Discrete fracture network model benchmarks developed and applied in a DECOVALEX-2023 repository performance assessment study

Journal Article · Wed Feb 05 00:00:00 EST 2025 · Geomechanics for Energy and the Environment

DOI:https://doi.org/10.1016/j.gete.2025.100647· OSTI ID:2584382

Mariner, Paul E. ^[1]; Leone, Rosie C. ^[1]; Stein, Emily R. ^[1]; Hyman, Jeffrey D. ^[2]; Thiedau, Jan ^[3]; Li, Zhenze ^[4]; Nguyen, Son ^[4]; Kim, Yong-Min ^[5]; Kim, Jung-Woo ^[5]; Chang, Chieh-Chun ^[6]; Briggs, Scott A. ^[7]; Gobien, Mark ^[7]; Mikláš, Ondrej ^[8]; Osuji, Nicholas I. ^[9]; Niemi, Auli ^[9]

---

1. Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
2. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
3. Federal Institute for Geosciences and Natural Resources (BGR), Hanover (Germany)
4. Canadian Nuclear Safety Commission (CNSC), Ottawa, ON (Canada)
5. Korea Atomic Energy Research Institute (KAERI), Daejeon (Korea, Republic of)
6. Taiwan National Atomic Research Institute (NARI), Taoyuan (Taiwan)
7. Nuclear Waste Management Organization (NWMO), Toronto, ON (Canada)
8. Czech Radioactive Waste Repository Authority (SÚRAO), Prague (Czech Republic)
9. Uppsala Univ. (Sweden)

This study presents newly developed benchmarks for modeling flow and transport within discrete fracture networks (DFNs) and useful methods for analyzing the results. The new benchmarks are designed to test modeling approaches for use in probabilistic performance assessment models of deep geologic repositories in fractured rock. The benchmarks simulate flow and transport through a 1 km³ block of fractured rock. The first simulates migration of a short pulse of tracer through a simple network of four intersecting fractures. The second adds 1089 stochastically generated fractures. The third changes the pulse to a continuous point source. Evaluation of model performance relies on moment analysis and comparison of the results of different models. The expected nondimensional first moment of the conservative tracer for each benchmark is 1. The benchmarks were simulated by teams from Canada, Czechia, Germany, Korea, Sweden, Taiwan, and the United States as part of a DECOVALEX-2023 study (decovalex.org). The teams used various approaches, including explicit DFN modeling, DFN upscaling to an equivalent continuous porous medium (ECPM), and a combination of both methods. Transport mechanisms are modeled using either the advection-dispersion equation or particle tracking. Results demonstrate strong agreement among the models in breakthrough behavior up to the 75th percentile. Significant deviations in first moments and well-clustered outputs led to the identification of inaccuracies in several models. Such findings exemplify the benefit of exercising these benchmarks and using the presented methods to test DFN flow and transport models.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: 89233218CNA000001; NA0003525
• OSTI ID: 2584382
• Journal Information: Geomechanics for Energy and the Environment, Journal Name: Geomechanics for Energy and the Environment Vol. 41; ISSN 2352-3808
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

Benchmark
Discrete fracture network
Equivalent continuous porous media
Fracture flow
Moment analysis
Solute transport