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Ojovan MI, Louzguine-Luzgin DV. The Minima of Viscosities. Materials (Basel) 2024; 17:1822. [PMID: 38673178 PMCID: PMC11051500 DOI: 10.3390/ma17081822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 04/04/2024] [Accepted: 04/10/2024] [Indexed: 04/28/2024]
Abstract
The Trachenko-Brazhkin equation of the minimal possible viscosity is analysed, emphasising its validity by the account of multibody interactions between flowing species through some effective masses replacing their true (bare) masses. Pressure affects the effective masses, decreasing them and shifting the minimal viscosity and the temperature at which it is attained to higher values. The analysis shows that effective masses in the Trachenko-Brazhkin equation are typically lighter compared bare masses; e.g., for tin (Sn) the effective mass is m = 0.21mSn, whereas for supercritical argon (Ar), it changes from m = 0.165mAr to m = 0.129mAr at the pressures of 20 and 100 MPa, respectively.
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Affiliation(s)
- Michael I. Ojovan
- Department of Materials, Imperial College London, South Kensington Campus, Exhibition Road, London SW7 2AZ, UK
- Department of Materials Science and Engineering, The University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Aoba-Ku, Sendai 980-8577, Japan;
| | - Dmitri V. Louzguine-Luzgin
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Aoba-Ku, Sendai 980-8577, Japan;
- MathAM-OIL, National Institute of Advanced Industrial Science and Technology (AIST), Sendai 980-8577, Japan
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Tournier RF, Ojovan MI. NiTi 2, a New Liquid Glass. Materials (Basel) 2023; 16:6681. [PMID: 37895662 PMCID: PMC10608734 DOI: 10.3390/ma16206681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 09/25/2023] [Accepted: 10/11/2023] [Indexed: 10/29/2023]
Abstract
Many endothermic liquid-liquid transitions, occurring at a temperature Tn+ above the melting temperature Tm, are related to previous exothermic transitions, occurring at a temperature Tx after glass formation below Tg, with or without attached crystallization and predicted by the nonclassical homogenous nucleation equation. A new thermodynamic phase composed of broken bonds (configurons), driven by percolation thresholds, varying from ~0.145 to Δε, is formed at Tx, with a constant enthalpy up to Tn+. The liquid fraction Δε is a liquid glass up to Tn+. The solid phase contains glass and crystals. Molecular dynamics simulations are used to induce, in NiTi2, a reversible first-order transition by varying the temperature between 300 and 1000 K under a pressure of 1000 GPa. Cooling to 300 K, without applied pressure, shows the liquid glass presence with Δε = 0.22335 as memory effect and Tn+ = 2120 K for Tm = 1257 K.
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Affiliation(s)
- Robert F. Tournier
- UPR 3228 Centre National de la Recherche Scientifique, Laboratoire National des Champs Magnétiques Intenses, European Magnetic Field Laboratory, Institut National des Sciences Appliquées de Toulouse, Université Grenoble Alpes, F-31400 Toulouse, France;
| | - Michael I. Ojovan
- Department of Materials, Imperial College London, London SW7 2AZ, UK
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Ojovan MI. The Flow of Glasses and Glass-Liquid Transition under Electron Irradiation. Int J Mol Sci 2023; 24:12120. [PMID: 37569496 PMCID: PMC10418639 DOI: 10.3390/ijms241512120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 07/22/2023] [Accepted: 07/26/2023] [Indexed: 08/13/2023] Open
Abstract
Recent discovery and investigation of the flow of glasses under the electron beams of transmission electron microscopes raised the question of eventual occurrence of such type effects in the vitrified highly radioactive nuclear waste (HLW). In connection to this, we analyse here the flow of glasses and glass-liquid transition in conditions of continuous electron irradiation such as under the e-beam of transmission electron microscopes (TEM) utilising the configuron (broken chemical bond) concept and configuron percolation theory (CPT) methods. It is shown that in such conditions, the fluidity of glasses always increases with a substantial decrease in activation energy of flow at low temperatures and that the main parameter that controls this behaviour is the dose rate of absorbed radiation in the glass. It is revealed that at high dose rates, the temperature of glass-liquid transition sharply drops, and the glass is fully fluidised. Numerical estimations show that the dose rates of TEM e-beams where the silicate glasses were fluidised are many orders of magnitude higher compared to the dose rates characteristic for currently vitrified HLW.
