5 5 Tab..: Sorption values measured at trace concentrations (< -8 M) for host rocks and MX-8 bentonite, and the predictions from and montmorillonite. For the cases where the ratio R d,pred /R d,meas is > implies that the sorption value is overpredicted, whereas ratios < imply underprediction. Rock Opalinus Clay 'Brauner Dogger' Location / Rock sequence Mont Terri Sample BGP--C (Tab. 5. & Fig. 5.) BGP--C (Tab. 5.5 & Fig. 5.) DI-A-. (Tab. 5.7 & Fig. 5.) Benken BEN (Fig. 5.) Schlattingen- SLA 98.8 (Tab. 5. & Fig. 5.5) Benken Clay-rich sequences Schlattingen- Sandy limestone sequences BEN 8. (Tab. 6. & Fig. 6.) SLA (Tab. 6.6 & Fig. 6.) Radionuclide Cs(I) Ni(II) Eu(III) Th(IV) Cs(I) Ni(II) Eu(III) Th(IV) U(VI) Cs(I) Co(II) log R d, pred. [L kg - ] log R d, meas. [L kg - ] R d,pred R d,meas Cs(I)..8. Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI) Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI) Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI)

67 5 NAGRA NTB -5 Tab..: (continued) Rock Location / Rock sequence Sample Radionuclide log R d, pred. [L kg - ] log R d, meas. [L kg - ] R d,pred R d,meas Bentonite Helvetic Marls Effingen Member Oftringen Calcareous marl sequences Oftringen Limestone sequences Wellenberg Silty to sandy argillaceous marl OFT 69.7 (Tab. 7. & Fig. 7.) OFT 9.65 (Tab. 7.6 & Fig. 7.) WLB SBa/v.6 (Tab. 8. & Fig. 8.) - MX-8 (Tab. 9. & Fig. 9.) Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI) Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI) Cs(I) Co(II) Ni(II) Eu(III) Th(IV) U(VI) Cs(I) Ni(II) Eu(III) Th(IV) U(VI)

68 NAGRA NTB -5 5 log R d [L kg - ] predicted log R d [L kg - ] measured Co(II): OPA & BD Co(II): EFF Co(II): MGL Ni(II): OPA & BD Ni(II): EFF Ni(II): MGL Ni(II): MX-8 Eu(III): OPA & BD Eu(III): EFF Eu(III): MGL Eu(III): MX-8 Th(IV): OPA & BD Th(IV): EFF Th(IV): MGL Th(IV): MX-8 U(VI): OPA & BD U(VI): EFF U(VI): MGL U(VI): MX-8 Fig..: Overview of the comparison of measured and predicted sorption for Co(II), Ni(II), Eu(III), Th(IV) and U(VI) on different rock types and MX-8 bentonite. The solid line is the : slope, the broken lines represent a band width of ±.8 log units..5 log R d [L kg - ] predicted.5.5 Opalinus Clay 'Brauner Dogger' Effinger Member Helvetic Marls MX log R d [L kg - ] measured Fig..: Overview of the Cs(I) sorption results on five different rock types (Opalinus Clay (OPA), 'Brauner Dogger' (BD), Effingen Member (EFF), Helvetic Marls (MGL) and bentonite (MX-8). The solid line is the : slope, the broken lines represent a band width of ±.5 log units.

69 5 NAGRA NTB -5 From the information presented here, and other recent studies carried out (Bradbury & Baeyens, b), there is now a substantial body of evidence which strongly supports the approach and methodology for developing SDBs for argillaceous rocks and bentonite described in Bradbury et al. (). This methodology was applied to produce SDBs as input to the provisional safety analyses required for stage of the Sectoral Plan (Baeyens et al. ). The results of the present report indicate that the sorption values given in these SDBs for a wide range of host rock mineralogies and water chemistry combinations have a high degree of reliability and capture the sorption in real systems within the uncertainty bounds given. Acknowledgements The contribution of A. Schaible to the experimental work is gratefully acknowledged. ICP-OES analyses were carried out by S. Köchli. The thorough review of the manuscript by Vinzenz Brendler (Helmholtz-Zentrum Dresden-Rossendorf, Germany) and Jens Mibus (Nagra) is gratefully acknowledged. Partial financial support was provided by Nagra.

