Uranium Mineralogy at the Askola Ore Deposit, Southern Finland

Markovaara‐Koivisto, Mira; Read, David; Lindberg, Antero; Siitari-Kauppi, Marja; Marcos, Nuria

doi:10.1557/proc-1124-q10-02

Cited by 4 publications

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“…The samples chosen for the above analyses were altered tonalite of more than 10% porosity. These samples were chosen because there was a great deal of detailed information available of them [Lindberg and Paananen, 1992;Anttila et al, 1993;Hölttä et al, 1998;Lindberg and Siitari-Kauppi, 1998;Markovaara-Koivisto et al, 2009]. In addition, the pore apertures in them were fairly large, which made feasible, especially the X-ray tomography analysis of the pore space and thus a detailed analysis of alteration effects.…”

Section: Discussionmentioning

confidence: 99%

Pore‐space characterization of an altered tonalite by X‐ray computed microtomography and the¹⁴C‐labeled‐polymethylmethacrylate method

Voutilainen¹,

Siitari-Kauppi²,

Sardini³

et al. 2012

J. Geophys. Res.

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[1] The structure of geological materials strongly affects migration processes that take place in them and are also important in their weathering and alteration processes. Further information of that structure will also be important for many applications that involve geological materials. The emphasis of this study was thus to characterize the pore structure and porosity of altered tonalite by combining different measuring techniques: X-ray tomography, the 14 C-polymethylmethacrylate method, electron microscopy, and argon pycnometry. Intragranular porosities were determined using chemical staining of rock surfaces. Three-dimensional distributions of minerals and porosities were evaluated with consistent values for the total porosity. Porosity and pore size distributions together with pore connectivities were also determined. Combining the results of different methods, a 3-D porosity map was outlined for one sample. This porosity map enabled us to model, for example, diffusion in a more realistic environment. Scanning electron microscopy was used to identify the minerals and to obtain information on mineral texture and alteration state. The methods introduced here can be applied to many porous materials.Citation: Voutilainen, M., M. Siitari-Kauppi, P. Sardini, A. Lindberg, and J. Timonen (2012), Pore-space characterization of an altered tonalite by X-ray computed microtomography and the 14 C-labeled-polymethylmethacrylate method,

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Section: Discussionmentioning

confidence: 99%

Pore‐space characterization of an altered tonalite by X‐ray computed microtomography and the¹⁴C‐labeled‐polymethylmethacrylate method

Voutilainen¹,

Siitari-Kauppi²,

Sardini³

et al. 2012

J. Geophys. Res.

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“…The experimental approach adopted is based on through-diffusion in a radial configuration (Markovaara-Koivisto et al, 2008;Felipe-Sotelo et al, 2014). NRVB is a high-porosity cement containing a specific ratio of OPC (450 kg m -3 ), calcium hydroxide (495 kg m -3 ), calcium carbonate (170 kg m -3 ) and water (615 kg m -3 ).…”

Section: Methodsmentioning

confidence: 99%

Retention of chlorine-36 by a cementitious backfill

Hinchliff

Felipe-Sotelo

et al. 2015

Mineral. mag.

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Radial diffusion experiments have been carried out to assess the migration of 36 Cl, as chloride, through a cementitious backfill material. Further experiments in the presence of cellulose degradation products were performed to assess the effect of organic ligands on the extent and rate of chloride diffusion. Results show that breakthrough of 36 Cl is dependent on chloride concentration: as the carrier concentration increases, both breakthrough time and the quantity retained by the cement matrix decreases. Experiments in the presence of cellulose degradation products also show a decrease in time to initial breakthrough. However, uptake at various carrier concentrations in the presence of organic ligands converges at 45% of the initial concentration as equilibrium is reached. The results are consistent with organic ligands blocking sites on the cement that would otherwise be available for chloride binding, though further work is required to confirm that this is the case. Post-experimental digital autoradiographs of the cement cylinders, and elemental mapping showed evidence of increased 36 Cl activity associated with black ash-like particles in the matrix, believed to correspond to partially hydrated glassy calciumsilicate-sulfate-rich clinker.

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“…uranophane, in oxic conditions. In this work, uranophane and other uranium silicates have been identified near a shallow uranium mineralization at Askola, Southern Finland [12]. The groundwater at the study site contains hexavalent uranium which originates from weathering of the primary uraninite ore and/or from dissolved secondary uranium phases.…”

Section: Introductionmentioning

confidence: 99%

Understanding uranium behaviour at the Askola uranium mineralization

Jokelainen¹,

Markovaara‐Koivisto

Read³

et al. 2010

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Uranium / Rock alteration processes / Uranium migrationSummary. Understanding the behaviour of uranium is essential when assessing the safety of a spent nuclear fuel repository. The geochemical behaviour of uranium, including its reactive transport chemistry, is also a matter of concern when assessing the environmental impact of uranium mining. Subsurface uranium mobility is believed to be primarily controlled by dissolution and (co)-precipitation of uranium mineral solids and adsorption to mineral surfaces. This paper describes a modelling exercise based on characterisation of samples taken from drilled cores at the uranium mineralization at Askola, Southern Finland. In the modelling exercise, current conditions are assumed to be oxidizing and saturated with groundwater. PHREEQC was used for modelling in conjunction with the Lawrence Livermore National Laboratory database, chosen for its extensive coverage of uranium species and mineral phases.It is postulated that weathering processes near the surface have led to uranium dissolution from the primary ore, leaching out from the matrix and migrating along water-conducting fractures with subsequent re-diffusion into the rock matrix. Electron microscopy studies show that precipitated uranium occupies intra-granular fractures in feldspars and quartz. In addition, secondary uranium was found to be distributed within goethite nodules as well as around the margins of iron-containing minerals in the form of silicate and phosphate precipitates. Equilibrium modelling calculations predict that uranium would be precipitated as uranyl silicates, most likely soddyite and uranophane, in the prevailing chemical conditions beneath Lakeakallio hill.

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Uranium Mineralogy at the Askola Ore Deposit, Southern Finland

Cited by 4 publications

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Pore‐space characterization of an altered tonalite by X‐ray computed microtomography and the¹⁴C‐labeled‐polymethylmethacrylate method

Pore‐space characterization of an altered tonalite by X‐ray computed microtomography and the¹⁴C‐labeled‐polymethylmethacrylate method

Retention of chlorine-36 by a cementitious backfill

Understanding uranium behaviour at the Askola uranium mineralization

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Uranium Mineralogy at the Askola Ore Deposit, Southern Finland

Cited by 4 publications

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Pore‐space characterization of an altered tonalite by X‐ray computed microtomography and the14C‐labeled‐polymethylmethacrylate method

Pore‐space characterization of an altered tonalite by X‐ray computed microtomography and the14C‐labeled‐polymethylmethacrylate method

Retention of chlorine-36 by a cementitious backfill

Understanding uranium behaviour at the Askola uranium mineralization

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Pore‐space characterization of an altered tonalite by X‐ray computed microtomography and the¹⁴C‐labeled‐polymethylmethacrylate method

Pore‐space characterization of an altered tonalite by X‐ray computed microtomography and the¹⁴C‐labeled‐polymethylmethacrylate method