TY - JOUR A1 - Nagel, Thomas A1 - Rühaak, Wolfram A1 - Amann, Florian A1 - Bracke, Guido A1 - Buske, Stefan A1 - Kowalski, Julia A1 - Reiche, Sönke A1 - Schäfer, Thorsten A1 - Scheytt, Traugott A1 - Stumpf, Thorsten A1 - Völzke, Holger A1 - Wellmann, Florian A1 - Kolditz, Olaf T1 - Deep geological disposal - Editorial to the topical collection N2 - The subsurface geological environment, historically a key source of fossil and mineral resources, has seen a significant broadening of its potential applications in recent years, with increasing emphasis on its use for energy production and storage. A critical factor in utilizing subsurface space is ensuring the sustainability of management practices, with particular attention to the potential environmental impacts that may result. The current Topical Collection on Deep Geological Disposal places greater emphasis on the geotechnical aspects of geological disposal, with a particular focus on the safe isolation of hazardous materials, including radioactive waste. The Topical Collection on Deep Geological Disposal covers both experimental (laboratory and in-situ) and theoretical studies of various geotechnical applications, such as geological disposal of radioactive or other materials, e.g. coal-based solid waste, carbon dioxide sequestration in fractured reservoirs, and brine solutions, but also aspects of uranium mining. The articles in the Topical Collections are arranged under the following headings: – Fundamental studies – Experimental studies – Numerical studies KW - Disposal KW - Radioactive Waste KW - Geology PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-624955 DO - https://doi.org/10.1007/s12665-024-12075-2 SN - 1866-6299 VL - 84 IS - 3 SP - 1 EP - 6 PB - Springer Nature AN - OPUS4-62495 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weber, Mike A1 - Völzke, Holger A1 - Nieslony, Gregor T1 - Consequences of an imperfectly mounted reinforcement cage in a generical cylindrical concrete container during mechanical specimen tests N2 - By highest court decision in 2007 the issued license for the Konrad repository (a former iron ore mine) for low and intermediate level radioactive waste was finally confirmed. Since then, the site is improved, prepared and equipped for the currently planned start of waste package emplacement by 2029. The Bundesanstalt fuer Materialforschung und -pruefung (BAM, Federal Institute for Materials Research and Testing) is regularly contracted by the Bundesgesellschaft für Endlagerung (BGE, Federal Company for Radioactive Waste Disposal) as the responsible authority for waste product control, waste container design testing, and waste package acceptance. In this context BAM is mainly responsible for design testing of various container types including the evaluation quality assurance measures for container manufacturing. In the written Konrad disposal requirements all acceptance criteria for potential final disposal containers are defined. In addition to general requirements concerning container design, materials, dimensions and others, specific mechanical load scenarios the casks have to withstand are derived from an analysis of the on-site handling and emplacement procedures. Drop tests from different heights under consideration of the most damaging drop orientation and a stacking test are two examples for safety demonstrations that have to be performed during the container design testing procedure to qualify the respective container type. The containers, whether cubic or cylindrical containers, can be made from different materials like ductile cast iron, reinforced concrete or as welded construction from steel plates and profiles. In case of concrete containers the reinforcement has the function to absorb tensile forces the concrete is not able to withstand by its own. Because of manufacturing imperfections of cylindrical concrete waste containers manufactured already decades ago, the reinforcement cages are not always exactly, axisymmetrically positioned when they were poured. This inspired BAM to perform various ABAQUS finite-element (FE) simulations by using the example of a simplified cylindrical container design with generic dimensions and pure elastic material properties. As outcome the stress conditions in the container during the drop test impact under different drop positions and during the stacking test were investigated and are explained and illustrated in this contribution. Different reinforcement cage positions were calculated and compared. On the basis of the calculated tensile and compressive stress distributions suggestions are derived on how a cylindrical concrete container with an imperfectly placed reinforcement cage has to be oriented for a drop or stacking test to ensure the most damaging test scenario. T2 - ASME 2024 Pressure Vessels & Piping