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Michael I. Ojovan is Chief Editor of journal “Science and Technology of Nuclear Installations”. He has been Nuclear Engineer of International Atomic Energy Agency (IAEA), works as Professor of Imperial College London and Associate Reader at the University of Sheffield, UK, Leading Scientist of Lomonosov Moscow State University and Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry (IGEM) of Russian Academy of Sciences. He has published 13 monographs including the “Handbook of Advanced Radioactive Waste Conditioning Technologies” by Woodhead and three editions of “An Introduction to Nuclear Waste Immobilisation” by Elsevier in 2005, 2013, and 2019. He has founded and led the IAEA International Predisposal Network (IPN) and the IAEA International Project on Irradiated Graphite Processing (GRAPA). M. Ojovan is known for the connectivity-percolation theory of glass transition, Sheffield model of viscosity of glasses and melts, theoretical bases of condensed Rydberg matter, metallic and glass-composite materials for nuclear waste immobilisation, and self-sinking capsules to investigate Earth’s deep interior.
An overview is given of status of projects for the disposal of radioactive waste in very deep boreholes in crystalline rocks which demonstrates all main pros and cons of this technology. New opportunities offered by drilling long horizontal drillholes in ductile formations can provide the basis for projects that have the potential to overcome many of the disadvantages of deep boreholes. The concept of disposal in horizontal drillholes brings together the technologies of borehole and mined repositories using the advantages of both, and therefore deserves an expert discussion at international level.
B. Kochkin; V. Malkovsky; S. Yudintsev; V. Petrov; M. Ojovan. Problems and perspectives of borehole disposal of radioactive waste. Progress in Nuclear Energy 2021, 139, 103867 .
AMA StyleB. Kochkin, V. Malkovsky, S. Yudintsev, V. Petrov, M. Ojovan. Problems and perspectives of borehole disposal of radioactive waste. Progress in Nuclear Energy. 2021; 139 ():103867.
Chicago/Turabian StyleB. Kochkin; V. Malkovsky; S. Yudintsev; V. Petrov; M. Ojovan. 2021. "Problems and perspectives of borehole disposal of radioactive waste." Progress in Nuclear Energy 139, no. : 103867.
Comments about a recent publication entitled "Improving glass forming ability of off-eutectic metallic glass formers by manipulating primary crystallization reactions." 'Acta Materialia, 200 (2020) 710-719 by Y. Q. Zeng, J. S. Yu, Y. Tian, A. Hirata, T. Fujita, X. H. Zhang, N. Nishiyama, H. Kato, J. Q. Jiang, A. Inoue, M. W. Chen. The liquidus temperatures Tl of Ni60Pd20P20-y-x SiyBx glass formers are equal to the disappearance temperatures Tn+ of liquid medium-range order resulting from the formation of an undercooled phase behind the glass phase. At this temperature, a volume fraction of about 15%, corresponding to the percolation threshold of configurons, melts accompanied by an endothermic enthalpy.
Robert F. Tournier; Michael I. Ojovan. Comments about a recent publication entitled "Improving glass forming ability of off-eutectic metallic glass formers by manipulating primary crystallization reactions”. Scripta Materialia 2021, 114039 .
AMA StyleRobert F. Tournier, Michael I. Ojovan. Comments about a recent publication entitled "Improving glass forming ability of off-eutectic metallic glass formers by manipulating primary crystallization reactions”. Scripta Materialia. 2021; ():114039.
Chicago/Turabian StyleRobert F. Tournier; Michael I. Ojovan. 2021. "Comments about a recent publication entitled "Improving glass forming ability of off-eutectic metallic glass formers by manipulating primary crystallization reactions”." Scripta Materialia , no. : 114039.
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.
Robert Tournier; Michael Ojovan. Building and Breaking Bonds by Homogenous Nucleation in Glass-Forming Melts Leading to Transitions in Three Liquid States. Materials 2021, 14, 2287 .
