BEACON: Bentonite Mechanical Evolution

Bentonite is a key component in many geological repositories. The objective of the BEACON project is to develop and test the tools necessary for assessment of the hydro-mechanical evolution of an installed bentonite barrier and its resulting performance.

Overview

Project Dates: 1/6/2017 – 31/05/2021

Project Status: Ongoing

Project Website: www.beacon-h2020.eu

The assessment of long-term safety of a geological repository has to rely on a robust model of a spatial and temporal distribution of the safety-relevant properties of bentonite.  Thus, developing predictive capabilities for the mechanical behaviour of bentonite buffers, seals and backfills is a common need for all radioactive waste management programs that use bentonite in one or more engineered barrier system (EBS) components.

The overall objective of the project is to develop and test the tools necessary for the assessment of the hydro-mechanical evolution of an installed bentonite barrier and its resulting performance. This will be achieved by cooperation between design and engineering, science and performance assessment.  Because of the complexity of the objectives, networking at the European level is key for development of integrated system understanding, skills, training and capabilities.

The evolution from an installed engineered system to a fully functioning barrier will be assessed. One of the challenges is to take into account initial heterogeneities introduced in the system by conception with a combination of block and pellets or due to the size of the bentonite component (several 100 m3).  It will require a more detailed understanding of material properties, of the fundamental processes that lead to homogenisation, of the role of scale effects and improved capabilities for numerical modelling.  The BEACON project aims to develop understanding of fundamental processes that lead to material homogenisation as well as to improve the capabilities of numerical modelling.  This will lead to a scientifically justified treatment of the involved processes in future safety assessments and licence applications for nuclear waste repositories.

BEACON is a collaborative project funded by the European Commission under the EURATOM Horizon 2020 Framework.  The project has 25 partners from 11 countries.

Objective

In earlier assessments of the long term performance of bentonite EBS, the mechanical evolution of the installed bentonite was neglected and an “ideal” final state was optimistically assumed.  Now that several European national programs are moving towards licensing, construction and operation of repositories, this assumption is no longer sufficient.  In order to verify the performance of current designs for buffers, backfills, seals and plugs the following is planned:

  • A well-documented and communicated collection of the available knowledge prior to the project.
  • Re-evaluation of a large part of the existing database to extract the important information, to compile the qualitative and quantitative observations and to develop conceptual understanding.
  • Enhanced, robust and practical numerical tools, firmly grounded on a good conceptual understanding, that have the required predictive capabilities concerning the behaviour of engineered barriers and seals.
  • A complete experimental database to meet the need of the assessment models.
  • Verified models based on experimental results from experiments at different scales.
  • Workshops dedicated to bentonite mechanical issues open to the scientific community.

The Beacon project is needed for the pan-European aims at building confidence amongst regulators and stakeholders regarding the performance of safety barriers in a geological repository.  It is also cost- and time-effective to progress development of the understanding regarding bentonite behaviour in a collaborative manner, and the pooling / sharing of information enhances the efficiency of the overall process.  The goal is to verify the performance of current designs for buffers, backfills, seals and plugs.

The overall driver for the project is the assessment cases that will be defined at the onset of the project (Work Package 1).  The quantitative models currently available are not fully able to represent all the complexities of the evolution of installed bentonite.  A substantial effort is needed to improve both the conceptual approaches and the numerical solutions in the current models (Work Package 3).  The updated/newly developed models need to be tested and verified using available data (Work Package 5).  There are some areas where fundamental data and the understanding of materials are incomplete.  An efficient experimental programme will support model development and testing (Work Package 4).  There is already a large database from experiments performed within EC projects and national programmes, both laboratory and Underground Research Laboratory (URL) experiments.  Many of the tests have been performed with other purposes in mind, but the results can be used in the BEACON project.  The objective of Work Package 2 is to collect the relevant information and process it to a level where it can be used in this project.