Ph.D. projects

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Numerical study of radionuclide migration and retention in fracture systems in granites

Wenyu Zhou

PD Dr. Cornelius Fischer (HZDR)

Reactive Transport

12/2021–12/2024

Fractures in crystalline rocks play a critical role in solute transport by providing the primary mass transfer through flow channels in low permeability rocks. Reactive transport modeling, which considers coupled processes including solute advection, diffusion and reaction in crystalline rock fractures, is widely recognized as an important approach to improving the fundamental understanding of radionuclide transport in the subsurface. Improved characterization of crystalline fracture geometry and intrface morphology can provide valuable insights into solute transport behavior in reactive transport modeling, which significantly influences both radionuclide sorption and diffusion on mineral surfaces. However, building a complete pore scale fracture reactive transport model is not an easy task. A quantitative study of the factors influencing fracture reactive transport behavior will lead to more accurate predictions and ultimately improve the reliability of safety assessments for deep nuclear repositories, as well as facilitate the evaluation of contamination migration.

In this project, three-dimensional reactive transport models will be used to investigate the effect of fracture aperture characteristics on fluid flow and transport. Other important reactive transport processes include dissolution or hydrothermal alteration kinetics and matrix diffusion. Both pore-scale and micro-scale fracture models will be tested and applied to provide a mechanistic understanding of reactive transport and retention behavior in the fracture-matrix system of granitic host rocks. Overall, this work will contribute to a more robust implementation of coupled advective-diffusive transport in numerical models of reactive transport at the pore scale.

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