Conference CY - Bellevue, Washington, USA DA - 28.07.2024 KW - Container design testing procedure KW - Reinforced concrete containers KW - Drop test KW - Stacking test KW - Imperfectly mounted reinforcement cage KW - Finite-element-analysis PY - 2024 SN - 978-0-7918-8851-3 DO - https://doi.org/10.1115/PVP2024-123797 VL - 5 SP - 1 EP - 8 PB - ASME CY - New York City, USA AN - OPUS4-62558 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Nagelschmidt, Sven T1 - Ein Beitrag zur Zusammenführung von Zeit-Temperatur-Äquivalenz-Methoden: Entwicklung und Anwendung am Beispiel ausgewählter Materialverhalten für Zeit-Temperatur-Parameter und Zeit-Temperatur-Superpositionsprinzip N2 - In der Wissenschaft und Technik gibt es verschiedene Gründe, um auf Basis geeigneter Modelle in die Zukunft schauen zu wollen, beispielsweise um zu bewerten, ob ein Bauteil auch noch deutlich länger verwendet werden kann als eigentlich einmal vorgesehen. Eine Methode dieses zu tun, basiert auf dem Zeit-Temperatur-Äquivalenz-Prinzip, welches besagt, dass ein Zustand oder eine Materialeigenschaft gleichwertig bei verschiedenen Zeit-Temperatur-Kombinationen auftritt oder erreicht werden kann. Höhere Temperaturen verkürzen in der Regel die Dauer und umgekehrt. In den letzten Jahrzehnten hat sich ein umfangreiches Methodenspektrum für unterschiedliche Werkstoffe und Anwendungsgebiete entwickelt, sodass die Identifikation einer geeigneten Methode für einen konkreten Anwendungsfall oder neue Materialien eine Herausforderung darstellt. These: „Fortschrittlich wäre, existierende Methoden zusammenzuführen, methodenspezifische Vorteile zu kombinieren, um mit geringerem Aufwand ein geeignetes Prognosemodell zu entwickeln.“ Für metallische Werkstoffe und Polymere verläuft die Entwicklung von Prognosemodellen mit Zeit-Temperatur-Korrelation seit ca. 1940 parallel und unabhängig voneinander. In diesem Zusammenhang bekannte Methoden sind das Zeit-Temperatur-Superpositionsprinzip und Zeit-Temperatur-Parameter, wie der LARSON-MILLER-Parameter. Die jeweiligen methodischen Ansätze sind in der Regel anwendungs- und materialspezifisch und nur einzelnen Fachartikeln zu entnehmen. Eine zusammenführende thematische Übersicht und Untersuchung existierender Methoden wurden bislang nicht publiziert. Diese Forschungsarbeit verfolgt dahingehend einen neuartigen methodischen Ansatz und zeigt untersuchte Gemeinsamkeiten und Unterschiede als auch Analogien für das Zeit-Temperatur-Superpositionsprinzip und Zeit-Temperatur-Parameter anhand bestimmter Merkmale auf. Dafür wurden verschiedene analytische und grafische Ansätze verwendet. Ferner wird eine zusammenführende Untersuchung anhand eines rheologischen Materialmodells sowie anhand eines praktischen Anwendungsbeispiels gezeigt. Hergeleitet wurde u. a., dass das Prinzip der Zeit-Temperatur-Superposition für sogenanntes thermorheologisch einfaches und komplexes Verhalten konkreten Zeit-Temperatur-Parametern zugeordnet werden können. Und dadurch Verschiebefunktionen nicht nur in Abhängigkeit der Temperatur, sondern auch abhängig vom Zustand untersucht und definiert werden können. Ferner ermöglicht eine Skalierung der Zeit-Temperatur-Parameter auf eine Referenztemperatur physikalisch anschaulichere Auswertungen analog zum Zeit-Temperatur-Superpositionsprinzip. Untersuchungen zeigen, dass sich für einen konkreten Anwendungsfall die geeignetste Zeit-Temperatur-Äquivalenz-Methode aus einer gegenseitigen Abhängigkeit bzw. Kompatibilität einzelner Elemente, wie zugrunde gelegte Daten, Koordinatenachsenskalierung, ermittelte Zeit-Temperatur-Äquivalenz, Masterfunktionsansatz und der geforderten Interpolationsgüte herleitet. Der gewählte Forschungsansatz und die erzielten Ergebnisse bieten eine Plattform für die weitere Entwicklung von Prognosemodellen auf Basis des Zeit-Temperatur-Äquivalenz-Prinzips, insbesondere im Hinblick auf eine Zusammenführung und Kombination existierender Methoden. KW - Zeit-Temperatur-Äquivalenz KW - Zeit-Temperatur-Korrelation KW - Zeit-Temperatur-Superposition KW - Extrapolation PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-601530 DO - https://doi.org/10.14279/depositonce-20439 SP - 1 EP - 145 CY - TU Bibliothek online AN - OPUS4-60153 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Keller, Christian T1 - Beitrag zur numerischen Beanspruchungsanalyse an dünnwandigen Stahlblechcontainern im Fallversuch - Schädigungsmechanische Materialmodellierung duktiler Werkstoffe unter Berücksichtigung der Dehnratenabhängigkeit der plastischen Instabilität N2 - Gegenstand der vorliegenden Arbeit ist die Bereitstellung expliziter numerischer Simulationen von Fallversuchen mit dünnwandigen Stahlblechcontainern, die als Endlagerbehälter für radioaktive Abfälle mit vernachlässigbarer Wärmeentwicklung, d. h. schwach- und mittelradioaktive Abfälle, für die