Mineralogical and isotopic record of biotic and abiotic diagenesis of the Callovian-Oxfordian clayey formation of Bure (France)

International audienceThe Callovian-Oxfordian (COx) clayey unit is being studied in the Eastern part of the Paris Basin at depths between 400 and 500 m depth to assess of its suitability for nuclear waste disposal. The present study combines new mineralogical and isotopic data to describe the sedimentary history of the COx unit. Petrologic study provided evidence of the following diagenetic mineral sequence: (1) framboidal pyrite and micritic calcite, (2) iron-rich euhedral carbonates (ankerite, sideroplesite) and glauconite (3) limpid calcite and dolomite and celestite infilling residual porosity in bioclasts and cracks, (4) chalcedony, (5) quartz/calcite. Pyrite in bioturbations shows a wide range of δ34S (−38‰ to +34.5‰), providing evidence of bacterial sulphate reduction processes in changing sedimentation conditions. The most negative values (−38‰ to −22‰), measured in the lower part of the COx unit indicate precipitation of pyrite in a marine environment with a continuous sulphate supply. The most positive pyrite δ34S values (−14‰ up to +34.5‰) in the upper part of the COx unit indicate pyrite precipitation in a closed system. Celestite δ34S values reflect the last evolutionary stage of the system when bacterial activity ended; however its deposition cannot be possible without sulphate supply due to carbonate bioclast dissolution. The 87Sr/86Sr ratio of celestite (0.706872-0.707040) is consistent with deposition from Jurassic marine-derived waters. Carbon and oxygen isotopic compositions of bulk calcite and dolomite are consistent with marine carbonates. Siderite, only present in the maximum clay zone, has chemical composition and δ18O consistent with a marine environment. Its δ13C is however lower than those of marine carbonates, suggesting a contribution of 13C-depleted carbon from degradation of organic matter. δ18O values of diagenetic chalcedony range between +27‰ and +31‰, suggesting precipitation from marine-derived pore waters. Late calcite crosscutting a vein filled with chalcedony and celestite, and late euhedral quartz in a limestone from the top of the formation have lower δ18O values (not, vert, similar+19‰), suggesting that they precipitated from meteoric fluids, isotopically close to present-day pore waters of the formation. Finally, the study illustrates the transition from very active, biotic diagenesis to abiotic diagenesis. This transition appears to be driven by compaction of the sediment, which inhibited movement of bacterial cells by reduction of porosity and pore sizes, rather than a lack of inorganic carbon or sulphates

Short communication : the dissolution of UK simulant vitrified high-level-waste in groundwater solutions

Dissolution of a simulant UK nuclear waste glass containing Mg, Ca and Zn was investigated over 35 d at 50 °C in water and simulant groundwater solutions. The dissolution rates were influenced subtly by the groundwater composition, following the trend, from least to most durable: clay > water > granite ≈ saline. Solutions were rapidly silica saturated but boron dissolution rates continued to increase. This is hypothesised to be due to the formation of secondary Mg-silicate precipitates, preventing the formation of a passivating silica gel layer and allowing glass dissolution to proceed at close to the maximum rate

Modelling the porewater chemistry of the Callovian–Oxfordian formation at a regional scale

International audienceIn ANDRA's studies to characterize the Callovian-Oxfordian formation, porewater chemistry is a key topic. Indeed, chemistry determines the durability of the repository materials (bentonite, concrete, metals, nuclear glass) and the speciation (and thus the mobility) of radionuclides. The method developed in the frame of the THERMOAR project enables the acquisition of a complete set of data from core samples to model the porewater chemistry. The method requires a detailed mineralogical study, a model of free-water/bound-water distribution, leaching experiments, adsorbed ion measurements, ion-exchange constant acquisition, and CO2 partial-pressure measurements. These experiments and measurements were done on samples from the site of the Meuse/Haute-Marne laboratory and from ANDRA's regional boreholes. The regional stability of a great number of parameters can be observed, except for a decrease of the Na and Cl concentration following a NE-SW axis passing through the laboratory. The water/rock equilibrium model makes it possible to calculate the chemical composition of interstitial waters of the formation

La documentation sur les produits pharmaceutiques par voie des nouvelles technologies de l'information et de la docmentation

Comment peut-on, grâce aux outils des Nouvelles Technologies de l'Information et de la Communication, favoriser l'accès à l'information sur la documentation des produits pharmaceutiques aux professionnels de santé, et/ou aux patients, en conservant la maîtrise et la sécurité de la médication et de l'automédication dans le cadre du bon usage du médicament ? Les outils sont conçus par des organismes publiques et des sociétés privées, parmi lesquelles figurent les grossistes répartiteurs, pour être mis à la disposition des pharmaciens dans le but d'améliorer la qualité du service auprès des patients. Les banques de données réalisées à l'aide de cette technologie sont commercialisées en France et dans le monde, elles sont un maillon de la chaîne de la connaissance, qui permet d'uniformiser le savoir dans le domaine de la santé, quelque soit le lieu et l'établissement.CHATENAY M.-PARIS 11-BU Pharma. (920192101) / SudocSudocFranceF

Experimental Design for in situ Characterization of the Callovo-Oxfordian Pore Water Composition at 85°C

AbstractWhen emplaced into deep geological disposal cells, the high-level radioactive waste packages will induce a transitory temperature increase in the surrounding geological environment. High temperatures will have an influence on the composition of water that will flow into the cells and come in contact with the disposal materials. An in situ experiment which aims at characterizing the Callovo- Oxfordian pore water at 85°C has been running since 2012. This paper presents the design of the experiment and the predictive thermo-hydro-mechanical (THM) modeling results