DECOVALEX

DEvelopment of COupled models and their VALidation against EXperiments

The DECOVALEX project is an international research and model comparison collaboration, initiated in 1992, for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems. Prediction of these coupled effects is an essential part of the performance and safety assessment of geologic disposal systems for radioactive waste and spent nuclear fuel, and also for a range of sub-surface engineering activities. The project has been conducted by research teams supported by a large number of radioactive-waste-management organizations and regulatory authorities. Research teams work collaboratively on selected modeling cases, followed by comparative assessment of model results. This work has yielded in-depth knowledge of coupled THM and THMC processes associated with nuclear waste repositories and wider geo-engineering applications, as well as the suitability of numerical simulation models for quantitative analysis. More »

DECOVALEX-2019: The Current Project Phase (2016-2019)

Brief Summary
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DECOVALEX-2019 is the current and 7th project phase and runs from 2016 through 2019. Modeling teams from 12 international partner organizations participate in the comparative evaluation of seven modeling tasks involving complex field and/or laboratory experiments in the UK, Switzerland, Japan, France and Sweden. Together, these tasks address a wide range of relevant issues related to engineered and natural system behavior in argillaceous and crystalline host rocks. More »

Task A
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A trail of aggregated gold nanoparticles trapped within the trace of a now closed pathway.

The primary purpose of Task A is to better understand the processes governing the advective movement of gas in two low permeability materials. The first material being considered is a compacted bentonite, which is frequently considered as a buffer and seal material. The second is the Callovo Oxfordian Claystone, a potential natural repository host rock. The task will focus on a series of laboratory experiments, initially considering the compacted bentonite and then moving on to the natural clay. More »

Task B
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Figure 1. Mt Terri fault activation experiment setting (Guglielmi, 2016).

Task B addresses important issues related to potential creation of permeable flow paths for contaminant transport in otherwise low permeability argillaceous rocks. The task focusses on the innovative data obtained from the fault activation experiments conducted at the Mont Terri underground research laboratory. The overall objective is to develop, compare and validate models for activation of minor and major faults, including mechanical responses and associated changes in fault permeability. The potential application of the work under Task B beyond radioactive waste disposal means we are seeking external collaboration - see here for more details.

Task C
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Hydrogeological condition is modelled based on the data obtained through geological observation and cross-hole hydraulic test.

The intention of Task C is to validate the simulation methodologies used to understand the long-term variation of hydro-mechanical-chemical (HMC) conditions during drift closure and resaturation in crystalline, fractured host rocks. The experimental basis for the modelling is the Groundwater REcovery Experiment in Tunnel (GREET) project, currently underway at the Mizunami underground research laboratory, Japan. The task will focus on the HMC couplings with a view to improving the predictive power of modelling tools for radioactive waste disposal. More »

Task D
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Figure 1. The EB experiment

The objective of Task D is to enhance the current knowledge of the evolution of a bentonite engineered barriers during the initial resaturation and heating (if present) transient period. There is a particular reference to the prediction of the final heterogeneity of the bentonite which is often a critical design consideration for engineered barriers. Task D will use the data from the EB experiment (Mont Terri, Switzerland) and FEBEX in-situ test (Grimsel, Switzerland), both of which used FEBEX bentonite and explore a wide range of test conditions. More »

Task E
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Layout of the TED in situ experiment

The primary purpose of Task E is to investigate upscaling of THM modeling from small size experiments (some cubic meters) to real scale cells (some ten cubic meters) and to the scale of the waste repository (cubic kilometers). The task us using two field-scale experiments at the Meuse/Haute-Marne underground research laboratory, France; the smaller scale TED experiment and the 1:1 scale ALC heating experiment. The results of this work will then be applied to predictive modelling of the behaviour of a single disposal cell at the repository scale, hence investigating the thermal-hydraulic-mechanical (THM) coupling across a range of spatial scales. More »

Task F
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Experimental observation on Fluid-migration after 156-hour run at 202°C ambient and 1.5°C/cm gradient (Roedder, 1984)

The emphasis of this work is to gain understanding of the physics and chemistry associated with small-scale fluid inclusions found in nearly all kinds of sedimentary rocks. Migration of these fluids may occur when stress states are disturbed and dilatancy-controlled mechanisms may operate. For the long-term performance of a potential radioactive waste disposal repository, depending on the disposal concept, the presence and evolution of these fluids may be of significance to the understanding of the system. Data for this task include extensive microscopic studies in addition to pressure, flow and geochemical data from more than 20 boreholes in underground laboratories. More »

Task G
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From Ericsson et al. (2014): Ground Penetrating Radar (GPR) reflectors under the TAS04 tunnel floor (top)

The aim of this task is to simulate the evolution of hydraulic transmissivity and conductivity throughout the lifetime of a repository for spent nuclear fuel in (sparsely) fractured competent rock mass primarily associated with the excavation disturbed and excavation damage zone (EDZ) around deposition tunnels. The primary data source is the TAS04 experiment, which was performed by SKB. This experiment was orignally intended at defining and developing standards, strategies and methods needed to design and construction. In this task, the data will be used to describe and model the hydraulic properties of the system and then to make forward predictions of the transmissivity of the system. More »

Current Partner Organizations

Logo Link Organization
link ANDRA
National Radioactive Waste Management Agency
France
link BGR
Federal Institute for Geosciences and Natural Resources
Germany
link CNSC
Canadian Nuclear Safety Commission
Canada
link DOE
Department of Energy
USA
link ENSI
Swiss Federal Nuclear Safety Inspectorate
Switzerland
link IRSN
Institut de Radioprotection et de Sûreté Nucléaire
France
link JAEA
Japan Atomic Energy Agency
Japan
link KAERI
Korea Atomic Energy Research Institute
Republic of Korea
link RWM
Radioactive Waste Management
UK
link SSM
Swedish Radiation Safety Authority
Sweden
link SURAO
Radioactive Waste Repository Authority
Czech Republic
link Taipower
Taiwan Power Company
Taiwan
link UFZ
Helmholtz Centre for Environmental Research
Germany