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Methods of Handling non Homogeneities at Different Scales in Radionuclide Transport

Objective

To develop a working set of equations to describe the transport of radionuclides in media with randomly varying material properties. To apply these equations to some well-defined geometrical situations and to highlight the deficiencies in current practice, much of which uses the classical advective-dispersion equation. To review the past work in the field. It is expected that the new equations will be applicable to practical situations in assessing the containment efficiency of waste repositories.
The objectives of this project are to develop a working set of equations to describe the transport of radionuclides in media with randomly varying material properties; to apply these equations to some well defined geometrical situations and to highlight the deficiencies in current practice, much of which uses the classical advective-dispersion equation; to review the past work in the field. It is expected that the new equations will be applicable to practical situations in assessing the containment efficiency of waste repositories.

A review of past papers relevant to the transport of radionuclides in fractured rock has been completed. In particular, the foundations of dispersion theory and the work in which geometrical models of capillaries were introduced have been examined. Finally, the most recent developments in which the advection dispersion equation has been treated as a stochastics differential equation has been assessed and reviewed. Work has also begun on the development of a set of equations to describe radionuclide behaviour based upon a completely new approach which uses the ideas of kinetic theory and introduces a fictitious marked particle which is tracked through the random matrix. Such an approach was introduced due to the intractability of the more conventional stochastic approach and the difficulty of applying it to complex practical situations.
Work programme:

The stated goals of this work were threefold:

1. A review of the relevant past work done in the field of spatially stochastic radionuclide transport.
2. The development of a set of equations to describe radionuclide transport in spatially random media.
3. The provision of numerical results for simple geometries to compare the new equations with the results from classical methods.

These tasks have been carried out successfully and the results and conclusions have been presented to the Commission in the following reports:

-"A review of selection of papers describing the theory of transport in anisotropic media", published as report EUR 14163.
-"A new model for describing the transport of radionuclides through fractured rock:
Part 1: General theory
Part 2: Numerical results and extension to overlapping fracture sets"
-A final report of the research project "Methods of handling non-homogeneities at different scales in radionuclide transport", summarizing the findings of the above report and to make some recommendations to future work using the new set of equations developed. This report will be published as EUR 14696.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Electrowatt Engineering Services Ltd
Address

BD Bradford
United Kingdom