TY - CONF A1 - Lay, Vera T1 - Sichere Verschlussbauwerke mittels innovativer Materialien, multisensorischem Monitoring und Ultraschall-Prüfung zur Qualitätssicherung N2 - Verschlussbauwerke sind für die untertägige Endlagerung im Salzgestein als eine wichtige technische Barriere vorgesehen. Diese Bauwerke müssen hohen Anforderungen an Sicherheit und Integrität genügen, weshalb im Projekt SealWasteSafe Werkstofftechnik, Prüfverfahren und Überwachungsmethoden für sichere Verschlussbauwerke verbessert werden. Dabei zeigen die untersuchten alkaliaktivierten Materialien (AAM) langsamere Reaktionskinetik bei der Erhärtung im Vergleich zu Salzbeton, was potenziell geringere Rissbildung erwarten lässt. Die Erhärtung wird an Probekörpern (100-300 l) multisensorisch über einen Zeitraum von mindestens 28 Tagen überwacht. Die Parameter Temperatur und Feuchtigkeit werden einerseits kabelgebunden, andererseits mittels drahtloser Radio Frequency Identification (RFID)-Technik aufgezeichnet. Zusätzlich kommen Schallemissionsmessungen sowie Dehnungsmessungen mittels verteilter faseroptischer Sensorik (FOS) zum Einsatz. Die Überwachung zeigt verschiedene Charakteristika beim Erhärten der Materialien mit geringerer Temperaturentwicklung des AAM. Zusätzlich werden Ultraschallmessungen genutzt, um Einbauteile und Störstellen wie Risse und Delaminationen im Rahmen der Qualitätssicherung am Probekörper und am Verschlussbauwerk zu detektieren. Dafür werden sowohl ein Ultraschallmesssystem mit großer Apertur (LAUS) als auch eine Ultraschall-Bohrlochsonde eingesetzt. Durch Erhöhung des Schalldrucks und Schallfeldbündelung im Beton wird die Aussagekraft der von der Bohrlochsonde aufgezeichneten Messsignale verbessert, was in Modellierungen und ersten Labortests gezeigt werden kann. Die Auswertung der Ultraschallmessungen zeigt das große Potenzial der Methode mit Eindringtiefen bis zu 9 m, wobei anspruchsvolle Abbildungsverfahren zu einer verbesserten Abbildung der internen Strukturen führen. Insgesamt verbessern die im Projekt SealWasteSafe entwickelten Materialien und Methoden die Möglichkeiten für sichere Verschlussbauwerke nuklearer Endlager. Obwohl die Konzepte speziell für Bauwerke im Salzgestein entwickelt werden, sind sie partiell gut auf andere Wirtsgesteine übertragbar. T2 - 3. Tage der Standortauswahl CY - Aachen, Germany DA - 08.06.2022 KW - SealWasteSafe KW - Salzbeton KW - Verschlussbauwerke KW - Monitoring KW - Ultraschall KW - Inspektion PY - 2022 AN - OPUS4-55093 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lay, Vera T1 - Zerstörungsfreie Prüfmethoden für Verschlussbauwerke nuklearer Endlager im Projekt SealWasteSafe N2 - Für die sichere Einlagerung von radioaktiven oder toxischen Abfällen kommen im Salzgestein technische Barrieren in Form von untertägigen Verschlussbauwerken zum Einsatz. Aufgrund der hohen Anforderungen an Sicherheit und Integrität dieser Verschlussbauwerke werden umfangreiche zerstörungsfreie Prüfmethoden zur Überwachung und Qualitätssicherung verwendet. Im BAM-Projekt SealWasteSafe werden Werkstofftechnik, Prüfverfahren und Überwachungsmethoden für sichere Verschlussbauwerke in Endlagern verbessert. Dabei wird der bisherige Salzbeton mit dem innovativen alkaliaktivierten Material (AAM) mit langsamerer Reaktionskinetik bei der Erhärtung und somit potenziell geringerer Rissbildung verglichen. Im Labormaßstab werden Probekörper mit Volumina von 100-300 l multisensorisch ausgestattet und somit die Zuverlässigkeit und Widerstandsfähigkeit der Sensoren gegenüber der hochalkalischen Umgebung nachgewiesen. Durch das Monitoring wird der Abbindevorgang des Betons überwacht und die Materialien über einen Zeitraum von mehreren Wochen charakterisiert. Dabei werden die Parameter Temperatur und Feuchtigkeit einerseits verkabelt als auch mittels drahtloser Radio Frequency Identification (RFID)-Technik aufgezeichnet. Zusätzlich kommen Schallemissionsmessungen sowie Dehnungsmessung mittels verteilter faseroptischer Sensorik (FOS) zum Einsatz. Das multisensorische Überwachungssystem wird durch aktive Ultraschallmessungen ergänzt, die durch die Detektion von Rissen, Delaminationen oder anderen Störstellen eine Qualitätssicherung der Verschlussbauwerke ermöglichen. Dafür werden sowohl ein Ultraschallsystem mit großer Apertur (LAUS) als auch eine Ultraschall-Bohrlochsonde eingesetzt. Durch Erhöhung des Schalldrucks und Bündelung der Schallsignale im Beton wird die Aussagekraft der von der Bohrlochsonde aufgezeichneten Messsignale verbessert, was in Modellierungen und ersten Labortests gezeigt werden kann. Die Auswertung der Ultraschallmessungen erfolgt mit auf Diffraktionssummation beruhenden Migrationsverfahren wie Kirchhoff-Tiefenmigration und Synthetic Aperture Focusing Technique (SAFT), die Abbildungen vom Inneren der Probekörper erzeugen. Insgesamt verbessert das Projekt