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  <doc>
    <id>54500</id>
    <completedYear/>
    <publishedYear>2021</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst/>
    <pageLast/>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>lecture</type>
    <publisherName/>
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    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Simulation and construction of a focussing borehole probe for ultrasonic investigations at sealing structures for radioactive waste repositories</title>
    <abstract language="eng">A novel ultrasonic borehole probe is developed for the quality assurance of sealing structures in radioactive waste repositories using existing research boreholes. The aim is to analyse the sealing structures made of salt concrete concerning potential cracks, delamination, and embedded objects. A first prototype of the probe uses 12 individual dry point contact (DPC) shear horizontal wave transducers separated by equidistant transmitter/receiver arrays, each consisting of six individual transducers. It is operated with a commercial handheld ultrasonic testing device used in civil engineering. In order to increase the generated sound pressure of the borehole probe, the number of transducers will be increased to 32 for the novel probe. In addition, a time-controlled excitation of the individual probes is used to steer a focused sound beam to a certain angle and focus on a certain distance based on calculated time delays. Hence, the sensitive test volume is more limited, and the signal-to-noise ratio of the received signals improved. This paper presents the validation of the newly developed phased array borehole probe by beam simulation and experimentally on a half-cylindrical test specimen to investigate the directional characteristics. In combination with geophysical reconstruction method, an optimised radiation characteristic of the probe, an improved signal quality and thus an increased reliability of the results in imaging is expected. This is of great importance to construct safe sealing structures needed for radioactive or toxic waste disposal.</abstract>
    <enrichment key="eventName">NDT UT-Online 21</enrichment>
    <enrichment key="eventPlace">Online meeting</enrichment>
    <enrichment key="eventStart">01.11.2021</enrichment>
    <enrichment key="eventEnd">30.11.2021</enrichment>
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    <author>Prathik Prabhakara</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Borehole probe</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Engineered Barrier System (EBS)</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>SealWasteSafe</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Phased array technique</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Monitoring</value>
    </subject>
    <collection role="ddc" number="621">Angewandte Physik</collection>
    <collection role="institutes" number="">8 Zerstörungsfreie Prüfung</collection>
    <collection role="institutes" number="">8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen</collection>
    <collection role="themenfelder" number="">Energie</collection>
    <collection role="fulltextaccess" number="">Datei im Netzwerk der BAM verfügbar ("Closed Access")</collection>
    <collection role="literaturgattung" number="">Präsentation</collection>
    <collection role="themenfelder" number="">Kerntechnische Entsorgung</collection>
  </doc>
  <doc>
    <id>53917</id>
    <completedYear/>
    <publishedYear>2021</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>127</pageFirst>
    <pageLast>128</pageLast>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume>1</volume>
    <type>conferenceobject</type>
    <publisherName>Copernicus</publisherName>
    <publisherPlace/>
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    <contributingCorporation/>
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    <completedDate>--</completedDate>
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    <title language="eng">SealWasteSafe: materials technology, monitoring techniques, and quality assurance for safe sealing structures in underground repositories</title>
    <abstract language="eng">Within the project SealWasteSafe, we advance construction materials and monitoring concepts of sealing structures applied for underground disposal of nuclear or toxic waste. As these engineered barriers have high demands concerning integrity, an innovative alkali-activated material (AAM) is improved and tested on various laboratory scales. This AAM has low reaction kinetics related to a preferential slow release of the heat of reaction in comparison to alternative salt concretes based on Portland cement or magnesium oxychloride cements. Hence, crack formation due to thermally induced strain is reduced. After successful laboratory scale analysis (Sturm et al., 2021), the AAM is characterised on a larger scale by manufacturing test specimens (100–300 L).&#13;
&#13;
