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Application of ultrasonic techniques for quality assurance of salt concrete engineered barriers: Shape, cracks and delamination

  • The closure of underground nuclear waste disposal facilities requires reliable gas- and water-tight engineered barriers. In Germany, barriers made from salt concrete have been evaluated in full scale. While the barriers seem to fulfill the requirements regarding permeability, some unexpected cracks have been detected at the surface and at depth. In cooperation between the Federal Company for Radioactive Waste Disposal (BGE) and the Federal Institute for Materials Research and Testing (BAM), several experiments have been carried out to evaluate the applicability for ultrasonic measurements in crack detection and general quality assurance. Both commercial instruments and specially developed devices have been tested on site. Using commercial ultrasonic echo devices designed for concrete inspection it was possible to detect cracks and objects in salt concrete up to a depth of 2 m. The check for delamination in shotcrete is another field of application. A unique device available at BAM,The closure of underground nuclear waste disposal facilities requires reliable gas- and water-tight engineered barriers. In Germany, barriers made from salt concrete have been evaluated in full scale. While the barriers seem to fulfill the requirements regarding permeability, some unexpected cracks have been detected at the surface and at depth. In cooperation between the Federal Company for Radioactive Waste Disposal (BGE) and the Federal Institute for Materials Research and Testing (BAM), several experiments have been carried out to evaluate the applicability for ultrasonic measurements in crack detection and general quality assurance. Both commercial instruments and specially developed devices have been tested on site. Using commercial ultrasonic echo devices designed for concrete inspection it was possible to detect cracks and objects in salt concrete up to a depth of 2 m. The check for delamination in shotcrete is another field of application. A unique device available at BAM, the wide aperture, deep penetration instrument LAUS, was able to locate cracks and objects up to a depth of 8 m so far, which is thought to be a record for ultrasonic echo measurements in concrete. Adapted imaging procedures, partly adopted from geophysics, helped to reveal 3D structure at depth. In addition, we have developed ultrasonic probes to be deployed in boreholes, currently at up to 20 m depth. They can collect information on cracks and other features in a radius of about 1.5 m around the borehole in the current version and might be used in echo or transmission mode. Evaluation experiments have been performed at an experimental barrier at the ERAM site in Morsleben, Germany. The results showed several empty and injected cracks as well as built-in instrumentation. The results have been verified using borehole endoscopy as well as core examination and will be used to set up a reliable quality assurance system for engineered barriers. All instruments are based on ultrasonic shear wave transducers with a frequency range between 25 kHz and 100 kHz. Current research focuses on the improvement of the hardware (e. g. optimization of array characteristics) and imaging techniques such as Reverse Time Migration, both aiming at the improvement of depth of penetration, resolution and probability of detection.zeige mehrzeige weniger

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Metadaten
Autoren/innen:Tyler Oesch
Koautoren/innen:Ernst Niederleithinger, Frank Mielentz, Ute Effner, Matthias Behrens, C. Friedrich, R. Mauke, C. Büttner
Dokumenttyp:Vortrag
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2019
Organisationseinheit der BAM:8 Zerstörungsfreie Prüfung
8 Zerstörungsfreie Prüfung / 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen
8 Zerstörungsfreie Prüfung / 8.5 Mikro-ZfP
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Angewandte Physik
Freie Schlagwörter:Engineered Barrier System (EBS); Large Aperture Ultrasonic System (LAUS); Morsleben Repository (ERAM); Reverse Time Migration (RTM); Ultrasonic-Echo Borehole Probe
Themenfelder/Aktivitätsfelder der BAM:Energie
Analytical Sciences
Analytical Sciences / Zerstörungsfreie Prüfung und Spektroskopie
Energie / Kerntechnische Entsorgung
Veranstaltung:2nd International Conference on Monitoring in Geological Disposal of Radioactive Waste
Veranstaltungsort:Paris, France
Beginndatum der Veranstaltung:09.04.2019
Enddatum der Veranstaltung:11.04.2019
Verfügbarkeit des Volltexts:Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:15.04.2019
Referierte Publikation:Nein