Proceedings of Global 2009 Paris, France: September 6-11, 2009 Paper 9038 Long-term behavior of vitrified waste packages Isabelle Ribet*, Sophie Bétrémieux **, Stéphane Gin *, F. Angeli *, Christophe Jégou * *CEA, Centre de Marcoule, DTCD, B.P. 17171, 30207 Bagnols sur Cèze, France **AREVA NC, BU-T / DIRP / RDP, Tour AREVA, 1 Place Jean Millier, 92084 PARIS - LA DEFENSE 6, France Email: isabelle.ribet@cea.fr Abstract – The VESTALE project (from the French acronym for “long-term alteration of glass in interim storage and in a waste repository) was undertaken to develop long-term behavior models of vitrified waste packages. The first stage of the project was completed in 2005, meeting the deadline set by the 1991 French nuclear waste management act, with the submission of long-term behavior models taking into account the current state of knowledge at that time. The subsequent waste management act of 2006 selected a clay medium (in the Meuse-Haute Marne area of northeastern France) as the reference option for a geological repository site. The second stage of the VESTALE project (2006– 2012) is therefore devoted to consolidating long-term behavior models of vitrified waste packages, by taking into account more precisely defined repository environmental conditions. The project addresses two main areas of investigation: first, a study of intrinsic glass behavior under the responsibility of the waste producers, which is the subject of this article; and second, a study of environmental coupling, especially as applied to the conditions prevailing in the Bure underground laboratory, under the responsibility of the French radioactive waste management agency, ANDRA, and which is not detailed here. The work now in progress on intrinsic glass behavior seeks not only to strengthen the hypotheses adopted in the existing models developed for the glass formulations currently in production, but also to acquire data for characterizing the long-term behavior of future glass packages. The following topics are covered: (1) self-irradiation effects: effects on the glass structure, consequences on macroscopic properties, helium behavior at high alpha doses; (2) alteration kinetics, especially over the long term: mechanisms controlling the residual glass alteration rate, modeling the alteration kinetics, assessment of glass composition effects; (3) estimation of the reactive surface area: thermomechanical modeling of the initial crack density, development of cracking under the effect of external mechanical stresses, coupling with the alteration kinetics to determine the quantities of altered glass in full-scale blocks; (4) natural and archaeological analogs: the issues of long-term validation of the experimental and modeling results. • I. INTRODUCTION Reprocessing is the reference process for spent fuel from pressurized water reactors in France; the resulting fission product solutions are then vitrified. This article focuses on research concerning the “R7T7” containment glass produced by AREVA NC in its La Hague plant. The French nuclear waste management act of 2006 specified geological disposal as the reference disposition route for vitrified wasteforms. Characterization of the long-term behavior of the glass in collaboration with the waste producers provides input data for investigations by ANDRA of package interaction with the repository environment. In this context, the VESTALE project is designed to develop glass behavior models that can be coupled with models of the other components of waste storage vaults to allow performance calculations of dose release from the repository. Two main issues must be addressed in characterizing long-term behavior: Glass behavior in a closed system: characterization of the potential changes in the glass structure due to heat and self-irradiation. • Glass behavior in a water-saturated open system: specification of the glass source term, i.e. the quantity of altered glass (or of radionuclides released) over time. A predictive behavior model known as V0Vr was developed and published in 2005 [1]. This conservative model incorporates the state of scientific knowledge available in 2005; its main hypotheses are reviewed in the next section of this article. The following sections discuss recent progress and prospects concerning self-irradiation effects for very high doses, the long-term alteration kinetics, estimating the reactive surface area and its potential long-term evolution, and validation by natural and archaeological analogs. The main milestone in the ongoing program is in 2012, when a