Thermodynamic assessment of the PdRhRu system using calphad and first-principles methods
TL;DR: In this paper, a thermodynamic model was developed on the ternary Pd Rh Ru system using the Calphad method to predict the thermodynamic properties of these PGM fission products.
About: This article is published in Journal of Nuclear Materials.The article was published on 2016-06-01. It has received 17 citations till now. The article focuses on the topics: CALPHAD & Fission products.
Citations
More filters
TL;DR: In this article, the authors present a summary of current knowledge on the formulation, irradiation resistance and chemical durability of these conditioning materials, with a special focus on the fate of radionuclides during glass processing and aging.
Abstract: Abstract 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 safety of the disposal of these long-lived waste forms in a deep geological repository. This article presents a summary of current knowledge on the formulation, irradiation resistance and the chemical durability of these conditioning materials, with a special focus on the fate of radionuclides during glass processing and aging. It is shown that, apart from the situation for certain elements with very low incorporation rate in glass matrices, vitrification in borosilicate glass can enable waste loadings of up to ~20 wt% while maintaining the glass homogeneity for geological time scales and guaranteeing a high stability level in spite of irradiation and water contact.
118 citations
Cites background from "Thermodynamic assessment of the PdR..."
...The principal compounds identified in waste conditioning glasses are noble metal alloys such as Pd–Te [32–34], Pd–Se [35], Pd–Rh [36], Pd–Rh–Te [37, 38], and Pd–Te–Ag, as well as metallic Ru associated with RuO2....
[...]
Université Paris-Saclay1, University of Ontario Institute of Technology2, Japan Atomic Energy Agency3, Royal Military College of Canada4, Nuclear Research and Consultancy Group5, Delft University of Technology6, University of South Carolina7, Lawrence Livermore National Laboratory8, Chalk River Laboratories9, Central Research Institute of Electric Power Industry10, Idaho National Laboratory11, National Nuclear Laboratory12, Nuclear Energy Agency13
TL;DR: The TAF-ID database as mentioned in this paper was developed using the Calphad method to provide a computational tool to perform thermodynamic calculations on nuclear fuel materials under normal and off-normal conditions.
Abstract: The Thermodynamics of Advanced Fuels – International Database (TAF-ID) was developed using the Calphad method to provide a computational tool to perform thermodynamic calculations on nuclear fuel materials under normal and off-normal conditions. Different kinds of fuels are considered: oxide, metallic, carbide and nitride fuels. Many fission products are introduced as well as structural materials (e.g., zirconium, steel, concrete, SiC) and absorbers (e.g., B4C), in order to investigate the thermochemistry of irradiated fuels and to predict their chemical interaction with the surrounding materials. The approach to develop the database and the models implemented in the database are described. Examples of models for key chemical systems are presented. Finally, a few examples of application calculations on severe accidents with UO2 fuels, irradiated fuel chemistry of MOX and metallic fuels and metallic fuel/cladding interaction show how this tool can be used. To validate the database, the calculations are compared to the available experimental data. A good agreement is obtained which gives confidence in the maturity degree and quality of the TAF-ID database. The working version is only accessible to the participants of the TAF-ID project (Canada, France, Japan, the Netherlands, Republic of Korea, United Kingdom, USA). A public version is accessible by all the NEA countries. The current version contains models on the Am–Fe, Am–Np, Am-O-Pu, Am–U, Am–Zr, C–O–U-Pu, Cr–U, Np–U, Np–Zr, O–U–Zr, Re–U, Ru–U, Si–U, Ti–U, U-Pu-Zr, U–W systems. It is progressively extended with our published assessments. Information on how to join the project is available on the website: https://www.oecd-nea.org/science/taf-id/ .
46 citations
TL;DR: In this paper, density functional theory (DFT) calculations were used to investigate the structure and composition of the T 1 phase by comparing the energetic stability of five previously-proposed models of the crystal structure of T 1.
34 citations
TL;DR: In this paper, the average particle sizes of Pd-rh nanoalloys have been shown to have a strong composition dependence for higher synthetic temperatures: it decreases from around 6 to 2 nm with increasing Rh content for the indirect method at 500°C, whereas it increases from around 10 nm for the direct method at 600°C with increasing rh content.
