2,1,- 1Gesellschaft für Anlagen- und Reaktorsicherheit, Site Selection, Cologne, Germany (marc.johnen@grs.de)
- 2Institute for Modelling Hydraulic and Environmental Systems, University of Stuttgart, Stuttgart, Germany
Nuclear waste that is not deposited in a repository must pass through officially approved clearance procedures, which are regulated in the German Radiation Protection Ordinance (StrlSchV 2024). After clearance, the materials can be fed into further material cycles or disposed of in accordance with the type of release. The release values of the Radiation Protection Ordinance are based on the 10 µSv criterion. Numerical groundwater models are used to simulate the distribution of radionuclides and provide information on concentrations in space and time, which are used as input data for calculating doses for different exposure paths.
The basic transport processes of advection, diffusion, dispersion, and sorption and decay are implemented in the simulation codes "distributed density-driven flow (d3f++)" (Fein & Schneider 1999, Fein 2004), “Dune for Multiphase flow and transport (DuMux)” (Koch et al. 2021) and "Simulation of Processes in Groundwater (SPRING)" (König et al. 2023). One model area represents a simple 2D column and a 2D generic landfill body with a drainage, a geological barrier and a connected aquifer.
The benchmark study demonstrated a good agreement between the three computational codes, reinforcing the robustness of the numerical transport models for further applications in the dose calculation for the clearance procedures.
The differences in the breakthrough curves can be attributed to the initial conditions for the saturation and the influence of the dispersion in the models of the different codes, highlighting the sensitivity to these parameters. While minor discrepancies emerge in the outcomes, the study demonstrates that the concentrations and the times of maximum concentration are largely comparable and are within a few percent and not orders of magnitude apart.
References
Fein, Eckard; Schneider, Anke (1999): d3f – Ein Programmpaket zur Modellierung von Dichteströmungen. Abschlussbericht. Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbH. Braunschweig. GRS-139, ISBN 3-923875-97-5, October 1999.
Fein, Eckard (2004): Software Package r3t. Model for Transport and Retention in Porous Media. Final report. Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbH. Braunschweig. GRS-192. ISBN 3 931995-60-7. April 2004.
Koch et al. (2021): DuMux 3 – an open-source simulator for solving flow and transport problems in porous media with a focus on model coupling.
König, Christoph M., Becker, Martin; Brömme, Katrin; Diehl, Annette; König, Timo; Rosen, Britta, Rüber, Otto; Schröder, Simon; Seidel, Torsten; Zimmermann, Christian (2023): SPRING Benutzerhandbuch. SPRING-Version 6. 30. Mai 2023. ISBN: 978-3-00-073433-5. p. 585. Witten.
StrlSchV (2024): Verordnung zum Schutz vor der schädlichen Wirkung ionisierender Strahlung (Strahlenschutzverordnung - StrlSchV) in the version dated 29. November 2018 (BGBl. I S. 2034, 2036; 2021 I S. 5261), last modified 23. October 2024 (BGBl. I Nr. 324).
How to cite: Johnen, M., Winter, R., Class, H., Flemisch, B., Seher, H., and Meyering, H.: Modelling contaminant transport of soil and landfills: A benchmark study of three numerical Codes, Third interdisciplinary research symposium on the safety of nuclear disposal practices, Berlin, Germany, 17–19 Sep 2025, safeND2025-18, https://doi.org/10.5194/safend2025-18, 2025.