70

71 55 NAGRA NTB -5 References Baeyens, B. & Bradbury, M.H. (997): A mechanistic description of Ni and Zn Sorption on Namontmorillonite. Part I: Titration and sorption measurements. J. Cont. Hydrol. 7, 99-. Baeyens, B., Thoenen, T., Bradbury, M.H. & Marques Fernandes, M. (): Sorption bases for argillaceous rocks and bentonite for the provisional safety analyses for SGT-E. Nagra Technical Report NTB -. Nagra, Wettingen, Switzerland. Baeyens, B. & Bradbury, M.H. (995): A Quantitative Mechanistic Description of Ni, Zn and Ca Sorption on Na-Montmorillonite, Part II: Sorption Measurements. PSI Report No. 95-, Paul Scherrer Institut, Villigen PSI, Switzerland and Nagra Technical Report NTB 95-5, Nagra, Wettingen, Switzerland. Bradbury, M.H. & Baeyens, B. (997a): Far-field sorption bases for performance assessment of a L/ILW repository in an undisturbed Palfris Marl host rock. PSI Report No. 97-5, Paul Scherrer Institut, Villigen PSI, Switzerland and Nagra Technical Report NTB 96-6, Nagra, Wettingen, Switzerland. Bradbury, M.H. & Baeyens, B.(997b): A mechanistic description of Ni and Zn Sorption on Na-montmorillonite. Part II: Modelling. J. Cont. Hydrol. 7, -8. Bradbury, M.H. & Baeyens, B. (): A generalised sorption model for the concentration dependent uptake of Cs by argillaceous rock. J. Cont. Hydrol., -6. Bradbury, M.H. & Baeyens, B. (a): Sorption of Eu on Na- and Ca-montmorillonites: Experimental investigations and modelling with cation exchange and surface complexation. Geochim. Cosmochim. Acta 66, 5-. Bradbury, M.H. & Baeyens, B. (b): Porewater chemistry in compacted re-saturated MX-8 bentonite: Physico-chemical characterisation and geochemical modelling. PSI Report No. -, Paul Scherrer Institut, Villigen PSI, Switzerland and Nagra Technical Report NTB -8, Nagra, Wettingen, Switzerland. Bradbury, M.H. & Baeyens, B. (a): Near-field sorption bases for compacted MX-8 bentonite for performance assessment of a high level radioactive waste repository in Opalinus Clay host rock. PSI Report No. -5, Paul Scherrer Institut, Villigen PSI, Switzerland and Nagra Technical Report NTB -8, Nagra, Wettingen, Switzerland. Bradbury, M.H. & Baeyens, B. (b): Far-field sorption bases for performance assessment of a HLW repository in an undisturbed Opalinus Clay host rock. PSI Report No. - 8, Paul Scherrer Institut, Villigen PSI, Switzerland and Nagra Technical Report NTB -9, Nagra, Wettingen, Switzerland. Bradbury, M.H. & Baeyens, B. (5): Experimental and modelling investigations on Na-: Acid-base behaviour and the sorption of strontium, nickel, europium and uranyl. PSI Report No. 5-, Paul Scherrer Institut, Villigen PSI, Switzerland and Nagra Technical Report NTB -, Nagra, Wettingen, Switzerland.