Verbringung in das Endlager Konrad vorgesehen sind. Die Betrachtung von potentiellen Absturzszenarien ist ein grundlegender und zentraler Bestandteil der Sicherheitsnachweise zur Auslegung der verschiedenen endlagergängigen Behälter- und Containertypen gegen mechanische Störfallbelastungen. Für dünnwandige Stahlblechcontainer existierten bislang keine sicherheitstechnischen Untersuchungen, die auf numerischen Bewertungsmethoden basieren und eine Bewertung der vorhandenen Sicherheitsreserven hinsichtlich der mechanischen Integrität ermöglichen. Daraus resultierte die Motivation, ein verifiziertes Finite-Elemente-Modell eines repräsentativen Referenzcontainers zu entwickeln, das das dynamische Verformungs- sowie duktile Schädigungs- und Versagensverhalten in numerischen Simulationen von dynamischen Lastfällen physikalisch mit der erforderlichen Güte beschreibt. Duktile Schädigungs- und Versagensvorgänge metallischer Werkstoffe gehen grundsätzlich mit großen plastischen Dehnungen einher und führen somit unweigerlich zu der Notwendigkeit der Diskussion von plastischer Instabilität und damit verknüpften Lokalisierungseffekten, die einen wesentlichen Einfluss auf die Entwicklung des lokalen Beanspruchungszustands haben. Für die schädigungsmechanische Materialmodellierung folgt hieraus das grundsätzliche Erfordernis der korrekten Berücksichtigung des Instabilitätsbeginns, der in der Regel dehnratenunabhängig angenommen wird. Für dynamische Randbedingungen ist der werkstoffspezifische Einfluss der Dehnrate auf das Einsetzen der Lokalisierung jedoch nicht uneingeschränkt vernachlässigbar, so dass im Rahmen dieser Arbeit ein theoretischer Ansatz ausgearbeitet wird, der die plastische Instabilität dehnratenabhängiger Werkstoffe anhand des zeit- und ortsabhängigen Dehnungsgradienten im einachsigen Zugversuch diskutiert. Darüber hinaus ist für eine hinreichend genaue Materialmodellierung neben der korrekten Prognose des Instabilitätsbeginns auch die korrekte Beschreibung des Verformungsverhaltens jenseits der Gleichmaßdehnung notwendig. Zu diesem Zweck wird in dieser Arbeit eine konstitutive Beziehung entwickelt, die sowohl unter Berücksichtigung der plastischen Instabilität als auch unter der Beachtung von ver- sowie entfestigenden Einflussfaktoren der dynamischen Plastizität formuliert werden kann. Insgesamt wird eine praxistaugliche Bewertungsmethode der mechanischen Integrität dünnwandiger Stahlblechcontainer unter Störfallbedingungen auf Basis expliziter dynamischer Simulationen erarbeitet, die die komplexen duktilen Schädigungs- und Versagensmechanismen dehnratenabhängiger Werkstoffe berücksichtigt. Mit der zur Simulation von Fallversuchen entwickelten numerischen Modellbildung und den zur Verifizierung entsprechend mit Testcontainern im Originalmaßstab durchgeführten Fallversuchen wird nachgewiesen, dass anhand des Finite-Elemente-Modells eines repräsentativen Referenzcontainers zum einen eine quantitativ belegte Bestimmung ungünstiger Fallorientierungen hinsichtlich maximaler Verformungen und zum anderen eine realistische Abbildung des duktilen Versagensverhaltens ermöglicht wird. Damit können tatsächlich vorhandene Sicherheitsreserven bei potentiell zu unterstellenden Behälterabstürzen quantitativ aufgezeigt und zukünftig eine verbesserte sicherheitstechnische Beurteilung von Stahlblechcontainern im Fallversuch bereitgestellt werden. Damit leistet die vorliegende Arbeit einen wichtigen Beitrag für die Bewertung von Sicherheitsnachweisen von Endlagerbehältern für radioaktive Abfälle und trägt dazu bei, den langfristigen Schutz von Mensch und Umwelt vor Schäden durch radioaktive Stoffe zu gewährleisten. N2 - The subject of the present work is the provision of explicit numerical simulations of drop tests with thin-walled sheet steel containers, which are intended as repository containers for radioactive waste with negligible heat generation, i.e. low and intermediate level waste, for shipment to the Konrad repository. The consideration of potential crash scenarios is a fundamental and central component of the safety analyses for the design of the various types of casks and containers suitable for final disposal against mechanical accident loads. For thin-walled sheet steel containers, no safety investigations based on numerical assessment methods existed so far that would allow an evaluation of the existing safety reserves with regard to mechanical integrity. This resulted in the motivation to develop a verified finite element model of a representative reference container that physically describes the dynamic deformation and ductile damage and failure behaviour in numerical simulations of dynamic load cases with the required quality. Ductile damage and failure processes of metallic materials are fundamentally accompanied by large plastic strains and thus