Abstract: Bulk immiscible Pd–Rh nanoalloys supported on carbon are easily formed with tunable compositions and average particle sizes by two different methods: an indirect method (incipient wetness impregnation followed by reduction under H 2 at 300 and 500 °C) along with a direct one (one-pot route heat treated at 600 °C under Ar). The main advantage of our synthetic methods is the easy implementation as well as the formation of nanoalloys with well controlled composition and particle size distribution. For the indirect route at 300 °C, the nanoalloys have an average particle size of around 2 nm, irrespective of the composition. However, the average particle sizes show a strong composition dependence for higher synthetic temperatures: it decreases from around 6 to 2 nm with increasing Rh content for the indirect method at 500 °C, whereas it increases from around 6 to 10 nm for the direct method at 600 °C with increasing Rh content. Moreover, our calculation of the phase diagram taking into account the size effect within the Nano-Calphad approach confirms that these nanoalloys are non-equilibrium phases. The change of the binary phase diagram due to the size effect (decrease of the melting points of pure elements, reduction of the critical temperature along with modifications in the solubility limits of the miscibility gap) cannot account for the formation of Pd–Rh solid solutions at nanoscale.
11 citations
01 Sep 2020
TL;DR: In this article, a sub-lattice model is derived from zero-temperature quantum mechanics calculations to estimate fairly accurate temperature and oxygen-partial-pressure-dependent off-stoichiometries in transition-metal and rare-earth oxides.
Abstract: Theoretical models that reliably can predict off-stoichiometry in materials via accurate descriptions of underlying thermodynamics are crucial for energy applications. For example, transition-metal and rare-earth oxides that can tolerate a large number of oxygen vacancies, such as CeO2 and doped CeO2, can split water and carbon dioxide via a two-step, oxide-based solar thermochemical (STC) cycle. The search for new STC materials with a performance superior to that of state-of-the-art CeO2 can benefit from predictions accurately describing the thermodynamics of oxygen vacancies. The sub-lattice formalism, a common tool used to fit experimental data and build temperature-composition phase diagrams, can be useful in this context. Here, sub-lattice models are derived solely from zero-temperature quantum mechanics calculations to estimate fairly accurate temperatureand oxygen-partial-pressure-dependent off-stoichiometries in CeO2 and Zr-doped CeO2. Physical motivations for deriving some of the “excess” sub-lattice model parameters directly from quantum mechanical calculations, instead of fitting to minimize deviations from experimental and/or theoretical data, are identified. Important limitations and approximations of the approach used are specified and extensions to multi-cation oxides are also suggested to help identify novel candidates for water and carbon dioxide splitting and related applications.
10 citations
References
More filters
TL;DR: An efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set is presented and the application of Pulay's DIIS method to the iterative diagonalization of large matrices will be discussed.
Abstract: We present an efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrices will be discussed. Our approach is stable, reliable, and minimizes the number of order ${\mathit{N}}_{\mathrm{atoms}}^{3}$ operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special ``metric'' and a special ``preconditioning'' optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calculations. It will be shown that the number of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order ${\mathit{N}}_{\mathrm{atoms}}^{2}$ scaling is found for systems containing up to 1000 electrons. If we take into account that the number of k points can be decreased linearly with the system size, the overall scaling can approach ${\mathit{N}}_{\mathrm{atoms}}$. We have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large number of different systems (liquid and amorphous semiconductors, liquid simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable. \textcopyright{} 1996 The American Physical Society.
81,985 citations
TL;DR: In this paper, the formal relationship between US Vanderbilt-type pseudopotentials and Blochl's projector augmented wave (PAW) method is derived and the Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional.