Conventional salt concrete (DBE, 2004) and the newly developed AAM are compared using two specimen geometries, i.e. cylindrical and cuboid. A comprehensive multisensor monitoring scheme is developed to compare the setting process of AAM and salt concrete for these manufactured specimens. The analysed parameters include temperature and humidity of the material, acoustic emissions, and strain variations. Passive sensor systems based on radiofrequency identification technology (RFID) embedded in the concrete, enable wireless access to temperature and humidity measurements and are compared to conventional cabled systems. Additionally, fibre-optic sensors (FOS) are embedded to record strain, but also have potential to record temperature and moisture conditions. Part of this project aims at demonstrating the high reliability of sensors and also their resistance to highly alkaline environments and to water intrusion along cables or at sensor locations. Further technical improvements were implemented so that first results clearly show the scalability of the setting process from previous small-scale AAM experiments and particularly the high potential of the newly developed approaches.&#13;
&#13;
Furthermore, ultrasonic methods are used for quality assurance to detect obstacles, potential cracks and delamination. On the one hand, both active and passive ultrasonic measurements complement the results obtained from the multisensor monitoring scheme for the produced specimens. On the other hand, the unique large aperture ultrasonic system (LAUS) provides great depth penetration (up to nearly 10 m) and can thus be applied at in situ sealing structures built as a test site in Morsleben by the Federal Company for Radioactive Waste Disposal (Bundesgesellschaft für Endlagerung, BGE) as shown by Effner et al. (2021). An optimised field lay-out identified from forward modelling studies and advanced imaging techniques applied to the measured data will further improve the obtained results. To characterise the inside of the test engineered barrier and achieve a proof-of-concept, an ultrasonic borehole probe is developed to enable phased arrays that can further improve the detection of potential cracks. Modelling results and first analysis of semispherical specimens confirmed the reliability of the directional response caused by the phased arrays of the newly constructed ultrasonic borehole probe.&#13;
&#13;
Overall, the project SealWasteSafe improves the construction material, multisensor monitoring concepts and ultrasonics for quality assurance. This will help to develop safe sealing structures for nuclear waste disposal. The outcomes are particularly valuable for salt as a host rock but partly also transferrable to alternative conditions.</abstract>
    <parentTitle language="eng">Safe Nuclear Waste Disposal</parentTitle>
    <identifier type="doi">10.5194/sand-1-127-2021</identifier>
    <identifier type="urn">urn:nbn:de:kobv:b43-539172</identifier>
    <enrichment key="eventName">Safe ND Interdisciplinary research symposium on the safety of nuclear disposal practices</enrichment>
    <enrichment key="eventPlace">Berlin, Germany</enrichment>
    <enrichment key="eventStart">10.11.2021</enrichment>
    <enrichment key="eventEnd">12.11.2021</enrichment>
    <enrichment key="opus.source">publish</enrichment>
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    <licence>Creative Commons - CC BY - Namensnennung 4.0 International</licence>
    <author>Vera Lay</author>
    <author>Franziska Baensch</author>
    <author>Sergej Johann</author>
    <author>Patrick Sturm</author>
    <author>Frank Mielentz</author>
    <author>Prathik Prabhakara</author>
    <author>Detlef Hofmann</author>
    <author>Ernst Niederleithinger</author>
    <author>Hans-Carsten Kühne</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Borehole probe</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>SealWasteSafe</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Engineered barrier</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Materials technology</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Monitoring</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>AAM</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Ultrasound</value>
    </subject>
    <collection role="ddc" number="621">Angewandte Physik</collection>
    <collection role="institutes" number="">8 Zerstörungsfreie Prüfung</collection>
    <collection role="institutes" number="">8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen</collection>
    <collection role="themenfelder" number="">Energie</collection>
    <collection role="fulltextaccess" number="">Datei für die Öffentlichkeit verfügbar ("Open Access")</collection>
    <collection role="literaturgattung" number="">Graue Literatur</collection>
    <collection role="themenfelder" number="">Kerntechnische Entsorgung</collection>
    <thesisPublisher>Bundesanstalt für Materialforschung und -prüfung (BAM)</thesisPublisher>
    <file>https://opus4.kobv.de/opus4-bam/files/53917/Lay_etal_SealWasteSafe_sand-1-127-2021.pdf</file>
  </doc>
  <doc>
    <id>56336</id>
    <completedYear/>
