Experimental Determination of Thermodynamical Quantities in Oxide Mixtures and Glasses
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): Pierre Benigni , Jacques Rogez , Sophie Schuller An overview of the experimental methods for the determination of thermodynamic functions in oxides systems is presented with a focus on two techniques: the solution calorimetry, which is applied in our laboratory both at room and at high temperature on oxide glasses and the Knudsen Effusion Mass Spectrometry (KEMS) which is under development in our team for activity measurement at high temperature. Emphasis is put on the description of the experimental setups and the measurement procedures. ...
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
Spectroscopic Investigation and Crystallization Study of Rare Earth Metaborate Glasses
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): H. Trégouët , D. Caurant , O. Majérus , Th. Charpentier , L. Cormier , D. Pytalev Besides their interesting optical properties, Rare Earths (RE) can be found abundantly as fission products at the end of the nuclear fuel cycle. After reprocessing, they are stored by dissolution in a borosilicate glassy matrix. RE are also used to simulate actinides when studying nuclear waste immobilization. It is very important to understand the environment of RE in such complex glasses. Moreover, composition changes can strongly affect RE solubility...
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
Redox Control of Nuclear Glass
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): Olivier Pinet , Isabelle Hugon , Sylvain Mure Vitrification is one of the recommended immobilization routes for nuclear waste, and is currently implemented on an industrial scale in several countries, notably for high-level waste. To optimize and extend the scope of nuclear waste vitrification, research is being conducted to specify suitable glass formulations and develop more effective processes. Vitrified nuclear waste often contains several multivalent species whose oxidation state can impact the properties of the melt and of the final ...
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
Conversion of Nuclear Waste into Nuclear Waste Glass: Experimental Investigation and Mathematical Modeling
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): Pavel Hrma The melter feed, slurry, or calcine charged on the top of a pool of molten glass forms a floating layer of reacting material called the cold cap. Between the cold-cap top, which is covered with boiling slurry, and its bottom, where bubbles separate it from molten glass, the temperature changes by up to 1000K. The processes that occur over this temperature interval within the cold cap include liberation of gases, conduction and consumption of heat, dissolution of quartz particles, formation and dissolution of intermediate crystalli...
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
In Situ ESEM Experiment Applied to the Description of Chemical Processes during Glass Elaboration
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): R. Podor , S. Schuller , J. Ravaux , A. Monteiro , H. Boucetta , O. Delattre , E. Nicoleau , E. Régnier The HT-ESEM design and image acquisition conditions to perform in situ experiments are fully described. Two examples of applications in the nuclear glass field are reported. (Source: Procedia Materials Science)
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
Electrochemical Behavior of Glass Melts: Application to Corrosion Processes
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): C. Petitjean , P.J. Panteix , C. Rapin , M. Vilasi , R. Podor Molten silicate glasses are complex media in which ionic species can be easily dissolved. That typically concerns the metallic cations or oxoanions. The as-described liquids have therefore the properties of electroactive solutions in which the ions displacements allow the electrical conduction. As a consequence, the use of electrochemical techniques adapted from those classically used in aqueous media allows the characterization of specific physico-chemical properties of the s...
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
Phase Separation and Crystallisation in UK HLW Vitrified Products
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): Rick Short Given the complex composition of the UK High Level nuclear Waste (HLW) streams and the single base glass frit composition used to vitrify these streams, some phase separation and/or crystallisation in the vitrified product is almost inevitable. Depending upon the specific composition(s), the presence of phase separated/crystalline material can be deleterious, inconsequential or even advantageous to the quality of the product. It can also determine (or be determined by) the operational plant parameters for HLW glass manufacture. Th...
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
Towards Increased Waste Loading in High Level Waste Glasses: Developing a Better Understanding of Crystallization Behavior
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): James C. Marra , Dong-Sang Kim A number of waste components in US defense high level radioactive wastes (HLW) have proven challenging for current Joule heated ceramic melter (JCHM) operations and have limited the ability to increase waste loadings beyond already realized levels. Many of these “troublesome” waste species cause crystallization in the glass melt that can negatively impact product quality or have a deleterious effect on melter processing. Recent efforts at US Department of Energy laboratories have focused on understanding c...
