Open this publication in new window or tab >>2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]
The focus of this thesis is on the development of new models to improve our understanding of radionuclide transport in the repository “far-field” in fractured rocks. The proposed models contribute to the channel network concept and describe the recently developed models with stagnant water zones (STWZs) and channels with variable aperture allowing to consider their possible impacts on the overall transport of radionuclides in fractured rocks. New conceptual models are also proposed to better understand hydrodynamic dispersion in fractured rocks by taking into account velocity distribution within tapered channels, i.e., Fickian-type dispersion, and between different flow paths, i.e., velocity dispersion, as embodied in the proposed multi-channel model.
The results of both deterministic and probabilistic analyses reveal that over the long times of interest for safety assessment of high-level radioactive waste repositories, STWZs can substantially enhance the retardation of both short- and long-lived nuclides, with the exception of the non-sorbing species, i.e., 36Cl and 129I. Nevertheless, over the short time-scales the impact of STWZs is not very strong and is not expected to affect the results of short-term field experiments. It is also shown that the proposed multi-channel model can explain the apparent scale dependency of the dispersion coefficient that is often observed in tracer experiments. It is further discussed that the interpreted results of short-range tracer experiments cannot necessarily give information on what would take place over longer distances because the spreading mechanisms are expected to be entirely different. Usefulness of the continuum model to interpret tracer experiments is, thereafter, discussed and arguments are presented to support the premise that it is more physically meaningful to describe flow and transport as taking place in a three-dimensional network of channels.
Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 37
Keywords
Channel network concept; radionuclide transport; stagnant water zones; velocity dispersion; modeling and simulation
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-214040 (URN)978-91-7729-523-5 (ISBN)
Public defence
2017-10-06, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20170911
2017-09-112017-09-102022-12-12Bibliographically approved