Sophie SchullerAtomic Energy and Alternative Energies Commission | CEA · DE2D
Sophie Schuller
Phd, Eng, HDR
Simulation of radioactive waste vitrification
and Long term behavior of nuclear glasses
About
73
Publications
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Introduction
Sophie Schuller currently works at Atomic Energy and Alternative Energies Commission. Sophie is project manager in Enrichment, Decommissioning and waste research department
Additional affiliations
July 2016 - July 2020
Publications
Publications (73)
Depuis l’Antiquité, l’Homme a appris à contrôler les propriétés des verres. Cette maitrise passe par un savoir-faire ancestral, mais aussi plus récemment par la compréhension fine des mécanismes qui s’opèrent lors de la fabrication des verres industriels. La diffusion chimique est l’un des plus importants. Depuis peu, des méthodologies ont été déve...
Phase separation in sodium borosilicate glasses containing molybdenum oxide has been studied in a compositional range of interest for nuclear glasses. Two series of quaternary compositions (63.5SiO2-19.6Na2O-16.9B2O3)1-x(MoO3)x with 0 ≤ x ≤ 3 mol.% MoO3 have been synthesized and characterized, by a range of complementary experimental techniques bot...
Several chemical reactions take place during the vitrification of high-level nuclear waste. The integration of these chemical aspects in process numerical simulation tools is one of the key points in the approach of improving the prediction capabilities of numerical tools today. In this study, based on simultaneous differential scanning calorimetry...
In this review, we provide a perspective on the science and technology of vitrification of waste. First, we provide a background on the general classes of wastes for which vitrification is currently used for immobilization or is proposed, including nuclear and industrial hazardous wastes. Next, we summarize the issues surrounding solubility of wast...
The question of silicate glass chemical durability is at the heart of many industrial and environmental issues, with certain glasses, such as bioglasses, needing to transform rapidly, while others, like nuclear glasses, extremely slowly. Due to the wide diversity of the chemical composition for these types of materials and their metastability—no th...
A side effect of high level waste vitrification at 1100°C is the volatilization of radioactive cesium (Cs), recaptured further on in the process as a solid aerosol by a dust scrubber. Feedback from industry suggests that Cs combines with technetium (Tc) – simulated here by rhenium (Re), chosen for its similar behavior – to form volatile species. Th...
A fundamental approach was taken to understand the implications of increased nuclear waste loading in the search for new materials for long-term radioisotope encapsulation. This study focused on the formation and radiation tolerance of glass ceramics with selectively induced CaMoO4 as a form to trap the problematic fission product molybdenum. Sever...
The aim of this paper was to assess factors affecting primary and secondary phase separation in simplified calcium borosilicate glasses studied for nuclear waste applications. Several glasses with varying [MoO3] and [B2O3] were synthesised and exposed to Au‐irradiation to examine compositional effects on the glass structure and domain size of separ...
A fundamental approach was taken to understand the implications of increased nuclear waste loading in the search for new materials for long-term radioisotope encapsulation. This study focused on the formation...
A series of calcium borosilicate glasses with varying [B2O3], [MoO3], and [CaO] were prepared and subjected to 92 MeV Xe ions used to simulate the damage from long-term α-decay in nuclear waste glasses. Modifications to the solubility of molybdenum, the microstructure of separated phases, and the Si–O–B network topology were investigated following...
The link between multicomponent diffusion and crystal growth has been investigated in a sodium borosilicate glass of interest to the nuclear industry. The growth rate of cristobalite, the principal crystal formed in this system, was studied between 700 °C and 900 °C. The growth rate was found to be linear with time and had an activation energy of 6...
In order to increase the waste loading efficiency in nuclear waste glasses, alternate glass ceramic (GC) materials are sought that trap problematic molybdenum in a water-durable CaMoO4 phase within a borosilicate glass matrix. In order to test the radiation resistance of these candidate wasteforms, accelerated external radiation can be employed to...
Multicomponent chemical diffusion has been investigated in the SiO2-Na2O-B2O3 system for melts with an average composition (mol.%) of 68SiO2-18B2O3-14Na2O. Three diffusion couples were studied at 5 different temperatures between 700°C and 1100°C. The extended form of Fick's second law was used to fit the data, derive the diffusion matrix at each te...
Borosilicate glasses for nuclear waste applications are limited in waste loading by the precipitation of water-soluble molybdates. In order to increase storage efficiency, new compositions are sought out that trap molybdenum in a water-durable CaMoO₄ crystalline phase. Factors affecting CaMoO₄ combination and glass-in-glass phase separation in calc...
Borosilicate glasses for nuclear waste applications are limited in waste loading by the precipitation of water-soluble molybdates. In order to increase storage efficiency, new compositions are sought out that trap molybdenum in a water-durable CaMoO4 crystalline phase. Factors affecting CaMoO4 combination and glass-in-glass phase separation in calc...
Molybdenum solubility is a limiting factor to actinide loading in nuclear waste glasses, as it initiates the formation of water-soluble crystalline phases such as alkali molybdates. To increase waste loading efficiency, alternative glass ceramic structures are sought that prove resistant to internal radiation resulting from radioisotope decay. In t...
