Long term behaviour of glass and steel in interaction with argillite in deep geological conditions O. Bildstein (1), V. Devallois (1), V. Pointeau (1), S. Bodeï (1), J.E. Lartigue (1), L. Trotignon (1) N. Michau (2), B. Cochepin (2) and I. Munier (2) (1) CEA, DEN, DTN/SMTM/LMTE, Saint-Paul-lez-Durance – France (2) ANDRA Châtenay-Malabry Cedex - France Sensitivity calculations The sensitivity analysis show that the relative amount and evolution in space and time of the secondary minerals strongly depend on the corrosion rate and the gas released (H 2 and possibly CH 4 ) in the system. The relative intensity of the transport process (diffusion coefficient) and mineral reaction rates (kinetic rate and reactive surface area) also strongly influence the evolution of the system (nature of secondary phases, porosity, gas pressure…). Conclusions These reaction pathways and paragenesis predicted by the calculations are qualitatively supported by “short-term” (~1 year) iron/argillite experiments (Schlegel et al., 2008). A significant reduction of porosity is systematically predicted at the interface between the different materials and is also locally observed in the different materials depending on the simulation conditions. Context : long term behaviour of materials in deep geological disposal of High Level Waste cell. The evolution of the near field system is complex since geochemical and transport processes are highly coupled. Steel corrosion and glass alteration produce an increase of pH which in turn affects the rate of glass dissolution. The concentration of dissolved silica is also one key to the rate of glass alteration and, along with the concentration of other elements such as iron and aluminum, it determines the nature of steel corrosion and clay alteration products. These interactions may also lead to partial dissolution of the initial clay minerals potentially affecting the overall properties such as permeability and diffusion coefficient. Aim of this study : predict nature of steel corrosion and glass alteration products + pH evolution + effect on near field properties (Andra, 2005) HLW packages Steel plug (biological protection) Clay plug (confinement function) Concrete plug (mechanical function) Drift head studied area Several scenarios are investigated which all involve (1) the geochemical interactions between iron and clay-rich materials, and (2) the alteration of glass in the presence of corrosion products. We compare a base case with the results from sensitivity calculations. Base case at 90°C Results Model parameters  canister corrosion in 25,000 yrs; glass alteration in 35,000 years; pH perturbation (pH>8) up to 2 m into the argillite.  glass alteration products mainly consist of gyrolite, natrolite and pure silica minerals (chalcedony).  steel corrosion products: iron oxides (magnetite or goethite) and iron silicates (cronstedtite) at the core of the canister; aluminosilicates (daphnite, Fe-saponite) and sulfides (pyrrhotite) precipitate at the interface between glass and argillite.  porosity clogging is predicted at the glass/steel and steel/argillite interfaces.  in the argillite, primary minerals such as dolomite, smectites and calcite are destabilized close to the canister surface. These minerals disappear in favour of zeolites (natrolite, phillipsite-K), gyrolite and saponite-Na. Glass/steel/argillite system at 90°C fixed porosity, water saturated medium D e = m 2 /s at 90°C Alteration of glass and steel starting at t = 0 Crunch code (Thermoddem database, kinetics from Palandri & Kharaka) Glass alteration (Si-B-Na-Al-Ca-Fe)-Glass + 1,1574 H + + 2,2205 H 2 O  0,5328 B(OH) 3 + H 4 SiO 4 + 0,4323 Na Al ,0952 Ca ,0497 Fe 3+  alteration rate = 6  m/yr Steel corrosion Fe (container) + 2 H +  Fe 2+ + H 2 (aq)  corrosion rate = 5  m/yr Argillite GlassSteelArgillite Simulated composition