SealWasteSafe mithilfe innovativer Multisensorik und Ultraschallmethodik die Überwachungs- und Qualitätssicherungskonzepte für sichere Verschlussbauwerke nuklearer Endlager. T2 - 82. Jahrestagung der Deutschen Geophysikalischen Gesellschaft CY - Online meeting DA - 07.03.2022 KW - SealWasteSafe KW - Ultraschall KW - Verschlussbauwerke KW - Abbildungsverfahren PY - 2022 AN - OPUS4-54533 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lay, Vera T1 - Advanced analysis of ultrasonic investigations at sealing structures N2 - Engineering barrier systems are a crucial part of the safe underground disposal of radioactive waste, particularly in salt as a host rock. Sealing structures made of tailored concrete are under test at various sites in Germany. To characterise the material properties of the concrete and potentially also the bonding to the host rock as part of the necessary subsurface structures, we apply non-destructive testing making use of advanced geophysical imaging methods. Ultrasonic investigations have been carried out at underground concrete structures in the Teutschenthal mine in Germany. Here, we show results from two distinct constructions produced in a shotcrete procedure. Our goal is to analyse the performance of ultrasonics to be used as quality assurance for sealing structures made from shotcrete. First, a ~10 m long shotcrete structure is investigated with the help of a unique Large Aperture Ultrasonic System (LAUS) allowing for depth penetration of > 9 m. We perform measurements at the front and from the side of the construction. Second, we obtain results from a 1 m thick shotcrete body containing several artificial defects (width up to 8 cm). Ultrasonic testing data were acquired using a commercial multi-static device. Additionally, a new device measuring with 3D mode instead of line mode is applied and preliminary results will be shown. Generally, the acquired ultrasonic data are analysed by the Synthetic Aperture Focusing Technique that is commonly applied in non-destructive testing. As a result, reflectors in the analysed shotcrete structures are imaged. Individual reflections from internal features and particularly the opposite wall are identified. An unexpected delamination wider than 30 cm is clearly imaged and later verified by boreholes. Thus, the method is – in general – suitable to serve as a quality measure. However, particularly the small and deep artificial defects can hardly be identified in the resulting images. Thus, we use advanced geophysical imaging methods to further enhance the quality of the obtained images. The recorded ultrasonic energy is focused to the physically reflective origin in the analysed volume. First results clearly show that we successfully improve the image quality regarding noise level and artifacts and hence facilitate the detection of objects. In total, we present a valuable experiment under realistic conditions for underground sealing structures made from shotcrete, where the locations of artificial reflectors are partly known. This experiment serves as a unique basis to analyse the performance of advanced analysis methods to obtain high-quality images of the structure’s interior. Hence, the developed ultrasonic testing and analysis schemes can serve as a part of quality assurance that will help to enable safe sealing structures for nuclear waste disposal. T2 - SafeND2023: Interdisciplinary research symposium on the safety of nuclear disposal practices CY - Berlin, Germany DA - 13.09.2023 KW - Ultrasound KW - Imaging KW - Engineered barrier systems KW - Shotcrete PY - 2023 DO - https://doi.org/10.5194/sand-2-67-2023 AN - OPUS4-58497 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lay, Vera T1 - Potential of 3D matrix ultrasonic measurements to image complex concrete structures N2 - Ultrasonic echo testing is a well-established non-destructive testing technique used to investigate the interior of concrete structures in civil engineering. For the reconstruction of internal features, methods similar to seismic imaging are applied. To improve the ultrasonic imaging capabilities, we investigate the potential of a newly available 3D matrix mode measurement device in combination with advanced imaging techniques. Commonly used ultrasonic array measurement devices rely on several ultrasonic transducers coupled to act as one transducer that transmits or receives transversal ultrasound waves. Although this approach is well suited to detect elongated structures such as pipes and rebars, it has limitations if 3D embedded objects are present. Hence, the ultrasonic device MiraA1040Pro used here is designed to measure the ultrasonic wavefield on a 4 by 16 matrix of individual transducers. For testing, we used laboratory specimens with linear and spheric embedded structures first. Both linear and matrix mode