summary of available knowledge must be submitted under the ANDRA repository licensing process. Proceedings of Global 2009 Paris, France: September 6-11, 2009 Paper 9038 II. THE V0Vr MODEL This model is designed to quantify the quantity of altered glass over time. It therefore postulates the very conservative hypothesis that all the radionuclides are released at the same rate as the glass alteration tracers, such as boron. The following additional hypotheses are assumed: • The effects of heat and self-irradiation do not degrade the physical and chemical properties of the glass over time. The glass matrix remains homogeneous and helium production due to the decay of alpha emitters does not lead to the formation of bubbles at micrometer scale. This hypothesis has been largely demonstrated for the glass packaged that are now produced industrially. • As long as the medium remains reactive with respect to silicon from the glass matrix, the glass alteration rate is assumed equal to the maximum observed rate, i.e. the initial rate V0, which depends only on the temperature and pH. The reactive surface area during this alteration phase is only a fraction of the total consisting of the external (geometric) surface area (S0) and the surface area of largeaperture cracks. The cracking factor is designated 0. The quantity of glass altered per unit time during this phase is equal to the product of V0 × S0 × 0. • After the initial phase of rapid alteration due to chemical reactions in the immediate environment of the glass (Si sorption on metal canister corrosion products), the alteration kinetics reach a residual rate (Vr) under conditions in which the water renewal rate is very low, as in the case of a geological repository. The reactive surface area comprises all the external surfaces and the crack surfaces. The cracking factor is designated r. The quantity of glass altered per unit time during this phase is equal to the product of Vr × S0 × r. The model parameters (alteration rates V0 and Vr, cracking factors 0 and r) were determined as a function of the temperature (between 25 and 100°C), the pH (between 7 and 10) and the glass composition throughout the R7T7 composition range. The uncertainties on the parameter values were also determined. The model can be used to calculate the lifetime of the glass from the time/temperature profile, the pH of the medium, the date of water ingress in contact with the glass, and the quantity of accessible silicon sorption sites on the canister metal products. Figure 1 is a typical calculated glass lifetime plot for two hypotheses concerning the quantity of unsaturated sorption sites during the initial rate phase, assuming water ingress in contact with the glass after 4000 years [1]. The graph illustrates the importance of the residual rate phase in determining the total package lifetime, and the need to better understand the mechanisms responsible for this rate regime. Figure 1. Total altered glass fraction in two cases: allowing for saturation of the canister corrosion products alone, allowing for saturation of the canister and overpack corrosion products. In both cases alteration begins after 4000 years. The corresponding uncertainties are indicated in broken lines, especially in the reference case . Compared with the state of knowledge in 2005, the objective of the ongoing studies is to consolidate the hypotheses of the V0Vr model in the following areas: • More precise characterization of the reactivity of the surrounding environment with respect to the glass; this is the subject of a study organized by ANDRA and is not discussed here. • Confirmation that the glass properties are not degraded at high alpha doses. • Clarification of the mechanisms controlling the residual rate. • Comparison of the cracking factors 0 and r obtained by indirect measurements with the estimated glass thermomechanical cracking factor. III. SELF-IRRADIATION EFFECTS ON GLASS PROPERTIES Increasingly higher fuel burnup implies the vitrification of fission product solutions with minor actinide concentrations higher than those initially specified. This requires an assessment of R7T7 glass behavior at alpha decay doses of about 1019 /g of glass. Actinide solubility tests in R7T7-type glass have shown that the minor actinide concentrations in question do not limit their incorporation in the glass network. Irradiation damage studies combine several approaches: • Glass specimens subjected to external irradiation: these methods are used to accumulate high doses in a thin glass layer near the surface, and allow