    <publishedYear>2022</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>1</pageFirst>
    <pageLast>4</pageLast>
    <pageNumber/>
    <edition/>
    <issue>27256</issue>
    <volume/>
    <type>conferenceobject</type>
    <publisherName>NDT.net</publisherName>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
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    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Evaluation of retroreflective corner echo for detection of surface breaking cracks in concrete by ultrasound</title>
    <abstract language="eng">The retroreflective corner echo is used, for example, in ultrasonic non-destructive testing of metals to find fatigue cracks in tubes or shafts. If the much weaker crack tip signal is additionally detected, the crack length can also be determined. A corner reflection occurs in cases of surface breaking cracks with predominantly perpendicular orientation to the surface. The intensity of the corner reflection depends on the angle of incidence and on the ultrasonic wave mode used. For the reliable detection of vertical surface breaking cracks in metals, transversal waves are commonly used, which propagate at an angle of 37° to 53° to the inspection surface. As shown in this contribution, the wide spread low frequency ultrasonic arrays with dry point contact sources available for ultrasonic testing of concrete also allow to receive corner echoes. These devices generate transversal waves in concrete structures with a large divergence of the sound field. A series of experiments was carried out with such dry point contact arrays on concrete specimens with artificial test defects and controlled induced cracks of different depths. The ultrasonic time-of-flight signals were recorded, exported and reconstructed utilising the SAFT (Synthetic Aperture Focusing Technique) algorithm. The SAFT reconstruction parameters were adjusted to visualize the corner echo indication. As will be shown, with this targeted processing, the reproducible detection of surface breaking cracks in concrete is possible. The retroreflective corner echo can thus be exploited in civil engineering for non-destructive inspection of concrete.</abstract>
    <parentTitle language="eng">Proceedings of NDT-CE 2022</parentTitle>
    <identifier type="url">https://www.ndt.net/article/ndtce2022/paper/27256_manuscript.pdf</identifier>
    <identifier type="urn">urn:nbn:de:kobv:b43-563365</identifier>
    <enrichment key="eventName">NDT-CE 2022</enrichment>
    <enrichment key="eventPlace">Zurich, Switzerland</enrichment>
    <enrichment key="eventStart">16.08.2022</enrichment>
    <enrichment key="eventEnd">18.08.2022</enrichment>
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    <licence>Creative Commons - CC BY - Namensnennung 4.0 International</licence>
    <author>U. Rabe</author>
    <author>S. Pudovikov</author>
    <author>H.-G. Herrmann</author>
    <author>H. Wiggenhauser</author>
    <author>Prathik Prabhakara</author>
    <author>Ernst Niederleithinger</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Concrete</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Crack depth</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Ultrasound</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>SAFT</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="ddc" number="624">Ingenieurbau</collection>
    <collection role="institutes" number="">8 Zerstörungsfreie Prüfung</collection>
    <collection role="institutes" number="">8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen</collection>
    <collection role="themenfelder" number="">Infrastruktur</collection>
    <collection role="themenfelder" number="">Chemie und Prozesstechnik</collection>
    <collection role="fulltextaccess" number="">Datei für die Öffentlichkeit verfügbar ("Open Access")</collection>
    <collection role="literaturgattung" number="">Graue Literatur</collection>
    <collection role="unnumberedseries" number="">Wissenschaftliche Artikel der BAM</collection>
    <thesisPublisher>Bundesanstalt für Materialforschung und -prüfung (BAM)</thesisPublisher>
    <file>https://opus4.kobv.de/opus4-bam/files/56336/27256_manuscript.pdf</file>
  </doc>
  <doc>
    <id>57463</id>
    <completedYear/>
    <publishedYear>2023</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>1</pageFirst>
    <pageLast>19</pageLast>
    <pageNumber/>
    <edition/>
    <issue>2</issue>
    <volume>42</volume>
    <type>article</type>
    <publisherName>Springer Nature</publisherName>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>1</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Using the Corner Reflection for Depth Evaluation of Surface Breaking Cracks in Concrete by Ultrasound</title>