AMA StyleRobert Tournier, Michael Ojovan. Building and Breaking Bonds by Homogenous Nucleation in Glass-Forming Melts Leading to Transitions in Three Liquid States. Materials. 2021; 14 (9):2287.
Chicago/Turabian StyleRobert Tournier; Michael Ojovan. 2021. "Building and Breaking Bonds by Homogenous Nucleation in Glass-Forming Melts Leading to Transitions in Three Liquid States." Materials 14, no. 9: 2287.
Glass crystalline materials (GCM) are of increasing interest as advanced nuclear wasteforms combining the advantages of vitreous and crystalline matrices. The GCM are versatile wasteforms envisaged for a wider use to immobilise various types of both radioactive and chemically hazardous wastes. They can be produced either via low temperature sintering using precursors composed of glass frit, oxides, and crystalline phases or through conventional melting aiming to produce first a parent glass, which is then crystallised by a controlled thermal schedule to obtain target crystalline phases within the GCM. Utilization of GCM is highlighted as a perspective wasteform for immobilization of partitioned radionuclide streams.
Michael Ojovan; Vladislav Petrov; Sergey Yudintsev. Glass Crystalline Materials as Advanced Nuclear Wasteforms. Sustainability 2021, 13, 4117 .
AMA StyleMichael Ojovan, Vladislav Petrov, Sergey Yudintsev. Glass Crystalline Materials as Advanced Nuclear Wasteforms. Sustainability. 2021; 13 (8):4117.
Chicago/Turabian StyleMichael Ojovan; Vladislav Petrov; Sergey Yudintsev. 2021. "Glass Crystalline Materials as Advanced Nuclear Wasteforms." Sustainability 13, no. 8: 4117.
A brief overview is presented of the modified random network (MRN) model in glass science emphasizing the practical outcome of its use. Then, the configuron percolation theory (CPT) of glass–liquid transition is concisely outlined, emphasizing the role of the actual percolation thresholds observed in a complex system. The MRN model is shown as an important tool enabling to understand within CPT the reduced percolation threshold in complex oxide systems.
Michael Ojovan. The Modified Random Network (MRN) Model within the Configuron Percolation Theory (CPT) of Glass Transition. Ceramics 2021, 4, 121 -134.
AMA StyleMichael Ojovan. The Modified Random Network (MRN) Model within the Configuron Percolation Theory (CPT) of Glass Transition. Ceramics. 2021; 4 (2):121-134.
Chicago/Turabian StyleMichael Ojovan. 2021. "The Modified Random Network (MRN) Model within the Configuron Percolation Theory (CPT) of Glass Transition." Ceramics 4, no. 2: 121-134.
Undercooled phase exists behind glass phase with superheated medium-range order between Tg and Tn+ > Tm. The ordered volume fraction stays equal to the percolation threshold F ≅ 0.15 of broken bonds up to Tn+. The difference ΔTg between Tg(bulk) of films with thickness (h > h0) and Tg(h) of ultrathin films of thickness (h < h0) is a linear function of (h-ho). Dense layer with minimum thickness hr is grafted against substrate by isothermal annealing, rinsed to reduce film thickness below hr/F, and finally dewetted at Tg. Similar thickness prepared and annealed near Tm and heated above Tm contains residual crystallized layer dewetting at Tn+. The prefrozen layer reproduces the glassy grafted layer in a crystallized state up to Tn+. Melting heat and melting temperature Tm are linear functions of h for h < h0. Prefrozen layers are due to melt-memories leading to new scenarios of crystallization.
Robert F. Tournier; Michael I. Ojovan. Dewetting temperatures of prefrozen and grafted layers in solid ultrathin films viewed as melt-memory effects. Physica B: Condensed Matter 2021, 611, 412796 .
AMA StyleRobert F. Tournier, Michael I. Ojovan. Dewetting temperatures of prefrozen and grafted layers in solid ultrathin films viewed as melt-memory effects. Physica B: Condensed Matter. 2021; 611 ():412796.
Chicago/Turabian StyleRobert F. Tournier; Michael I. Ojovan. 2021. "Dewetting temperatures of prefrozen and grafted layers in solid ultrathin films viewed as melt-memory effects." Physica B: Condensed Matter 611, no. : 412796.
