Periodic Reporting for period 3 - Beacon (Bentonite mechanical evolution)
Reporting period: 2020-06-01 to 2022-05-31
The Beacon project has addressed key technical issues that must be tackled to support the implementation of planned geological disposal projects for high-level radioactive wastes across the EU.
The overall objective of the project has been to evaluate the performance of an inhomogeneous bentonite barrier from an installed engineered system to a fully functioning barrier, achieved by developing and testing the tools necessary for the assessment of the mechanical evolution of an installed bentonite barrier and the resulting performance of the barrier. The goal was to verify the performance of current designs for buffers, backfills, seals and plugs. For some repository designs mainly in crystalline host rock, the results can also be used for the assessment of consequences of mass loss from a bentonite barrier in long term perspective.
The driver for this project has been repository safety, and the demands of waste management organizations to verify that the material selection and initial state design fulfil the long-term performance expectations. In this project, the initial state refers to the period at installation of the barrier, while long-term performance refers to the period for barrier saturation and evolution of the hydro-mechanical state, which could range from 10 to 1000s of years. In current and future applications for repositories, the regulators will expect the applicants to have a sufficient predictive capability of the barrier evolution from the installed to the final state. This will require an increased understanding of material properties and fundamental processes that lead to homogenisation as well as improved capabilities for numerical modelling.
The output of the project is a verification of the performance of current designs for buffers, backfills, seals and plugs and an improved handling of mass losses in long term assessments.
The overall objective of the project has been to evaluate the performance of an inhomogeneous bentonite barrier from an installed engineered system to a fully functioning barrier, achieved by developing and testing the tools necessary for the assessment of the mechanical evolution of an installed bentonite barrier and the resulting performance of the barrier. The goal was to verify the performance of current designs for buffers, backfills, seals and plugs. For some repository designs mainly in crystalline host rock, the results can also be used for the assessment of consequences of mass loss from a bentonite barrier in long term perspective.
The driver for this project has been repository safety, and the demands of waste management organizations to verify that the material selection and initial state design fulfil the long-term performance expectations. In this project, the initial state refers to the period at installation of the barrier, while long-term performance refers to the period for barrier saturation and evolution of the hydro-mechanical state, which could range from 10 to 1000s of years. In current and future applications for repositories, the regulators will expect the applicants to have a sufficient predictive capability of the barrier evolution from the installed to the final state. This will require an increased understanding of material properties and fundamental processes that lead to homogenisation as well as improved capabilities for numerical modelling.
The output of the project is a verification of the performance of current designs for buffers, backfills, seals and plugs and an improved handling of mass losses in long term assessments.
The scientific-technical work in Beacon was structured in 5 WPs, dissemination and training was handled in WPs 6-7, coordination & management covered in WP8.
The objective of WP1 was to define the important issues concerning the mechanical properties of bentonite and to define how these should be treated. This resulted in a number of specified assessment cases with focus on long term performance and/or repository engineering. A state-of-the-art report (D1.1) on the treatment of the mechanical evolution of the bentonite buffers, backfills and seals in the most recent safety assessment in the national programs was submitted. A report synthesizing the findings in the frame of the 3 assessment cases within the BEACON project reports the modelling results from the different groups assessing the HM evolution of the three assessment cases and evaluates these results in view of the respective safety case.
Modelling teams were able to model assessment cases representative of the engineered barrier and sealing concepts proposed by SKB, Nagra and Andra in the final modelling stage.
Also the final workshop had its roots in WP1 and was deliverable D1.2.
In WP2 the existing knowledge base was treated. During the first months of Beacon, WP2 collected and compiled data from ongoing and decommissioned large scale URL experiments, from partners and non-partners. These data were "reused" in Beacon. A database with the assembled data and information has been created, available at the project web www.beacon-h2020.eu and two reports describe the results.
The strongest driver for a joint project is the current limitations in the predictive capability in the numerical models. The issue of homogenisation and swelling is challenging both from a conceptual and a numerical point of view. The purpose of WP3 was to identify and resolve the shortcomings of current models. The state of the constitutive models of the 12 different modelling teams were presented and discussed, and assessed with reference to a set of key features of the hydromechanical behaviour of the bentonite. The bulk of the work carried out within WP3 has been the further development, improvement and verification of the constitutive models that were available to the various modelling teams at the start of the project. Three deliverables were submitted.