inevitably lead to the need to discuss plastic instability and associated localisation effects, which have a significant influence on the development of the local stress state. For damage-mechanical material modelling this results in the fundamental requirement of correctly considering the onset of instability, which is usually assumed to be strain-rate independent. For dynamic boundary conditions, however, the material-specific influence of the strain rate on the onset of localisation cannot be neglected without restriction, so that a theoretical approach is elaborated within the scope of this work that discusses the plastic instability of strain-rate-dependent materials on the basis of the time- and location-dependent strain gradient in the uniaxial tensile test. Furthermore, for a sufficiently accurate material modelling, besides the correct prediction of the onset of instability, the correct description of the deformation behaviour in the postcritical region, i.e., beyond the uniform strain, is necessary. For this purpose, a constitutive relationship is developed in this work, which can be formulated both under consideration of the plastic instability as well as under consideration of hardening as well as softening influencing factors of the dynamic plasticity. Overall, a practical assessment method of the mechanical integrity of thin-walled sheet steel containers under accident conditions is developed based on explicit dynamic simulations, which takes into account the complex ductile damage and failure mechanisms of strain rate-dependent materials. With the numerical modelling developed for the simulation of drop tests and the drop tests carried out accordingly with full-scale test containers for verification, it is demonstrated that, on the basis of the finite element model of a representative reference container, on the one hand a quantitatively proven determination of unfavourable drop orientations with regard to maximum deformations and, on the other hand, a realistic representation of the ductile failure behaviour is made possible. This allows it to quantitatively demonstrate actually existing safety reserves in case of potential container crashes and to provide an improved safety assessment of sheet steel containers in drop tests in the future. This work thus makes an important contribution to the evaluation of safety verifications of final storage containers for radioactive waste and helps to ensure the long-term protection of humans and the environment from damage caused by radioactive substances. KW - FEM KW - Dynamische Plastizität KW - Plastische Instabilität KW - Duktile Schädigung KW - Endlager Konrad PY - 2024 DO - https://doi.org/10.14279/depositonce-21874 SP - 1 EP - 188 PB - DepositOnce CY - Berlin AN - OPUS4-61581 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schilling, O. A1 - Neumann, Martin T1 - System of Quality Assurance Measures in Manufacturing and Operation of Dual Purpose Casks for Spent Nuclear Fuel and High Level Waste in Germany N2 - German spent nuclear fuel and high level waste is stored in dry conditions in interim storage facilities until a final repository will be ready for operation in the future. Dual purpose casks are used for the packaging of the materials to ensure transportability at any time during long-term interim storage and fulfilling both requirements from interim storage as well as transport. Germany’s 2011 decision to phase out utilization of nuclear energy has led to a high demand for casks for decommissioning power plants as quickly as possible. Cask serial production will continue at a high level for the next few years. In the process, a system of quality assurance measures ensures that every cask reliably complies with design specification according the transport approval certificate and storage license. When the first casks were manufactured in Germany about 40 years ago, quality assurance was oriented towards pressure vessel and general nuclear manufacturing. The system was continuously adapted to the state of the art. In particular serial production, globalization of manufacturing and deep supplier chains had to be taken into account. The system of quality assurance measures applied today for cask manufacturing shall be presented here. The quality assurance measures can be categorized as system-related and design-related. With respect to transport regulations for example, they are independently approved and monitored by the competent authority BAM and its authorized inspection experts. The qualification of the applicant is reviewed first in the context of the design approval procedure and then periodically. The qualification of component and cask manufacturers is also checked at the start of manufacturing and then periodically. Before the start of manufacturing documents such as quality plans