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@ARTICLE{Soler:909536,
author = {Soler, Josep and Meng, Shuo and Moreno, Luis and
Neretnieks, Ivars and Liu, Longcheng and Kekäläinen, Pekka
and Hokr, Milan and Říha, Jakub and Vetešník, Aleš and
Reimitz, Dan and Višňák, Jakub and Vopálka, Dušan and
Kröhn, Klaus-Peter and Tachi, Yukio and Ito, Tsuyoshi and
Svensson, Urban and Iraola, Aitor and Trinchero, Paolo and
Voutilainen, Mikko and Deissmann, Guido and Bosbach, Dirk
and Park, Dong Kyu and Ji, Sung-Hoon and Gvoždík, Libor
and Milický, Martin and Polák, Michal and Gylling, Björn
and Lanyon, Bill},
title = {{M}odelling of the {LTDE}-{SD} radionuclide diffusion
experiment in crystalline rock at the Äspö {H}ard {R}ock
{L}aboratory ({S}weden)},
journal = {Geologica acta},
volume = {20},
issn = {0567-7505},
address = {Barcelona},
reportid = {FZJ-2022-03225},
pages = {1 - 32},
year = {2022},
abstract = {This study shows a comparison and analysis of results from
a modelling exercise concerning a field experiment involving
the transport and retention of different radionuclide
tracers in crystalline rock. This exercise wasperformed
within the Swedish Nuclear Fuel and Waste Management Company
(SKB) Task Force on Modelling of Groundwater Flow and
Transport of Solutes (Task Force GWFTS). Task 9B of the Task
Force GWFTS was the second subtask within Task 9 and focused
on the modelling of experimental results from the Long Term
Sorption Diffusion Experiment in situ tracer test. The test
had been performed at a depth of about 410m in the Äspö
Hard Rock Laboratory. Synthetic groundwater containing a
cocktail of radionuclide tracers was circulated for 198 days
on the natural surface of a fracture and in a narrow slim
hole drilled in unaltered rock matrix. Overcoring of the
rock after the end of the test allowed for the measurement
of tracer distribution profiles in the rock from the
fracture surface (A cores) and also from the slim hole (D
cores). The measured tracer activities in the rock samples
showed long profiles (several cm) for non- or weakly-sorbing
tracers (Cl-36, Na-22), but also for many of the more
strongly-sorbing radionuclides. The understanding of this
unexpected feature was one of the main motivations for this
modelling exercise. However, re-evaluation and revision of
the data during the course of Task 9B provided evidence that
the anomalous long tails at low activities for strongly
sorbing tracers were artefacts due to cross-contamination
during rock sample preparation. A few data points remained
for Cs-137, Ba-133, Ni-63 and Cd-109, but most measurements
at long distances from the tracer source (>10mm) were now
below the reported detection limits. Ten different modelling
teams provided results for this exercise, using different
concepts and codes. The tracers that were finally considered
were Na-22, Cl-36, Co-57, Ni-63, Ba-133, Cs-137, Cd-109,
Ra-226 and Np-237. Three main types of models were used: i)
analytical solutions to the transport-retention equations,
ii) continuum porous-medium numerical models, and iii)
microstructure-based models accounting for small-scale
heterogeneity (i.e. mineral grains, porosities and/or
microfracture distributions) and potential centimetre-scale
fractures. The modelling by the different teams led to some
important conclusions, concerning for instance the presence
of a disturbed zone (a few mm in thickness) next to the
fracture surface and to the wall of the slim hole and the
role of micro-fractures and cm-scale fractures in the
transport of weakly sorbing tracers. These conclusions could
be reached after the re-evaluation and revision of the
experimental data (tracer profiles in the rock) and the
analysis of the different sets of model results provided by
the different teams.},
cin = {IEK-6},
ddc = {550},
cid = {I:(DE-Juel1)IEK-6-20101013},
pnm = {1411 - Nuclear Waste Disposal (POF4-141)},
pid = {G:(DE-HGF)POF4-1411},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000847357100001},
doi = {10.1344/GeologicaActa2022.20.7},
url = {https://juser.fz-juelich.de/record/909536},
}