72 NAGRA NTB Bradbury, M.H. & Baeyens, B. (9a): Sorption modeling on Part I: Titration measurements and the sorption of Ni, Co, Eu and Sn. Geochim. Cosmochim. Acta 7, 99-. Bradbury, M.H. & Baeyens, B. (9b): Sorption modeling on Part II: Actinide sorption and linear free energy relationships. Geochim. Cosmochim. Acta 7, -. Bradbury, M.H. & Baeyens, B. (): Comparison of the reference Opalinus Clay and MX-8 bentonite sorption bases used in the Entsorgungsnachweis with sorption bases predicted from sorption measurements on and montmorillonite. PSI Report No. - 9, Paul Scherrer Institut, Villigen PSI, Switzerland and Nagra Technical Report NTB 9-7, Nagra, Wettingen, Switzerland. Bradbury, M.H. & Baeyens, B. (a): Predictive sorption modelling of Ni(II), Co(II), Eu(III), Th(IV) and U(VI) on MX-8 bentonite and Opalinus Clay: A "bottom-up" approach. Appl. Clay Sci. 5, 7-. Bradbury, M.H. & Baeyens, B. (b): Physico-chemical characterisation and sorption measurements of Cs, Ni, Eu, Th, U, Cl, I and Se on MX-8 bentonite. PSI Report No. - 5, Paul Scherrer Institut, Villigen PSI, Switzerland and Nagra Technical Report NTB 9-8. Nagra, Wettingen, Switzerland. Bradbury, M.H., Baeyens, B. & Thoenen, T. (): Sorption bases for generic Swiss argillaceous rock systems. Nagra Technical Report NTB 9-. Nagra, Wettingen, Switzerland. Gorgeon, L. (99): Contribution à la modélisation physico-chimique de la retention de radioeléments à vie longue par des materiaux argileux. Unpublished PhD Thesis. Université Paris 6. Lauber, M., Baeyens, B. & Bradbury, M.H. (): Physico-Chemical Characterisation and Sorption Measurements of Cs, Sr, Ni, Eu, Th, Sn and Se on Opalinus Clay from Mont Terri. PSI Report No. -, Paul Scherrer Institut, Villigen PSI, Switzerland and Nagra Technical Report NTB -, Nagra, Wettingen, Switzerland. Mäder, U. (9): Reference pore water for the Effingen Member (Standortregion Südjura) for the provisional safety-analysis in the framework of the sectoral plan interim results (SGT-ZE). Nagra Working Report NAB 9-. Nagra, Wettingen, Switzerland. Mäder, U. (): Reference pore water for the Helvetic Marls for the provisional safetyanalysis in the framework of the sectoral plan interim results (SGT-ZE). Nagra Working Report NAB 9-5. Nagra, Wettingen, Switzerland. Marques Fernandes, M., Baeyens, B. & Bradbury, M.H. (8): The influence of carbonate complexation on lanthanide/actinide sorption on montmorillonite. Radiochim. Acta 96, Marques Fernandes, M., Baeyens, B., Dähn, R., Scheinost, A.C. & Bradbury, M.H. (): U(VI) sorption on montmorillonite in the absence and presence of carbonate: A macroscopic and microscopic study. Geochim. Cosmochim. Acta 9, Müller-Vonmoos, M. & Kahr, G. (98): Bereitstellung von Bentoniten für Laboruntersuchungen. Nagra Technical Report NTB 8-. Nagra, Wettingen, Switzerland.

73 57 NAGRA NTB -5 Müller-Vonmoos, M. & Kahr, G. (98): Mineralogische Untersuchungen von Wyoming Bentonit MX-8 und Montigel. Nagra Technical Report NTB 8-. Nagra, Wettingen, Switzerland. Nagra (997): Geosynthese Wellenberg 996 Ergebnisse der Untersuchungsphasen I und II. Nagra Technical Report NTB 96-. Nagra, Wettingen, Switzerland. Nagra (): Sondierbohrung Benken: Untersuchungsbericht. Nagra Technical Report NTB -. Nagra, Wettingen, Switzerland. Nagra (a): Project Opalinus Clay: Safety Report. Demonstration of disposal feasibility (Entsorgungsnachweis) for spent fuel, vitrified high-level waste and long-lived intermediate-level waste. Nagra Technical Report NTB -5. Nagra, Wettingen, Switzerland. Nagra (b): Projekt Opalinuston: Synthese der geowissenschaftlichen Untersuchungsergebnisse Entsorgungsnachweis für abgebrannte Brennelemente, verglaste hochaktive sowie langlebige mittelaktive Abfälle. Nagra Technical Report NTB -. Nagra, Wettingen, Switzerland. Nagra (8): Vorschlag geologischer Standortgebiete für das SMA- und das HAA-Lager. Begründung der Abfallzuteilung, der Barrierensysteme und der Anforderungen an die Geologie. Bericht zur Sicherheit und technischen Machbarkeit. Nagra Technical Report NTB 8-5. Nagra, Wettingen, Switzerland. Neck, V. & Kim, J.I. (): Solubility and hydrolysis of tetravalent actinides. Radiochim. Acta 89, -6. Pearson, F.J. (998): Opalinus Clay experimental water: A Type. Version 988. PSI Internal Report TM Paul Scherrer Insitut, Villigen PSI, Switzerland. Pearson, F.J. (): Sondierbohrung Benken: Artificial pore water for experimental use Version 5. Unpubl. Nagra Internal Report. Nagra, Wettingen, Switzerland. Schultess, C.P. & Huang, C.P. (99): Adsorption of heavy metals by silicon and aluminium oxide surfaces on clay minerals. Soil Sci. Soc. Am. J. 5, Thoenen, T. (): Uncertainty estimates of the speciation factors using Monte-Carlo error propagation. PSI Internal Report TM---6. Paul Scherrer Institut, Villigen PSI, Switzerland. Thoenen, T., Hummel, W., Berner, U. & Curti, E. (): The PSI/Nagra Chemical Thermodynamic Database /7. Nagra Working Report NAB -9. Nagra, Wettingen, Switzerland. Thury, M. & Bossart, P. (999): The Mont Terri rock laboratory, a new international research project in a Mesozoic shale formation in Switzerland. Eng. Geol. 5, Turner, D.R., Bertetti, F.P. & Pabalan, R.T. (6): Applying surface complexation modelling to radionuclide sorption. Interface Science and Technology: In: Lützenkirchen, J. (ed.): Surface complexation modelling, Vol.. Elsevier, Amsterdam, 55-6.