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Affiliation(s)
- Michael I. Ojovan
- Department of Materials, Imperial College London, London SW7 2AZ, UK;
- Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, UK
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Yudintsev SV, Nickolsky MS, Ojovan MI, Stefanovsky OI, Nikonov BS, Ulanova AS. Zirconolite Polytypes and Murataite Polysomes in Matrices for the REE-Actinide Fraction of HLW. Materials (Basel) 2022; 15:6091. [PMID: 36079472 PMCID: PMC9458050 DOI: 10.3390/ma15176091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 08/16/2022] [Accepted: 08/29/2022] [Indexed: 06/15/2023]
Abstract
Electron backscatter diffraction (EBSD) has been used for more than 30 years for analyzing the structure of minerals and artificial substances. In recent times, EBSD has been widely applied for investigation of irradiated nuclear fuel and matrices for the immobilization of radioactive waste. The combination of EBSD and scanning electron microscopy (SEM/EDS) methods allows researchers to obtain simultaneously data on a specimen's local composition and structure. The article discusses the abilities of SEM/EDS and EBSD techniques to identify zirconolite polytype modifications and members of the polysomatic murataite-pyrochlore series in polyphase ceramic matrices, with simulations of Pu (Th) and the REE-actinide fraction (Nd) of high-level radioactive waste.
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Affiliation(s)
- Sergey V. Yudintsev
- Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences (IGEM RAS), 119017 Moscow, Russia
| | - Maximilian S. Nickolsky
- Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences (IGEM RAS), 119017 Moscow, Russia
| | - Michael I. Ojovan
- Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences (IGEM RAS), 119017 Moscow, Russia
| | - Olga I. Stefanovsky
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences (IPCE RAS), 119071 Moscow, Russia
| | - Boris S. Nikonov
- Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences (IGEM RAS), 119017 Moscow, Russia
| | - Amina S. Ulanova
- Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences (IGEM RAS), 119017 Moscow, Russia
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Ojovan MI, Louzguine-Luzgin DV. On Structural Rearrangements during the Vitrification of Molten Copper. Materials (Basel) 2022; 15:ma15041313. [PMID: 35207852 PMCID: PMC8877703 DOI: 10.3390/ma15041313] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Revised: 01/30/2022] [Accepted: 02/07/2022] [Indexed: 12/10/2022]
Abstract
We utilise displacement analysis of Cu-atoms between the chemical bond-centred Voronoi polyhedrons to reveal structural changes at the glass transition. We confirm that the disordered congruent bond lattice of Cu loses its rigidity above the glass transition temperature (Tg) in line with Kantor–Webman theorem due to percolation via configurons (broken Cu-Cu chemical bonds). We reveal that the amorphous Cu has the Tg = 794 ± 10 K at the cooling rate q = 1 × 1013 K/s and that the determination of Tg based on analysis of first sharp diffraction minimum (FDSM) is sharper compared with classical Wendt–Abraham empirical criterion.
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Affiliation(s)
- Michael I. Ojovan
- Department of Materials, South Kensington Campus, Imperial College London, Exhibition Road, London SW7 2AZ, UK
- Department of Radiochemistry, Faculty of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1, Bd. 3, 119991 Moscow, Russia
- Correspondence:
| | - Dmitri V. Louzguine-Luzgin
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan;
- MathAM-OIL, National Institute of Advanced Industrial Science and Technology (AIST), Sendai 980-8577, Japan
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Kovalenko ІО, Panasiuk МI, Skorbun АD, Sosonna NV, Ojovan MI, Shevchenko OL, Оnyshchenko ІP. Correlation between chemical composition and 90Sr concentrations in groundwater of the Chornobyl NPP industrial site. J Environ Radioact 2021; 240:106756. [PMID: 34649194 DOI: 10.1016/j.jenvrad.2021.106756] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 09/28/2021] [Accepted: 10/02/2021] [Indexed: 06/13/2023]
Abstract
The volumetric activity of the divalent 90Sr ion in groundwater at the Chornobyl NPP industrial site ranges from 1 to 2 to 400-3800 Bq/l. The increase in groundwater radionuclides concentrations is associated with the reduced sorption properties of local sediments, which affect the migration capacity of radionuclides in the environment. The decrease of the 90Sr sorption properties of sediments is caused by changes in the chemical composition of groundwater. A new statistical method has been performed. Method based on the Monte Carlo method in order to evaluate the correlations between the 90Sr volumetric activity and the groundwater chemical composition components. Simulation results using this method suggest a correlation between the volumetric activity of 90Sr, the concentrations cations, the pH, and the oxidation index (organic contents). A direct correlation was established between the volumetric activity of 90Sr, Ca2+ concentrations and the pH of groundwater in the range from 7 to 12.4. It was revealed that the concentrations of Na+ and K+ do not affect the conditions of 90Sr migration with groundwater. There is an inverse correlation between the concentration of 90Sr and the oxidation index, which is an indirect indicator of the organic substances content in water. Thus, the presence of organic substances in the groundwater effectively promotes sorption of 90Sr. The proposed method of geochemical statistics enables a quantitative assessment of groundwater monitoring results.
