Florence Bart

Cement-Based Materials for Nuclear Waste Storage

Part I: Methods of Production of Cement-Waste Forms.- A Summary of IAEA-Coordinated Research Project on Cementitious Materials for Radioactive Waste Management.- R&D on Cementation of Pulp with Complex Physical and Chemical Composition Stored in Tanksat the Mining Chemical Combine.- Cementation in High Energy Mixer of ILW Surrogate Slurry: Demonstration of the Process at Semi-Industrial Scale.- Part II: Physico-Chemical Processes Occurring in Cement-Waste Forms at Early Age.- Hydration of Blended Cements.- Application of a Sub-Lattice Model to Predictions of Cement Hydrate Chemistry.-Characterization and Solubility Determination of the Solid-Solution Between AFm-I2 and AFm-SO4.- Part III:Influence of External and Internal Factors on Long-Term Properties of Cement-Waste Package and Cement Barriers.- Coupling Between Leaching and Mechanical Behavior of Concrete.- Coupled Mechanical and Chemo-Transport Model for the Simulation of Cementitious Materials Subjected to External Sulfate Attack.- Micro- and Macroscopic Investigations of Actinide Binding in Cementitious Materials.- A New Radionuclide Sorption Database for Benchmark Cement Accounting for Geochemical Evolution of Cement.- On the Determination of the Diffusion Coefficient of Ionic Species Through Porous Materials.-Moisture Transport Properties of Cement-Based Materials for Engineered Barriers in Radioactive Waste Disposal.- Simulation of Gas Hydrogen Diffusion through Partially Water-Saturated Mono-Modal Materials.- Microbial Catalysis of Redox Reactions in Concrete Cells of Nuclear Waste Repositories: A Review and Introduction.- Leaching of Nuclear Waste Glass in Cement Pore Water: Effect of Calcium in Solution.- Emerging and Alternative Cementitious Systems.- Alternative Binders to Ordinary Portland Cement for Radwaste Solidification and Stabilization.- Leaching of a simulated ZnCl2-Rich Radwaste Stabilized with Calcium Sulfoaluminate Cement: Experimental Investigation and First Attempt of Modelling.- Conditioning Highly Concentrated Borate Solutions with Calcium Sulfoaluminate Cement.- The Effect of Supplementary Pulverized Fuel Ash on Calcium Aluminate Phosphate Cement for Intermediate-Level Waste Encapsulation.- Rheological Behavior of Alkali-Activated Metakaolin During Geopolymerization.- Prediction of Long-Term Chemical Evolution of a Low-pH Cement Designed for Underground Radioactive Waste Repositories.-Round Robin Test for Define an Accurate Protocol to Measure the Pore Fluid pH of low-pH Cementitious Materials.

Reactivity of NH4H2PO4 toward LaCl3 in LiCl-KCl melt flux. Step by step formation of monazite-like LaPO4.

The synthesis of lanthanum phosphates in molten LiCl-KCL eutectic was chosen to address the preliminary treatment of chlorinated wastes containing fission products that are already present in a Li/Cl eutectic. The obtained monazite compound shows interesting properties to be considered as a good candidate to trap lanthanum for a long-time. The synthesis route based on LaCl(3) reaction with NH(4)H(2)PO(4) in a stoichiometric amount is a key point to obtain monazite as a pure phase. Hence, the salt composition is not modified during the synthesis reaction. The chemical reactivity of ammonium dihydrogenphosphate (NH(4)H(2)PO(4), hereafter abbreviated ADP) toward lanthanum chloride (LaCl(3)) in molten LiCl-KCl eutectic is probed by NMR spectroscopy to follow the formation of LaPO(4). Formally, a direct transformation of the two aforementioned precursors into LaPO(4), NH(4)Cl and HCl can be discarded on the basis of the low thermal stability of ADP. To shed some light on the formation of LaPO(4), in situ and ex situ NMR experiments were carried out on LiCl-KCl/LaCl(3)/ADP, as well as LiCl-KCl/ADP, KCl/ADP, and LiCl/ADP mixtures. First, the reactivity of the precursors in contact with the eutectic was studied from room temperature to 600 degrees C by means of (31)P, (35)Cl, and (139)La high temperature NMR. Second, ex situ room temperature magic angle spinning (MAS) and RadioFrequency driven recoupling (RFDR) (31)P solid-state NMR experiments were carried out on solid samples prepared in different conditions (i.e., temperature and atmosphere) and quenched at room temperature to identify frozen intermediate species in their metastable state. On the basis of this approach, we propose a model for the LaPO(4) formation based on a multistep mechanism which highlights the strong reactivity of ADP toward the alkaline salts but without final change in the composition of the solvent.

Modelling and quantification of intergrowth in γ-MnO2 by laboratory pair distribution function analysis

γ-MnO2 is a material formed by random intergrowth of two phases, β-MnO2 and R-MnO2. It is demonstrated here on seven γ-MnO2 samples that pair distribution function analysis using a conventional X-ray diffraction setup (Bragg–Brentano geometry with a molybdenum anode) allows the quantification of this intergrowth simply via a simulation of the actual material by a mixture of β-MnO2 and R-MnO2 phases. Although this method does not take into account specifically the relaxed distances in the vicinity of the intergrowth zone, it is found to be very robust, accurate and in full agreement with the widely used quantification based on the empirical approach of Chabre & Pannetier [Prog. Solid State Chem. (1995), 23, 1–130].