are pre-assessed. Manufacturing and inspection are then performed according to the pre-assessed documents. Cask manufacturing is completed by a final inspection before commissioning. Periodic inspections during operation ensure preservation of the properties specified in the approval certificate over package life time. The type and the time interval of periodic inspections depend on the use of the package. For transport after interim storage a system of specific tests and inspections is prescribed. T2 - 20th International Symposium on the Packaging and Transportation of Radioactive Materials (PATRAM 22) CY - Juan-les-Pins, France DA - 11.06.2023 KW - Radioactive material KW - Quality Assurance Measures KW - Dual Purpose Casks KW - Independent Surveillance PY - 2023 AN - OPUS4-57705 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nagelschmidt, Sven T1 - Application study of time-temperature correlation methods on test data of metal seals N2 - Reliable experimental data and prediction models are required to evaluate the behavior of components and materials over long periods of time. One method is based on the time-temperature equivalence principle, according to which a state or material property occurs or can be achieved equivalently at different time-temperature combinations. Higher temperatures generally shorten the duration and vice versa. Based on this approach, the long-term behavior of metal seals, as used in storage containers for spent nuclear fuels and high-level radioactive waste, has been studied at BAM and other institutions around the world for several years. However, such tests are often not planned as a preliminary point regarding the basic conditions of time-temperature related models. Gaps are then sometimes identified during the evaluation, for example because certain temperature values are missing, or the measurement intervals were not selected appropriately. This study evaluates exemplarily the status of the test data of metal seals at the BAM regarding the applicability of existing time-temperature correlation methods and corresponding models. Based on the existing database, the aim is to show which method and model are more likely to be applicable and which additional tests might be necessary to obtain a more suitable database. The tests so far have provided important findings for the planning and adaptation of possible further tests and for suitable model developments. Identified gaps in the data basis led to further development of the methods. In the present work, a time-temperature correlation was determined based on a time-temperature parameter from GRAHAM and WALLES for a selected data range. T2 - Pressure Vessels & Piping Conference PVP2025 CY - Montreal, Canada DA - 20.07.2025 KW - Time-temperature equivalence KW - Metal seals, KW - Time-temperature superposition KW - Time-temperature parameters PY - 2025 VL - 2025 SP - 1 EP - 4 PB - ASME CY - USA AN - OPUS4-63789 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zencker, Uwe A1 - Simbruner, Kai A1 - Völzke, Holger T1 - Analysis of Zirconium Hydride Structures in Spent Fuel Claddings Subjected to Storage Conditions N2 - Pre-storage drying and the early stage of storage can subject spent fuel claddings to higher temperatures and higher tensile hoop stresses than those associated with in-reactor operation. Under these conditions, existing circumferential hydrides in zirconium-based alloys can be partly reoriented into radial ones that may result in embrittlement of the cladding material. As a consequence, the failure limits may be reduced under mechanical loads caused by handling or during transport after storage. The potential occurrence of brittle fracture strongly depends on the specific location, size, and orientation of the zirconium hydrides. The morphology of such hydride structures was experimentally investigated in unirradiated, hydrogen-loaded samples made of a zirconium-based alloy. The hydrogen was introduced into the cladding sample by means of a cathodic charging process. The loading process was followed by a thermal treatment to precipitate the hydrides in the circumferential direction and then a thermomechanical treatment to reorient the hydrides in the radial direction. Metallographic methods were used to describe and classify the hydride morphology. The resulting metallographic micrographs were evaluated using suitable radial hydride metrics. The determination of the maximum length of a hydride structure was carried out in two different ways, each with its own advantages and disadvantages. Both methods consider neighboring hydrides as continuous according to the definition of the Radial Hydride Continuity Factor (RHCF). The first option is to measure the Euclidean distance between the two most distant pixels of the hydride structure in the image