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.
Michael I. Ojovan. On Viscous Flow in Glass-Forming Organic Liquids. Molecules 2020, 25, 4029 .
AMA StyleMichael I. Ojovan. On Viscous Flow in Glass-Forming Organic Liquids. Molecules. 2020; 25 (17):4029.
Chicago/Turabian StyleMichael I. Ojovan. 2020. "On Viscous Flow in Glass-Forming Organic Liquids." Molecules 25, no. 17: 4029.
Self-irradiation can affect durability of glasses used to immobilize high-level nuclear waste (HLW). The stability of glasses can also be indirectly affected by the radiolytic changes in contact water leading to decrease in its pH although this is unlikely to occur for disposal systems where the interaction of groundwater with glass is delayed to times when radiation dose rates are decreased to levels insignificant to cause such effects. Besides, interaction of the water influenced by radiation with other repository protective elements (container and bentonite) will suppress the radiolytic changes. Literature analysis shows practical absence or very weak effect of self-irradiation on structure and characteristics of borosilicate glasses with typical content of nuclear waste. Data for aluminophosphate glass used in Russia have showed that, after γ-irradiation with a dose of 6.2·107 Gy, the leaching rates of elements were decreased approximately twice relatively to pristine samples.
Viktor I. Malkovsky; Sergey V. Yudintsev; Michael I. Ojovan; Vladislav A. Petrov. The Influence of Radiation on Confinement Properties of Nuclear Waste Glasses. Science and Technology of Nuclear Installations 2020, 2020, 1 -14.
AMA StyleViktor I. Malkovsky, Sergey V. Yudintsev, Michael I. Ojovan, Vladislav A. Petrov. The Influence of Radiation on Confinement Properties of Nuclear Waste Glasses. Science and Technology of Nuclear Installations. 2020; 2020 ():1-14.
Chicago/Turabian StyleViktor I. Malkovsky; Sergey V. Yudintsev; Michael I. Ojovan; Vladislav A. Petrov. 2020. "The Influence of Radiation on Confinement Properties of Nuclear Waste Glasses." Science and Technology of Nuclear Installations 2020, no. : 1-14.
We examined the degradation of nuclear waste borosilicate and phosphate glasses containing strong alpha-emitter 238Pu at a specific activity of 6.33 × 105 MBq/g in comparison with similar non-radioactive, non-radioactive irradiated and radioactive samples containing beta- and gamma-emitters, namely radionuclides 134Cs and 137Cs. For irradiation and leaching experiments, we used borosilicate and phosphate glasses, which are well-known and currently used to immobilize high-level radioactive waste. The main focus was the observation of the surface of altered glasses. Comparative analysis of hydrolytic surface alteration of borosilicate and phosphate nuclear waste glasses reveals that the behavior of radioactive samples differs significantly from that of non-radioactive glasses.
Bella Y. Zubekhina; Boris E. Burakov; Michael I. Ojovan. Surface Alteration of Borosilicate and Phosphate Nuclear Waste Glasses by Hydration and Irradiation. Challenges 2020, 11, 14 .
AMA StyleBella Y. Zubekhina, Boris E. Burakov, Michael I. Ojovan. Surface Alteration of Borosilicate and Phosphate Nuclear Waste Glasses by Hydration and Irradiation. Challenges. 2020; 11 (2):14.
Chicago/Turabian StyleBella Y. Zubekhina; Boris E. Burakov; Michael I. Ojovan. 2020. "Surface Alteration of Borosilicate and Phosphate Nuclear Waste Glasses by Hydration and Irradiation." Challenges 11, no. 2: 14.