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Affiliation(s)
- Іhor О Kovalenko
- Institute for Safety Problems of Nuclear Power Plants National Academy of Sciences of Ukraine, Kirova str 36a, Chornobyl, 07270, Ukraine.
| | - Мykola I Panasiuk
- Institute for Safety Problems of Nuclear Power Plants National Academy of Sciences of Ukraine, Kirova str 36a, Chornobyl, 07270, Ukraine.
| | - Аnatolii D Skorbun
- Institute for Safety Problems of Nuclear Power Plants National Academy of Sciences of Ukraine, Kirova str 36a, Chornobyl, 07270, Ukraine.
| | - Natalia V Sosonna
- Institute for Safety Problems of Nuclear Power Plants National Academy of Sciences of Ukraine, Kirova str 36a, Chornobyl, 07270, Ukraine.
| | - Michael I Ojovan
- Department of Radiochemistry, Moscow State University Named After M.V. Lomonosov, Leninskie Gory 1, Bd.3, 119991 Moscow, Russia and Immobilisation Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, UK.
| | | | - Іhor P Оnyshchenko
- Radioenvironmental Centre of NAS of Ukraine, Ukraine, 55-b, O. Gonchar Str, Kiev, 01054, Ukraine.
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Tournier RF, Ojovan MI. Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics Simulations. Materials (Basel) 2021; 14:ma14216509. [PMID: 34772033 PMCID: PMC8585396 DOI: 10.3390/ma14216509] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 10/19/2021] [Accepted: 10/26/2021] [Indexed: 12/01/2022]
Abstract
A second melting temperature occurs at a temperature Tn+ higher than Tm in glass-forming melts after heating them from their glassy state. The melting entropy is reduced or increased depending on the thermal history and on the presence of antibonds or bonds up to Tn+. Recent MD simulations show full melting at Tn+ = 1.119Tm for Zr, 1.126Tm for Ag, 1.219Tm for Fe and 1.354Tm for Cu. The non-classical homogeneous nucleation model applied to liquid elements is based on the increase of the Lindemann coefficient with the heating rate. The glass transition at Tg and the nucleation temperatures TnG of glacial phases are successfully predicted below and above Tm. The glass transition temperature Tg increases with the heating rate up to Tn+. Melting and crystallization of glacial phases occur with entropy and enthalpy reductions. A universal law relating Tn+ and TnG around Tm shows that TnG cannot be higher than 1.293Tm for Tn+= 1.47Tm. The enthalpies and entropies of glacial phases have singular values, corresponding to the increase of percolation thresholds with Tg and TnG above the Scher and Zallen invariant at various heating and cooling rates. The G-phases are metastable up to Tn+ because the antibonds are broken by homogeneous nucleation of bonds.
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Affiliation(s)
- Robert F. Tournier
- UPR 3228 Centre National de la Recherche Scientifique, Laboratoire National des Champs Magnétiques Intenses, European Magnetic Field Laboratory, Institut National des Sciences Appliquées de Toulouse, Université Grenoble Alpes, F-31400 Toulouse, France
- Correspondence:
| | - Michael I. Ojovan
- Department of Materials, Imperial College London, London SW7 2AZ, UK;
- Department of Radiochemistry, Moscow State University, 119991 Moscow, Russia
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Ojovan MI, Tournier RF. On Structural Rearrangements Near the Glass Transition Temperature in Amorphous Silica. Materials (Basel) 2021; 14:ma14185235. [PMID: 34576458 PMCID: PMC8466242 DOI: 10.3390/ma14185235] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 09/04/2021] [Accepted: 09/08/2021] [Indexed: 12/29/2022]
Abstract
The formation of clusters was analyzed in a topologically disordered network of bonds of amorphous silica (SiO2) based on the Angell model of broken bonds termed configurons. It was shown that a fractal-dimensional configuron phase was formed in the amorphous silica above the glass transition temperature Tg. The glass transition was described in terms of the concepts of configuron percolation theory (CPT) using the Kantor-Webman theorem, which states that the rigidity threshold of an elastic percolating network is identical to the percolation threshold. The account of configuron phase formation above Tg showed that (i) the glass transition was similar in nature to the second-order phase transformations within the Ehrenfest classification and that (ii) although being reversible, it occurred differently when heating through the glass–liquid transition to that when cooling down in the liquid phase via vitrification. In contrast to typical second-order transformations, such as the formation of ferromagnetic or superconducting phases when the more ordered phase is located below the transition threshold, the configuron phase was located above it.
