International benchmarking for the verification and validation of TH2M simulators, especially with regard to fluid-dynamic processes in repository systems (BenVaSim-II) 

Country / Region: Weltweit

Begin of project: February 1, 2023

End of project: October 31, 2025

Status of project: October 8, 2024

German Version

Fig. 1: Good agreement between the results calculated by the different project partners and numerical codes. Shown are pore water pressure profiles over a quasi-1-dimensional bar model at different points in time [3] Source: Report [3]

Motivation: Numerical codes are used worldwide for the reliable prediction of the behaviour of a radioactive waste repository in deep underground geological formations. The BGR, too, uses the finite element programme OpenGeoSys [1], which is being developed as open-source code by the Helmholtz Centre for Environmental Research GmbH in Leipzig. Before such a program system can be used for integrity and safety verifications for example, it must be extensively tested and quality assured.

Strategy: In addition to the numerical post-modelling of laboratory and in-situ investigations [2], the comparison of different codes is a proven means of testing a given implementation, and demonstrating its performance [3]. In this way, it can be shown under which circumstances the compared numerical simulation tools provide matching results, and under which circumstances deviations exist. In the previous BenVaSim-I project, in which the BGR was already involved, and in the current BenVaSim-II project, process implementations and their results are analysed and explained. In this way, the project partners increase the confidence in each of the codes involved, and thus make an important contribution to their future use. In addition, the BenVaSim project contributes to the general understanding of thermal-hydraulic-mechanical coupled processes to be expected in a future repository, through the well-defined and analysed benchmark examples.

Literature:

[1] L. Bilke et al. “Development of Open-Source Porous Media Simulators: Principles and Experiences”. In: Transport in Porous Media 130.1 (2019), pp. 337–361. doi: 10.1007/s11242019-01310-1.

[2] J. T. Birkholzer et al. “25 years of DECOVALEX - Scientific advances and lessons learned from an international research collaboration in coupled subsurface processes”. In: International Journal of Rock Mechanics and Mining Sciences 122 (2019), p. 103995. issn:1365-1609. www.sciencedirect.com/science/article/pii/S1365160918308451.

[3] K.-H. Lux et al. Synthesis report. BenVaSim – International Benchmarking for Verification and Validation of TH2M Simulators with Special Consideration of Fluid Dynamical Processes in Radioactive Waste Repository Systems. Tech. rep. 2022.

[4] Michael Pitz, Norbert Grunwald, Bastian Graupner, Kata Kurguyis, Eike Radeisen, Jobst Maßmann, Gesa Ziefle, Jan Thiedau, and Thomas Nagel (2023): ”Benchmarking a new TH2M implementation in OGS-6 with regard to processes relevant for nuclear waste disposal”. In: Environmental Earth Sciences 82, 319 (2023). https://doi.org/10.1007/s12665-023-10971-7

Partner:

Project partners: For the verification and validation of the numerical codes by code comparison in BenVaSim-II, international institutions have joined forces: from the USA, the Lawrence Berkeley National Lab (LBNL) is participating, from Switzerland, the Swiss Federal Nuclear Inspectorate (ENSI), and from Germany, in addition to the BGR, the Federal Office for the Safety of Nuclear Waste Management (BASE), the Gesellschaft für Anlagen- und Reaktorsicherheit gGmbH (GRS) and the Clausthal University of Technology. The latter initiated and manages the project, which receives funding via the Karlsruhe Project Management Agency (PTKA).