Chemical Thermodynamics Chemical Thermodynamics of Solid Solutions of Interest in Radioactive Waste Management

This volume provides a state-of-the-art report on the modelling of aqueous-solid solution systems by the combined use of chemical thermodynamics and experimental and computational techniques. These systems are ubiquitous in nature and therefore intrinsic to the understanding and quantification of radionuclide containment and retardation processes present in geological repositories of radioactive waste. Representative cases for study have been chosen from the radioactive waste literature to illustrate the application of the various approaches. This report has been prepared by a team of four leading experts in the field under the auspices of the OECD/NEA Thermochemical Database (TDB) Project. Table of Content : Part I. Extended Summary -Introduction: Scope, Objectives and the Audiene of guidelines -Definitions -From Aqueous to Solid Solutions -Basic Thermodynamics of Solid Solutions -Experimental and Analystical Aspects -Testing the Aq-SS Concepts and Methods in Nuclear Waste Management Relevant Systems -Report Conclusions Part II. Theory, Experimental Aspects and Cases for Study -Theoretical Asptcts of Solid Solutions and their Solubility -Experimental and Analytical Aspects -Cases of Specific Interest in Relevant Systems Bibliography Preface......Page 7 Acknowledgements......Page 9 Editor's note......Page 11 I.1.1 Motivation......Page 23 I.1.3 Audience......Page 25 I.2 Definitions......Page 26 I.3 From Aqueous to Solid Solutions......Page 29 I.4 Basic Thermodynamics of Solid Solutions......Page 34 I.4.2 The entropy of mixing......Page 35 I.4.5 On the relevance of non-ideality......Page 36 I.4.6 Solid solution versus other uptake modes......Page 38 I.4.7 Concepts and approximations in geochemical modelling of Aq-SS systems......Page 39 I.4.8 Kinetic and thermodynamic approximations to Aq-SS in geochemical reactive transport modelling......Page 40 I.5 Experimental and analytical aspects......Page 41 I.5.2 Characterization of the solid solution......Page 42 I.5.4 Partition/distribution experiments......Page 44 I.5.5.2 Calorimetry......Page 45 I.6.1.1 The radium-barite relationship in natural and anthropogenic environments......Page 47 I.6.1.2 Numerical modelling involving (Ba,Ra)SO4 solid solutions......Page 48 I.6.2.2 Thermodynamic modelling of C-S-H and its limitations......Page 49 I.6.2.3 Geochemical modelling of C-S-H systems of interest in radioactive waste management......Page 50 I.6.3.1 The relevance of calcite for radioactive waste management......Page 51 I.6.3.3 Spectroscopic information on the incorporation of f-elements into the calcite structure......Page 52 I.6.4.1 The applicability of Aq-SS thermodynamics to spent nuclear fuel......Page 53 I.6.4.3 Application of Aq-SS thermodynamics to spent fuel dissolution data......Page 54 I.7 Report conclusions......Page 55 II.1.1.1 Introduction......Page 57 II.1.1.2 Thermodynamic formalism......Page 59 II.1.1.3 The entropy of mixing......Page 62 II.1.1.4 Regular, subregular and generalised mixing models......Page 66 II.1.1.4.1 Dilute solid solutions......Page 71 II.1.1.5 Phases with different structures......Page 73 II.1.1.6.1 General comments......Page 77 II.1.1.6.2 An example: carbonates with calcite and dolomite structures......Page 78 II.1.2 Methods and tools for thermodynamic description of aqueous-solid solution (Aq-SS) equilibria......Page 82 II.1.2.1 Definitions and basic thermodynamics relations......Page 84 II.1.2.1.1 Mole fraction scale......Page 86 II.1.2.1.2 Molality scale......Page 87 II.1.2.1.3 Aqueous activity coefficients......Page 88 II.1.2.1.3.1 SIT model......Page 91 II.1.2.1.3.3 Extended UNIQUAC model......Page 92 II.1.2.1.4 Gas mixtures and gas solubility......Page 93 II.1.2.1.5 Solid solubility......Page 94 II.1.2.1.6 Unified theory of ionic solid solution solubilities......Page 96 II.1.2.1.7 Multicomponent ionic Aq-SS system (following [2003GAM/KON])......Page 98 II.1.2.2 Lippmann diagrams, a tool to visualise binary Aq-SS systems......Page 99 II.1.2.2.1 Example of the use of Lippmann diagrams......Page 102 II.1.2.3 Law of mass action (LMA) method for computing equilibrium speciation......Page 108 II.1.2.4 Gibbs energy minimisation (GEM) method......Page 116 II.1.2.4.1 GEM IPM algorithm......Page 119 II.1.2.4.2 GEM dual-thermodynamic calculations in forward modelling.......Page 123 II.1.2.4.3 Multiple solid solutions and miscibility gaps......Page 125 II.1.3.1 The “activity ratios” technique......Page 127 II.1.3.2 Dual Thermodynamic retrieval calculations......Page 131 II.1.3.2.2 Retrieval of activity coefficients and mixing parameters......Page 132 II.1.3.2.3 Retrieval of end-member standard molar Gibbs energy and solubility product at equilibrium......Page 134 II.1.3.2.5 DualTh retrieval