a broader range of characterization methods than doped glass (Raman spectroscopy, XANES). Proceedings of Global 2009 Paris, France: September 6-11, 2009 Paper 9038 • Atomistic modeling (molecular dynamics): computation of cumulative displacement cascades is a mean of estimating the impact of irradiation on macroscopic properties such as the density or the modulus of elasticity. • Actinide-doped glass specimens quickly reach high cumulative doses throughout the glass volume. The doped glass with the highest activity prepared for this study contained 3.5 wt% curium-244 oxide; by 2008 it had reached an accumulated dose of 1019 /g, corresponding to the dose sustained by R7T7 glass after 10 000 years. The three approaches all yield consistent results: due to the effect of alpha decay the glass density diminishes slightly and its mechanical properties appreciably improve, especially its resistance to cracking. The variations in these properties reach a saturation level and stabilize beyond 2 × 1018 /g (Figure 2). Accumulated alpha dose (α/g) 0.0E+00 0.1 2.0E+18 4.0E+18 6.0E+18 8.0E+18 1.0E+19 0 Density variation (%) -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 -0.7 0.04wt% 244CmO2 0.4wt% 244CmO2 3.25wt% 244CmO2 fit Marples model 1.2wt% 244CmO2 Figure 2. Density of R7T7-type glass versus alpha decay dose. Data from [2] [3]. Nuclear interactions caused by recoil nuclei induce slight structural changes, especially a drop in the boron coordination number and residual depolymerization of the borosilicate network (~1%). These changes are comparable to the effects of local thermal quenching of zones partially disorganized by recoil nuclei. A local thermal quenching accumulation model has been developed to describe the origin of these structural changes: each alpha disintegration locally damages the glass, which stabilizes in a new glass structure corresponding to a hypothetical high-temperature state. The accumulation of these events throughout the glass volume gradually produces a new glass corresponding to this slightly modified structure. This description accounts for the stabilization of the macroscopic properties observed beyond 2 × 1018 disintegrations per gram of glass by postulating a damage threshold affecting the entire material volume. [4]. The results of these studies reveal no measurable specific effect of helium generation in the glass up to the maximum dose of 1019 /g. The data acquired establish that the properties of R7T7-type glass will be not modified by an accumulated dose of about 1019 /g glass, and do not call into question its long-term behavior. [5] In order to pursue our research on a possible accumulation limit of alpha decay in the glass (above 1019 /g), a program specifically targeting helium behavior in the glass was undertaken to assess feasibility of subjecting glass to higher doses. The program should allow us to predict the consequences of helium behavior over the very long term (diffusion as a function of the temperature and degree of glass network damage; bubble formation; effect on the cracking factor). It will include the examination of glass specimens irradiated in a reactor to generate large quantities of helium by the 10B(n,)7Li reaction. IV. GLASS ALTERATION KINETICS: The GRAAL Model (Glass Reactivity with Allowance for the Alteration Layer) Observations during R7T7-type glass leaching experiments in a closed system or with very slow renewal have shown that very low alteration rates are reached (about 5 nm/year at 50°C). A detailed investigation of glass alteration mechanisms identified the following features when glass is placed in contact with water (Figure 3) [6]: • Exchange and hydrolysis reactions involving the mobile glass constituents (alkalis, boron, etc.) rapidly occur during the initial instants. • Slower hydrolysis, especially of silicon, results in the existence of an initial glass dissolution rate. • The difference between these two kinetics results in the creation of an amorphous layer at the glass/solution interface regardless of the alteration conditions. This layer is gradually reorganized by hydrolysis and condensation mechanisms. • The amorphous layer dissolves as long as the solution is not saturated with respect to its constituent elements (Si, Zr, Al, Ca, etc.). Renewal of a pure water solution sustains the dissolution process. • The amorphous layer constitutes a barrier against the transport of water toward the glass and of solvated glass ions into solution. The existence of this transportinhibiting effect rapidly causes this layer to