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
A Thermodynamic Approach to Predict the Metallic and Oxide Phases Precipitations in Nuclear Waste Glass Melts
The objective of this work is to calculate thermodynamic properties for complex fission product systems in order to predict the precipitation of platinoids or molybdate phases. This thermodynamic database is being developed on the Mo-Pd-Rh-Ru-Se-Te-O complex system. This flexible tool enables to predict phase diagrams, composition and relative stability of the metallic or oxide precipitated phases as a function of both temperature and oxygen potential in the glass melt. (Source: Procedia Materials Science)
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
Simulations of Phase-field Models for Crystal Growth and Phase Separation
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): Alain Cartalade , Amina Younsi , Élise Régnier , Sophie Schuller Phase-field theory is a thermodynamically consistent approach for modeling and simulating phenomena that exhibit complex structures such as those encountered in fluid flows and materials science. In this work, the main features of the theory will be reviewed, i.e. mathematical models which arise from the minimization of a thermodynamic potential such as the Helmholtz free energy describing the phenomenology of bulk phases and their interactions. An order parameter is also ...
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
Nucleation in Glasses – New Experimental Findings and Recent Theories
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): Laurent Cormier Nucleation is the initial process and the key operation to control and predict devitrification in glasses. The classical nucleation theory is widely used to describe qualitatively this phenomenom though it is well known that considerable discrepancies exist with experimental results. Recent theories have been developed (Generalized Gibbs Approach, two-steps model) to overcome the approximations in the classical model. They are based on experimental observations, considering explicitly non-classical pathways driving to the cri...
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
Structural Behavior of Tc and I Ions in Nuclear Waste Glass
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): Isabelle S. Muller , David A. McKeown , Ian L. Pegg Technetium-99 (Tc) and iodine-129 (I) are two long-lived fission products of high volatility, which makes their study in glass structure challenging. Both technetium and iodine have broad ranging multivalent chemistry and complex reactivity dependent on redox conditions; technetium and iodine redox may vary from Tc0 to Tc7+ and from I- to I7+. Relatively few studies have been done on their speciation in glass, in part because of their low retention at the temperatures required for glass m...
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
Building Monte Carlo Models of Glasses Using Neutron and/or X-ray Diffraction Data
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): D.T. Bowron Neutron and X-ray diffraction are key techniques that are used to investigate the atomic and nanometric mesoscale structure of glasses and amorphous materials. These experimental methods probe the nuclear (neutron) or atomic (X-ray) pair correlation func- tions between atoms. For a glass containing N atom types, the information content of the data is low, considering that the data are a weighted sum of N(N+1)/2 partial pair correlation terms. This complexity can often make direct interpretation of results difficult or impossible....
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
Application of the Empirical Potential Structure Refinement Technique to a Borosilicate Glass of Nuclear Interest
We present how the Empirical Potential Structure Refinement (EPSR) technique developed by A. Soper and co-workers can be applied to borosilicate glasses of nuclear interest to build realistic atomistic models. In particular, we show how the atomistic configuration for a six-oxide glass is modified by the introduction of the empirical potential during the simulation. EPSR strengths and weaknesses are then brought out by comparing simulation results with experimental data. (Source: Procedia Materials Science)
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
The Structural Properties of Cations in Nuclear Glasses
Publication date: 2014 Source:Procedia Materials Science, Volume 7 Author(s): Georges Calas , Laurence Galoisy , Laurent Cormier , Guillaume Ferlat , Gérald Lelong The structure of nuclear glasses and of simplified surrogates has been investigated using complementary diffraction and spectroscopic methods, together with numerical modeling. The diversity of structural surroundings of cations in glasses is reviewed at various scales. Cations usually occur in smaller sites in glasses than in crystals, with unusual site geometries such as 5-coordination. These sites may correspond to different structural positions. Ne...
Source: Procedia Materials Science - December 19, 2014 Category: Materials Science Source Type: research