74 NAGRA NTB Van Loon, L.R., Baeyens, B. & Bradbury, M.H. (9): The sorption behaviour of caesium on Opalinus Clay: A comparison between intact and crushed material. Appl. Geochem., Waber, H.N. (8): Borehole Oftringen: mineralogy, porosimetry, geochemistry, pore water chemistry. Nagra Working Report NAB 8-8. Nagra, Wettingen, Switzerland. Wersin, P., Mazurek, M., Waber, H.N., Mäder, U.K., Gimmi, T., Rufer, D. & De Haller, A. (): Rock and porewater characterisation on drillcores from the Schlattingen borehole. Nagra Working Report NAB -5. Nagra, Wettingen, Switzerland.

75 A- NAGRA NTB -5 Appendix A Composition of the Calculated Porewaters Used in the Sorption Measurements Tab. A: Compositions of the calculated Opalinus Clay porewaters used for the sorption measurements on Opalinus Clay Mont Terri sample BGP--C (Lauber et al., Table ). ph pco [bar] Ionic strength [M] Dissolved constituents [M] Na K Mg Ca Sr Cl SO C inorg F Si Tab. A: Composition of the calculated Opalinus Clay porewater used in the sorption experiments on Opalinus Clay Mont Terri sample DI-A (Van Loon et al. 9). ph pco [bar] Ionic strength [M] Dissolved constituents [M] Na. - K.6 - Mg.7 - Ca.6 - Sr 5. - Cl. - SO. - C inorg Si.8 -

76 NAGRA NTB -5 A- Tab. A: Compositions of the calculated Opalinus Clay porewaters used for the sorption measurements on the Opalinus Clay Benken sample BEN (Pearson ). ph pco [bar] Ionic strength [M] Dissolved constituents [M] Na.5 - K. - Mg 5. - Ca 7. - Sr. - Cl.6 - SO. - C inorg.. - Tab. A: Composition of the calculated Opalinus Clay porewater used in the sorption experiments for Schlattingen- Opalinus Clay (Wersin et al. ). ph pco [bar] Ionic strength [M] Dissolved constituents [M] Na.6 - K.55 - Mg Ca.9 - Cl.6 - SO. - C inorg Si.8 -

77 A- NAGRA NTB -5 Tab. A5: Calculated porewater composition for Effingen Member ('low-salinity' in Mäder 9). ph pco [bar] Ionic strength [M] Dissolved constituents [M] Na.7 - K.99 - Mg.5 - Ca 6. - Sr 8. - SO.5 - Cl C inorg.7 - Si.7 - Fe.9 - Tab. A6: Calculated porewater composition for Helvetic Marls ('Na-Cl base-case' in Mäder ). ph pco [bar] Ionic strength [M] Dissolved constituents [M] Na.98 - K. - Mg Ca.5 - Sr.6 - SO. - Cl. - C inorg.5 - Si.78 - Fe. -5

78 NAGRA NTB -5 A- Tab. A7: Calculated MX-8 bentonite porewater (Bradbury & Baeyens a). ph pco [bar] Ionic strength [M] Dissolved constituents [M] Na K.8 - Mg. - Ca. - Sr.66 - Al.6-8 F. - Cl SO.9 - C inorg.. - Si.8 -

