Through diffusion experiments to study the diffusion and sorption of HTO, 36Cl, 133Ba and 134Cs in crystalline rock

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Aromaa , H , Voutilainen , M , Ikonen , J , Yli-Kaila , M , Poteri , A & Siitari-Kauppi , M 2019 , ' Through diffusion experiments to study the diffusion and sorption of HTO, 36Cl, 133Ba and 134Cs in crystalline rock ' , Journal of Contaminant Hydrology , vol. 222 , pp. 101-111 . https://doi.org/10.1016/j.jconhyd.2019.03.002

Title: Through diffusion experiments to study the diffusion and sorption of HTO, 36Cl, 133Ba and 134Cs in crystalline rock
Author: Aromaa, Hanna; Voutilainen, Mikko; Ikonen, Jussi; Yli-Kaila, Maarit; Poteri, Antti; Siitari-Kauppi, Marja
Contributor: University of Helsinki, Department of Chemistry
University of Helsinki, Department of Chemistry
University of Helsinki, Department of Chemistry
University of Helsinki, Department of Chemistry
Date: 2019-04
Language: eng
Number of pages: 11
Belongs to series: Journal of Contaminant Hydrology
ISSN: 0169-7722
URI: http://hdl.handle.net/10138/301336
Abstract: The spent nuclear fuel in Finland will be deposited in crystalline granitic rock in Olkiluoto, Finland. As a part of the safety assessment of the repository, series of extensive in-situ sorption and diffusion experiments and supplementary laboratory work has been done in the Olkiluoto site. Through Diffusion Experiment in a laboratory (TDElab) aims to provide applicable data for the ongoing in-situ experiment in Olkiluoto. This laboratory scale experiment resembles the in-situ experiment and aims to gain information on possible effects in values of distribution coefficients, effective diffusion coefficient and porosity that are caused by differences in laboratory and in-situ conditions. The through diffusion and sorption of tracer solution with known activities of HTO, 36Cl, 133Ba and 134Cs were studied in a decimeter scale sample of veined gneiss, which is one of the main rock types in Olkiluoto. The measured breakthrough curves were modeled taking into account the porosity of the rock and diffusion and sorption of the radionuclides using Time-Domain Random Walk (TDRW) simulations. The porosities of 0.7–0.8% were determined for the rock and effective diffusion coefficients of (3.5 ± 1.0) × 10−13 m2/s and (3.0 ± 1.0) × 10−13 m2/s were determined for HTO and 36Cl, respectively. The porosity and effective diffusion coefficients were found to be in agreement with previous results for veined gneiss. Furthermore, distribution coefficients of (1.0 ± 0.3) × 10−4 m3/kg and (2.0 ± 0.5) × 10−3 m3/kg were determined for 133Ba and 134Cs, respectively, using information about the effective diffusion coefficient determined for HTO. The distribution coefficients were found to be significantly smaller than the ones determined for crushed rock in previous studies and slightly smaller than the ones from previous in-diffusion experiments.
Subject: Diffusion
Sorption
Porosity
Crystalline rock
Radionuclides
Time-domain random walk
IN-SITU
TRANSPORT
POROSITY
SIMULATION
OLKILUOTO
CHLORIDE
GRANITE
SAMPLES
MATRIX
MICROTOMOGRAPHY
114 Physical sciences
116 Chemical sciences
1171 Geosciences
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