    <abstract language="eng">The corner echo is a well-known effect in ultrasonic testing, which allows detection of surface breaking cracks with predominantly perpendicular orientation to the surface as, for example, corrosion cracks in metal pipes or shafts. This echo is formed by two planes, the surface of the crack and the surface which the crack breaks. It can also be classified as a half-skip method, since a reflection of the pulse occurs on the backwall before the reflection at the defect takes place. In combination with the diffraction from the crack tip, the corner echo also allows crack sizing. As shown in this paper, the corner reflection can be used in civil engineering for nondestructive inspection of concrete. Commercially available low frequency ultrasonic arrays with dry point contact sources generate SH transversal waves with sufficient divergence of the sound field in order to detect corner reflections. Ultrasonic line-scans and area-scans were acquired with a linear array on flat concrete specimens, and the data were reconstructed by the Synthetic aperture focusing technique. If the angles and the area of reconstruction are chosen accordingly, the corner echo reflection can be distinguished from other ultrasonic information. The corner echo can thus be used as a method for deciding whether a crack is a partial-depth crack or a full-depth crack and thus for obtaining a statement about crack depth. This paper presents corresponding experimental results obtained on concrete specimens with artificial test defects and cracks induced under controlled conditions.</abstract>
    <parentTitle language="eng">Journal of Nondestrctive Evaluation</parentTitle>
    <identifier type="doi">10.1007/s10921-023-00956-8</identifier>
    <identifier type="urn">urn:nbn:de:kobv:b43-574631</identifier>
    <identifier type="issn">0195-9298</identifier>
    <enrichment key="opus.source">publish</enrichment>
    <enrichment key="date_peer_review">31.05.2023</enrichment>
    <enrichment key="PaperofMonth">1</enrichment>
    <licence>Creative Commons - CC BY - Namensnennung 4.0 International</licence>
    <author>U. Rabe</author>
    <author>S. Pudovikov</author>
    <author>H.-G. Herrmann</author>
    <author>H. Wiggenhauser</author>
    <author>Prathik Prabhakara</author>
    <author>Ernst Niederleithinger</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Ultrasound</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Crack depth</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Concrete</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Corner echo</value>
    </subject>
    <collection role="ddc" number="543">Analytische Chemie</collection>
    <collection role="ddc" number="624">Ingenieurbau</collection>
    <collection role="institutes" number="">8 Zerstörungsfreie Prüfung</collection>
    <collection role="institutes" number="">8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen</collection>
    <collection role="themenfelder" number="">Infrastruktur</collection>
    <collection role="themenfelder" number="">Chemie und Prozesstechnik</collection>
    <collection role="literaturgattung" number="">Verlagsliteratur</collection>
    <collection role="fulltextaccess" number="">Datei für die Öffentlichkeit verfügbar ("Open Access")</collection>
    <collection role="unnumberedseries" number="">Wissenschaftliche Artikel der BAM</collection>
    <thesisPublisher>Bundesanstalt für Materialforschung und -prüfung (BAM)</thesisPublisher>
    <file>https://opus4.kobv.de/opus4-bam/files/57463/s10921-023-00956-8.pdf</file>
  </doc>
  <doc>
    <id>59242</id>
    <completedYear/>
    <publishedYear>2024</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>1</pageFirst>
    <pageLast>23</pageLast>
    <pageNumber/>
    <edition/>
    <issue>1</issue>
    <volume>24</volume>
    <type>article</type>
    <publisherName>MDPI</publisherName>
    <publisherPlace>Basel, Switzerland</publisherPlace>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>1</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Enhancing the Performance of a Large Aperture Ultrasound System (LAUS): A Combined Approach of Simulation and Measurement for Transmitter–Receiver Optimization</title>
    <abstract language="eng">The Large Aperture Ultrasound System (LAUS) developed at BAM is known for its ability to penetrate thick objects, especially concrete structures commonly used in nuclear waste storage and other applications in civil engineering. Although the current system effectively penetrates up to ~9 m, further optimization is imperative to enhance the safety and integrity of disposal structures for radioactive or toxic waste. This study focuses on enhancing the system’s efficiency by optimizing the transducer spacing, ensuring that resolution is not compromised. An array of twelve horizontal shear wave transducers was used to find a balance between penetration depth and resolution. Systematic adjustments of the spacing between transmitter and receiver units were undertaken based on target depth ranges of known reflectors at depth ranges from 5 m to 10 m. The trade-offs between resolution and artifact generation were meticulously assessed. This comprehensive study employs a dual approach using both simulations and measurements to investigate the performance of transducer units spaced at 10 cm, 20 cm, 30 cm, and 40 cm. We found that for depths up to 5 m, a spacing of 10 cm for LAUS transducer units provided the best resolution as confirmed by both simulations