analysis, whereby the actual maximum size of the hydride structure is determined. The second possibility is to measure the maximum size of a hydride or a hydride structure within a certain arc length in the radial direction of the cladding tube. This value is of particular interest because the ratio of the maximum radial size of a hydride structure to the wall thickness of the cladding tube is used for the safety assessment of spent fuel claddings with radial hydrides using the RHCF. T2 - 21st International Symposium on the Packaging and Transportation of Radioactive Materials - PATRAM 2025 CY - San Antonio, TX, USA DA - 27.07.2025 KW - Extended Interim Storage KW - Nuclear Fuel Cladding KW - Zirconium Hydride Structure KW - Ring Compression Test KW - Micrograph Analysis PY - 2025 SP - 1 EP - 8 CY - Indianapolis, IN, USA AN - OPUS4-63875 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zencker, Uwe T1 - Analysis of Zirconium Hydride Structures in Spent Fuel Claddings Subjected to Storage Conditions N2 - Pre-storage drying and the early stage of storage can subject spent fuel claddings to higher temperatures and higher tensile hoop stresses than those associated with in-reactor operation. Under these conditions, existing circumferential hydrides in zirconium-based alloys can be partly reoriented into radial ones that may result in embrittlement of the cladding material. As a consequence, the failure limits may be reduced under mechanical loads caused by handling or during transport after storage. The potential occurrence of brittle fracture strongly depends on the specific location, size, and orientation of the zirconium hydrides. The morphology of such hydride structures was experimentally investigated in unirradiated, hydrogen-loaded samples made of a zirconium-based alloy. The hydrogen was introduced into the cladding sample by means of a cathodic charging process. The loading process was followed by a thermal treatment to precipitate the hydrides in the circumferential direction and then a thermomechanical treatment to reorient the hydrides in the radial direction. Metallographic methods were used to describe and classify the hydride morphology. The resulting metallographic micrographs were evaluated using suitable radial hydride metrics. The determination of the maximum length of a hydride structure was carried out in two different ways, each with its own advantages and disadvantages. Both methods consider neighboring hydrides as continuous according to the definition of the Radial Hydride Continuity Factor (RHCF). The first option is to measure the Euclidean distance between the two most distant pixels of the hydride structure in the image analysis, whereby the actual maximum size of the hydride structure is determined. The second possibility is to measure the maximum size of a hydride or a hydride structure within a certain arc length in the radial direction of the cladding tube. This value is of particular interest because the ratio of the maximum radial size of a hydride structure to the wall thickness of the cladding tube is used for the safety assessment of spent fuel claddings with radial hydrides using the RHCF. T2 - 21st International Symposium on the Packaging and Transportation of Radioactive Materials - PATRAM 2025 CY - San Antonio, TX, USA DA - 27.07.2025 KW - Extended Interim Storage KW - Nuclear Fuel Cladding KW - Zirconium Hydride Structure KW - Ring Compression Test KW - Micrograph Analysis PY - 2025 AN - OPUS4-63876 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Völzke, Holger A1 - Cherkouk, Andrea A1 - Zajec, Bojan A1 - Debelle, Aurélien A1 - Alonso, Ursula A1 - Ganster, Patrick A1 - Generelo-Casajus, Lidia A1 - Merroun, Mohamed L. A1 - Morales-Hidalgo, Mar A1 - Pakarinen, Janne A1 - Rossignol, Fabrice A1 - Trentin, Andressa T1 - Durability of traditional and innovative disposal container materials and coatings: State-of-the-art and further research within InCoManD N2 - This document provides a consolidated state-of-the-art overview of current knowledge on containers designed to safely isolate heat-generating high-level radioactive waste in deep geological repositories (DGRs). These containers form a vital part of the multi-barrier safety system that ensures long-term protection of people and the environment. Their durability — especially their resistance to corrosion and mechanical stress — is essential, as they are expected to perform over time scales ranging from hundreds to hundreds of thousands of years. The findings presented here are taken from recent research studies out of the EURAD programme and also from the EURAD-1 ConCorD project (Work Package 15, 2021–2024), which reviewed the performance of various container materials, including copper, carbon steel and silicon carbide. The report covers experimental results under