control glass alteration. • Some glass constituent elements precipitate as crystallized secondary phases. The precipitation of these crystallized phases on the external surface or in solution can sustain glass alteration. Proceedings of Global 2009 Paris, France: September 6-11, 2009 Paper 9038 Water diffusion through the PRI 100000 PRI dissolution from the outer face Tracers Pristine glass PRI Precipitation of secondary phases GRAAL Modeling H2O Glass hydration at the glass/PRI interface Mass of altered g based on boron t release at the en each experime (mg of glass) Log scale is chose that each experim can have the sa weight on the fig 10000 1000 100 Water 10 Figure 3. The four processes involved in glass alteration. A model describing all these mechanisms was developed. The glass-related parameters are the solubility limit of the passivating reactive interphase (PRI), the water diffusion coefficient in this interphase, the gel dissolution rate, and the initial hydration rate of the pristine glass at the internal interface. The other model parameters concern the secondary phases likely to precipitate, depending on the chemical elements supplied by the glass or by the surrounding medium: phase solubility limits and precipitation kinetics. When R7T7 glass is leached in initially pure water, the secondary phases are mainly phyllosilicates (Figure 4). The simulations show a good agreement with experimental data (Figure 5) [7]. Figure 4. SEM image of an R7T7 glass sample altered for 4 months in initially pure water at 150°C, showing the outer layer of phyllosilicates precipitated from solution, the porous gel formed by in situ condensation, and the underlying pristine glass. 10 100 1000 10000 100000 Experimental Measurements Figure 5. Altered glass mass calculated by the model compared with experimentally measured values. Calculations were performed at the last sampling interval of each experiment. A simplified analytical solution of the model shows that the residual glass alteration rate depends on the water renewal rate. With rapid renewal the residual rate is limited by the dissolution kinetics of the passivating reactive interphase; with slow or zero renewal the residual rate is governed by the secondary phase precipitation kinetics. Work is now in progress to refine the model parameters as a function of the temperature, pH and glass composition, but especially to identify the secondary phases and their kinetic parameters in order to couple this glass alteration model with a geochemistry-transport model describing the glass environment (a diffusive reactive medium characteristic of a repository environment). Moreover, very sophisticated experimental approaches have been developed to study the gel structure (highresolution solid-state NMR [8] [9]]) and its morphology (small angle X-ray scattering, neutron scattering, ToF-SIMS [10]). These techniques have been coupled with mesoscopic scale models (kinetic Monte Carlo method [11] [12]). This approach has identified pore closure processes, establishing for the first time a direct cause-effect relationship between the altered layer morphology and the alteration kinetics in simplified borosilicate glass simulating nuclear containment glass compositions. It has been shown that substituting an insoluble oxide for a significant fraction of silica retards the gel structural reorganization and, by inhibiting the pore closure mechanism, leads to greater alteration. The very large drop in the leach rate observed for some glass compositions is due to pore closure by gel densification, which transforms the glass from a state in which dissolution is controlled mainly by hydrolysis to a state in which it is controlled by the accessibility of the reaction interface to water. Under these conditions, saturation of the solution with respect to silica becomes a prerequisite to the formation of a passivating layer but is not a criterion for the end of alteration. Regardless of the degree of reaction progress, even Proceedings of Global 2009 Paris, France: September 6-11, 2009 Paper 9038 under “saturation” conditions, aqueous alteration of nuclear glasses always leads to the diffusive release of glass constituents, even if in only very minute quantities [13] [6]. The alteration film constitutes a diffusion barrier with (in the case of R7T7 nuclear glass) an apparent diffusion coefficient of about 10-21 to 10-24 m-2·s-1 [13] [14], very near the values found in solids. Such very low values could not be reached if the porosity were open, allowing percolation of the elements