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253 results on '"Siitari-Kauppi, Marja"'

2. Comparing fracture openings in mortar using different imaging techniques

Author

Marliot Jonathan, Hedan Stephen, Siitari-Kauppi Marja, Sammaljärvi Juuso, Landesman Catherine, Henocq Pierre, and Sardini Paul

Subjects
mortar, fracture apertures, characterisation method, process duration, disadvantages, Engineering geology. Rock mechanics. Soil mechanics. Underground construction, TA703-712
Abstract

This paper presents a quantitative characterisation of the fracture openings obtained in triaxial shear tests on several cement mortar samples. The comparison was carried out on three samples with various apertures using different methods of semi-destructive and non-destructive characterisation: optical microscopy, scanning electron microscopy, X-ray computed tomography, digital volume correlation and the 14C-polymethylmethacrylate method. The fracture aperture distribution results are in good agreement between the different methods. Although the opening results obtained are comparable, the most advantageous method was considered to be XRCT profile analysis based on the size of the target area studied and the specific characteristics of each technique.

Published
2024
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9. Modeling of a radionuclide transport experiment in granitic rock matrix at the Grimsel Test Site (Switzerland). The role of advection

Author

Ministerio de Ciencia e Innovación (España), 0000-0003-0741-249X, Soler, Josep M., Jurado, Deby, Saaltink, Maarten W., Martínez, Lurdes, Hidalgo, Juan J., Lanyon, G. William, Heule, Martin, Fukatsu, Yuta, Siitari-Kauppi, Marja, Havlová, Vaclava, Bedrníková, Eva, Martin, Andrew J., Ministerio de Ciencia e Innovación (España), 0000-0003-0741-249X, Soler, Josep M., Jurado, Deby, Saaltink, Maarten W., Martínez, Lurdes, Hidalgo, Juan J., Lanyon, G. William, Heule, Martin, Fukatsu, Yuta, Siitari-Kauppi, Marja, Havlová, Vaclava, Bedrníková, Eva, and Martin, Andrew J.

Abstract

Within the framework of the GTS-LTD project (Grimsel Test Site – Long-Term Diffusion), a radionuclide transport experiment in unfractured granitic rock matrix was performed. Grimsel groundwater containing several radionuclide tracers (3H as HTO, 36Cl−, 22Na+, 134Cs+, 133Ba2+) was continuously circulated through a packed-off borehole interval. The decrease in tracer concentrations in the solution was monitored for a period of 1266 days (March 05, 2014–August 22, 2017). Additionally, tracer breakthrough was monitored in an observation borehole at a distance of 18.6 cm. Initial modeling of the experiment (1D radial), considering transport only by diffusion, showed that the evolution of tracer concentrations departed from the expected trend after some time, with concentrations in the injection borehole decreasing faster than expected. Additional 2D calculations (section normal to the boreholes) were performed to check the possible effect of advection through the rock matrix. Advection could explain the evolution of concentrations in the injection borehole, but concentrations in the observation borehole were overestimated. Core samples from new boreholes were collected immediately after the end of the experiment, allowing the measurement of tracer distributions in the rock. The observed patterns for the non-sorbing tracers (HTO, 36Cl−) showed clear preferential transport directions, consistent with advective flow towards the gallery from which the boreholes were drilled. Final 3D modeling of the experiment can explain the measured concentrations in the boreholes and in the rock. Tracer transport for the conservative tracers (HTO, 36Cl−) is affected by both diffusion and advection through the granitic rock matrix. Also, in situ accessible porosities deduced from the modeling (0.0014) are smaller than those measured in rock samples (about 0.009), pointing to unloading and destressing of the rock samples after drilling. At the spatial and temporal scales of the experiment

Published
2024

26. Improved Radio-Cesium Detection Using Quantitative Real-Time Autoradiography

Author

Ang, Joyce W. L., Bongrand, Arthur, Duval, Samuel, Donnard, Jérôme, Parkkonen, Joni, Utsunomiya, Satoshi, Koivula, Risto, Siitari-Kauppi, Marja, and Law, Gareth T. W.

Subjects
microparticles, mathematical methods, härmistyminen, matemaattiset menetelmät, electrical energy, paksuus, pienhiukkaset, deposition, thickness, sähköenergia
Abstract

Cesium-134 and -137 are prevalent, long-lived, radio-toxic contaminants released into the environment during nuclear accidents. Large quantities of insoluble, respirable Cs-bearing microparticles (CsMPs) were released into the environment during the Fukushima Daiichi nuclear accident. Monitoring for CsMPs in environmental samples is essential to understand the impact of nuclear accidents. The current detection method used to screen for CsMPs (phosphor screen autoradiography) is slow and inefficient. We propose an improved method: real-time autoradiography that uses parallel ionization multiplier gaseous detectors. This technique permits spatially resolved measurement of radioactivity while providing spectrometric data from spatially heterogeneous samples a potential step-change technique for use after nuclear accidents for forensic analysis. With our detector configuration, the minimum detectable activities are sufficiently low for detecting CsMPs. Further, for environmental samples, sample thickness does not detrimentally affect detector signal quality. The detector can measure and resolve individual radioactive particles ≥465 μm apart. Real-time autoradiography is a promising tool for radioactive particle detection. peerReviewed

Published
2023

33. Diffusion and Sorption Studies of Cs, Sr and Co in Intact Crystalline Rock

Author

Li, Xiaodong, Sammaljarvi, Juuso, Meng, Shuo, Liu, Longcheng, Siitari-Kauppi, Marja, Martin, Andrew, Li, Xiaodong, Sammaljarvi, Juuso, Meng, Shuo, Liu, Longcheng, Siitari-Kauppi, Marja, and Martin, Andrew

Abstract

Three cationic tracers, Sr2+, Co2+ and Cs+ were tested with a modified electromigration device by applying 2V, 3V and 4V voltage gradients over an intact Grimsel granodiorite rock sample. An ideal plug-flow model and an advection-dispersion model were applied to analyze the breakthrough curves. Matrix characterization by C-14-PMMA autoradiography and scanning electron microscopy showed that in the centimeter scale of Grimsel granodiorite rock, the interconnected matrix porosity forms a well-connected network for diffusion. Micrometer-scale fissures are transecting biotite and chlorite minerals, indicating sorption of the studied cations. The ideal plug-flow model indicated that the effective diffusion coefficients (D-e values) for Sr2+, Co2+ and Cs+ tracer ions within the Grimsel granodiorite rock were 3.20 x 10(-13) m(2)/s, 1.23 x 10(-13) m(2)/s and 2.25 x 10(-12) m(2)/s, respectively. D-e values were also derived from the advection-dispersion model, from which 2.86 x 10(-13) m(2)/s, 1.35 x 10(-13) m(2)/s and 2.26 x 10(-12) m(2)/s were calculated. The diffusion speed for the tracers was in the sequence of Cs+ > Sr2+ > Co2+ that is in the same sequence as their diffusion in diluted water. The distribution coefficients (K-d values) calculated from the models covered the range of two magnitudes (from 10(-7) m(3)/kg to 10(-5) m(3)/kg). The result indicated that the sorption process of the studied elements did not reach equilibrium during the electromigration process, mainly due to the too much acceleration of the migration speed by the voltage gradients applied over the rock sample., QC 20220421

Published
2022
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