Structural properties and water dissolution of six sodium–aluminum–phosphate (NAP) glasses have been investigated before and after irradiation by a gamma-ray source based on 60Co. Two of these samples were of simple composition, and four samples had a complex composition with radionuclide simulants representing actinides, fission, and activated corrosion products. Samples of the simple composition are fully vitreous, whereas samples of the complex composition contained up to 10 vol.% of aluminum–phosphate, AlPO4, and traces of ruthenium dioxide, RuO2. Based on the study of pristine and irradiated glasses, it was established that the radiation dose of 62 million Gray had practically no effect on the phase composition and structure of samples. At the same time, the rate of leaching of elements from the irradiated samples by water was decreased by about two times.
Alexey V. Luzhetsky; Vladislav A. Petrov; Sergey V. Yudintsev; Viktor I. Malkovsky; Michael I. Ojovan; Maximilian S. Nickolsky; Andrey A. Shiryaev; Sergey S. Danilov; Elizaveta E. Ostashkina. Effect of Gamma Irradiation on Structural Features and Dissolution of Nuclear Waste Na–Al–P Glasses in Water. Sustainability 2020, 12, 4137 .
AMA StyleAlexey V. Luzhetsky, Vladislav A. Petrov, Sergey V. Yudintsev, Viktor I. Malkovsky, Michael I. Ojovan, Maximilian S. Nickolsky, Andrey A. Shiryaev, Sergey S. Danilov, Elizaveta E. Ostashkina. Effect of Gamma Irradiation on Structural Features and Dissolution of Nuclear Waste Na–Al–P Glasses in Water. Sustainability. 2020; 12 (10):4137.
Chicago/Turabian StyleAlexey V. Luzhetsky; Vladislav A. Petrov; Sergey V. Yudintsev; Viktor I. Malkovsky; Michael I. Ojovan; Maximilian S. Nickolsky; Andrey A. Shiryaev; Sergey S. Danilov; Elizaveta E. Ostashkina. 2020. "Effect of Gamma Irradiation on Structural Features and Dissolution of Nuclear Waste Na–Al–P Glasses in Water." Sustainability 12, no. 10: 4137.
Transformation of glasses into liquids is discussed in terms of configuron (broken chemical bond or transformation of an atom from one to another atomic shell) percolation theory with structural changes caused. The first sharp diffraction minimum (FSDM) in the pair distribution function (PDF) is shown to contain information on structural changes in amorphous materials at the glass transition temperature (Tg). A method to determine the glass transition temperature is proposed based on allocating Tg to the temperature when a sharp kink in FSDM occurs. The method proposed is more sensitive compared with empirical criterion of Wendt-Abraham e.g. for amorphous Ni the kink that determines Tg is almost twice sharper. Connection between the kink in fictive temperature behaviour of PDF and Wendt-Abraham criterion is discussed.
Michael I. Ojovan; Dmitri V. Louzguine-Luzgin. Revealing Structural Changes at Glass Transition via Radial Distribution Functions. The Journal of Physical Chemistry B 2020, 124, 3186 -3194.
AMA StyleMichael I. Ojovan, Dmitri V. Louzguine-Luzgin. Revealing Structural Changes at Glass Transition via Radial Distribution Functions. The Journal of Physical Chemistry B. 2020; 124 (15):3186-3194.
Chicago/Turabian StyleMichael I. Ojovan; Dmitri V. Louzguine-Luzgin. 2020. "Revealing Structural Changes at Glass Transition via Radial Distribution Functions." The Journal of Physical Chemistry B 124, no. 15: 3186-3194.
Salt cake radioactive waste is a remnant solid salt concentrate after deep evaporation of radioactive evaporator concentrate at WWER NPP’s. The traditional cementing of borate-containing liquid radioactive waste, to which the salt cake belongs, leads to a significant increase in the volume of the final product. This work describes borosilicate vitreous wasteforms developed to immobilize radioactive salt cake waste and comprises data on both glass synthesis and characterization. The composition of glass selected for the purpose of immobilisation of the salt cake radioactive waste allows to include up to 40 wt. % of the oxides contained in the salt cake and to reduce the volume of the final product by more than 2 times compared with the cement compound. The batches were melted in a cold crucible melter at 1200 °C. The normalized cesium leaching rate of the vitrified wasteform product was within range 3.0·10-5 – 3.7·10-6 g/(cm2·day).
