Computed tomography of granitic samples with natural fracture

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F26722445%3A_____%2F24%3AN0000092" target="_blank" >RIV/26722445:_____/24:N0000092 - isvavai.cz</a>

Výsledek na webu

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DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

Computed tomography of granitic samples with natural fracture

Popis výsledku v původním jazyce

The studied rock sample with a natural fracture was taken as part of the project "Research on fracture connectivity in the underground research laboratory Bukov" (Zuna et al. 2023). The deep repository is planned at a depth of about 550 m and so the rock samples are taken from these depths for laboratory experiments. The diffusion cell is a device for dynamic transport experiments at low flow rates of tracer through a rock sample with a natural fracture. It was registered with the Industrial Property Office as a utility model. The experiment studied the possibility of tomographic scanning of samples directly inside the diffusion cell. In addition to the lower risk of contamination of the workplace, this arrangement has significant potential for time-lapse recording of the course of migration of the radioactive tracer through the sample (so-called 4D scanning). Time-lapse recording can provide information about the kinematics of groundwater migration processes in the geological subsoil of sites selected for the construction of a future permanent radioactive waste repository. Measurement of the distribution of radionuclides using a gamma tomography was carried out in September 2023, after injection of a radioactive cocktail of tracers (134Cs + 133Ba). The scanning algorithm took 70 hours using a pinhole camera 3 mm in diameter and a scanning head feed rate of 20 mm per minute. In total, a sample area of ​​100 mm along the cylinder axis was scanned. Despite the relatively low dose equivalent rate on the sample surface (11 µSv/h) the Fourier image of the crack inside was very clear and its position could be determined with an accuracy of 1 mm. The reconstruction of the sample slices was performed using the inverse Radon transform in the ImageJ software. By composition all 50 tomograms in space, the resulting 3D object was obtained. Inside the analyzed sample, the position, dimensions and shape of the fracture zone were precisely determined. On the last 12 slices, a branched fracture with absorbed tracer is visible. It extends to a depth of approximately 24 mm. Non-destructive 3D imaging of the volume distribution of radioactive tracer in fractures of rock samples allows visualization of sorption positions without the need to destroy the sample. The laboratory study of the migration of radionuclide tracers through conductive fractures in crystalline rock samples allows characterizing migration processes in the rock environment on a real scale in order to evaluation the safety of deep radioactive waste repositories. Gamma tomography opens up new possibilities for non-destructive testing of low-activity rock and building materials or other porous samples directly inside diffusion cells. It also offers time-lapse recording of the penetration of the radioactive tracer through the sample.

Název v anglickém jazyce

Computed tomography of granitic samples with natural fracture

Popis výsledku anglicky

The studied rock sample with a natural fracture was taken as part of the project "Research on fracture connectivity in the underground research laboratory Bukov" (Zuna et al. 2023). The deep repository is planned at a depth of about 550 m and so the rock samples are taken from these depths for laboratory experiments. The diffusion cell is a device for dynamic transport experiments at low flow rates of tracer through a rock sample with a natural fracture. It was registered with the Industrial Property Office as a utility model. The experiment studied the possibility of tomographic scanning of samples directly inside the diffusion cell. In addition to the lower risk of contamination of the workplace, this arrangement has significant potential for time-lapse recording of the course of migration of the radioactive tracer through the sample (so-called 4D scanning). Time-lapse recording can provide information about the kinematics of groundwater migration processes in the geological subsoil of sites selected for the construction of a future permanent radioactive waste repository. Measurement of the distribution of radionuclides using a gamma tomography was carried out in September 2023, after injection of a radioactive cocktail of tracers (134Cs + 133Ba). The scanning algorithm took 70 hours using a pinhole camera 3 mm in diameter and a scanning head feed rate of 20 mm per minute. In total, a sample area of ​​100 mm along the cylinder axis was scanned. Despite the relatively low dose equivalent rate on the sample surface (11 µSv/h) the Fourier image of the crack inside was very clear and its position could be determined with an accuracy of 1 mm. The reconstruction of the sample slices was performed using the inverse Radon transform in the ImageJ software. By composition all 50 tomograms in space, the resulting 3D object was obtained. Inside the analyzed sample, the position, dimensions and shape of the fracture zone were precisely determined. On the last 12 slices, a branched fracture with absorbed tracer is visible. It extends to a depth of approximately 24 mm. Non-destructive 3D imaging of the volume distribution of radioactive tracer in fractures of rock samples allows visualization of sorption positions without the need to destroy the sample. The laboratory study of the migration of radionuclide tracers through conductive fractures in crystalline rock samples allows characterizing migration processes in the rock environment on a real scale in order to evaluation the safety of deep radioactive waste repositories. Gamma tomography opens up new possibilities for non-destructive testing of low-activity rock and building materials or other porous samples directly inside diffusion cells. It also offers time-lapse recording of the penetration of the radioactive tracer through the sample.

Druh

O - Ostatní výsledky

CEP obor

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OECD FORD obor

20701 - Environmental and geological engineering, geotechnics

Projekt

<a href="/cs/project/FW01010115" target="_blank" >FW01010115: ALternativní výplňové MAtrice pro ukládání RAdioaktivních odpadů z vyřazování jaderných elektráren (ALMARA)</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2024

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů