Task F of DECOVALEX-2023 involves comparison of the models and methods used in post-closure performance assessment of deep geologic repositories. The task will center around two generic disposal concepts for commercial spent nuclear fuel (SNF): a reference case describing a generic repository in a fractured crystalline host rock and a generic repository in a salt formation (bedded or domal). Although a direct comparison cannot be made between simulations of a crystalline repository and simulations of a salt repository, it is expected that foundational aspects will be transferable between concepts, for instance, methods of coupling process models, propagating uncertainty, or conducting sensitivity analysis.

The primary objectives of Task F are to build confidence in the models, methods, and software used for performance assessment (PA) of deep geologic repositories, to bring to the fore additional research and development needed to improve PA methodologies, and to cultivate awareness of international PA practices among participating countries and teams. The objectives will be accomplished through a staged comparison of the models and methods used by participating teams in their PA frameworks, including: (1) coupled-process submodels (e.g., waste package corrosion, spent fuel dissolution, radionuclide transport) comprising the full PA model; (2) deterministic simulation(s) of the entire PA model for defined reference scenario(s); (3) probabilistic simulations of the entire PA model; and (4) uncertainty quantification (UQ) and sensitivity analysis (SA) methods/results for probabilistic simulations of defined reference scenario(s).

Figure 1. Task F workflow. Items in blue rectangles will be given by the task lead or developed as a group. Items in green rectangles will be completed by individual teams. Comparisons to be performed are in ovals.

Reference Cases

Generic repository in fractured crystalline host rock

The DECOVALEX-2023 crystalline reference case uses the KBS-3V emplacement concept developed for the Swedish and Finnish repository programs (Pettersson and Lönnerberg 2008). The KBS-3V concept is developed for a repository mined at a depth of approximately 500 m in sparsely fractured crystalline rock. Copper canisters, each containing a nominal inventory of 4 pressurized water reactor (PWR) assemblies, are emplaced within rings of compacted bentonite in vertical deposition holes beneath the floor of a deposition tunnel, and tunnels are backfilled. Processes of interest include radionuclide transport in fractured rock, influence of the stress field on fracture transmissivity, and coupling between fracture flow, bentonite erosion, and canister corrosion.

Figure 2. Example of a flow and transport model domain with generic repository in fractured crystalline rock.

Generic repository in salt host rock

Development of the DECOVALEX-2023 reference case for a generic repository in a salt formation will be lagged behind development of the crystalline reference case. Interested teams will agree upon the type of salt deposit (bedded or domal), characterization of the natural and engineered barriers, key Features, Events, and Processes (FEPs), conceptual models and parameterization, and choose individual process models for benchmarking and comparison (e.g., salt creep, crushed salt reconsolidation, thermal conduction). Reference cases previously published in the United States (bedded salt), Germany (bedded and domal salt), and the Netherlands (domal salt) will provide the basis for the DECOVALEX-2023 salt reference case, including Sevougian et al. (2016), Bollingerfehr et al. (2018), and Prij et al. (1989).


The following outline structure is proposed for each reference case:

  • Step 0: Review the DECOVALEX-2023 reference case proposal. Agree on key FEPs to include. Finalize details of conceptual model specification and parameterization for one scenario.
  • Step 1: Identify individual process models for benchmark comparisons and make the comparisons.
  • Step 2: Perform a reference case deterministic simulation.
  • Step 3: Identify uncertain inputs and appropriate probability distributions. Compare mean, median, and other quantitative metrics of uncertainty for performance measures. Calculate prescribed measure of sensitivity such as partial correlation coefficients and standardized regression coefficients and compare them.
  • Step 4 (optional): Interested teams may apply sensitivity analysis methods of their choice to the reference case for a comparison of sensitivity analysis methods.

Participating Groups

Crystalline reference case:

  • United States Department of Energy (DOE – USA)
  • Canadian Nuclear Safety Commission (CNSC - Canada)
  • Nuclear Waste Management Organization (NWMO – Canada)
  • Gesellschaft für Anlagen- und Reaktorsicherheit (GRS – Germany)
  • Bundesamt für die Sicherheit der nuklearen Entsorgung (BASE – Germany)
  • Federal Institute for Geosciences and Natural Resources (BGR – Germany)
  • Korea Atomic Energy Research Institute (KAERI – Republic of Korea)
  • Taiwan Power Company (TPC – Taiwan)
  • Swedish Radiation Safety Authority (SSM – Sweden)

Salt reference case:

  • United States Department of Energy (DOE – USA)
  • Gesellschaft für Anlagen- und Reaktorsicherheit (GRS – Germany) with the Federal Company for Radioactive Waste Disposal (BGE – Germany)
  • Centrale Organisatie Voor Radioactief Afval (COVRA – Netherlands)

Further Information

For further information, please contact the task leader, Emily Stein.


  1. Bollingerfehr, W., Bertrams, N., Buhmann, D., Eickemeier, R., Fahland, S., Filbert, W., Hammer, J., Kindlein, J., Knauth, M., and Wenting, L., 2018. Concept developments for a generic repository for heat-generating waste in bedded salt formations in Germany. Synthesis Report (No. BGE TEC 2018-13). BGE TECHNOLOGY GmbH
  2. Pettersson, S. and B. Lönnerberg 2008, 16-18 June 2008. Final Repository for Spent Nuclear Fuel in Granite - The KBS-3V Concept in Sweden and Finland. Paper presented at the International Conference Underground Disposal Unit Design & Emplacement Processes for a Deep Geological Repository, Prague.
  3. Prij, J., van Dalen, A., Englund-Borowiec, G., Glasbergen, P., de Haas, J.B.M., Jong, C.T.J., de Jong, E.J., Köster, H.W., Nijhoff-Pan, I., Roodbergen, H.A., Slagter, W., van Weers, A.W., and Znastra, D.A., 1989. Safety Evaluation of Disposal Concepts in Rock Salt. Final Report (IL 369; OPLA 89-08)
  4. Sevougian, S. D., E. R. Stein, M. B. Gross, G. E. Hammond, J. M. Frederick, and P. E. Mariner 2016. Status of Progress Made Toward Safety Analysis and Technical Site Evalutations for DOE Managed HLW and SNF. SAND2016-11232R. Sandia National Laboratories, Albuquerque, NM.