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Affiliation(s)
- Michael I. Ojovan
- Department of Materials, Imperial College London, South Kensington Campus, Exhibition Road, London SW7 2AZ, UK
- Department of Radiochemistry, Moscow State University Named after M.V. Lomonosov, Leninskie Gory 1, Bd.3, 119991 Moscow, Russia
- Correspondence: ; Tel.: +44-747-828-9098
| | - Robert F. Tournier
- Laboratoire National des Champs Magnétiques Intenses, European Magnetic Field Laboratory, UPR 3228 Centre National de la Recherche Scientifique, Université Grenoble Alpes, Institut National des Sciences Appliquées de Toulouse, F-31400 Toulouse, France;
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Tournier RF, Ojovan MI. Building and Breaking Bonds by Homogenous Nucleation in Glass-Forming Melts Leading to Transitions in Three Liquid States. Materials (Basel) 2021; 14:ma14092287. [PMID: 33925086 PMCID: PMC8124720 DOI: 10.3390/ma14092287] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 04/21/2021] [Accepted: 04/26/2021] [Indexed: 12/11/2022]
Abstract
The thermal history of melts leads to three liquid states above the melting temperatures Tm containing clusters-bound colloids with two opposite values of enthalpy +Δεlg × ΔHm and -Δεlg × ΔHm and zero. All colloid bonds disconnect at Tn+ > Tm and give rise in congruent materials, through a first-order transition at TLL = Tn+, forming a homogeneous liquid, containing tiny superatoms, built by short-range order. In non-congruent materials, (Tn+) and (TLL) are separated, Tn+ being the temperature of a second order and TLL the temperature of a first-order phase transition. (Tn+) and (TLL) are predicted from the knowledge of solidus and liquidus temperatures using non-classical homogenous nucleation. The first-order transition at TLL gives rise by cooling to a new liquid state containing colloids. Each colloid is a superatom, melted by homogeneous disintegration of nuclei instead of surface melting, and with a Gibbs free energy equal to that of a liquid droplet containing the same magic atom number. Internal and external bond number of colloids increases at Tn+ or from Tn+ to Tg. These liquid enthalpies reveal the natural presence of colloid-colloid bonding and antibonding in glass-forming melts. The Mpemba effect and its inverse exist in all melts and is due to the presence of these three liquid states.
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Affiliation(s)
- Robert F. Tournier
- LNCMI-EMFL, CNRS, Université Grenoble Alpes, INSA-T, UPS, 38042 Grenoble, France
- Correspondence:
| | - Michael I. Ojovan
- Department of Materials, Imperial College London, London SW7 2AZ, UK;
- Department of Radiochemistry, Lomonosov Moscow State University, 119991 Moscow, Russia
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Abstract
The two-exponential Sheffield equation of viscosity η(T) = A1·T·[1 + A2·exp(Hm/RT)]·[1 + C·exp(Hd/RT)], where A1, A2, Hm, C, and Hm are material-specific constants, is used to analyze the viscous flows of two glass-forming organic materials-salol and α-phenyl-o-cresol. It is demonstrated that the viscosity equation can be simplified to a four-parameter version: η(T) = A·T·exp(Hm/RT)]·[1 + C·exp(Hd/RT)]. The Sheffield model gives a correct description of viscosity, with two exact Arrhenius-type asymptotes below and above the glass transition temperature, whereas near the Tg it gives practically the same results as well-known and widely used viscosity equations. It is revealed that the constants of the Sheffield equation are not universal for all temperature ranges and may need to be updated for very high temperatures, where changes occur in melt properties leading to modifications of A and Hm for both salol and α-phenyl-o-cresol.