released from the glass into solution, because the interdiffusion coefficients (for transfer by direct contact between the pristine glass and solution) are much higher [15]. V. GLASS REACTIVE SURFACE AREA After the melt has been poured, industrial nuclear glasses exhibit a temperature gradient between the hot core and the cool outer surface. The gradient results from a combination of the thermal cooling scenario, the thermal power due to decay of radioactive elements, and the low thermal conductivity of the glass. This results in mechanical stresses whose release leads to cracking. The glass surface area potentially accessible to aqueous leaching thus exceeds the geometric surface area of the package. The quantity of radionuclides released during glass alteration under repository conditions is directly proportional to surface area accessible to water, which is currently taken into account in performance models by two effective cracking factors, 0 and r. The cracking factors are measured by leaching experiments performed on full-scale inactive glass blocks [1]. These experiments are designed to maintain the water renewal rate to ensure leaching at the maximum rate, V0, based on well-known parameter values. The accessible surface area is estimated from the quantity of altered glass determined by analysis of alteration tracers (boron, lithium). Leaching a large block in a perforated basket in a Soxhlet device gives a value for 0. Leaching the loose fragments of a large fractured block in the same device provides an estimate of the total surface area developed by the cracks, from which r is inferred. Two areas of investigation were defined to consolidate this phenomenological approach and to develop a model capable of evaluating the potential progression of the cracking under the lithostatic stress loading in a repository. behavior law implemented in the ABAQUS code, and finally a 3D cooling simulation. The second step will produce a 3D simulation of package cracking based on a damage and cracking law in the ABAQUS code. • Experiments on small blocks, a few centimeters in size, to determine the crack densities versus the applied stress loading. • Smaller scale experiments at crack scale are carried out to evaluate the cracking mechanisms and to improve the behavior laws and rupture criteria. The model will be validated on full-scale inactive blocks on which the crack network has been characterized by various methods (tomography, particle size analysis). V.B. Chemistry-transport coupling in the cracks; modeling the quantity of altered glass in a full-scale block Experiments with crack models (two glass tiles separated by a known gap, typically 40 to 500 µm) identified coupling in the cracks between chemistry and transport phenomena with an intensity dependent on the crack aperture; the coupling is characterized by a difference in the altered thickness according to the position in the finest cracks (less than about one hundred micrometers), whereas the thickness is constant for cracks with larger apertures. Transport is mainly diffusive in the finest cracks, but convection phenomena can also occur (thermal convection or convection due to density gradients in vertical cracks) (Figure 6) [16]. Figure 6. Photographs of crack models altered in diffusive conditions (left) and in convective conditions (right). The variation of color reflects the variation of altered thickness. V.A. Thermomechanical cracking The objective is to develop a thermomechanical model to obtain a sufficiently explicit statistical description of the crack network (crack density, length, spacing) depending on the active or inactive glass thermal scenario. The model can then be used to quantify the initial cracking and its progression under given mechanical stresses. The methodology combines the following approaches: • Simulation: the first step consists in a thermomechanical analysis (finite-element calculation of structure stress and strain phenomena) by solving the heat transfer equation coupled with the equation of motion, using a viscoelastic Coupling between chemistry and transport in the cracks rapidly leads to a significant drop in the glass alteration rate in the finest cracks, where the low solution renewal rate causes a rapid transition to the residual rate regime; in the case of R7T7 glass at 90°C the residual rate is four orders of magnitude lower than the initial rate. This is perfectly consistent with the fact that the effective cracking factor 0 is much lower than the total cracking factor (for R7T7 glass, 0 is 5 ± 1 and r is 