Calcination is an efficient process for volume reduction and stabilization of nuclear liquid wastes. It is often the first step of waste containment processes such as vitrification or grouting. The CEA (French Alternative Energies and Atomic Energy Commission) and AREVA have acquired a high-level experience in the field of calcination through more...
This work demonstrates the formulation of glass ceramics for nuclear waste storage that increases the incorporation rate of problematic molybdenum in a stable crystallite without affecting physiochemical properties. It further tests the durability of this material when subjected to β-irradiation proportional to 1000 years of radioisotope decay proj...
Radioactive waste vitrification has been carried out industrially in several countries for nearly 40 years. Research into the formulation and long term behavior of high and intermediate level waste glasses, mainly borosilicate compositions, is still continuing in order to (i) safely condition new types of wastes and (ii) design and demonstrate the...
Sodium borosilicate base glasses modeled on French nuclear waste materials were prepared to test the dependence of crystallization product quantity and distribution on cesium- and molybdenum-loading and glass cooling rate. Scanning electron microscopy shows the presence of micrometer-sized domains of Mo-rich crystalline precipitates. X-ray diffract...
Among the large number of matrixes explored as hosts for high-level nuclear wastes, conditioning of fission products and minor actinides into a homogeneous borosilicate glass is the most promising technique already implemented at the industrial scale. The advantage of this vitrification process is the volume reduction of the high level waste coming...
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.
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...
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 su...
Phase-field theory is a thermodynamically consistent approach for modeling and simulating phenomena that exhibit complex structures such as crystals that are encountered in glasses. The content of this presentation is separated into four sections. The first one will introduce the context and motivation of this work by reminding the conditions for w...
The aim of this work is to determine the impact of a thermal gradient on the crystallization kinetics of apatites (Ca2Nd8(PO4)(SiO4)5O2) and powellite (CaMoO4) in a borosilicate glass containing rare earth elements and molybdenum, typically incorporated in nuclear waste glasses. An automated SEM allows the acquisition of images over a large area of...
Highly-active liquid wastes arising from reprocessing of spent uranium oxide fuel are confined in a sodium borosilicate glass matrix in France and Japan. The complementarity of the scientific and methodological approaches developed in the two institutes, CEA, France and Nagoya University, Japan had allowed the cooperation program to mutually enrich...
Ruthenium, a fission product arising from the reprocessing of spent uranium oxide (UOX) fuel, crystallizes in the form of acicular RuO(2) particles in high-level waste containment glass matrices. These particles are responsible for significant modifications in the physicochemical behavior of the glass in the liquid state, and their formation mechan...
The influence of the temperature and quenching rate on the structure of a borosilicate glass was studied by high-resolution solid-state 11B, 23Na, 29Si nuclear magnetic resonance (NMR) and high-temperature Raman spectroscopy. Data were obtained for glass in the solid state after annealing and quenching at cooling rates covering four orders of magni...
In nuclear borosilicate glasses, when molybdenum is in too high concentration and when it combines with other elements such as alkali and alkaline-earth elements it may form crystalline molybdates, including sodium molybdate, Na2MoO4, during melt cooling. In a nuclear vitrification context, the origin of this phenomenon must be understood to contro...
In this work, the Eu3+5D0→7F0 transition is used as a structural probe to follow the Eu3+ environment modification in powellite CaMoO4 under irradiation or when its composition is varying. Six ceramics with compositions ranging from Ca0.99Eu0.01MoO4 to Ca0.76Sr0.1Na0.07 Eu0.01La0.02Nd0.02Pr0.02 MoO4 were synthesized and each composition has a speci...
ALUMINO-BOROSILICATE GLASS FOR THE CONFINEMENT OF RADIOACTIVE LIQUID
EFFLUENTS, AND METHOD FOR TREATING
Short and medium range order of silica and sodium silicate glasses have been investigated from a quantitative analysis of 29Si MAS NMR and 23Na, 17O MQMAS NMR spectra. The method described enables the extraction of the underlying 17O NMR parameter distributions of bridging oxygens (BOs) and non-bridging oxygens (NBOs), and yields site populations w...
In high level radioactive glasses, the low solubility platinoids (Pd, Ru, Rh) precipitate to form (Pd-Rh-Te, Ru-Rh, Ru) metallic particles and (RuO 2 , Rh 2 O 3 ) oxides during the vitrification process. The composition and microstructures of these phases can significantly modify the physico-chemical properties and the electrical or thermal conduct...
The waste management process of the French nuclear spent fuels is managed by a new vitrification conditioning step. High level radioactive borosilicate glasses are melted by induction in a cold crucible to accommodate a wide range of minor actinides and fission products. Among the fission products, platinoids precipitate in the form of (Pd-Te, Ru-R...
Les verres de confinement de produits de fission et actinides sont élaborés à l’échelle industrielle par un
procédé de vitrification à partir d’un précurseur vitreux et d’un composé complexe d’oxydes et nitrates issu
de la calcination des solutions de produits de fission et actinides isolées après traitement du combustible
usé. Au cours de l'élabor...
