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Bentonite barriers in integrated performance assessment

Risultati finali

The relevant design concepts for bentonite barriers, the safety functions and the design requirements assigned to these barriers have been summarised. This implies a better knowledge and understanding of the roles of the bentonite barriers. The necessity of using predictive models to assess potential consequences in performance assessment is well recognised. The assessment of the influence of many significant FEPs requires the development of conceptual models. An in depth analysis and cross comparison of the different models available for the numerical simulation of the behaviour of bentonite barriers at any level of detail has been generated, in order to establish their role in Integrated performance Assessments and verification exercises. The consistency of data need of the models has been evaluated. The overall result has been a better understanding of the modelling and computer programs related to the performance of bentonite barriers. Calculations (including sensitivity analysis) have been performed using the analysed models and codes at process and integrated level. Conclusions have been extracted on the performance of the bentonite barriers in geological repositories for clay and granite.
The evaluation of the level of knowledge on the FEP's concerning bentonite barriers and the basis for their treatment in Performance Assessment, has been complemented in BENIPA with the review of experimental and scientific bases, obtained in multiple theoretical studies, laboratory and in-situ experiments, natural analogues, etc. A Project handbook of relevant data for safety assessment of bentonite barriers has been produced as a reference book for internal consultation in future assessments. This is a thorough understanding of the relevant data for performance assessment relative to bentonite barrier materials. All the organisations involved in BENIPA have analysed the information (studies, experiments findings and conclusions) available in their national programmes. Also, information from other EU countries (i.e.: Sweden) non-participating in the project or from non-EU countries (i.e.: Canada, Japan) has been selected and analysed. Results of the analysis have been compiled and elaborated further in BENIPA to reach an understanding of the degree of support that scientific and experimental studies provide for the justification of the decisions made in Integrated Performance Assessment on the treatment of the FEPs influencing the performance of Bentonite Barriers.
A key activity in development of a repository safety or performance assessment is the identification of the relevant factors or FEPs and the selection of factors that should be included in quantitative analysis. The project has reviewed of all the features events and process FEPs relevant to the performance of bentonite barriers in granite and clay formations. Completeness and consistency of available databases have been discussed. A FEPs database (differentiated for granite and clay) to be used as a reference in future performance assessments exercises have been obtained. Existing data relative to these FEPs have been drawn from relevant references and databases. The FEP descriptions consist of the following common components: identification and name, description, main sources of description, discussion of potential treatment in performance assessment, related FEPs, comments and references.