Thermodynamic Modelling and Aqueous Chemistry in the CaO-Al2O3-SiO2-H2O System

1990 ◽  
Vol 212 ◽  
Author(s):  
A. Atkinson ◽  
J. A. Hearne ◽  
C. F. Knights
Keyword(s):  
Experimental Data ◽  
Solid Solution ◽  
Radioactive Waste ◽  
Solid Solutions ◽  
Chemical Properties ◽  
Average Composition ◽  
Radioactive Waste Repositories ◽  
Waste Repositories ◽  
Hydrolysis Of ◽  
Main Influence

ABSTRACTThe chemical properties of the CaO-Al2O3-SiO2-H2O system are important for understanding and predicting the behaviour of Portland cements in cementitious wasteforms and radioactive waste repositories. Solids of known average composition in this system have been synthesised by the co-hydrolysis of mixed alkoxides. The solids have been equilibrated with water at 25°C and the composition of the aqueous phase characterised. A thermodynamic model for the system has been developed by extending an earlier model of solid solutions in amorphous gels to include aluminium compounds. The model accounts for most of the experimental data and predicts that the main influence of aluminium is to form a hydrogarnet solid solution of general composition C3AH6−2xSx The model can be used to predict the chemistry of hydrated cements and the interaction of cements with groundwaters.

Solubility and hydrolysis of Zr oxides: a review and supplemental data

2002 ◽  
Vol 90 (9-11) ◽  
Author(s):  
E. Curti ◽  
C. Degueldre
Keyword(s):  
Radioactive Waste ◽  
Aqueous Solutions ◽  
Nuclear Reactor ◽  
Published Data ◽  
Reactor Technology ◽  
Hydrolysis Constants ◽  
Radioactive Waste Repositories ◽  
Waste Repositories ◽  
Hydrolysis Of

SummaryThermodynamic data for Zr(IV) have been reviewed in the context of a recent update of the Nagra/PSI thermochemical database, which is primarily used in safety assessment calculations for radioactive waste repositories in Switzerland. In spite of the important role of Zr in nuclear reactor technology and as fission product in radioactive waste, the thermodynamic properties of this element in aqueous solutions are poorly constrained and published data are frequently contradictory. Specifically, hydrolysis constants, which are critical to any geochemical calculation of Zr speciation in aqueous solutions, may vary by several orders of magnitude.Published solubility and hydrolysis data for Zr oxides were reviewed and evaluated. Recent solubility measurements on crystalline ZrOAll solubility data of (hydrous) Zr oxides can be reproduced satisfactorily by a single set of hydrolysis constants, provided that only data measured from undersaturation are considered. This set includes the species Zr

Modelling Porewater Chemistry in Hydrated Portland Cement

1986 ◽  
Vol 84 ◽  
Author(s):  
Urs R. Berner
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Radioactive Waste ◽  
Portland Cement ◽  
Pore Water ◽  
Blended Cements ◽  
Radioactive Waste Repositories ◽  
Consistent Picture ◽  
Solid Phases ◽  
Waste Repositories

AbstractExtensive employment of concrete is foreseen in radioactive waste repositories. A prerequisite for modelling the interactions between concrete and formation waters is characterisation of the concrete system. Available experimental data from high pressure squeezing of cement pore-water indicate that, besides the high pH due to alkali hydroxide dissolution, cement composition itself influences the solubility determining solid phases. A model which simulates the hydration of Portland cement assuming complete hydration of the main clinker minerals is presented. The model also includes parameters describing the reactions between the cement and blending agents.Comparsion with measured pore-water data generally gives a consistent picture and, as expected, the model gives correct predictions for pure Portland cements. For blended cements, the required additional parameters can, to some extent, be derived from pore-water analysis.

The Modelling of Gas Migration through Compacted Bentonite Buffers in Radioactive Waste Repositories: the Work of the GAMBIT Club

2003 ◽  
Vol 807 ◽  
Author(s):  
William R Rodwell ◽  
Andrew R Hoch ◽  
Ben T Swift
Keyword(s):  
Experimental Data ◽  
Radioactive Waste ◽  
Geological Environment ◽  
Gas Migration ◽  
Compacted Bentonite ◽  
Radioactive Waste Repositories ◽  
Water Saturated ◽  
Waste Repositories ◽  
Modelling Approaches

ABSTRACTUse of compacted bentonite buffers is frequently planned in radioactive waste repositories to isolate waste canisters from the geological environment. When gas is generated from the wastes or their containers, it will need to migrate through the bentonite if pressure rises local to the canisters are to be avoided. Assessment of the effect of gas produced from waste canisters in bentonite buffers requires both experimental data on and models of gas migration through initially water-saturated bentonite. Several different approaches to modelling gas migration through bentonite are described. Some example comparison of model results with experimental data are provided, and some general discussion about the modelling approaches is offered.

An Assessment of the Long-Term Durability of Concrete in Radioactive Waste Repositories

1985 ◽  
Vol 50 ◽  
Author(s):  
A. Atkinson ◽  
D. J. Goult ◽  
J. A. Hearne
Keyword(s):  
Reinforced Concrete ◽  
Radioactive Waste ◽  
Concrete Slab ◽  
Laboratory Studies ◽  
Preliminary Assessment ◽  
Reinforced Concrete Slab ◽  
Radioactive Waste Repositories ◽  
Waste Repositories ◽  
Durability Of Concrete

AbstractA preliminary assessment of the long-term durability of concrete in a repository sited in clay is presented. The assessment is based on recorded experience of concrete structures and both field and laboratory studies. It is also supported by results of the examination of a concrete sample which had been buried in clay for 43 years.The enoineering lifetime of a 1 m thick reinforced concrete slab, with one face in contact with clay, and the way in which pH in the repository as a whole is likely to vary with time have both been estimated from available data. The estimates indicate that engineering lifetimes of about 103 years are expected (providing that sulphate resisting cement is used) and that pH is likely to remain above 10.5 for about 106 years.

scholarly journals Integrated approach to risk assessment of potential surface radioactive waste storage

2019 ◽  
Vol 95 (2) ◽  
pp. 133-139
Author(s):  
I. P. Korenkov ◽  
Tatyana N. Lashchenova ◽  
N. K. Shandala ◽  
V. V. Romanov
Keyword(s):  
Radioactive Waste ◽  
Potential Surface ◽  
Integrated Approach ◽  
Comprehensive Approach ◽  
Potential Danger ◽  
Management Decisions ◽  
Near Surface ◽  
Waste Storage ◽  
Radioactive Waste Repositories ◽  
Waste Repositories

Algorithm for management of decision-making on the decommissioning of nuclear and radiation hazardous objects (RHO) should be both based on an comprehensive approach, with taking into account all the potential dangers, and relied upon on the requirements of a modern regulatory framework, as well as economically sound and socially oriented. The aim of the work was a development of a comprehensive approach to the assessment of the degree of the potential danger of near surface radioactive waste repositories in RHO, on the base of which it is possible to make substantiated management decisions for their decommissioning. Tasks: To develop an array of radio-ecological approaches, including radiation-hygienic, hydrogeological and engineering criteria for the assessment of the potential danger of radioactive waste repositories. Results There are presented radiation hygienic, hydrogeological and engineering and technical criteria on the basis of which there are calculated coefficients of the relative hazard of storages. In dependence to the value of the coefficients there are suggested four categories of danger - a safe, low dangerous, dangerous and very dangerous. There are elaborated approaches on management decisions-making in various variants of decommissioning - the conversion, renovation, conservation and liquidation.

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