Abstract: The formal relationship between ultrasoft (US) Vanderbilt-type pseudopotentials and Bl\"ochl's projector augmented wave (PAW) method is derived. It is shown that the total energy functional for US pseudopotentials can be obtained by linearization of two terms in a slightly modified PAW total energy functional. The Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional. A simple way to implement the PAW method in existing plane-wave codes supporting US pseudopotentials is pointed out. In addition, critical tests are presented to compare the accuracy and efficiency of the PAW and the US pseudopotential method with relaxed core all electron methods. These tests include small molecules $({\mathrm{H}}_{2}{,\mathrm{}\mathrm{H}}_{2}{\mathrm{O},\mathrm{}\mathrm{Li}}_{2}{,\mathrm{}\mathrm{N}}_{2}{,\mathrm{}\mathrm{F}}_{2}{,\mathrm{}\mathrm{BF}}_{3}{,\mathrm{}\mathrm{SiF}}_{4})$ and several bulk systems (diamond, Si, V, Li, Ca, ${\mathrm{CaF}}_{2},$ Fe, Co, Ni). Particular attention is paid to the bulk properties and magnetic energies of Fe, Co, and Ni.
57,691 citations
TL;DR: For the molecules Be2, F2, and P2 of Table I, the unrestricted Hartree-Fock solution breaks the singlet spin symmetry, even though the density functional solutions do not.
Abstract: For the molecules Be2, F2, and P2 of Table I, the unrestricted Hartree-Fock solution breaks the singlet spin symmetry, even though the density-functional solutions do not. For these broken-symmetry solutions, the UHF atomization energies become 17, 220, and 141 kcalymol, respectively, and the mean absolute error of all the UHF atomization energies becomes 69.8 kcalymol. The PBE correlation energy of the two-electron ions of nuclear charge Z ! ` should be corrected to 20.0479 hartree, consistent with the PBE value v 0.046644 stated in the Letter. The quoted value 20.0482 hartree was obtained from the more refined v 0.046920 of G. G. Hoffman, Phys. Rev. B 45, 8730 (1992). Reference [6] should have been “A. C. Scheiner, J. Baker, and J. W. Andzelm, J. Comput. Chem. (to be published)”.
11,883 citations
TL;DR: In this article, the authors present the data for the condensed phases of 78 elements as currently used by SGTE (Scientific Group Thermodata Europe) as a sound basis for the critical assessment of thermodynamic data, thereby, perhaps, limiting unnecessary duplication of effort.
Abstract: Thermodynamic data for the condensed phases of 78 elements as currently used by SGTE (Scientific Group Thermodata Europe) are tabulated. SGTE is a consortium of seven organisations in Western Europe engaged in the compilation of a comprehensive, self consistent and authoritative thermochemical database for inorganic and metallurgical systems. The data are being published here in the hope that they will become widely adopted within the international community as a sound basis for the critical assessment of thermodynamic data, thereby, perhaps, limiting unnecessary duplication of effort. The data for each phase of each element considered aie presented as expressions showing, as a function of temperature, the variation of (a) G-HSER, the Gibbs energy relative to the enthalpy of the “Standard Element Reference” ie the reference phase for the element at 298.15 K and (b) the difference in Gibbs energy between each phase and this reference phase (ie lattice stability). The variation of the heat capacity of the various phases and the Gibbs energy difference between phases are also shown graphically. For certain elements the thermodynamic data have been assessed as a function of pressure as well as temperature. Where appropriate a temperature— pressure phase diagram is also shown.
Throughout this paper the thermodynamic data are expressed in terms of J mol−1. The temperatures of transition between phases have been assessed to be consistent with the 1990 International Temperature Scale (ITS90).
4,116 citations
TL;DR: Using the facilities of Thermo-Calc one can tabulate thermodynamic data, calculate the heat change of chemical reactions and their driving force, evaluate equilibria for chemical systems and phase transformations and calculate various types of multicomponent phase diagrams by an automatic mapping procedure.
Abstract: A description is given of Thermo-Calc, a databank for thermochemistry and metallurgy developed at the division of Physical Metallurgy of the Royal Institute of Technology (KTH) in Stockholm. Using the facilities of Thermo-Calc one can tabulate thermodynamic data, calculate the heat change of chemical reactions and their driving force, evaluate equilibria for chemical systems and phase transformations and calculate various types of multicomponent phase diagrams by an automatic mapping procedure. The databank is quite general and can be applied to all systems where data assessed by a model implemented in the databank are available. The assessment procedure necessary to develop and extend the the databank is discussed. A brief description of the modules of Thermo-Calc is given and two examples are included which demonstrate how flexibly the calculations can be made. These examples will also show that the system is quite easy to use and that there are extensive on-line help facilities.
2,977 citations