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Affiliation(s)
- Michael I. Ojovan
- Department of Materials, Imperial College London, South Kensington Campus, Exhibition Road, London SW7 2AZ, UK; or ; Tel.: +44-747-828-9098
- Department of Radiochemistry, Moscow State University Named after M.V. Lomonosov, Leninskie Gory 1, Bd.3, 119991 Moscow, Russia
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Affiliation(s)
- Michael I. Ojovan
- Department of Materials, Imperial College London, South Kensington Campus, Exhibition Road, London SW7 2AZ, United Kingdom
- Institute of Geology of Ore Deposits, Petrography Mineralogy and Geochemistry (IGEM), Russian Academy of Sciences, 119017 Moscow, Russia
| | - Dmitri V. Louzguine-Luzgin
- WPI Advanced Institute for Materials Research, Tohoku University, Aoba-Ku, Sendai 980-8577, Japan
- MathAM-OIL, National Institute of Advanced Industrial Science and Technology (AIST), Sendai 980-8577, Japan
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Orlova AI, Ojovan MI. Ceramic Mineral Waste-Forms for Nuclear Waste Immobilization. Materials (Basel) 2019; 12:ma12162638. [PMID: 31430956 PMCID: PMC6719191 DOI: 10.3390/ma12162638] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 08/07/2019] [Accepted: 08/12/2019] [Indexed: 01/12/2023]
Abstract
Crystalline ceramics are intensively investigated as effective materials in various nuclear energy applications, such as inert matrix and accident tolerant fuels and nuclear waste immobilization. This paper presents an analysis of the current status of work in this field of material sciences. We have considered inorganic materials characterized by different structures, including simple oxides with fluorite structure, complex oxides (pyrochlore, murataite, zirconolite, perovskite, hollandite, garnet, crichtonite, freudenbergite, and P-pollucite), simple silicates (zircon/thorite/coffinite, titanite (sphen), britholite), framework silicates (zeolite, pollucite, nepheline /leucite, sodalite, cancrinite, micas structures), phosphates (monazite, xenotime, apatite, kosnarite (NZP), langbeinite, thorium phosphate diphosphate, struvite, meta-ankoleite), and aluminates with a magnetoplumbite structure. These materials can contain in their composition various cations in different combinations and ratios: Li-Cs, Tl, Ag, Be-Ba, Pb, Mn, Co, Ni, Cu, Cd, B, Al, Fe, Ga, Sc, Cr, V, Sb, Nb, Ta, La, Ce, rare-earth elements (REEs), Si, Ti, Zr, Hf, Sn, Bi, Nb, Th, U, Np, Pu, Am and Cm. They can be prepared in the form of powders, including nano-powders, as well as in form of monolith (bulk) ceramics. To produce ceramics, cold pressing and sintering (frittage), hot pressing, hot isostatic pressing and spark plasma sintering (SPS) can be used. The SPS method is now considered as one of most promising in applications with actual radioactive substances, enabling a densification of up to 98-99.9% to be achieved in a few minutes. Characteristics of the structures obtained (e.g., syngony, unit cell parameters, drawings) are described based upon an analysis of 462 publications.
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Affiliation(s)
- Albina I Orlova
- Lobachevsky State University of Nizhny Novgorod, 23 Gagarina av., 603950 Nizhny Novgorod, Russian Federation
| | - Michael I Ojovan
- Department of Radiochemistry, Lomonosov Moscow State University, Moscow 119991, Russia.
- Imperial College London, South Kensington Campus, Exhibition Road, London SW7 2AZ, UK.
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Wickham A, Steinmetz HJ, O'Sullivan P, Ojovan MI. Updating irradiated graphite disposal: Project 'GRAPA' and the international decommissioning network. J Environ Radioact 2017; 171:34-40. [PMID: 28167371 DOI: 10.1016/j.jenvrad.2017.01.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Revised: 12/13/2016] [Accepted: 01/24/2017] [Indexed: 06/06/2023]
Abstract
Demonstrating competence in planning and executing the disposal of radioactive wastes is a key factor in the public perception of the nuclear power industry and must be demonstrated when making the case for new nuclear build. This work addresses the particular waste stream of irradiated graphite, mostly derived from reactor moderators and amounting to more than 250,000 tonnes world-wide. Use may be made of its unique chemical and physical properties to consider possible processing and disposal options outside the normal simple classifications and repository options for mixed low or intermediate-level wastes. The IAEA has an obvious involvement in radioactive waste disposal and has established a new project 'GRAPA' - Irradiated Graphite Processing Approaches - to encourage an international debate and collaborative work aimed at optimising and facilitating the treatment of irradiated graphite.
