Impact of Updated OECD/NEA Thermodynamic Database on the Safety Assessment of Radioactive Waste Repository Studied Using RESRAD-OFFSITE Code

A RESRAD-OFFISTE computational code for the safety assessment model of a radioactive waste repository was utilized to evaluate the influence of the updated OECD/NEA thermodynamic database on the safety assessment model in terms of exposure dose. The solubility data as the input parameter for the RESRAD-OFFSITE code obtained with two different sets of chemical thermodynamic databases such as JAEA-TDB and amended JAEA-TDB reflecting the updates of the OECD/NEA thermodynamic database were calculated and compared with each other. As a result, almost identical exposure doses were obtained due to the remarkable similarity between the solubility data of various radionuclides for both chemical thermodynamic databases. In contrast, dramatic changes in exposure dose were observed with varying distribution coefficients. Thermodynamic calculations indicated that the aqueous species distribution can be significantly changed by the selection of a chemical thermodynamic database and thus the relevant distribution coefficient can also be influenced as a consequence. Accordingly, the result obtained in the present work indicated that (i) the impact of the updated chemical thermodynamic data was somewhat minor from the viewpoint of the solubility and (ii) the distribution coefficient, which can be sensitively influenced by the predominant chemical species, produced a remarkable change in the exposure dose. This work provided an insight into the precise exposure dose calculation in terms of the reliable estimation of the distribution coefficient by means of a surface complexation model, which can predict the distribution coefficient as a function of groundwater composition coupled with a chemical speciation calculation based on up to date chemical thermodynamic data.

The effect of Al2O3 on fayalite-based copper smelting slags in equilibrium with matte and tridymite at 1 2008C and P(SO2) = 0.25 atm

Experimental investigations have been undertaken to determine the effect of Al2O3in slag on the gas/slag/matte/tridymite equilibria in the multi-component Cu-Fe-O-S-Si-Al system at 1 200 8C, and P(SO2) = 0.25 atm. The experimental technique involves high temperature equilibration of synthetic samples on the open silica substrate in controlled gas atmospheres (CO/CO2/SO2/Ar), rapid quenching after a designated equilibration time followed by the compositional analysis of the condensed phases with electron probe X-ray microanalyzer. The experimental data of the present study provide information on the effect of alumina on the slag composition, such as the chemically dissolved copper, dissolved sulphur, and Fe/SiO2 ratio in slag at tridymite saturation at different Cu in matte. The new data have been used as inputs for the optimization of the thermodynamic databases for the copper-containing systems and can also be used to evaluate the fluxing strategy in the copper smelting operation.

Introducing Thermolab: a toolbox for Thermodynamics in MATLAB

<p>We present a set of MATLAB codes that can be used to perform equilibrium and non-equilibrium thermodynamic calculations. This will be of general use in geomaterial research and education, from the calculation of equilibrium phase diagrams to the development of dynamic models of reaction, deformation, mass and heat transport processes. The main MATLAB function calculates Gibbs energies of pure substances and mixtures using internally consistent thermodynamic databases, for rocks, minerals, melts and fluids. A general formulation of calculating Gibbs energy of mixtures based on linear algebra allows users to add custom solution models in an easy manner. The main Gibbs energy function can also be further extended, updated and customized, for example to involve other thermodynamic databases and equations of state.</p><p>We show three methods on how these Gibbs energies can be used to calculate chemical equilibrium based on optimization techniques and linear programming: 1) A brute-force method in which Gibbs energies of all possible phases and solutions are generated as a set of discrete phases. 2) A method of refining and restricting the Gibbs energies of solution phases to save computational resources and 3) A method that further saves computational resources by using system composition to generate Gibbs energies of solutions in a subset of the compositional space.</p><p>Finally, we demonstrate how these codes can be used in non-equilibrium thermodynamic processes such as reactive-fluid flow involving density and porosity changes.</p>

Experimental Investigation of Phase Equilibria in the Co-Re-Ta Ternary System

In this study, the isothermal sections of the Co-Re-Ta ternary system at 1100, 1200, and 1300 °C have been experimentally investigated by means of electron probe microanalysis and X-ray diffraction. The results indicated the following: (1) The solid solubilities of the λ3, (εCo, Re), χ-Re7Ta3, and bcc-(Ta) phases were large and changed very little from 1100 to 1300 °C; (2) more interestingly, the λ2 phase, with a very limited solubility of Re, was surrounded by the λ3 phase; (3) the solubility of Re for the μ-Co6Ta7 phase increased slowly from 1100 to 1300 °C. These experimental results will be useful for Co-based high-temperature alloys, especially as a supplement for thermodynamic databases.