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Hoch A.,Serco | Wendling J.,92298 Chatenay Malabry Cedex
Physics and Chemistry of the Earth | Year: 2011

Andra is studying the feasibility of constructing a repository for radioactive waste in the Callovo-Oxfordian mudstones. The high-activity, long-lived vitrified wastes, in particular, will be stored in cells that are about 40. m long, with a single access aperture from an access gallery. The wall of each cell will be supported by a steel sleeve. As long as the access galleries are ventilated, corrosion of the steel sleeve by oxygen in air will be important. This study estimates the thickness of the steel sleeve corroded during this phase, in order to be able to design the sleeve with an appropriate initial thickness to maintain integrity. In addition, at the end of the cell farthest from the ventilated access gallery, it is possible that the oxygen concentration will be so low that corrosion occurs under reducing (anaerobic) conditions. This chemical reaction produces hydrogen gas, which will migrate towards the access gallery. This study estimates the transfer rate of hydrogen to the access gallery, which is necessary to evaluate the fire and/or explosion hazards (a hydrogen-oxygen mixture is highly flammable and/or explosive at certain concentrations) and maintain operational safety. Specifically, we have developed a capability to simulate flows of multi-component (i.e. nitrogen, oxygen and hydrogen) gas in porous media, and then we have applied that capability to predict: first, the flow rate of hydrogen from each cell to the access gallery; second, the hydrogen (and oxygen) mole fractions in the annular void between the steel sleeve and the rock; and third, the corrosion rate of the metal sleeve along the cell. © 2011 Elsevier Ltd.

Blanc P.,Bureau de Recherches Géologiques et Minières | Gailhanou H.,Bureau de Recherches Géologiques et Minières | Rogez J.,Aix - Marseille University | Mikaelian G.,Aix - Marseille University | And 10 more authors.
Physics and Chemistry of Minerals | Year: 2014

In the context of the deep waste disposal, we have investigated the respective stabilities of two iron-bearing clay minerals: berthierine ISGS from Illinois [USA; (Al0.975FeIII0.182FeII1.422Mg0.157Li0.035Mn0.002)(Si1.332Al0.668)O5(OH)4] and chlorite CCa-2 from Flagstaff Hill, California [USA; (Si2.633Al1.367)(Al1.116FeIII0.215Mg2.952FeII1.712Mn0.012Ca0.011)O10(OH)8]. For berthierine, the complete thermodynamic dataset was determined at 1 bar and from 2 to 310 K, using calorimetric methods. The standard enthalpies of formation were obtained by solution-reaction calorimetry at 298.15 K, and the heat capacities were measured by heat-pulse calorimetry. For chlorite, the standard enthalpy of formation is measured by solution-reaction calorimetry at 298.15 K. This is completing the entropy and heat capacity obtained previously by Gailhanou et al. (Geochim Cosmochim Acta 73:4738-4749, 2009) between 2 and 520 K, by using low-temperature adiabatic calorimetry and differential scanning calorimetry. For both minerals, the standard entropies and the Gibbs free energies of formation at 298.15 K were then calculated. An assessment of the measured properties could be carried out with respect to literature data. Eventually, the thermodynamic dataset allowed realizing theoretical calculations concerning the berthierine to chlorite transition. The latter showed that, from a thermodynamic viewpoint, the main factor controlling this transition is probably the composition of the berthierine and chlorite minerals and the nature of the secondary minerals rather than temperature. © 2014 Springer-Verlag Berlin Heidelberg.

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