Vladimir A. Kashcheev; Nikolay D. Musatov; Michael I. Ojovan. Advanced Vitreous Wasteforms for Radioactive Salt Cake Waste Immobilisation. MRS Advances 2020, 5, 121 -129.
AMA StyleVladimir A. Kashcheev, Nikolay D. Musatov, Michael I. Ojovan. Advanced Vitreous Wasteforms for Radioactive Salt Cake Waste Immobilisation. MRS Advances. 2020; 5 (3-4):121-129.
Chicago/Turabian StyleVladimir A. Kashcheev; Nikolay D. Musatov; Michael I. Ojovan. 2020. "Advanced Vitreous Wasteforms for Radioactive Salt Cake Waste Immobilisation." MRS Advances 5, no. 3-4: 121-129.
Alkali-borosilicate glasses (ABS) are used as host immobilization matrices for different radioactive waste streams and are characterized by their ability to incorporate a wide variety of metal oxides with respectively high waste loadings. The vitreous wasteform is also characterized by very good physical and chemical durability. The durability of three ABS compositions were analyzed by investigating their leaching behavior using the MCC1 test protocol and these data were used to investigate the waste components retention in the altered layer and the evolution of the interfacial water composition during the test. The results indicated that the Mg species evolution is exceptional with respect to other alkaline elements and dependent on glass matrix composition and leaching progress, while transition elements speciation is fairly constant throughout leaching process and independent on glass compositions. Si and B species are changing during leaching process and are affected by waste composition. For modified wasteform sample, evolution of Mg, Si and B species is respectively constant, whereas at highest waste loading, these elements have fairly constant speciation evolution within the first 2 weeks of leaching.
Osama M. Farid; M. I. Ojovan; R. O. Abdel Rahman. Evolution of cations speciation during the initial leaching stage of alkali-borosilicate-glasses. MRS Advances 2020, 5, 185 -193.
AMA StyleOsama M. Farid, M. I. Ojovan, R. O. Abdel Rahman. Evolution of cations speciation during the initial leaching stage of alkali-borosilicate-glasses. MRS Advances. 2020; 5 (3-4):185-193.
Chicago/Turabian StyleOsama M. Farid; M. I. Ojovan; R. O. Abdel Rahman. 2020. "Evolution of cations speciation during the initial leaching stage of alkali-borosilicate-glasses." MRS Advances 5, no. 3-4: 185-193.
The three generically accepted stages of glass corrosion are reviewed with focus on final stage termed alteration rate renewal (or resumption) stage when the glass may re-start corroding with the rate similar to that at the initial stage. It is emphasized that physical state and physical changes that occur in the near-surface layers can readily lead to an effective increase of leaching rate which is similar to alteration rate renewals. Experimental data on long-term (during few decades) corrosion of radioactive borosilicate glass K26 designed to immobilize high-sodium operational NPP radioactive waste evidence on resumption-like effects of radionuclides (137,134Cs) leaching. The cause of that was however related not to chemical changes in the leaching environment but rather to physical state of glass surface due to formation of small cracks and new pristine glass areas in contact with water.
Michael I. Ojovan. On Alteration Rate Renewal Stage of Nuclear Waste Glass Corrosion. MRS Advances 2020, 5, 111 -120.
AMA StyleMichael I. Ojovan. On Alteration Rate Renewal Stage of Nuclear Waste Glass Corrosion. MRS Advances. 2020; 5 (3-4):111-120.
Chicago/Turabian StyleMichael I. Ojovan. 2020. "On Alteration Rate Renewal Stage of Nuclear Waste Glass Corrosion." MRS Advances 5, no. 3-4: 111-120.
Selection of wasteform materials for higher activity nuclear waste containment is considered. Utilization of materials such as glasses, ceramics, glass composite materials and cements is discussed as practiced in different countries. Emphasis is on multiple parameter approach on selecting the wasteform where the durability is not solely the most important characteristic.