and measurements. This optimal distance is particularly effective in achieving clear reflections and a satisfactory signal-to-noise ratio (SNR) in imaging scenarios with materials such as thick concrete structures. However, when targeting depths greater than 10 m, we recommend increasing the distance between the transducers to 20 cm. This increased spacing improves the SNR in comparison to other spacings, as seen in the simulation of a 10 m deep backwall. Our results emphasize the critical role of transducer spacing in achieving the desired SNR and resolution, especially in the context of depth imaging requirements for LAUS applications. In addition to the transducer spacing, different distances between individual sets of measurement positions were tested. Overall, keeping the minimal possible distance between measurement position offsets provides the best imaging results at greater depths. The proposed optimizations for the LAUS in this study are primarily relevant to applications on massive nuclear structures for nuclear waste management. This research highlights the need for better LAUS efficiency in applications such as sealing structures, laying the foundation for future technological advances in this field.</abstract>
    <parentTitle language="eng">Enhancing the Performance of a Large Aperture Ultrasound System (LAUS): A Combined Approach of Simulation and Measurement for Transmitter–Receiver Optimization</parentTitle>
    <identifier type="doi">10.3390/s24010100</identifier>
    <identifier type="urn">urn:nbn:de:kobv:b43-592426</identifier>
    <enrichment key="opus_doi_flag">true</enrichment>
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Although the current system effectively penetrates up to ~9 m, further optimization is imperative to enhance the safety and integrity of disposal structures for radioactive or toxic waste. This study focuses on enhancing the system\u2019s efficiency by optimizing the transducer spacing, ensuring that resolution is not compromised. An array of twelve horizontal shear wave transducers was used to find a balance between penetration depth and resolution. Systematic adjustments of the spacing between transmitter and receiver units were undertaken based on target depth ranges of known reflectors at depth ranges from 5 m to 10 m. The trade-offs between resolution and artifact generation were meticulously assessed. This comprehensive study employs a dual approach using both simulations and measurements to investigate the performance of transducer units spaced at 10 cm, 20 cm, 30 cm, and 40 cm. We found that for depths up to 5 m, a spacing of 10 cm for LAUS transducer units provided the best resolution as confirmed by both simulations and measurements. This optimal distance is particularly effective in achieving clear reflections and a satisfactory signal-to-noise ratio (SNR) in imaging scenarios with materials such as thick concrete structures. However, when targeting depths greater than 10 m, we recommend increasing the distance between the transducers to 20 cm. This increased spacing improves the SNR in comparison to other spacings, as seen in the simulation of a 10 m deep backwall. Our results emphasize the critical role of transducer spacing in achieving the desired SNR and resolution, especially in the context of depth imaging requirements for LAUS applications. In addition to the transducer spacing, different distances between individual sets of measurement positions were tested. 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    <abstract language="eng">Low-frequency ultrasonic testing is a well-established non-destructive testing (NDT) method in civil engineering for material characterization and the localization of cracks, reinforcing bars and delamination. A novel ultrasonic borehole probe is developed for in situ quality assurance of sealing structures in radioactive waste repositories using existing research boreholes. The aim is to examine the sealing structures made of salt concrete for any possible cracks and delamination and to localize built-in components. A prototype has been developed using 12 individual horizontal dry point contact (DPC) shear wave transducers separated by equidistant transmitter/receiver arrays. The probe is equipped with a commercially available portable ultrasonic flaw detector used in the NDT civil engineering industry. To increase the sound pressure generated, the number of transducers in the novel probe is increased to 32 transducers. In addition, the timed excitation of each transducer directs a focused beam of sound to a specific angle and distance based on the previously calculated delay time. This narrows the sensitivity of test volume and improves the signal-to-noise ratio of the received signals. In this paper, the newly designed phased array borehole probe is validated by beam computation in the CIVA software and experimental investigations on a half-cylindrical test specimen to investigate the directional characteristics. In combination with geophysical reconstruction methods, it is expected that an optimised radiation pattern of the probe will improve the signal quality and thus increase the reliability of the imaging results. This is an important consideration for the construction of safe sealing structures for the safe disposal of radioactive or toxic waste.</abstract>
