Multi-Parametric Devices with Innovative Solid Electrodes for Long-Term Monitoring of pH and Redox-Potential of the actual pore water of COx formation in a future Nuclear Waste Repository

International audienceWe present innovative electrochemical probes for the monitoring of pH and redox potential in pore water in near-field rocks of a future deep geological radioactive waste repository at 500 m depth within the clayey Callovian-Oxfordian (COx) formation. The conceived experimental setup assembles two multi-parameter probes (MPPs), used together throughout two series of several months duration measurements in situ into the underground research laboratory of Andra at Bure, France. The two MPPs, connected in series, were up-flow fed with actual pore water of COx formation during several with a very low flowrate. Each MPP is composed of different individual probes containing the following: two monocrystalline antimony electrodes for pH sensing; eight AgCl/Ag-based reference or Cl − selective electrodes; four Ag 2 S/Ag-based reference or S 2− selective electrodes; eight platinum electrodes; two gold electrodes; two glassy-carbon electrodes; two ruthenium and two inox 316 electrodes, for redox potential measurements. The Open Circuit Potential (OCP) measurements of the developed sensors under different conditions and in quasi-actual conditions were compared to conventional reference electrode and pH electrodes in terms of performance, reliability and robustness and allowed to create calibration curves. Conductivity measurements, carried out along MPPs, will not be presented here. Overall, the conceived bundle of electrodes as designed works reliably during a timescale that is promising for monitoring the COx formation during its envisaged use for hosting a nuclear waste repository

Substantially improved pharmacokinetics of recombinant human butyrylcholinesterase by fusion to human serum albumin

<p>Abstract</p> <p>Background</p> <p>Human butyrylcholinesterase (huBChE) has been shown to be an effective antidote against multiple LD₅₀of organophosphorus compounds. A prerequisite for such use of huBChE is a prolonged circulatory half-life. This study was undertaken to produce recombinant huBChE fused to human serum albumin (hSA) and characterize the fusion protein.</p> <p>Results</p> <p>Secretion level of the fusion protein produced <it>in vitro </it>in BHK cells was ~30 mg/liter. Transgenic mice and goats generated with the fusion constructs expressed in their milk a bioactive protein at concentrations of 0.04–1.1 g/liter. BChE activity gel staining and a size exclusion chromatography (SEC)-HPLC revealed that the fusion protein consisted of predominant dimers and some monomers. The protein was confirmed to have expected molecular mass of ~150 kDa by Western blot. The purified fusion protein produced <it>in vitro </it>was injected intravenously into juvenile pigs for pharmacokinetic study. Analysis of a series of blood samples using the Ellman assay revealed a substantial enhancement of the plasma half-life of the fusion protein (~32 h) when compared with a transgenically produced huBChE preparation containing >70% tetramer (~3 h). <it>In vitro </it>nerve agent binding and inhibition experiments indicated that the fusion protein in the milk of transgenic mice had similar inhibition characteristics compared to human plasma BChE against the nerve agents tested.</p> <p>Conclusion</p> <p>Both the pharmacokinetic study and the <it>in vitro </it>nerve agent binding and inhibition assay suggested that a fusion protein retaining both properties of huBChE and hSA is produced <it>in vitro </it>and <it>in vivo</it>. The production of the fusion protein in the milk of transgenic goats provided further evidence that sufficient quantities of BChE/hSA can be produced to serve as a cost-effective and reliable source of BChE for prophylaxis and post-exposure treatment.</p

From experimental variability to the sorption related retention parameters necessary for performance assessment models for nuclear waste disposal systems: The example of Pb adsorption on clay minerals

International audienceSurface complexation models (SCMs) have been developed in the last decades to describe metal ion sorption to clay minerals and especially to montmorillonite. In principle, these models can provide relevant information about sorption of radionuclides to be used in performance assessment (PA) of radioactive waste disposal systems. However, these SCMs have been developed in parallel with the acquisition of distinct adsorption datasets, which are not always consistent with each other. The objective of this study was to compare new experimental adsorption results with literature data to understand these discrepancies and to propose a SCM approach that could be amenable to determine sorption related retention parameters necessary for PA calculations. This study focused on lead (Pb) adsorption on montmorillonite, illite and in a natural clay (Callovo Oxfordian) as case studies of a strongly sorbing radionuclide that undergoes a range of retention processes depending on the chemical conditions. The experiments showed that many experimental artifacts lead to misinterpretations of the processes underlying the measured retention values. These include Pb precipitation in the presence of carbonate in solution. The determination of SCM parameters to provide sorption related information for PA of clay minerals should rely on preliminary building of an adequate adsorption database, where adequate means that all experimental conditions are met to quantify surface complexation only

Weathering of an argillaceous rock in the presence of atmospheric conditions: A flow-through experiment and modelling study

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Natural gas extraction and artificial gas injection experiments in Opalinus Clay, Mont Terri rock laboratory (Switzerland)

International audienceTwo experiments have been installed at Mont Terri in 2004 and 2009 that allowed gas circulation within a borehole at a pressure between 1 and 2 bar. These experiments made it possible to observe the natural gases that were initially dissolved in pore-water degassing into the borehole and to monitor their content evolution in the borehole over several years. They also allowed for inert (He, Ne) and reactive (H2) gases to be injected into the borehole with the aim either to determine their diffusion properties into the rock pore-water or to evaluate their removal reaction kinetics. The natural gases identified were CO2, light alkanes, He, and more importantly N2. The natural concentration of four gases in Opalinus Clay pore-water was evaluated at the experiment location: N2 2.2 mmol/L ± 25%, CH4 0.30 mmol/L ± 25%, C2H6 0.023 mmol/L ± 25%, C3H8 0.012 mmol/L ± 25%. Retention properties of methane, ethane, and propane were estimated. Ne injection tests helped to characterize rock diffusion properties regarding the dissolved inert gases. These experimental results are highly relevant towards evaluating how the fluid composition could possibly evolve in the drifts of a radioactive waste disposal facility