C. M. Jantzen; M. I. Ojovan. On Selection of Matrix (Wasteform) Material for Higher Activity Nuclear Waste Immobilization (Review). Russian Journal of Inorganic Chemistry 2019, 64, 1611 -1624.
AMA StyleC. M. Jantzen, M. I. Ojovan. On Selection of Matrix (Wasteform) Material for Higher Activity Nuclear Waste Immobilization (Review). Russian Journal of Inorganic Chemistry. 2019; 64 (13):1611-1624.
Chicago/Turabian StyleC. M. Jantzen; M. I. Ojovan. 2019. "On Selection of Matrix (Wasteform) Material for Higher Activity Nuclear Waste Immobilization (Review)." Russian Journal of Inorganic Chemistry 64, no. 13: 1611-1624.
Nuclear energy is clean, reliable, and competitive with many useful applications, among which power generation is the most important as it can gradually replace fossil fuels and avoid massive pollution of environment. A by-product resulting from utilization of nuclear energy in both power generation and other applications, such as in medicine, industry, agriculture, and research, is nuclear waste. Safe and effective management of nuclear waste is crucial to ensure sustainable utilization of nuclear energy. Nuclear waste must be processed to make it safe for storage, transportation, and final disposal, which includes its conditioning, so it is immobilized and packaged before storage and disposal. Immobilization of waste radionuclides in durable wasteform materials provides the most important barrier to contribute to the overall performance of any storage and/or disposal system. Materials for nuclear waste immobilization are thus at the core of multibarrier systems of isolation of radioactive waste from environment aimed to ensure long term safety of storage and disposal. This Special Issue analyzes the materials currently used as well as novel materials for nuclear waste immobilization, including technological approaches utilized in nuclear waste conditioning pursuing to ensure efficiency and long-term safety of storage and disposal systems. It focuses on advanced cementitious materials, geopolymers, glasses, glass composite materials, and ceramics developed and used in nuclear waste immobilization, with the performance of such materials of utmost importance. The book outlines recent advances in nuclear wasteform materials including glasses, ceramics, cements, and spent nuclear fuel. It focuses on durability aspects and contains data on performance of nuclear wasteforms as well as expected behavior in a disposal environment.
Neil C. Hyatt; Michael I. Ojovan. Special Issue: Materials for Nuclear Waste Immobilization. Materials 2019, 12, 3611 .
AMA StyleNeil C. Hyatt, Michael I. Ojovan. Special Issue: Materials for Nuclear Waste Immobilization. Materials. 2019; 12 (21):3611.
Chicago/Turabian StyleNeil C. Hyatt; Michael I. Ojovan. 2019. "Special Issue: Materials for Nuclear Waste Immobilization." Materials 12, no. 21: 3611.
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.
Albina I. Orlova; Michael I. Ojovan. Ceramic Mineral Waste-Forms for Nuclear Waste Immobilization. Materials 2019, 12, 2638 .
AMA StyleAlbina I. Orlova, Michael I. Ojovan. Ceramic Mineral Waste-Forms for Nuclear Waste Immobilization. Materials. 2019; 12 (16):2638.
Chicago/Turabian StyleAlbina I. Orlova; Michael I. Ojovan. 2019. "Ceramic Mineral Waste-Forms for Nuclear Waste Immobilization." Materials 12, no. 16: 2638.
Initial leaching characteristics of simulated nuclear waste immobilized in three alkali- borosilicate glasses (ABS-waste) were studied. The effects of matrix composition on the containment performance and degradation resistance measures were evaluated. Normalized release rates are in conformance with data reported in the literature. High Li and Mg loadings lead to the highest initial de-polymerization of sample ABS-waste (17) and contributed to its thermodynamic instability. Ca stabilizes non-bridging oxygen (NBO) and reduces the thermodynamic instability of the modified matrix. An exponential temporal change in the alteration thickness was noted for samples ABS-waste (17) and Modified Alkali-Borosilicate (MABS)-waste (20), whereas a linear temporal change was noted for sample ABS-waste (25). Leaching processes that contribute to the fractional release of all studied elements within the initial stage of glass corrosion were quantified and the main controlling leach process for each element was identified. As the waste loading increases, the contribution of the dissolution process to the overall fractional release of structural elements decreases by 43.44, 5.05, 38.07, and 52.99% for Si, B, Na, and Li respectively, and the presence of modifiers reduces this contribution for all the studied metalloids. The dissolution process plays an important role in controlling the release of Li and Cs, and this role is reduced by increasing the waste loading.
