Abstract
Task 6 studies solute transport through fractured rock both in the site characterisation and performance assessment conditions and especially the simplification made in the performance assessment models compared to the site characterisation models. The framework of the Task 6 modelling is a semi-synthetic model of the hydraulic features and microstructural model of the immobile pore space in the Task 6 modelling volume.
Modelling of the Tasks 6D, 6E, 6F and 6F2 presented in this report employs directly the semi-synthetic DFN and microstructural models of the Task 6C. This means that the geometry of the structures and the microstructural model are taken into account as they are defined in the Task 6C model or in the task definition.
Modelling indicates that it is very difficult to extrapolate performance assessment scale transport properties from the transport properties of the site characterisation scale. Solute transport in the site characterisation scale is governed by the microstructural model along the expected transport paths. In the performance assessment scale the averaging of the immobile zone transport properties extends much deeper in the rock matrix than in the site characterisation flow conditions. This may result a significant contrast between the retention properties that are observed in the site characterisation and in the performance assessment, because the governing retention zones can be totally different.
Modelling suggests that it is better to link the site characterisation and performance assessment models in the level of the retention processes than in the level of the retention parameters. Tracer experiments in the site characterisation conditions and the related modelling can be used to build confidence that the retention processes involved in the performance assessment models are appropriate for the fractured rock.
Modelling of the Tasks 6D, 6E, 6F and 6F2 presented in this report employs directly the semi-synthetic DFN and microstructural models of the Task 6C. This means that the geometry of the structures and the microstructural model are taken into account as they are defined in the Task 6C model or in the task definition.
Modelling indicates that it is very difficult to extrapolate performance assessment scale transport properties from the transport properties of the site characterisation scale. Solute transport in the site characterisation scale is governed by the microstructural model along the expected transport paths. In the performance assessment scale the averaging of the immobile zone transport properties extends much deeper in the rock matrix than in the site characterisation flow conditions. This may result a significant contrast between the retention properties that are observed in the site characterisation and in the performance assessment, because the governing retention zones can be totally different.
Modelling suggests that it is better to link the site characterisation and performance assessment models in the level of the retention processes than in the level of the retention parameters. Tracer experiments in the site characterisation conditions and the related modelling can be used to build confidence that the retention processes involved in the performance assessment models are appropriate for the fractured rock.
| Original language | English |
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| Place of Publication | Stockholm |
| Publisher | Svensk Kärnbränslehantering AB (SKB) |
| Number of pages | 75 |
| Publication status | Published - 2006 |
| MoE publication type | D4 Published development or research report or study |
Publication series
| Series | International Progress Report |
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| Number | IPR-06-17 |