BELBAR

Bentonite Erosion: effects on the Long term performance of the engineered Barrier and Radionuclide Transport (BELBaR)

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 Obiettivo del progetto (Objective)

'Recent safety assessments nuclear waste repositories have shown that the formation and stability of colloids may have a direct impact on the overall performance of the repository. The main aim of the BELBaR project is increase the knowledge of the processes that controls clay colloid stability, generation and ability to transport radionuclides. The overall purpose of the project will be to suggest a treatment of the issues in long-term safety assessment. The key areas of research will be: • erosion of bentonite buffers, the main objective of these studies will be to understand the main mechanisms of erosion from the bentonite surface and to quantify the extent of the possible erosion under different conditions • clay colloid stability studies under different geochemical conditions. The colloids formed at the near/far field interface would be stable only if favourable conditions exist and therefore their relevance for radionuclide transport will be strongly dependent on the local geochemical conditions • interaction between colloids and radionuclides and the host rock, how colloid mobility may be affected be the composition of the host rock and the mechanism of sorption and de-sorption of radionuclides on the colloids In these areas substantial laboratory studies will be undertaken. The modelling studies will support the laboratory studies through development of conceptual and mathematical descriptions of the observed phenomena. The final outcome is to consider how colloids and related phenomena can be considered in the long term safety case and to make recommendations on how the safety case could pursue to address this potentially very significant issue. The project will have strong focus on cooperation and integration. This will be achieved by exchange of staff between partners and arrangement of frequent seminars. The BELBaR consortium consists of research institutes, implementers and universities from within and outside the European Union.'

Introduzione (Teaser)

Nuclear energy, literally energy released from the nuclei of atoms, is clean, renewable, powerful and reliable. EU-funded scientists are now decreasing uncertainties associated with geological disposal of waste for enhanced public support.

Descrizione progetto (Article)

Further enhancing the safety of radioactive waste disposal will foster greater public support and implementation. This in turn will decrease dependence on problematic fossil fuel imports, leading to larger decreases in greenhouse gas emissions and amelioration of global climate change.

EU-funded scientists are studying important processes occurring in geological disposals, the internationally agreed-upon safe method for final disposal of high-level radioactive waste. Experiments conducted and models developed within the scope of the http://www.belbar.eu (BELBAR) project should reduce uncertainties associated with erosion as well as instability issues in engineered barrier systems (EBSs) and fractured host rock.

The formation of clay colloids may degrade the EBS and adversely affect transport of radionuclides, reducing the efficiency of the natural barrier. Scientists are first determining the conditions for colloidal stability as instability and short lifetimes would make it unnecessary to include them in updated models. Their next focus is the improvement of quantitative models for erosion of the EBS for the scenarios in which the colloids are stable. This includes enhancing understanding of radionuclide attachment to and transport by clay colloids to realistically model processes.

Scientists have developed several experimental setups to evaluate transport of radionuclides in stagnant water and in fractures. The latter includes artificial fracture systems to study extrusion of swelling clay into nearby fractures. Preliminary results under a variety of conditions suggest strong colloid attachment to fracture surfaces even under what are conventionally considered unfavourable scenarios.

The second line of inquiry is investigating colloid stability. Investigations of five different clays from five different origins demonstrated growing aggregation resulting in destabilisation of colloids with increasing ionic strength.

Consideration of clay erosion is required to implement safe geologic waste disposal in line with EU policy and best practices. BELBAR expects to make an important contribution to this effort, increasing the robustness of safety analyses and thus minimising uncertainty associated with potential risks.