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    <title language="eng">Construction and validation of a novel phased array borehole probe for ultrasonic investigations at sealing structures in radioactive repositories</title>
    <abstract language="eng">A new type of ultrasonic borehole probe is currently under development for the quality assurance of sealing structures in radioactive waste repositories using existing research boreholes. The goal is to examine the sealing structures made of salt concrete for possible cracks, delamination, and embedded objects. Earlier prototype probes use 12 or 16 individual dry point contact (DPC) horizontal shear wave transducers grouped into a transmitter and a receiver array, each made up of six or eight individual transducers. They are operated with a commercially available portable ultrasonic flaw detector used in the civil engineering industry. To increase the generated sound pressure of the borehole probe, the number of transducers in the novel probe is increased to 32. In addition, timed excitation of each probe is used to direct a focused sound beam to a specific angle and distance based on calculated time delays. Hence, the sensitive test volume is limited, and the signal-to-noise ratio of the received signals is improved. This paper presents the validation of the newly developed phased array borehole probe by beam computation in CIVA software and experimental investigations on a semi-cylindrical test specimen to investigate the directional characteristics. In combination with geophysical reconstruction techniques, an optimised radiation pattern of the probe is expected to improve the signal quality and thus increase the reliability of the imaging results.&#13;
This is of great importance for the construction of safe sealing structures needed for the disposal of radioactive or toxic waste.</abstract>
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    <issue>9</issue>
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    <title language="eng">Multi–sensory Monitoring and Non–destructive Testing of New Materials for Concrete Engineered Barrier Systems</title>
    <abstract language="eng">The crucial part of nuclear waste storage is the construction of sealing structures made of reliable, safe and well–understood materials. We present an extended analysis of long-term multi–sensory monitoring and non–destructive testing (NDT) inspection of two laboratory specimens aiming at potential materials for sealing structures for nuclear waste repositories. Specimens with a volume of 340 litres made from newly developed alkali–activated materials (AAM) and established salt concrete (SC) were analysed using embedded acoustic emission and wireless radio-frequency identification (RFID) sensors, ultrasonic echo imaging, active thermography, and X–ray computed tomography. The monitoring analysis showed lower heat of reaction and 50% less acoustic emission events in AAM compared to SC. However, due to the surface effects of the AAM material, the number of acoustic emission events increased significantly after approximately two months of monitoring. Subsequently performed NDT inspections reliably located embedded sensors and confirmed the absence of major cracks or impurities. The presented laboratory results show the feasibility and potential of comprehensive NDT monitoring and inspection to characterise cementitious and alternative materials as well as the need for multi–parameter long–term monitoring. Thus, our study demonstrates that tailored NDT investigations will help to develop safe sealing structures for nuclear waste repositories.</abstract>
    <parentTitle language="eng">Journal of Advanced Concrete Technology</parentTitle>
    <identifier type="issn">1347-3913</identifier>
    <identifier type="doi">10.3151/jact.22.516</identifier>
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V."},{"key":"50","unstructured":"50) Simo, E., Herold, P., Keller, A., Lommerzheim, A., Matteo, E., Hadgu, T., Jayne, R., Kuhlman, K. and Mills, M., (2022). \u201c&lt;i&gt;Rangers: State of the art and science on engineered barrier systems in salt formations&lt;\/i&gt;.\u201d Albuquerque, New Mexico, USA: Sandia National Laboratories."},{"key":"51","doi-asserted-by":"crossref","unstructured":"51) Strangfeld, C., Johann, S. and Bartholmai, M., (2019). \u201cSmart RFID sensors embedded in building structures for early damage detection and long-term monitoring.\u201d &lt;i&gt;Sensors&lt;\/i&gt;,&lt;i&gt; &lt;\/i&gt;19(24), 5514.","DOI":"10.3390\/s19245514"},{"key":"52","doi-asserted-by":"crossref","unstructured":"52) Sturm, P., Moye, J., Gluth, G. J., Vogler, N., Taffe, A. and K\u00fchne, H. C., (2021). \u201cProperties of alkali-activated mortars with salt aggregate for sealing structures in evaporite rock.