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Affiliation(s)
- Anthony Wickham
- Nuclear Graphite Consultancy, Builth Wells, and the School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, UK.
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Spasova LM, Ojovan MI, Gibb FG. Acoustic emission on melting/solidification of natural granite simulating very deep waste disposal. Nuclear Engineering and Design 2012. [DOI: 10.1016/j.nucengdes.2012.03.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Drace Z, Mele I, Ojovan MI, Abdel Rahman RO. An overview of research activities on cementitious materials for radioactive waste management. ACTA ACUST UNITED AC 2012. [DOI: 10.1557/opl.2012.584] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTAn overview is given on research activities on cementitious materials for radioactive waste management systems based on the IAEA Coordinated Research Project (CRP) held in 2007-2010. It has been joined by 26 research organizations from 22 countries which shared their research and practical activities on use of cementitious materials for various barrier purposes. The CRP has initially formulated the research topics considered within four specific streams: A) Conventional cementitious systems; B) Novel cementitious materials and technologies; C) Testing and waste acceptance criteria; and D) Modelling long term behaviour.The CRP has analysed both barrier functions and interactions envisaged between various components with focus on predisposal stage of waste management. Cementation processes have achieved a high degree of acceptance and many processes are now regarded as technically mature. A large body of information is currently available on proven waste conditioning technologies although novel approaches are continuing to be devised.Most of the existing technologies have been developed for conditioning of large amounts of operational radioactive waste from nuclear power plants and other nuclear fuel cycle facilities. However new waste streams including those resulting from legacy and decommissioning activities required improved material performance and technologies.The most important outcome of CRP was the exchange of information and research co-operation between different institutions and has contributed towards general enhancement of safety by improving waste management practices and their efficiency. The paper presents the most important results and trends revealed by CRP participants. The research contributions of participating organizations will be published as country contributions in a forthcoming IAEA technical publication.
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Sobolev IA, Dmitriev SA, Barinov AS, Varlakova GA, Golubeva ZI, Startceva IV, Ojovan MI. 39-years Performance of Cemented Radioactive Waste in a Mound Type Repository. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-932-43.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTLong-term field tests of cemented aqueous radioactive wastes in an experimental mound type surface repository were carried out at Moscow Scientific and Industrial Association “Radon” from 1965 to 2004. Aqueous radioactive wastes of different compositions containing short-lived radionuclides including 90Sr and 137Cs at concentrations from 0.34 to 1.8 MBq/L were immobilized using cementation technology. Water solution to cement ratio was 0.66, grout mixing time 10-15 minutes, and cement paste hardening time 7 days. 73 cement blocks with a volume of 0.027 m3 were disposed of for long-term tests in a simple mound type surface repository. The atmospheric precipitates, which contacted radioactive cement blocks, were collected and analyzed for the content of radionuclides. In August 2004 the experimental repository was opened, cemented blocks, underlying and covering materials were retrieved for analyses. XRD analyses showed that along with amorphous tobermorite gel the main crystal phases in cements are calcite and portlandite. Both visual inspection and radiometric analyses demonstrate that cemented blocks are in good condition and that the cement paste has retained radionuclides from the wastes. Thus after 39 years of storage in the mound type repository the cemented aqueous wastes are reliable immobilized.
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Ojovan MI, Varlackova GA, Golubeva ZI, Burlaka ON. Long-term field and laboratory leaching tests of cemented radioactive wastes. J Hazard Mater 2011; 187:296-302. [PMID: 21269765 DOI: 10.1016/j.jhazmat.2011.01.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 12/24/2010] [Accepted: 01/05/2011] [Indexed: 05/30/2023]
Abstract
Experiments with real and simulated radioactive cementitious wasteforms were set up to compare the leaching behaviour of cementitious wasteforms containing nuclear power plant operational waste in field and laboratory test conditions. Experiments revealed that the average annual (137)Cs leach rate in deionised water was about thirty-five times greater compared with the measured average value for the 1st year of the field test. Cumulative leached fraction of (137)Cs for 1st year (3.74%) was close to values reported in literature for similar laboratory experiments in deionised water, however more than two orders of magnitude higher than the 1st year leached fraction of (137)Cs in the repository test (0.01%). Therefore, to compare field and laboratory test results, a scaling factor is required in order to account for surface to volume factor difference, multiplied by a temperature factor and a leach rate decrease coefficient related to the ground water composition.