calculations at minimum stoichiometric saturation......Page 135 II.1.3.2.6 Statistical DualTh calculations......Page 137 II.1.3.2.7 Example: EuIII in calcite......Page 138 II.1.3.3 Graphical fitting and regression methods......Page 142 II.1.3.3.1 Weighted least-squares and Bayesian estimation techniques......Page 143 II.1.3.4 Retrieval of excess Gibbs energy from electrochemical measurements......Page 144 II.1.3.5 Estimation of interaction parameters from the position of miscibility gaps......Page 147 II.1.3.5.1 Miscibility gap data......Page 148 II.1.3.5.2 Critical mixing-point data......Page 149 II.1.3.6 Estimation of interaction parameters from distribution coefficients......Page 151 II.2 Experimental and analytical aspects......Page 152 II.2.1.1 Limitations and points to notice......Page 153 II.2.1.1.1 Synthesis procedures......Page 156 II.2.2 Solubility measurements in aqueous solutions......Page 158 II.2.2.1 Thermodynamic equilibrium solubility......Page 159 II.2.2.2 Stoichiometric saturation......Page 161 II.2.3 Solid phase characterisation......Page 164 II.3.1.1 Introduction to the barite isostructural family......Page 177 II.3.1.2.1 The radium-barium relationship in natural and anthropogenic environments......Page 180 II.3.1.2.2 Numerical modelling involving (Ba,Ra)SO4 solid solutions......Page 182 II.3.1.3 Conclusions......Page 190 II.3.2 Cases study/Cement phases – Solubility of calcium silicate hydrates (C-S-H)......Page 191 II.3.3 Structural incorporation of trivalent actinides/lanthanides into calcite......Page 206 II.3.4.1 Introduction......Page 215 II.3.4.2.1 Uraninite and non-irradiated fuel......Page 216 II.3.4.2.2 Irradiated UO2......Page 217 II.3.4.3 Application of Aq-SS thermodynamics to spent fuel dissolution experimental data......Page 218 II.3.4.3.1 Strontium......Page 219 II.3.4.3.2 Barium......Page 221 II.3.4.3.3 Neptunium......Page 222 II.3.4.3.4 Plutonium......Page 223 II.3.4.3.5 Lanthanides......Page 224 II.3.4.4 Final remarks......Page 225 [1958HAR/OWE]......Page 227 [1969OAT]......Page 228 [1974BRO/SKI]......Page 229 [1977PAR/MOL]......Page 230 [1981FUJ/KON]......Page 231 [1982REE2]......Page 232 [1984HAR/MOL]......Page 233 [1985PAG/PIN]......Page 234 [1987BUR]......Page 235 [1987PLU/BUS]......Page 236 [1988HOC]......Page 237 [1989GAL/DAN]......Page 238 [1990ERI/HAC]......Page 239 [1990NOR/PLU]......Page 240 [1991TAI/STR]......Page 241 [1992GRE/FUG]......Page 242 [1992STI/HOC]......Page 243 [1993NIK/RAS]......Page 244 [1994NAV/RAP]......Page 245 [1995SIL/BID]......Page 246 [1996HER/WES]......Page 247 [1997GRE/PLY2]......Page 248 [1997PIR/FED]......Page 249 [1998BRU/CER]......Page 250 [1998PIA/TOU]......Page 251 [1999GRU]......Page 252 [1999PER/PAL]......Page 253 [2000GLY]......Page 254 [2000PRI/FER]......Page 255 [2001GAN]......Page 256 [2001PAR/VAN]......Page 257 [2001ZIE/OTT]......Page 258 [2002HEL/NAV]......Page 259 [2002MAN/MAR]......Page 260 [2003BLA/AGU]......Page 261 [2003JOH/GLA]......Page 262 [2003TIT/STU]......Page 263 [2004KLE]......Page 264 [2004ROU/ELZ]......Page 265 [2005BRO/CUR]......Page 266 [2005LEE/WAN]......Page 267 [2005VIL/THO]......Page 268 [2006VIL/THO]......Page 269 List of cited authors......Page 271 This volume is intended as a state-of-the-art report on the modelling of aqueous-solid solution systems by the combined use of chemical thermodynamics and experimental and computational techniques, in the context of radioactive waste management, and more specifically oriented towards underground disposal. These systems are ubiquitous in nature and therefore intrinsic to the understanding and quantification of radionuclide containment and retardation processes present in geological repositories of radioactive waste. Representative cases for study have been chosen from the radioactive waste literature to illustrate the application of the various approaches. No attempt has been made to systematically review the literature dealing with all aspects of solid solutions or to select data, although particular emphasis has been placed on the application of the thermodynamic formalism to systems encountered in radioactive waste management which can be described as solid solutions.--Publisher description. From aqueous to solid solutions Basic thermodynamics of solid solutions Experimental and analytical aspects Testing the Aq-SS concepts and methods in nuclear waste management relevant systems Theoretical aspects of solid solutions and their solubility Experimental and analytical aspects Cases of specific interest in relevant systems: 1. Sulphates : the barite isostructural family and the incorporation of radioactive isotopes of Ra; 2. Cases study/cement phases : solubility of calcium silicate hydrates (C-S-H); 3. Structural incorporation of trivalent actinides/lanthanides into calcite; 4. Solid solutions in the nuclear fuel cycle.