measurements were conducted and analysed using the Synthetic Aperture Focusing Technique (SAFT) which is similar to Kirchhoff migration. Second, we used a data set from Teutschenthal mine at a shotcrete specimen constructed to simulate engineered barriers tailored for nuclear waste repositories. Ultrasonic measurements were investigated as a tool for quality assurance of these structures. The specimen contains both artificial 3D artifacts as well as naturally occurring defects such as a delamination. To make use of the advanced data acquisition, focusing 3D imaging techniques are applied to further improve the imaging quality. Generally, the reconstructed images from the 3D matrix mode data have a lower level of Signal-to-Noise-Ratio than the 2D linear mode because the source signal is weaker compared to the linear mode. Moreover, complex wave conversions of the SH-transversal wave occur that are reduced in the 2D linear scenario. However, clearer images can be achieved at non-linear features, particularly with focusing imaging methods. Thus, combining 3D data acquisition techniques with advanced imaging methods improves the success in imaging complex concrete structures. This is of particular interest for thick concrete structures in nuclear barrier systems or foundations. Additionally, we demonstrate opportunities to use well-constrained test laboratory scenarios from non-destructive testing as a practical test case for geophysical methods. T2 - Jahrestagung der Deutschen Geophysikalischen Gesellschaft (DGG) CY - Jena, Germany DA - 11.03.2024 KW - Ultrasound KW - Imaging KW - Quality assurance PY - 2024 AN - OPUS4-59729 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Skłodowska, Anna A1 - Lay, Vera A1 - Baensch, Franziska A1 - Niederleithinger, Ernst A1 - Kühne, Hans-Carsten T1 - Acoustic emission monitoring for engineered barriers in nuclear waste disposal N2 - To safely dispose of nuclear waste in underground facilities, engineered barrier systems are needed to seal shafts and galleries. The material used in these barriers must be adapted to the host rock parameters. Shrinking and cracking must be avoided to provide a barrier with almost zero permeability. For repositories in salt rock environments, several types of salt concrete (SC) are possible construction materials. Within the project SealWasteSafe, we compared the behavior of an innovative alkali-activated material (AAM) with standard SC in their hydration and hardening phase. To monitor the microstructural changes within the two materials SC and AAM, acoustic emission (AE) signals have been recorded for up to ~250 days on 340-liter-cubic specimens. The phenomenon of AE is defined as the emission of elastic waves in materials due to the release of localized internal energy. Such energy release can be caused by the nucleation of micro-fracture, e.g., in concrete while curing or when exposed to load. The occurrence of AE events gives first rough indications of microstructural changes and potentially occurring cracking and thus, provides insights for structural health monitoring (SHM). The results show, that for the first 28 days after casting, less AE activity was detected in the AAM compared to SC. After 61 days, in the AAM material, the number of AE events exceeded those observed in the SC. However, the majority of the AE detected and located in AAM was related to surface effects, and not to microstructural changes or occurring cracks within the bulk volume. Additionally, the source location analysis indicated, that despite lower activity in SC, we observed some clustering of the events. In contrast, in AAM, the activity inside the specimen is randomly distributed over the whole volume. The monitoring results help to estimate the material’s sealing properties which are crucial to assess their applicability as sealing material for engineered barriers. T2 - 11th European Workshop on Structural Health Monitoring (EWSHM 2024) CY - Potsdam, Germany DA - 10.06.2024 KW - Acoustic emission monitoring KW - Nuclear waste repositories KW - Event localization KW - SealWasteSafe project PY - 2024 AN - OPUS4-60552 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Skłodowska, Anna A1 - Lay, Vera A1 - Baensch, Franziska A1 - Niederleithinger, Ernst A1 - Kühne, Hans-Carsten T1 - Microseismicity monitoring in materials for nuclear waste storage repositories N2 - One of the major tasks in nuclear waste management is to design safe and reliable sealing structures for radioactive waste repositories. Particularly for salt as a host rock, engineered barrier systems for underground waste disposal must be constructed of well-understood (cementitious) materials that will sustain environmental conditions and ensure high durability. Within the SealWasteSafe project, we studied two materials with a potential for sealing structures