79 B- NAGRA NTB -5 Appendix B Experimental Procedures The experimental procedures for the sorption measurements on Opalinus Clay (Lauber et al. ) and on MX-8 (Bradbury & Baeyens b) are described in detail in the respective reports. For the newly measured on the host rocks the same methods have generally been applied and only a brief summary is given in this appendix. Reagents and Analytical Methods All chemicals used in this study were of highest available grade of purity and were purchased from Merck (Darmstadt, Germany) or Fluka (Buchs, Switzerland). Solutions were prepared with ultrapure de-ionised water obtained from a Milli-Q Reagent Grade Water System purchased from Millipore (Molsheim, France). The cations (Na, K, Mg, Ca, Sr, Si, Al, Fe, Cs, Co, Ni, Eu, Th, U) and sulphur were analysed by inductively coupled plasma-optical emission spectroscopy (ICP-OES, Applied Research Laboratory ARL D ICP-AES). ph measurements were carried out on a ph-meter 69 from Metrohm using Inlab (Mettler) and Metrohm combined ph-electrode. Buffer solutions (ph = 7 and 9) were purchased from Merck (Titrisol ampoules). Two point calibrations were made using the buffer solutions above. The ph values of all the porewaters of the host rocks were between these two values. Conditioning of the argillaceous rocks with the synthetic porewaters Prior to the sorption measurements the crushed core sample was conditioned to the porewaters. The aim of this procedure was to produce an argillaceous rock suspension in equilibrium with the synthetic porewater. The procedure was as follows: Dialysis bags were washed with de-ionised water before filling with 5 to 5 g of crushed rock and 8 ml synthetic porewater. The bags were sealed so that an air pocket was trapped inside which promoted a good mixing during end-over-end shaking. Two such dialysis bags were placed in a L polyethylene flask filled with synthetic porewater and then shaken for hours. After this time, the equilibrated solutions in the flasks were replaced by fresh synthetic porewater and the bottles were again shaken for hours. This procedure was repeated four times. Finally the suspensions inside the dialysis bags were emptied into a quantity of the last equilibrated synthetic porewater in order to give a suspension having a sorbent concentration of ~ to g L -. The exact clay content was determined by heating 5 ml of the suspension overnight at 5 C and weighing the residue. The dry weight of ml synthetic porewater was determined in the same manner in order to make salt corrections. For each radionuclide isotherm determination on the different host rocks, a separate conditioning step was carried out, and in each case the synthetic and equilibrated porewater was analysed by ICP-OES. The results are compiled in Appendix A. The major ion concentrations in the synthetic and equilibrated porewater after the conditioning process are essentially the same.

80 NAGRA NTB -5 B- Experimental procedures for sorption measurements Sorption isotherms, i.e. the uptake of radionuclides as function of the radionuclide equilibrium concentration at constant ph in the equilibrated porewaters, were performed for Cs(I), Co(II), Ni(II), Eu(III), Th(IV) and U(VI). The experiments were carried out under atmospheric conditions. The equilibration times were always 7 days for the newly measured isotherms. Sorption isotherm measurements were carried out in the equilibrated synthetic waters at the corresponding ph of the porewaters. Standard solutions having a range of nuclide concentrations were prepared by successively diluting an original equilibrated porewater containing a high concentration of the nuclide in question. The standard solutions were labelled by adding known quantities of radioisotope. These labelled standard solutions were allowed to stabilise for at least one day in their polyethylene containers before use in the sorption tests in order to allow wall sorption to proceed to completion. A number of samples of these standard solutions (standard samples) were always counted simultaneously with the sample solutions from the batch sorption tests. Two types of isotherm experiments were carried out. In the first case the total concentration of radionuclide was varied at constant S:L ratio whereas in the second case the total concentration of radionuclide was kept constant and the S:L ratio varied. Changing the S:L ratio allowed the radionuclide equilibrium concentrations to be varied up to near the maximum stable level. This procedure was used for Th(IV) and U(VI) because the solubility of these radionuclides in very low in the porewater. The radioisotopes Cs, 6 Co, 6 Ni, 5 Eu and 8 Th were purchased from Isotope Products Laboratories (California, USA). A. - M solution of U was available in house. An ICP- MS analysis (VG Elemental Plasma Quad ) of this U solution yielded the following isotopic composition: 99.9 % U,. % U and. % 8 U indicating that the purity of the U solution was sufficient and could be used in the sorption experiments. Radiochemical assays of 6 Ni and U were carried out on a Canberra Packard TRI-CARB 5CA or TRI-CARB 75 TR/LL liquid scintillation analyser. The radioisotopes Cs, 6 Co, 5 Eu and 8 Th were radio assayed on a Canberra Packard COBRA QUANTUM -Counter. Uncertainties Estimates of the maximum error in each operation in similar batch sorption tests to those performed in this work have been done by Baeyens & Bradbury (995) and yielded an uncertainty in log R d of ~.5 log units. When sorption experiments were repeated the R d values varied within. log units. This error estimate includes all possible sources of errors (e.g. weighing, volumetric and counting errors). In some cases the R d values are very high (e.g. Eu, Th) or very low (U). For these measurements the uncertainty increases up to.5 log units. This uncertainty was taken to be realistic and all measured R d values in this work are given with this error.

81 B- NAGRA NTB -5 Presentation of the The sorption isotherms are presented as distribution ratios R d [L kg - ] against equilibrium concentrations. The equilibrium aqueous concentration of the radionuclide is calculated from the measured activity of the supernatant solution and the known activity of the initial solution. The distribution ratio R d is defined as: R d = C in - C eq C eq L S where: C in = initial nuclide concentration [M] C eq = equilibrium nuclide concentration [M] L = volume of the liquid phase [L] S = mass of the solid phase [kg]

82

83 C- NAGRA NTB -5 Appendix C Characteristics of the Used Rock Samples The rock samples used in this study were characterised by Martin Mazurek (University of Bern). The main characteristics are given in this Appendix. Note: For Mont Terri samples BGP--C und DI-A-. no sheets exist. The mineralogical composition is documented in Lauber et al. ().

84 NAGRA NTB -5 C- BEN Sample factsheet Uni BE PSI Benken Borehole: Formation: Opalinus Clay Quartz Calcite Dolomite K-feldspar Plagioclase 5 % %. %. %. % Top depth: m Lithology: Mineralogy Illite Illite-Smectite mixed layer Chlorite Kaolinite Total clays 7 % % % 7 % 67 % Host rock: Opalinus Clay Base depth: 66.8 m Total S C inorganic C organic Pyrite Total. %.7 %. % : From powder XRD : From CS-Mat; Cc/Dol ratio from powder XRD; All S as pyrite Bulk dry density not determined Petrophysics Grain density Water content not determined not determined Physical Porosity not determined Sample history Drilling of borehole Benken; Storage in Nagra core shed, no air-tight conservation Transfer of samples to PSI Cutting of sample ( m) with a diamond saw and pieces embedded in Epoxy resin Aliquot of sample powder used for experiments at PSI delivered to Martin Mazurek (RWI, Bern) for mineralogical re-analysis. Available additional BET CEC Noble Gases Hg Porosimetry Water activity Aqueous extracts Porewater stable isotopes Diffusive exchange porosity Advective displacement exp. Photo Remarks The mineralogical analysis refers to a sample which was used for the sorption measurements (see sample history). References Nagra (): Sondierbohrung Benken: Untersuchungsbericht. Nagra Technical Report NTB -.

85 C- NAGRA NTB -5 Sample factsheet Uni BE - PSI SLA 98.8 Host rock: Opalinus Clay Borehole: Schlattingen SLA- Top depth: 98. m Base depth: 98. m Formation: Opalinus Clay Lithology: Homogeneous clay rich Mineralogy Quartz 9. % Illite 6.8 % Total S.5 % Calcite 6.9 % Illite-Smectite mixed layer. % C inorganic.7 % Dolomite/Ankerite.6 % Chlorite 5.7 % C organic. % K-feldspar. % Kaolinite.7 % Pyrite.9 % Siderite 6. % Total clays 7. % Total 99.7 % Petrophysics Bulk wet density Grain density Water content WC wet Physical Porosity.5 ±. g/cm.7 ±.7 g/cm.8 wt.-%. vol.-% : Uncertainty: Standard deviation of measurements : Uncertainty: Standard deviation of 6 measurements Sample history - Kernmarsch SLA-8, Delivery of sample to PSI Available additional BET CEC Noble Gases Hg Injection Water activity Aqueous extracts Porewater stable isotopes Diffusive exchange porosity Advective displacement exp. Out-diffusion Vitrinite reflectance Sr, C-O isotopes Ultra-centrifugation Photo Remarks Sample stored in air-tight plastic and aluminium bag Dry sawing of original core to produce samples for diffusion experiments Analyses refer to material taken along the whole sample length (ca. cm) Sample for diffusion experiment protected against desiccation using simple plastic foil after sawing; immediate delivery to PSI. Pulverised sample for sorption experiments dried at 5 C References Analysen Uni Bern gem. Mail M. Mazurek 8..

86 NAGRA NTB -5 C- Sample factsheet Uni BE PSI BEN 8. Host rock: 'Brauner Dogger' Borehole: Benken Top depth: 8.9 m Base depth: 8.8 m Formation: Parkinsoni-Württembergica Beds Lithology: Sandy argillaceous marl Mineralogy Quartz % Illite % Total S.8 % Calcite 5 % Illite-Smectite mixed layer 5 % C inorganic. % Dolomite % Chlorite % C organic.5 % K-feldspar % Kaolinite 7 % Pyrite.5 % Plagioclase % Total clays 7 % Total % : From powder XRD : From CS-Mat; Cc/Dol ratio from powder XRD; All S as pyrite Petrophysics Bulk dry density Grain density Water content Physical Porosity.9 ±. g/cm.7 ±. g/cm not determined.9 ±.5 vol.-% : Uncertainty: Standard deviation of measurements : Uncertainty: Gaussian law of uncertainty propagation Sample history Nov/Dec 9 Feb Jun Drilling of borehole Benken; Storage in Nagra core shed, no air-tight conservation Sampling by Dimitri Meier Sample splitting: Sawing of two pieces of entire core vertically separated subsamples Delivery of sample to PSI, no special packaging XRD, CS-Mat, densities measured at Uni Bern by Dimitri Meier Aliquot of sample powder used for experiments at PSI delivered to Martin Mazurek (RWI, Bern) for mineralogical re-analysis. New results compare well with those given in AN -5 note that the 9 given in that AN originate from adjacent but not identical sample materials Available additional BET CEC Noble Gases Hg Porosimetry Water activity Aqueous extracts Porewater stable isotopes Diffusive exchange porosity Advective displacement exp. Photo Remarks References Nagra (): Sondierbohrung Benken: Untersuchungsbericht. Nagra Technical Report NTB -.

87 C-5 NAGRA NTB -5 Sample factsheet Uni BE PSI SLA Host rock: 'Brauner Dogger' Borehole: Schlattingen SLA- Top depth: 795. m Base depth: 795. m Formation: Blagdeni Beds Lithology: Limestone bank Mineralogy Quartz 7. % Illite.8 % Total S. % Calcite 85 % Illite-Smectite mixed layer.7 % C inorganic.5 % Dolomite/Ankerite.5 % Chlorite. % C organic <. % K-feldspar. % Kaolinite. % Pyrite. % Siderit. % Total clays. % Total. % Petrophysics Bulk wet density Grain density Water content WC wet Physical Porosity.65 ±.9 g/cm.78 ±.5 g/cm.9 wt.-%.7 vol.-% : Uncertainty: Standard deviation of measurements Sample history - Kernmarsch SLA-6, : Delivery of sample to PSI Available additional BET CEC Noble Gases Hg Injection Water activity Aqueous extracts Porewater stable isotopes Diffusive exchange porosity Advective displacement exp. Out-diffusion Vitrinite reflectance Sr, C-O isotopes Ultra-centrifugation Photo Remarks Sample stored in air-tight plastic and aluminium bag Dry sawing of original core to produce samples for diffusion experiments Analyses refer to material taken along the whole sample length (ca. cm) Sample for diffusion experiment protected against desiccation using simple plastic foil conditioned after sawing; immediate delivery to PSI. Pulverised sample for sorption experiments dried at 5 C References Analysen Uni Bern gem. Mail M. Mazurek 8..

88 NAGRA NTB -5 C-6 Sample factsheet Uni BE PSI OFT 69.7 Host rock: Effingen Mb. Borehole: Oftringen Top depth: m Base depth: 69.5 m Formation: Effingen Member Lithology: Sandy calcareous marl Mineralogy Quartz % Illite % Total S. % Calcite % Illite-Smectite mixed layer 9 % C inorganic 5.5 % Dolomite. % Chlorite 6 % C organic.9 % K-feldspar. % Kaolinite % Pyrite.7 % Plagioclase < % Total clays 7 % Total 99.6 % : From powder XRD : From CS-Mat; Cc/Dol ratio from powder XRD; All S as pyrite Petrophysics Bulk dry density Grain density Water content WC wet Physical Porosity.59 ±. g/cm.78 ±. g/cm.55 ±.5 wt.-% 9.9 vol.-% : Uncertainty: Standard deviation of measurements : Uncertainty: Standard deviation of measurements Sample history Drilling, sampling and air-tight core protection within minutes after core recovery Sub-sampling by dry-cutting by diamond saw Storage in evacuated plastic bags, inside evacuated plastic-coated aluminium bag, Kept in a refrigerator at C until sample preparation Delivery of sample to PSI, Aliquot of sample powder used for experiments at PSI delivered to Martin Mazurek (RWI, Bern) for mineralogical re-analysis. Available additional BET CEC Noble Gases Hg Injection Water activity Aqueous extracts Porewater stable isotopes Diffusive exchange porosity Advective displacement exp. Out-diffusion Vitrinite reflectance Sr, C-O isotopes Ultra-centrifugation Photo Remarks No photo of sample available Alternative sample ID: OFT-6 The mineralogical analysis refers to a subsample from the core interval which was used for the sorption measurements (see sample history). References Waber (8): Borehole Oftringen: Mineralogy, Porosimetry, Geochemistry, Pore Water Chemistry. Nagra Working Report NAB 8-8.

89 C-7 NAGRA NTB -5 Sample factsheet Uni BE - PSI OFT 9.65 Host rock: Effingen Mb. Borehole: Oftringen Top depth: 9.5 m Base depth: 9.8 m Formation: Effingen Member Lithology: Argillaceous limestone Mineralogy Quartz 7 % Illite % Total S.5 % Calcite 77 % Illite-Smectite mixed layer % C inorganic 9.7 % Dolomite % Chlorite < % C organic. % K-feldspar < % Kaolinite % Pyrite. % Plagioclase < % Total clays % Total 99. % : From powder XRD : From CS-Mat; Cc/Dol ratio from powder XRD; All S as pyrite Petrophysics Bulk dry density Grain density Water content WC wet Physical Porosity.66 ±. g/cm.76 ±. g/cm. ±..8 % : Uncertainty: Standard deviation of measurements : Uncertainty: Standard deviation of measurements..7 Nov 9 Sample history Drilling, sampling and air-tight core protection within minutes after core recovery Sub-sampling by dry-cutting by diamond saw Storage in evacuated plastic bags, inside evacuated plastic-coated aluminium bag, Kept in a refrigerator at C until sample preparation Delivery of sample to PSI Available additional BET CEC Noble Gases Hg Injection Water activity Aqueous extracts Porewater stable isotopes Diffusive exchange porosity Advective displacement exp. Out-diffusion Vitrinite reflectance Sr, C-O isotopes Ultra-centrifugation Photo Remarks No photo of sample available Typical, representative limestone Has been dried at 5 C Alternative sample ID: OFT-9 References Waber (8): Borehole Oftringen: Mineralogy, Porosimetry, Geochemistry, Pore Water Chemistry. Nagra Working Report NAB 8-8.

90 NAGRA NTB -5 C-8 Sample factsheet Uni BE PSI WLB SBa/v.6 Host rock: Helvetic Marls Borehole: Wellenberg SBa/v Top depth:.6 m Base depth:.6 m Formation: Palfris-Formation Lithology: Silty to sandy argillaceous marl Mineralogy Quartz % Illite % Total S.6 % Calcite 5 % Illite-Smectite mixed layer % C inorganic 6.6 % Dolomite/Ankerite % Chlorite 6 % C organic.9 % K-feldspar % Kaolinite % Pyrite. % Plagioclase % Total clays % Total. % : From powder XRD; all S as pyrite : From powder XRD, corrected Petrophysics Bulk dry density Grain density Water content WC wet Physical Porosity.689 ±. g/cm.7 ±. g/cm : Uncertainty: Standard deviation of measurements Sample history Long-term storage before analyses / delivery to PSI Available additional BET CEC Noble Gases Hg Injection Water activity Aqueous extracts Porewater stable isotopes Diffusive exchange porosity Advective displacement exp. Out-diffusion Vitrinite reflectance Sr, C-O isotopes Ultra-centrifugation Photo Remarks Photo of sample available (Nagra Photo Archive) Silty to (fine-grained) sandy argillaceous marl References Nagra (997): Geosynthese Wellenberg 996 Ergebnisse der Untersuchungsphasen I und II. Nagra Technical Report NTB 96-.