Equation of State of Uranium Dioxide: Data Collection

ISBN-13: 9783540221227 / Angielski / Twarda / 2004 / 356 str.

Claudio Ronchi; C. Ronchi; I. L. Iosilevski

Opis

In the beginning of the 1990's, in the course of the events which were rapidly cha- ing the political con?guration of the East European countries, the crisis which - vested the vast research apparatus of the former Soviet Union was entailing con- quences whose dimension and depth were immediately realized by the international scienti?c community. In the same years, however, the most important branch of nuclear energy - searchanddevelopment, inparticularthatconcerning?ssionreactor, wasworldwide undergoing a substantial reduction due to a variety of decisional situations. Yet, paradoxically, it was a very good fortune that a number of concerns on the future of nuclear research were shared by East- and West-European scientists, especially those who were working in advanced ?elds. In fact, the only hope for coping with an uncertain future was to erect bridges between similar institutions and employ safeguarding tactics linked to a long term collaboration strategy. A decade later, this proved to be a winning decision, since the revival of nuclear energy is presently starting from a basis of common intentions and a network of established cooperation, whose seeds are to be searched in those initial, individual e?orts.

Spis treści

1 Introduction.- 1.1 Reactor Accident Analysis and Fuel Equation of State.- 1.2 The Role of Equation of State.- 1.3 Equation of State for Liquid UO2: Historical.- 1.4 Summary of the New Equation of State Features.- 1.5 General Notations.- 2 Governing Equations and Fundamental Formulae.- 2.1 Introduction.- 2.2 The Concept of Equation-of-State.- 2.3 Model Equations of State.- 2.3.1 Ideal Gas.- 2.3.2 Ideal Reacting Gas.- 2.3.3 Hard Bodies.- 2.3.4 Soft Spheres.- 2.3.5 Van der Waals’ Model.- 2.3.6 Lennard-Jones Fluid.- 2.3.7 Charged Spheres.- 2.3.8 Composite Models.- 2.4 Physical and Chemical Models in Thermodynamics of Reacting Fluids.- 2.4.1 The Concept of Composition.- 2.4.2 Neutral Models of UO2±x.- 2.4.3 Ionic Models.- 2.4.4 MIX Models.- 2.5 Conclusions.- 3 Ionic Models for Liquid Urania.- 3.1 Restricted Primitive Ionic Model.- 3.2 Extended Ionic Model.- 3.3 Local Equations of State for the Liquid Phase: General Requirements.- 3.4 Improved Restricted Primitive Ionic Model.- 3.5 Compatibility Conditions.- 3.6 Determination of the Coulomb Contribution.- 3.7 Conclusions.- 4 Gas-Liquid Coexistence in Uranium Dioxide.- 4.1 General Conditions of the Phase Equilibrium.- 4.1.1 Single-Component Fluids.- 4.1.2 Chemically Reactive Systems without Ionisation.- 4.1.3 Congruently Coexisting (Azeotropic) Compositions.- 4.1.4 Extremal Properties of the Thermodynamic Functions in the Azeotropic Points.- 4.1.5 Systems of Charged Species.- 4.1.6 Chemically Reacting Fluids with Ionisation.- 4.2 Calculation of the Equilibrium Composition and Thermodynamic Functions.- 4.3 General Structure of the Liquid-Vapour Phase Boundaries in UO2±x.- 4.4 Equilibrium Properties and Composition of UO2±x.- 4.4.1 Liquid Phase at Low Temperatures.- 4.4.2 Vapour Phase without Ionisation.- 4.4.3 Partially Ionised Vapour Phase.- 5 Application of the Chemical Model within the van der Waals Approximation.- 5.1 Non-Congruent Evaporation over UO2±x.- 5.1.1 Assumptions.- 5.1.2 Calibration.- 5.1.3 Results.- 5.2 Oxygen Potential.- 5.2.1 Simplified Calibration Procedure.- 5.2.2 Calibration in the Case of Non-Congruent Evaporation.- 5.3 Composition of the Liquid Phase.- 5.4 Discussion.- 5.5 Justification of the MIX Models.- 6 New Equation of State for Fluid Uranium Dioxide Based on Thermodynamic Perturbation Theory.- 6.1 Thermodynamic Perturbation Theory.- 6.1.1 Simple Fluids.- 6.1.2 One-Fluid Approximation.- 6.2 Fluids Composed of Molecules with Anisotropic Interaction.- 6.2.1 Averaged Diameter of Non-Spherical Molecules.- 6.2.2 Effective Molecular Diameter.- 6.2.3 Estimation of the Anisotropy Parameter.- 6.3 Conclusions.- 7 Thermodynamic Properties of UO2, as Predicted by the New Equation of State.- 7.1 Summary of the Model Features.- 7.2 Calibration.- 7.3 Validation of the INTAS-99-EOS.- 7.3.1 Density.- 7.3.2 Total vapour pressure.- 7.3.3 Heat capacity and thermal coefficients.- 7.4 Non-Congruent Equilibrium and Critical Point.- 7.4.1 Oxygen potential of liquid UO2.- 7.4.2 Enthalpy on the vapour-liquid boundary.- 7.4.3 Equilibrium composition and non-ideality effects.- 7.4.4 Azeotropic compositions.- 7.4.5 Critical point in FCE approximation.- 7.4.6 Critical point under non-congruent evaporation.- 7.5 Concluding Remarks.- A Appendix.- A.1.2 Volume Changes on Melting.- A.1.3 Thermal Expansion.- A.1.4 Elastic Properties and Adiabatic Compressibility.- A.1.6 Enthalpy and Entropy of Fusion.- A.1.8 The Congruently Vaporising Compositions of Urania.- A.2 Individual Components. Tables of Thermodynamic Functions.- A.3 Estimated Molecular and Ionic Interaction Constants.- A.3.1 Polarisability of Atomic O and U.- A.3.3 Dispersion Constants.- A.3.6 Conclusions.- A.4 Thermodynamic Tables.- References.

Blurb

The monograph deals with the thermodynamic properties of fluid uranium dioxide, one of the most investigated materials of the last century, up to its critical point. It presents an exhaustive theoretical introduction to "quasi-chemical" models of liquids, as well as their behaviour under non-congruent vaporisation conditions. Particular emphasis is given to the properties of pure Coulombic systems and to the pseudoparticle approach, which enables the partition function to be expressed in a simple, but physically rigorous formulation. The construction of the equation of state of stoichiometric and non-stoichiometric uranium dioxide is described in distinct steps, from a critical assessment of the theoretical fundamentals to a thorough review of the pertinent thermochemical and thermophysical data. Calculations of the thermodynamic properties of UO_2+x are performed for temperatures up to 11,000 K both for the condensed and gas phase. More than one hundred tables are collected in the Appendix containing all relevant thermodynamic data.