Nuclear Energy and Waste



DOE-NE-Nuclear Energy

DEvelopment of COupled Models and their VALidation Against EXperiments in Nuclear Waste Isolation

The DECOVALEX Project is a unique international research collaboration for advancing the understanding and mathematical modeling of coupled thermo-hydro-mechanical (THM) and thermo-hydro-chemical (THC) processes in geological systems. DECOVALEX is an acronym for “Development of Coupled Models and their Validation against Experiments.” Starting in 1992, the project has made important progress and played a key role in the development of numerical modeling of coupled processes in fractured rocks and buffer/backfill materials. The project has been conducted by research teams supported by a large number of radioactive-waste-management organizations and regulatory authorities, including those of Canada, China, Finland, France, Japan, Germany, Spain, Sweden, UK, South Korea, Czech Republic, and the USA. Through this project, in-depth knowledge has been gained of coupled THM and THMC processes associated with nuclear waste repositories, as well as numerical simulation models for their quantitative analysis. The knowledge accumulated from this project, in the form of a large number of research reports and international journal and conference papers in the open literature, has been applied effectively in the implementation and review of national radioactive-waste-management programs in the participating countries.

The DECOVALEX Project is typically conducted in separate 3-4 year project phases. Each phase features a small number (typically three to six) modeling test cases of importance to radioactive waste disposal. Many test cases are laboratory and field experiments that have been conducted by one of the project partners and are then collectively studied and modeled by DECOVALEX participants. Numerical modeling of these test cases can assist both to interpret the test results and to test the models used. Over the years, a number of large-scale, multiyear field experiments have been studied within the project (e.g., the Kamaishi THM Experiment, FEBEX, and the Yucca Mountain drift-scale heater test). Thus, the project provides access to valuable technical data and expertise to DECOVALEX partner organizations; this is particularly useful in disposal programs that are starting their research on certain disposal or repository environments and have no underground research laboratories (URLs). DECOVALEX has a modeling focus, but with tight connection to experimental data.

Energy Geosciences Division Director, Jens Birkholzer was recently named the Chairman of the DECOVALEX Project, and LBNL is now serving as the coordinating organization for DECOVALEX. In addition, LBNL scientists have participated as modeling teams in various past DECOVALEX phases and several DECOVALEX projects. The current DECOVALEX Project phase (referred to as D-2019) started in Spring 2016 and will run through the end of 2019. Modeling tasks tackled in the current phase are:

  • Task A: ENGINEER – Modeling advective gas flow through low permeability materials.
  • Task B: Fault Slip Test – Modelling the induced slip of a fault in argillaceous rock.
  • Task C: GREET – Hydro-mechanical-chemical-biological processes during groundwater recovery.
  • Task D: INBEB – Hydro-mechanical interactions in bentonite engineered barriers.
  • Task E: Upscaling Heater Tests – Upscaling of modelling and experimental results from small scale to one-to-one scale.
  • Task F: FINITO – Fluid inclusion and movement in tight rock.
  • Task G: EDZ Evolution – Reliability, feasibility and significance of Measurements of conductivity and transmissivity of the rock mass for the understanding of the evolution of a repository of spent nuclear fuel.