There was a substantial experimental database available for the project, but WP4 coordinated the necessary additional experiments that were totally adapted to the needs of WP3 and WP5. During the first period an experiment table was developed containing the essential information about the experiments planned and performed in Beacon in order to facilitate interaction between WP4 and the modelling work packages. This table was developed during the project, and three deliverables were produced and submitted in the WP
The core component and main effort of Beacon was in WP5 - testing the models. The overall objective of WP5 was to simulate the assessment cases defined by WP1. In order to do this, the available models had to be tested first on results from earlier performed laboratory experiments and later on results from large scale field test to gain confidence in their predictive capability. Seven deliverables were submitted.
The objective of WP1 was to define the important issues concerning the mechanical properties of bentonite and to define how these should be treated. This resulted in a number of specified assessment cases with focus on long term performance and/or repository engineering. A state-of-the-art report (D1.1) on the treatment of the mechanical evolution of the bentonite buffers, backfills and seals in the most recent safety assessment in the national programs was submitted. A report synthesizing the findings in the frame of the 3 assessment cases within the BEACON project reports the modelling results from the different groups assessing the HM evolution of the three assessment cases and evaluates these results in view of the respective safety case.
Modelling teams were able to model assessment cases representative of the engineered barrier and sealing concepts proposed by SKB, Nagra and Andra in the final modelling stage.
Also the final workshop had its roots in WP1 and was deliverable D1.2.
In WP2 the existing knowledge base was treated. During the first months of Beacon, WP2 collected and compiled data from ongoing and decommissioned large scale URL experiments, from partners and non-partners. These data were "reused" in Beacon. A database with the assembled data and information has been created, available at the project web www.beacon-h2020.eu and two reports describe the results.
The strongest driver for a joint project is the current limitations in the predictive capability in the numerical models. The issue of homogenisation and swelling is challenging both from a conceptual and a numerical point of view. The purpose of WP3 was to identify and resolve the shortcomings of current models. The state of the constitutive models of the 12 different modelling teams were presented and discussed, and assessed with reference to a set of key features of the hydromechanical behaviour of the bentonite. The bulk of the work carried out within WP3 has been the further development, improvement and verification of the constitutive models that were available to the various modelling teams at the start of the project. Three deliverables were submitted.
There was a substantial experimental database available for the project, but WP4 coordinated the necessary additional experiments that were totally adapted to the needs of WP3 and WP5. During the first period an experiment table was developed containing the essential information about the experiments planned and performed in Beacon in order to facilitate interaction between WP4 and the modelling work packages. This table was developed during the project, and three deliverables were produced and submitted in the WP
The core component and main effort of Beacon was in WP5 - testing the models. The overall objective of WP5 was to simulate the assessment cases defined by WP1. In order to do this, the available models had to be tested first on results from earlier performed laboratory experiments and later on results from large scale field test to gain confidence in their predictive capability. Seven deliverables were submitted.
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. When several European national programs are moving towards licensing, construction and operation of repositories, this assumption was no longer sufficient.
In order to verify the performance of current designs for buffers, backfills, seals and plugs the following work has been performed:
I. A well-documented and communicated collection of the available knowledge prior to the Project
II. Re-evaluation of a large part of the, at the beginning of the project, existing database to extract the important information, to compile the qualitative and quantitative observations and to develop the conceptual understanding
III. 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
IV. A complete experimental database for the need of the assessment models
V. Verified models based on experimental results from experiments in different scales
VI. Workshops dedicated to the mechanical issues in bentonite open to the scientific community
VII. A very successful training course
The Beacon project was needed for the pan-European aims at building confidence amongst regulators and stakeholders regarding the performance of safety barriers in a geological repository. It was also cost- and time-effective to progress development of understanding regarding bentonite behaviour in a collaborative manner, and the pooling / sharing of precedent information enhanced efficiency of overall process.
In order to verify the performance of current designs for buffers, backfills, seals and plugs the following work has been performed:
I. A well-documented and communicated collection of the available knowledge prior to the Project
II. Re-evaluation of a large part of the, at the beginning of the project, existing database to extract the important information, to compile the qualitative and quantitative observations and to develop the conceptual understanding
III. 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
IV. A complete experimental database for the need of the assessment models
V. Verified models based on experimental results from experiments in different scales
VI. Workshops dedicated to the mechanical issues in bentonite open to the scientific community
VII. A very successful training course
The Beacon project was needed for the pan-European aims at building confidence amongst regulators and stakeholders regarding the performance of safety barriers in a geological repository. It was also cost- and time-effective to progress development of understanding regarding bentonite behaviour in a collaborative manner, and the pooling / sharing of precedent information enhanced efficiency of overall process.