for nuclear waste repositories: an innovative alkali-activated material (AAM) and standard salt concrete (SC). To analyze the development of microstructural changes within the materials, we monitored microseismicity (aka acoustic emission monitoring) occurring during the hardening and setting period in two 340-liter-cubic specimens for up to ~250 days. The monitoring results showed, that in the first 61 days, fewer events occurred in AAM compared to SC. After this time the number of events in AAM sharply increased and significantly exceeded those observed in SC. However, the source localization analysis revealed that the increase of microseismicity in AAM material was not related to the formation of macro-cracks within the material but was mainly caused by the surface effects. Accompanying analysis of the test specimens with additional methods (such as e.g., X-ray CT) proved that no macro-cracks were observed inside the AAM specimen. Further analysis in the time and frequency domains helped to characterize the tested materials and to estimate their potential to be used for engineered barriers in nuclear waste repositories. Overall, our study shows the potential of microseismicity monitoring for feasibility studies and quality assurance in a broad range of applications, also in structural health monitoring. T2 - 84. Jahrestagung der Deutschen Geophysikalischen Gesellschaft CY - Jena, Germany DA - 10.03.2024 KW - Microseismicity KW - Nuclear waste repositories KW - Acoustic emission KW - SealWasteSafe project KW - Salt rock KW - Alkali-activated materia PY - 2024 AN - OPUS4-60549 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Johann, Sergej A1 - Baensch, Franziska A1 - Strurm, Patrick A1 - Tiebe, Carlo A1 - Pötschke, Samuel A1 - Lay, Vera ED - Hall, H. T1 - HF RFID-based Measurement Comparison for Method Optimization in M2 Concrete and Alkali-Activated Mortars N2 - The internal project "SealWasteSafe" of the Federal Institute for Materials Research and Testing is dedicated to the further improvement in the construction of sealing systems for underground repositories of radioactive waste. Particularly, a multi-sensory concept is developed to ensure quality assurance and continuous long-term monitoring on the engineered barriers. Therefore, beside other measures, the temperature and equilibrium moisture of the construction shall be monitored and respective multi-sensoric monitoring concepts are tested first on the laboratory scale. One focus in this project is on embedded application in alkali-activated mortars (AAM), which results in special requirements for the resistance of the sensors to strongly alkaline environments with up to pH 14. In addition, the ingress of water along cables or at sensor positions is critical for sensors embedded in concrete, as the cable access of the sensor housing is a major weak point. It is therefore advisable to equip wireless high frequent radio frequency identification-based sensors, so called HF RFID sensors (short: RFID), that do not require cable access and thus have a stable and leak-proof sensor housing for long-term monitoring. In this contribution, the results from temperature, moisture and transmitted power monitoring of a AAM and a M2 specimens by means of HF RFID sensor systems are presented. T2 - 35th Danubia - Adria Symposium on Advances in Experimental Mechanics CY - Linz, Österreich DA - 21.09.2021 KW - Passive sensor interface KW - RFID KW - Structural Health Monitoring KW - Alkali-Activated Mortars PY - 2021 SN - 978-3-9504997-0-4 SP - 116 EP - 117 AN - OPUS4-53397 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baensch, Franziska A1 - Hofmann, Detlef A1 - Johann, Sergej A1 - Tiebe, Carlo A1 - Basedau, Frank A1 - Sturm, Patrick A1 - Lay, Vera A1 - Niederleithinger, Ernst T1 - Multi-sensor conception for safe sealing structures in underground repositories N2 - The project "SealWasteSafe" of the Bundesanstalt für Materialforschung und -prüfung (BAM, Berlin) deals with sealing structures applied for underground disposal of nuclear waste from two perspectives: (1) material improvement for application in sealing constructions and (2) feasibility study regarding multi-sensor approaches to ensure quality assurance and long-term monitoring. One specimen of 150 l made of alkali-activated material, which was found innovative and suitable for sealing constructions based on preliminary laboratory studies, and, for comparison purpose, another one made of salt concrete, are manufactured with an integrated multi-sensory setup for quality assurance and long-term-monitoring. The specimens were left in their cast form and additionally thermally insulated to simulate the situation in the repository. The multi-sensory concept comprises RFID technology embedded in the specimens suppling material temperature and moisture