40 ± 17). When a large block is altered under initial rate conditions, only the largest cracks contribute significantly to the quantity of altered glass. Proceedings of Global 2009 Paris, France: September 6-11, 2009 Paper 9038 The final step in increasing the robustness of the V0Vr model is the coupling between the GRAAL mechanistic alteration model and transport in the cracks in a full-scale block to compute the quantity of altered glass versus time. The methodology adopted is to model flow in the crack network, define a simplified porous equivalent model, and combine it with the GRAAL model. VI. LONG-TERM VALIDATION ON ARCHAEOLOGICAL ANALOGS (Embiez glass) Validating predictive models is one of the major difficulties of investigating the long-term behavior of containment materials because the relevant time scales largely exceed what is accessible to laboratory experimentation. Whenever possible, therefore, natural or archaeological analogs are examined for this purpose. quantitative agreement with the observations of the archaeological glass block (Figure 8). Table I. Simulated thicknesses of the alteration products at the crack tip a (µm) Dsol (m2∙s-1) Total altered Total smectite glass thickness thickness (µm) (µm) 1.5 × 10-9 1.5 × 10-9 1.5 × 10-10 1.5 × 10-9 20 10 10 2 38 34 25 26 8 5.5 0.7 3 6 µm < 0,3 µm 8 µm 20 µm 25 µm Figure 7. Fractured archaeological glass sample Archaeological glass blocks (Figure 7) from a shipwreck discovered near the French Mediterranean island of Embiez have been examined because of their morphological analogy with nuclear glasses and their known, stable environment. Like nuclear glasses, these blocks were fractured after production; they were then leached for 1800 years in seawater. A geochemical model capable of simulating the alteration of a fractured archaeological glass block was developed using the same methodology as for characterizing the long-term behavior of nuclear glass (GRAAL). The model was validated by comparing the results given by the model with observations on the sampled materials [17] [18]. From these experiments we determined the kinetic constants of the mechanisms involved (interdiffusion and dissolution of the glass network) and the thermodynamic parameters (affinity, secondary phases) of the model, which was implemented in the HYTEC geochemical code to simulate alteration in the cracks over 1800 years. The simulations were carried out on internal cracks several centimeters long and with variable apertures (again assuming alteration in seawater at 15°C). Table I indicates the total altered glass thicknesses and clay precipitates after 1800 years of alteration versus the crack aperture and diffusion coefficient. The simulation results are in remarkable 10 µm 17 µm < 0,7 µm 10 µm 30 µm 7 µm < 0,3 µm Figure 8. Micrographs of internal cracks in the archaeological glass block: measured thicknesses of the altered glass (black) and secondary phases (white). Simulating the crack alteration over 1800 years accounts for the thicknesses observed on the actual glass blocks. Cracks with an initial aperture of 100 µm are sufficient to allow renewal of the leaching medium. However, in the case of smaller apertures (< 20 µm), with or without crack filling, the model predicts total altered glass thicknesses of 25 to 38 µm near the crack tips, which corresponds to the Proceedings of Global 2009 Paris, France: September 6-11, 2009 Paper 9038 thicknesses (between 5 and 30 µm) observed on the internal cracks in the archaeological glass block. The simulation results for the finest cracks (< 2 µm) should lead to even smaller thicknesses. The saponite thicknesses are also consistent with the measured values (1 to 5 µm near the crack tips). The agreement of the simulated alteration thicknesses and the values measured on the blocks validates the predictive performance of the model. The analogous behavior of archaeological and nuclear glass allows us to consider applying the model to nuclear glass under geological repository conditions. The same methodology could be applied to much older basaltic glasses for which the environment can be characterized. These glasses not only exhibit the same behavior, mechanisms, and kinetics as nuclear glasses in short-term experiments, but their alteration products also reveal strong similarities, especially between the palagonite on basaltic glasses and the gel on nuclear containment glasses, which can constitute a diffusion barrier. These studies can contribute to a finer definition of the chemical model of nuclear glasses and to the long-term validation of the gel protective properties. 3. 4. 5. 6. 7. 8. VII. CONCLUSIONS An investigation of long-term glass behavior allowed us to develop a conservative predictive model known as V0Vr. Work is now in progress to consolidate the robustness of this model by comparison with mechanistic approaches that provide more accurate but more complex assessments of long-term behavior. The ongoing work addresses the effect of self-irradiation at high doses, modeling of helium behavior, modeling of long-term alteration kinetics (GRAAL), quantification of the initial cracking, coupling of chemistry and transport phenomena in the cracks of a full-scale fractured block, and long-term validation based on natural and archaeological analogs. 9. 10. 11. ACKNOWLEDGMENTS The authors are grateful to AREVA and the CEA for their financial support. 12. REFERENCES 1. 2. C. FILLET, I. Ribet, S. Gin, S. Peuget, E. Vernaz. Long-Term Behavior of French R7T7 Glass. XXI International Congress on Glass ICG2007, Strasbourg, 01/07-06/07/2007. S. PEUGET, J.-N. Cachia, C. Jégou, X. Deschanels, D. Roudil, V. Broudic, J-M. Delaye, J.-M. Bart, Irradiation stability of R7T7-type borosilicate glass. J. Nucl. Mater. 354, 1-13(2006). 13. Hj. MATZKE, Alpha self-irradiation of waste glasses : state of the knowlegde. Proceedings of the Université d’été CEA-Valrho, 149-166, (1997). G. BUREAU, J.M. Delaye, S. Peuget, G. Calas, Proc. of the International Conference Atalante 2008, 19-23 Mai 2008, Montpellier, France. F. CHAMSSEDINE, T. Sauvage, S. Peuget, G. Martin. Measurements of the helium diffusion coefficient in R7T7 nuclear glass by using 3He(d, α)1H nuclear reaction analysis technique. Submitted to Journal of Nuclear Materials. P. FRUGIER, S. Gin, Y. Minet, T. Chave, B. Bonin, N. Godon, J.E. Lartigue, P. Jollivet, A. Ayral, L. De Windt, G. Santarini. SON68 nuclear glass dissolution kinetics: Current state of knowledge and basis of the new GRAAL model, J. Nucl. Mater. 381 (1-3), 8-21 (2008). P. FRUGIER, T. Chave, S. Gin, J-E. Lartigue. Application of the GRAAL Model to Leaching Experiments with SON68 Nuclear Glass in Initially Pure Water. Submitted to Journal of Nuclear Materials. F. ANGELI, M. Gaillard, P. Jollivet, T. Charpentier, Influence of glass composition and alteration solution on leached silicate glass structure: A solidstate NMR investigation, Geochimica et Cosmochimica Acta 70 (10) 2577-2590 (2006) F. ANGELI, T. Charpentier, M. Gaillard, P. Jollivet, Influence of Zirconium on the Structure of Pristine and Leached Soda-Lime Borosilicate Glasses: Towards a Quantitative Approach by 17O MQMAS NMR, Journal of Non-Crystalline Solids 354, 37133722 (2008) C. CAILLETEAU, F. Angeli, F. Devreux, S. Gin, J. Jestin, P. Jollivet, O. Spalla, Insight into Silicate Glass Aqueous Alteration Mechanisms, Nature Materials 7, 978-983 (2008) M. ARAB, C. Cailleteau, F. Angeli, F. Devreux, Experimental Study and Monte Carlo Modeling of Calcium Borosilicate Glasses Leaching, in Scientific Basis for Nuclear Waste Management XXX, edited by D.S. Dunn, C. Poinssot, B. Begg (Mater. Res. Soc. Symp. Proc. 985, Warrendale, PA, 0985NN06-02 (2007) M. ARAB, C. Cailleteau, F. Angeli, F. Devreux, L. Girard, O. Spalla, Aqueous Alteration of Five-Oxide Silicate Glasses: Experimental Approach and Monte Carlo Modeling, Journal of Non-Crystalline Solids 354 (2008) 155–161 T. CHAVE, P. Frugier, A. Ayral and S. Gin, Solid state diffusion during nuclear glass residual alteration in solution. J. Nucl. Mater. 362, 466-473 (2007) Proceedings of Global 2009 Paris, France: September 6-11, 2009 Paper 9038 14. K. FERRAND, A. Abdelouas, and B. Grambow, Water diffusion in the simulated French nuclear waste SON 68 contacting silica rich solutions: experimental and modeling. J. Nucl. Mater. 355, 5467 (2006). 15. B.C. BUNKER, Molecular mechanisms for corrosion of silica and silicate glasses, J. Non-Cryst. Solids 179, 300-308 (1994) 16. L. CHOMAT, F. Bouyer, S. Gin, S. Roux. Single idealized cracks: a tool for understanding fractured glass block leaching. MRS2007 Symposium on the Scientific Basis for Nuclear Waste Management, MRS Proceedings. Sheffield,16-21/09/2007. 17. A. VERNEY-CARRON, S. Gin, G. Libourel. A fractured Roman glass block altered 1 800 years in seawater: analogy with nuclear waste glass in deep geological repository. Geochimica et Cosmochimica Acta, 72, 5372-5385, 2008. 18. A. VERNEY-CARRON, S. Gin, P. Frugier, G. Libourel. Long-term modeling of alteration-transport coupling: application to a fractured Roman glass. Submitted to Geochimica Cosmochimica Acta.