\u201d &lt;i&gt;Open Ceramics&lt;\/i&gt;,&lt;i&gt; &lt;\/i&gt;5, 100041.","DOI":"10.1016\/j.oceram.2020.100041"},{"key":"53","doi-asserted-by":"crossref","unstructured":"53) Thiede, T., Mishurova, T., Evsevleev, S., Serrano-Munoz, I., Gollwitzer, C. and Bruno, G., (2019). \u201c3D shape analysis of powder for laser beam melting by synchrotron x-ray CT.\u201d &lt;i&gt;Quantum Beam Science&lt;\/i&gt;,&lt;i&gt; &lt;\/i&gt;3(1), 0003.","DOI":"10.3390\/qubs3010003"},{"key":"54","doi-asserted-by":"crossref","unstructured":"54) Toscano, C., Meola, C. and Carlomagno. G. M., (2013). \u201cPorosity distribution in composite structures with infrared thermography.\u201d &lt;i&gt;Journal of Composites&lt;\/i&gt;,&lt;i&gt; &lt;\/i&gt;2013, 140127.","DOI":"10.1155\/2013\/140127"},{"key":"55","doi-asserted-by":"crossref","unstructured":"55) Van Den Abeele, K., Desadeleer, W., De Schutter, G. and Wevers, M., (2009). \u201cActive and passive monitoring of the early hydration process in concrete using linear and nonlinear acoustics.\u201d &lt;i&gt;Cement and Concrete Research&lt;\/i&gt;, 39(5), 426-432.","DOI":"10.1016\/j.cemconres.2009.01.016"},{"key":"56","doi-asserted-by":"crossref","unstructured":"56) Wiecek, B., (2006). \u201cReview on thermal image processing for passive and active thermography.\u201d In: &lt;i&gt;Proc.&lt;\/i&gt; &lt;i&gt;27th Annual International Conference of the IEEE Engineering in Medicine and Biology&lt;\/i&gt;, Shanghai, China 17-18 January 2006. New Jersey, USA: IEEE Engineering in Medicine &amp;amp; Biology Society, 686-689.","DOI":"10.1109\/IEMBS.2005.1616506"},{"key":"57","doi-asserted-by":"crossref","unstructured":"57) Wiggenhauser, H., (2008). \u201cAdvanced NDT methods for the assessment of concrete structures.\u201d In: H. Wiggenhauser, Ed. &lt;i&gt;Concrete Repair, Rehabilitation and Retrofitting II&lt;\/i&gt;. Boca Raton, Florida: CRC Press, 37-48.","DOI":"10.1201\/9781439828403-7"}],"container-title":["Journal of Advanced Concrete Technology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.jstage.jst.go.jp\/article\/jact\/22\/9\/22_516\/_pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2024,9,7]],"date-time":"2024-09-07T04:41:24Z","timestamp":1725684084000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.jstage.jst.go.jp\/article\/jact\/22\/9\/22_516\/_article"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,9,6]]},"references-count":57,"journal-issue":{"issue":"9","published-print":{"date-parts":[[2024]]}},"URL":"http:\/\/dx.doi.org\/10.3151\/jact.22.516","relation":{},"ISSN":["1346-8014","1347-3913"],"issn-type":[{"type":"print","value":"1346-8014"},{"type":"electronic","value":"1347-3913"}],"subject":[],"published":{"date-parts":[[2024,9,6]]}}}</enrichment>
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    <author>Vera Lay</author>
    <author>Franziska Baensch</author>
    <author>Anna Skłodowska</author>
    <author>Tobias Fritsch</author>
    <author>Michael Stamm</author>
    <author>Prathik Prabhakara</author>
    <author>Sergej Johann</author>
    <author>Patrick Sturm</author>
    <author>Hans-Carsten Kühne</author>
    <author>Ernst Niederleithinger</author>
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      <type>uncontrolled</type>
      <value>Radioactive waste</value>
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    <subject>
      <language>eng</language>
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      <value>Barrier</value>
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      <value>Concrete</value>
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      <language>eng</language>
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      <value>AAM</value>
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      <language>eng</language>
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      <value>Non-destructive testing</value>
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    <title language="eng">Multi-sensory monitoring and ultrasound for quality assurance at underground sealing structures</title>
    <abstract language="eng">Within the safety concepts of underground disposal sites of nuclear waste, engineered barriers play an important role. As these sealing structures have high demands concerning integrity, we aim at advancing the available construction materials, monitoring, and inspection techniques within the project SealWasteSafe. A specifically developed alkali-activated material is compared to classical salt concrete. A comprehensive multi-sensory monitoring scheme is used at 150-340 l specimens to monitor setting and hardening of both materials. All sensors are demonstrated to resist the highly alkaline environments. Besides cabled and wireless temperature and humidity of the materials, strain variations using fibre optic sensors and acoustic emissions are recorded over periods of at least 28 days, partly for more than eight months. After hardening of the specimens, further nondestructive evaluations using ultrasonic echo and thermographic measurements are conducted.&#13;