measurements, integrated fibre optic sensing allowing strain measurement and acoustic emission testing for monitoring possible crack formation. Overall, the suitability and the functionality of the sensors embedded into and attached to strongly alkaline (pH > 13 for the AAM) and salt corrosive (NaCl) environment was proven for the first 672 h. First temperature measurement based on RFID succeeded after 626 h for the alkali-activated material and after 192 h for the conventional salt concrete. Strain measurement based on distributed fibre optic sensing turned out the alkali-activated material with > 1 mm m-1 undergoing approximately twice the compression strain as the salt concrete with strains < 0.5 mm m-1. In contrast, the acoustic emission first and single hits representing crack formation in numbers, was found for alkali-activated material half of that detected at the salt concrete. T2 - SMIRT 26 CY - Berlin/Potsdam, Germany DA - 10.07.2022 KW - SealWasteSafe KW - Monitoring KW - Acoustic emission KW - Fibre optic sensing KW - RFID technology KW - alkali-activated material PY - 2022 SP - 1 EP - 10 AN - OPUS4-55371 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Johann, Sergej A1 - Baensch, Franziska A1 - Sturm, Patrick A1 - Tiebe, Carlo A1 - Pötschke, Samuel A1 - Lay, Vera ED - Holl, H. T1 - HF RFID-based measurement comparison for method optimization in M2 concrete and alkali-activated mortars N2 - Monitoring of repositories for radioactive waste requires techniques which can be applied long-term under harsh conditions. In this work, the reliability and suitability of materials and a capacitive sensor for measuring relative humidity are investigated, which are to be embedded in the special concrete components for the closure structures of underground repository. Preliminary tests with accelerated aging of the materials used, validation of the sensors under difficult conditions, investigations of the surfaces after aging by pH 14 solution, defined exposure of the sensors in a climatic chamber and the microscope images are discussed. The results will be used for further development and optimization of the RFID based sensor systems which can be applied to monitor the condition of different building structures without cabling. T2 - 37th Danubia - Adria Symposium on Advances in Experimental Mechanics CY - Linz, Austria DA - 21.09.2021 KW - Alkali-activated mortars KW - Passive sensor interface KW - RFID KW - Structural health monitoring KW - Smart structures PY - 2022 DO - https://doi.org/10.1016/j.matpr.2022.03.465 SN - 2214-7853 VL - 62 IS - 5 SP - 2571 EP - 2576 PB - Elsevier CY - Amsterdam AN - OPUS4-54697 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lay, Vera T1 - Multi-sensor conception for safe sealing structures in underground repositories N2 - The project "SealWasteSafe" of the Bundesanstalt für Materialforschung und -prüfung (Berlin) deals with sealing structures applied for underground disposal of nuclear waste from two perspectives: material improvement for application in sealing constructions and feasibility study regarding multi-sensor approaches to ensure quality assurance and long-term monitoring. One specimen of 150 l made of alkali-activated material, which was found innovative and suitable for sealing constructions based on preliminary laboratory studies, and another one made of conventional salt concrete, are manufactured with an integrated multi-sensory setup for quality assurance and long-term-monitoring. The specimens were left in their cast form and additionally thermally insulated to simulate the situation in the repository. The multi-sensory concept comprises RFID technology embedded in the specimens suppling material temperature and moisture measurements, integrated distributed fibre optic sensing allowing strain measurement and acoustic emission testing for monitoring crack formation. Overall, the suitability and the functionality of the sensors embedded into and attached to strongly alkaline (pH > 13 for the AAM) and salt corrosive (NaCl) environment was proven for the first 672 h. First RFID measurement succeeded after 626 h for the alkali-activated material and after 192 h for the conventional salt concrete. Strain measurement based on fibre optic sensing turned out the alkali-activated material (> 1 mm/m) undergoing approximately twice the compression strain as the salt concrete (< 0.5 mm/m). In contrast, the acoustic emission first and single hits representing crack formation in numbers, was found for alkali-activated material half of that detected at the salt concrete. T2 - SMIRT 26 CY - Berlin, Germany DA - 10.07.2022 KW - SealWasteSafe KW - Monitoring KW - Acoustic emission KW - Fibre optic sensing KW - RFID technology KW - Alkali-activated material PY - 2022 AN - OPUS4-55372 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -