Formulation of Alternative Cement Matrix for Solidification/stabilization of Nuclear Wastes

International audienc

Effet de la variation d’échelle sur la résistance en compression des mortiers

National audienc

Etude de la décomposition thermique du peroxyde d’uranyle : Influence du traitement thermique sur les caractéristiques physico-chimiques de UO3

National audienc

Formulation d’un éco-matériau à base de ciment phospho-magnésien : effet de la présence de fines

National audienc

Development of a stoichiometric magnesium potassium phosphate cement (MKPC) for the immobilization of powdered minerals

International audienceOrdinary Portland Cement (OPC)-based materials are not systematically adapted for immobilizing industrial hazardous waste, e.g. for aluminium powder or plutonium waste sludge. In such case, Magnesium Potassium Phosphate Cements (MKPC) represent an interesting alternative. The originality of this research is to develop a formulation of a MKPC paste for hazardous waste immobilization, which incorporates a maximum amount of such waste, preferably in powdered form. To this purpose, a stoichiometric MKPC paste is selected, and its properties are improved by powdered waste addition. Firstly, the physico-chemical mechanisms generating expansion in stoichiometric MKPC paste are analyzed. Swelling is attributed to a pH gradient in the paste, due to the progressive sedimentation of MgO particles in the fresh mix. Secondly, over-stoichiometric MgO is replaced by varying amounts of minerals simulating the waste, of different mineralogy and granulometry, in order to achieve sufficient workability and no swelling. An optimal formulation is proposed, which incorporates powdered fly ash at a fine-to-cement mass ratio (F/C) of 1. Its mechanical performance and endogenous dimensional changes are comparable to typical over-stoichiometric pastes, and they stabilize between 7 and 28 days

Characteristics of chemical bonding of pentavalent uranium in La-doped UO2

The effect of La doping on the electronic structure of U in UO2 was studied using an advanced technique, namely, X-ray absorption spectroscopy (XAS) in the high-energy-resolution fluorescence-detection (HERFD) mode, at the U 3d3/2 (M4) edge. Thanks to a significant reduction of the core–hole lifetime broadening and distinct chemical shifts of the HERFD-XAS lines, the U(V) formation as a result of La doping was identified. The isolated contribution of U(V) in the M4 HERFD-XAS spectrum reveals the so-called charge-transfer satellites due to the U 5f–O 2p hybridization. The analysis of the experimental data within the framework of the Anderson impurity model (AIM) indicates a significant change in the characteristics and degree of covalency for the chemical bonding in the U(V) subsystem of UO2 as compared to undoped UO2, which is a Mott–Hubbard system. The results are also supported by AIM calculations of X-ray photoelectron and optical absorption data.JRC.G.I.5-Advanced Nuclear Knowledg

Precipitation of Mixed ZirconiumIV CeriumIV Molybdate in Nitric Acid.

International audienc

Formulation of alternative cement matrix for solidification/stabilisation of nuclear waste

2ème meilleure présentation de l’EPIC ChallengeInternational audienc

Single-Crystal to Single-Crystal Transformation in the Thorium-TEDGA-Oxalate-Nitrate System Description and Comparison of the Main Structural Features

International audienc