Preliminary results proof the suitability of the tested sensors and clearly highlight differences between the tested materials. Particularly, the newly developed alkali-activated material shows lower acoustic emission activity indicating less cracking activity. Additionally, unique ultrasonic methods will enable better images of potential internal objects and cracks at in-situ sealing structures. A largescale ultrasonic system is optimised to reliably detect objects at a depth exceeding 9 m while still obtaining a good resolution. Modelling studies show the potential of further increasing the distance between individual transducer arrays. Additionally, a new ultrasonic borehole probe using phased arrays allowing for beam focussing is constructed and tested. Laboratory measurements at a halfcylindrical concrete specimen coincide well with the previous modelling. In total, the presented safe materials, detailed monitoring approaches and ultrasonic quality assurance methods will help to obtain safe sealing structures within salt as a host rock. The concepts can partly be transferred to sealing structures in alternative host rocks and will also be valuable for non-nuclear waste repositories.</abstract>
    <parentTitle language="eng">Proceedings of the International Conference on Non-destructive Evaluation of Concrete in Nuclear Applications</parentTitle>
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    <author>Vera Lay</author>
    <author>Frank Mielentz</author>
    <author>Prathik Prabhakara</author>
    <author>Franziska Baensch</author>
    <author>Sergej Johann</author>
    <author>Detlef Hofmann</author>
    <author>Patrick Sturm</author>
    <author>Michael Stamm</author>
    <author>Ernst Niederleithinger</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>SealWasteSafe</value>
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    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Engineered barriers</value>
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    <subject>
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      <value>Monitoring</value>
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    <subject>
      <language>eng</language>
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      <value>Embedded sensors</value>
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    <subject>
      <language>eng</language>
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      <value>Ultrasonic imaging</value>
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    <title language="eng">Construction and Simulation of a Novel Phased Array Borehole Probe for Ultrasonic Investigations at Sealing Structures in Radioactive Repositories</title>
    <abstract language="eng">A novel ultrasonic borehole probe is developed for the quality assurance of sealing structures in radioactive waste repositories using existing research boreholes. The goal is to examine the sealing structures made of salt concrete for possible cracks, delamination, and embedded objects. A prototype probe uses 12 individual horizontal dry point contact (DPC) shear wave transducers separated by equidistant transmitter/receiver arrays of six individual transducers each. It is operated with a commercially available portable ultrasonic flaw detector used in the civil engineering industry. To increase the generated acoustic pressure of the borehole probe, the number of transducers in the novel probe is increased to 32. In addition, a timed excitation of each probe directs a focused beam of sound to a specific angle and distance based on calculated time delays. This limits the sensitive test volume and improves the signal-to-noise ratio of the received signals. This paper presents the validation of the newly developed phased array borehole probe by investigating the directivity through beam computation in the CIVA software and experimental investigations on a semi-cylindrical test specimen. It is expected that an optimised radiation pattern of the probe in combination with geophysical reconstruction methods will improve the signal quality and thus increase the reliability of the imaging results. This is of great importance for the construction of safe sealing structures needed for the disposal of radioactive or toxic waste.</abstract>
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    <enrichment key="eventPlace">Online meeting</enrichment>
    <enrichment key="eventStart">09.12.2021</enrichment>
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    <author>Prathik Prabhakara</author>
    <subject>
      <language>eng</language>
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      <value>Borehole probe</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Engineered barrier</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Phased array technique</value>
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    <subject>
      <language>eng</language>
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      <value>SealWasteSafe</value>
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    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Monitoring</value>
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