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Affiliation(s)
- Michael I Ojovan
- Immobilisation Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK.
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Drace Z, Ojovan MI. The Behaviours of Cementitious Materials in Long Term Storage and Disposal: An Overview of Results of the IAEA Coordinated Research Project. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-1193-663] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractCementitious materials are widely used in waste management systems with different aims and requirements for long term performance. Both conventional and novel cementitious materials are used to create reliable immobilising elements for safe storage and disposal of wastes. The barrier elements as well as interactions envisaged between various components are important to ultimately ensure the overall safety of a storage/disposal system. The behaviour and performance of cementitious materials including waste package components, wasteform and backfilling were analysed within the IAEA Coordinated Research Project which involved 26 research organizations from 21 Member States MS). The paper presents briefly the main research outcomes for conventional cementitious systems; novel materials and technologies; testing and waste acceptance criteria; and modelling long term behaviour.
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Abstract
AbstractMetals and alloys with relatively low melting temperatures such as lead and lead-based alloys are considered in Russia as prospective matrices for encapsulation of spent nuclear fuel in containers in preparation for final disposal in underground repositories. Now lead and leadbased alloys are being used for conditioning spent sealed radioactive sources at radioactive waste disposal facilities.
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Ojovan MI, Travis KP, Hand RJ. Thermodynamic parameters of bonds in glassy materials from viscosity-temperature relationships. J Phys Condens Matter 2007; 19:415107. [PMID: 28192319 DOI: 10.1088/0953-8984/19/41/415107] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Doremus's model of viscosity assumes that viscous flow in amorphous materials is mediated by broken bonds (configurons). The resulting equation contains four coefficients, which are directly related to the entropies and enthalpies of formation and motion of the configurons. Thus by fitting this viscosity equation to experimental viscosity data these enthalpy and entropy terms can be obtained. The non-linear nature of the equation obtained means that the fitting process is non-trivial. A genetic algorithm based approach has been developed to fit the equation to experimental viscosity data for a number of glassy materials, including SiO2, GeO2, B2O3, anorthite, diopside, xNa2O-(1-x)SiO2, xPbO-(1-x)SiO2, soda-lime-silica glasses, salol, and α-phenyl-o-cresol. Excellent fits of the equation to the viscosity data were obtained over the entire temperature range. The fitting parameters were used to quantitatively determine the enthalpies and entropies of formation and motion of configurons in the analysed systems and the activation energies for flow at high and low temperatures as well as fragility ratios using the Doremus criterion for fragility. A direct anti-correlation between fragility ratio and configuron percolation threshold, which determines the glass transition temperature in the analysed materials, was found.
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Affiliation(s)
- Michael I Ojovan
- Immobilisation Science Laboratory, Department of Engineering Materials, University of Sheffield, UK
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Spasova LM, Ojovan MI. Acoustic emission detection of microcrack formation and development in cementitious wasteforms with immobilised Al. J Hazard Mater 2006; 138:423-32. [PMID: 16828968 DOI: 10.1016/j.jhazmat.2006.05.067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2006] [Revised: 05/23/2006] [Accepted: 05/23/2006] [Indexed: 05/10/2023]
Abstract
An acoustic emission (AE) technique was applied for early detection, characterisation and time progress description of cracking phenomenon caused by the corrosion of Al encapsulated in cement matrix. The study was conducted on an ordinary Portland cement (OPC) system encapsulating high purity Al bar. Acoustic signals were generated and released during immersing of the sample in deionised water. A computer controlled PCI-2 based AE system processed the signals detected by piezoelectric transducers. A subsequent comparative study of the AE data collected with those obtained from a reference OPC sample has been applied. Recorded AE activity confirmed that the process of initiation and development of Al corrosion causes significant mechanical stresses within the cement matrix. Our analysis demonstrated possibility to differentiate AE signals based on their characteristics, and potentially correlate detected AE with the fracture processes in the cement system encapsulating Al.
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Affiliation(s)
- L M Spasova
- Immobilisation Science Laboratory, Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK.
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