Osama M. Farid; Michael I. Ojovan; A. Massoud; R.O. Abdel Rahman. An Assessment of Initial Leaching Characteristics of Alkali-Borosilicate Glasses for Nuclear Waste Immobilization. Materials 2019, 12, 1462 .
AMA StyleOsama M. Farid, Michael I. Ojovan, A. Massoud, R.O. Abdel Rahman. An Assessment of Initial Leaching Characteristics of Alkali-Borosilicate Glasses for Nuclear Waste Immobilization. Materials. 2019; 12 (9):1462.
Chicago/Turabian StyleOsama M. Farid; Michael I. Ojovan; A. Massoud; R.O. Abdel Rahman. 2019. "An Assessment of Initial Leaching Characteristics of Alkali-Borosilicate Glasses for Nuclear Waste Immobilization." Materials 12, no. 9: 1462.
Experiments with actinide-containing insulating wasteforms such as devitrified glasses containing 244Cm, Ti-pyrochlore, single-phase La-monazite, Pu-monazite ceramics, Eu-monazite and zircon single crystals containing 238Pu indicate that mechanical self-irradiation-induced destruction may not reveal itself for many years (even decades). The mechanisms causing these slowly-occurring changes remain unknown therefore in addition to known mechanisms of wasteform degradation such as matrix swelling and loss of solid solution we have modelled the damaging effects of electrical fields induced by the decay of radionuclides in clusters embedded in a non-conducting matrix. Three effects were important: (i) electric breakdown; (ii) cluster shape change due to dipole interaction, and (iii) cluster shape change due to polarisation interaction. We reveal a critical size of radioactive clusters in non-conducting matrices so that the matrix material can be damaged if clusters are larger than this critical size. The most important parameters that control the matrix integrity are the radioactive cluster (inhomogeneity) size, specific radioactivity, and effective matrix electrical conductivity. We conclude that the wasteform should be as homogeneous as possible and even electrically conductive to avoid potential damage caused by electrical charges induced by radioactive decay.
Michael I. Ojovan; Boris E. Burakov; William E. Lee. Radiation-induced microcrystal shape change as a mechanism of wasteform degradation. Journal of Nuclear Materials 2018, 501, 162 -171.
AMA StyleMichael I. Ojovan, Boris E. Burakov, William E. Lee. Radiation-induced microcrystal shape change as a mechanism of wasteform degradation. Journal of Nuclear Materials. 2018; 501 ():162-171.
Chicago/Turabian StyleMichael I. Ojovan; Boris E. Burakov; William E. Lee. 2018. "Radiation-induced microcrystal shape change as a mechanism of wasteform degradation." Journal of Nuclear Materials 501, no. : 162-171.
Michael I Ojovan; William E. Lee. About U-shaped Glass Corrosion Rate/pH Curves for Vitreous Nuclear Wasteforms. Innovations in Corrosion and Materials Science (Formerly Recent Patents on Corrosion Science) 2017, 7, 30 -37.
AMA StyleMichael I Ojovan, William E. Lee. About U-shaped Glass Corrosion Rate/pH Curves for Vitreous Nuclear Wasteforms. Innovations in Corrosion and Materials Science (Formerly Recent Patents on Corrosion Science). 2017; 7 (1):30-37.
Chicago/Turabian StyleMichael I Ojovan; William E. Lee. 2017. "About U-shaped Glass Corrosion Rate/pH Curves for Vitreous Nuclear Wasteforms." Innovations in Corrosion and Materials Science (Formerly Recent Patents on Corrosion Science) 7, no. 1: 30-37.