In the context of French nuclear waste vitrification, specific borosilicate glass waste forms are being developed to immobilize the large quantities (>6 mol%) of molybdenum and phosphorus (2 mol%) oxides produced by reprocessing uranium–molybdenum spent fuel. The presence of these elements at high concentrations induces liquid–liquid phase separati...
Calcium molybdate, CaMoO4 (powellite) is the main micro phase crystallizing during the cooling of molybdenum rich borosilicate glasses studied for the development of future containment matrices. The composition and the structure of the vitreous and the crystalline phases of such a glassceramic is determinant for the long-term behaviour understandin...
Double-resonance nuclear magnetic resonance (NMR) techniques are used in addition to single-resonance NMR experiments to probe the degree of mixing between network-forming cations Si and B, along with the modifier cations Cs þ and Na þ in two molybdenum-bearing model nuclear waste glasses. The double-resonance experiments involving 29 Si in natural...
The heat treatment conditions are a key factor in fabricating zirconolite ceramics and glass-ceramics following high-temperature melting. An oxide mixture melted at 1450°C and subsequently heat-treated at 1200°C yielded a glass-ceramic containing crystallized zirconolite–2M. The silica-enriched residual glass represented about 60-70 vol% of the tot...
Crystalline precipitates from molybdenum-containing nuclear waste glasses are complex, often containing multiple cations which confound routine structural techniques. A simplified mixed-alkali borosilicate model glass was found to have minor crystalline phases which could not be identified by x-ray diffraction. Multinuclear magnetic resonance (NMR)...
In borosilicate glasses, molybdenum combined with other elements such as alkali and alkaline-earth elements may form crystalline molybdates during melt cooling, among which sodium molybdate, Na(2)MoO(4), is water-soluble. The solubility limit of MoO(3) was found to be 2.5 mol% in a simplified SiO(2)-B(2)O(3)-Na(2)O-CaO nuclear glass at about 1300 d...
The incorporation of molybdenum is one of the major challenges in the nuclear glass formulation issues, since its relatively low incorporation rate could induce the crystallization of Mo-rich soluble phases during the cooling down of the glass. In the scope of the reprocessing of increased burn up rates of UO 2 spent fuels, a new glassy material wi...
95Mo magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy is surprisingly sensitive to the local environment of tetrahedral molybdate species. A series of compounds related to expected crystallization products in nuclear waste glasses are probed to calibrate their spectral characteristics. Glasses formed with fast and slow quenchi...
Phase separation and crystallisation processes may arise in molten glass when the MoO3 content exceeds its solubility limit. Molybdenum combined with other elements such as alkali and alkaline-earth may form crystalline molybdates, known as "yellow phases" in nuclear glasses. In order to establish the sequence of phase separation and crystallizatio...
Borosilicate glasses with high molybdenum, phosphorus, calcium and zirconium oxide concentrations are partially crystallized. Their final microstructure reveals the contribution of microphase separation and crystallization phenomena during cooling. Rapid quenching of melts between copper rollers and by air blowing was investigated at various meltin...
The invention concerns a method for making a glass frit for confining by vitrification a substance comprising at least one oxidizable or reducible chemical species, as well as a method for confining by vitrification said substance. The method for making a glass frit includes a step of incorporating in a raw glass frit an oxidoreduction couple where...
Glass was selected to immobilize nuclear waste because the capacity of the glass network to incorporate a very wide range of chemical species. Until now, efforts to optimize glass matrices have focused on their chemical composition or melting temperature. Vitrification studies in recent years have shown that the redox state of the glass, i.e. the o...
Reprocessing of spent UMo metal fuel has produced fission product solutions in nitric acid. The vitrification of these Mo-rich highly active solutions is currently being studied. The high Mo concentration combined with notable amounts of phosphorus has led to the formulation of a glass-ceramic wasteform characterized by MoP -Zn enriched nodules uni...
Structural and bonding characteristics of simplified (Pd, Te) precipitates have been determined in a simulated nuclear French glass using extended x-ray absorption fine structure (EXAFS) and x-ray diffraction. In this sample, these precipitates have a homogeneous composition, with about 10 wt.% Te. They retain a face-centered cubic structure as in...
Projects
Projects (6)
Feasbility Study - To extend the existing thermodynamic bases (for corium and nuclear glasses) to evaluate the interfacial stresses using a recently developed thermodynamic approach based on the homogeneous phase representation offered by a CALPHAD base.
This is the first step towards a qualitative leap in the numerical simulation of the associated segregation transients.
To evaluate the potential of a recently proposed thermodynamic modeling approach of interfacial stresses for metallic systems based on the homogeneous phase representation offered by a CALPHAD base. This feasibility study therefore focuses on the extension of existing thermodynamic bases (for corium and nuclear glasses) to the evaluation of interfacial stresses. This is a prerequisite for a qualitative leap in the numerical simulation of the associated segregation transients.
To work with electron microscopes at high temperatures.
To develop image processing to rationalize the datasets
To develop original methods to observe materials at high temperature in conditions that are as close as possible to their operating conditions