Evaluation of Colloid Transport Experiments in a Quarried Block
2009 (English)In: SCIENTIFIC BASIS FOR NUCLEAR WASTE MANAGEMENT XXXII / [ed] Hyatt NC; Pickett DA; Rebak RB, 2009, Vol. 1124, 519-524 p.Conference paper (Refereed)
Colloid tracer experiments were performed in a single, heterogeneous fracture contained in a quarried block (QB) under the configuration of dipole tracer tests. The experiments were first performed using bentonite and 100 nm latex colloids, as well as conservative tracer iodide and bromide, under conditions of different flow rates in order to identify the flow rates that favour colloid transport. The tracer experiments were later expanded to include experiments with different colloid sizes and longer transport distances. The aims of the present study are to identify the processes that affect colloid transport in the QB fracture and to estimate the retention parameters for the different sized colloids. We model the measured breakthrough curves (BTCs) using an advection-retention approach. The key feature of the advection-retention model is that advective transport and retention processes are related in a dynamic manner through the flow equation. Two Lagrangian random variables, tau and beta, that depend solely on flow conditions, control the retention processes. Here tau is the nonreactive travel time and beta is related to tau but also depends on the local aperture value. We assume the water residence time distribution g(tau) to be inverse-gaussian. The first two moments of g(tau) were obtained by calibrating the measured BTCs of conservative tracers. We then model the colloid BTCs using g(tau) and take into account the retention processes. The modelling results indicate that dominating retention processes include first-order linear kinetic attachment/detachment on the fracture surface, and mass loss (removal) by filtration/sedimentation. Diffusion into the rock matrix is of a much lesser importance.
Place, publisher, year, edition, pages
2009. Vol. 1124, 519-524 p.
, Materials Research Society Symposium Proceedings, ISSN 0272-9172 ; 1124
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-30414DOI: 10.1557/PROC-1124-Q11-03ISI: 000270898900068ScopusID: 2-s2.0-70449337499ISBN: 978-1-60511-096-7OAI: oai:DiVA.org:kth-30414DiVA: diva2:400879
32nd Symposium on Scientific Basis for Nuclear Waste Management held at the 2008 MRS Fall Meeting, Boston, MA, DEC 01-05, 2008
QC 201102282011-02-282011-02-242011-02-28Bibliographically approved