relevant disposal conditions, the impact of manufacturing and sealing processes, and the current capabilities of modelling tools to simulate the complex underground environment in which these containers will operate. In addition to summarising knowledge on traditional materials, the document highlights recent progress and remaining challenges related to innovative ceramic-based containers. Key issues include ensuring effective sealing and mechanical integrity, particularly under harsh and evolving conditions over long periods. The report also emphasizes the importance of understanding how different environmental and mechanical factors interact to influence container degradation. Neither corrosion nor stress alone can fully explain long-term behaviour, and both must be studied together. Finally, this state-of-the-art sets the stage for future work, especially the EURAD-2 InCoManD project (Work Package 9), which will build on these findings to improve testing methods, refine models, and explore promising new materials and design solutions for safer and more reliable waste containment. Research activities within InCoManD are hence briefly described throughout this document. KW - Disposal container KW - Radioactive waste KW - Deep geological repository KW - Corrosion resistance KW - Durability PY - 2025 UR - https://www.ejp-eurad.eu/sites/default/files/2025-06/EURAD2_WP09_INCO_T02_01_D09.1_SOTA_0.pdf N1 - This document is a deliverable of the European Partnership on Radioactive Waste Management 2 (EURAD-2); EURAD-2 is co-funded by the European Union under Grant Agreement N°101166718. VL - Deliverable 9.1 SP - 1 EP - 60 PB - Agence Nationale pour la Gestion des Déchets Radioactifs (ANDRA) CY - Châtenay-Malabry AN - OPUS4-63303 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zencker, Uwe T1 - Failure Analysis on Spent Fuel Claddings Subjected to Long-Term Dry Interim Storage N2 - Long-term dry interim storage may adversely affect the mechanical properties of spent fuel claddings, possibly resulting in a reduced resilience during handling or transport after storage. Pre-storage drying and the early stage of interim storage can subject the cladding to higher temperatures and higher tensile hoop stresses than those associated with in-reactor operation and pool storage. Under these conditions, radial hydrides may precipitate in zirconium-based alloys (Zircaloy) during slow cooling, which result in embrittlement of the cladding material and eventually a possible sudden failure of cladding integrity under additional mechanical loads. Especially long, continuous radial hydride structures and low temperature can cause severe embrittlement of claddings and finally failure by fracture even at small deformations. Therefore, the study of hydride morphology plays an important role in describing the brittle failure behaviour of the claddings. The focus of the presented research is on the development of appropriate numerical methods for predicting the mechanical behaviour and identification of limiting conditions to prevent brittle fracture of Zircaloy claddings. An established experimental method for characterising cladding materials is the Ring Compression Test (RCT). Some test results on irradiated cladding tubes after operation in pressure water reactors are publicly available. However, it is helpful to carry out studies on unirradiated surrogate claddings with similar material properties to reduce the effort associated with irradiated samples in hot cells and to perform material tests with a wider range of parameters. On the basis of such experimental data, load-displacement curves have been numerically analysed for a selection of cladding materials. Radial hydrides can cause a sample to break suddenly. Noticeable load drops in the RCT are caused by unstable crack propagation through the radial hydride network. The failure mechanism is quasi-cleavage in the hydrides and micro-void nucleation, growth, and coalescence in the zirconium matrix, with ductile tearing patches connecting adjacent hydrides. The cohesive zone approach was used to simulate the failure process taking into account the radial hydride morphology. Experimental investigations, numerical analyses and evaluation methods for both the deformation and failure behaviour of irradiated as well as unirradiated claddings of zirconium-based alloys with radial hydrides are discussed. Limiting conditions can be expressed in terms of fracture energy and cohesive strength. T2 - IAEA Technical Meeting on the Behaviour of Spent Fuel and Cladding During Storage and the Performance of Spent Fuel Storage Systems CY - Seoul, South Korea DA - 23.06.2025 KW - Extended Interim Storage KW - Nuclear Fuel Cladding KW - Numerical Failure Analysis KW - Ring Compression Test KW - Spent Fuel Characterization PY - 2025 AN - OPUS4-63597 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nagelschmidt, Sven A1 - Herbrich, Uwe A1 - Keller, Christian A1 - Qiao, Linan T1 - Re-evaluation of tensile and creep rupture data of metals using a modified Larson–Miller approach N2 - More than 70 years ago, in 1952 Larson and Miller adapted an existing relationship whichevaluates the relative effects of time and temperature on creep rupture behavior of various alloys by using existing data and by constructing so-called master curves. Since that time, the formulated Larson–Miller relation, commonly known as Larson–Miller parameter, is a widely used time–temperature parameter for various applications, e.g. for rupture life, creep and relaxation analyses of metals and some other materials such as polymers, concrete and ceramics.Nevertheless, the physical meaning of this parameter as well as the determination of master curves are still the subject of major criticism. In this work, both aspects are reviewed and analyzed with data originally considered in thepaper of Larson and Miller based on the following approach: (a) the parameter was modifiedregarding a reference time and a reference temperature according to the time–temperature superposition principle; (b) master curves were generated for five materials investigated originally by Larson and Miller, based on a stretched exponential function type. It has been shown, that: (1) With normalized time and temperature, the Larson–Miller parameter corresponds to real logarithmic rupture time. (2) For the relationship between Creep rupture stress and the modified Larson–Miller parameter, the stretched exponential function is a good choice as a master function. (3) Corresponding model parameters have physical meaning and can be easily determined based on data from creep test data. The investigations provide a better understanding and applicability of Larson–Miller approach. KW - Larson–Miller parameter KW - Creep rupture time KW - Time–temperature equivalence KW - Stretched exponential function KW - Extrapolation of short-term data PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-644486 DO - https://doi.org/10.1016/j.engfracmech.2025.111582 SN - 0013-7944 VL - 329 SP - 1 EP - 16 PB - Elsevier Ltd. AN - OPUS4-64448 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brunk, Gerd A1 - Herbrich, Uwe A1 - Weckner, Olaf A1 - Smith, Jay A1 - Rossi, John T1 - Geometrically non-linear large planar deformations of shear deformable beams: Derivation, approximation, and numerical validation using Finite Element analysis N2 - In this paper, we present derivations for the dynamic equations of motion of a shear deformable beam undergoing geometrically non-linear large deformations in a single plane. In the static case, these governing equations are given by six coupled, non-linear ordinary differential equations of first order which we present in the Lagrangian frame of reference and henceforth refer to as the Brunk–Herbrich–Weckner (BHW) beam theory. We confirm analytically that under pure bending an initially straight beam deforms into a circle, a known bench-mark solution. Next, we confirm numerically that our results agree well with the commercial Finite-Element code Abaqus for several example problems with increasing complexity, including the effect of axial preload as well as varying property domains along the beam. Abaqus is regarded as the state-of-the-art for non-linear structural analysis within the aerospace industry. Next, we show that the well-known Timoshenko–Ehrenfest and Euler–Bernoulli beam theory can be obtained from the general Brunk-Herbrich-Weckner beam theory in the limit of small deformations. Finally, we introduce the Iterative Projection Method which improves the results of the linearized Timoshenko–Ehrenfest beam theory without the computational cost associated with the fully non-linear analysis for all numerical test cases considered. KW - Linear and non-linear beam theory KW - Deformation problem KW - Euler–Bernoulli, Timoshenko–Ehrenfest and Brunk–Herbrich–Weckner beam KW - Iterative projection method KW - Finite Element analysis PY - 2025 DO - https://doi.org/https://doi.org/10.1177/10812865251342777 SN - 1081-2865 SP - 1 EP - 26 PB - Sage CY - Thousand Oaks, Calif. AN - OPUS4-64383 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Völzke, Holger T1 - Innovative Disposal Container Materials: Improved Durability and Manufacturing Feasibility N2 - Deep geological disposal of high-level radioactive waste (HLW) is the internationally preferred final waste management option to prevent the biosphere from radiologically relevant release of radioactive nuclides for at least 100,000 to 1 million years. Current repository concepts are based on a multi-barrier system consisting of geological, geo-technical and technical barriers as an engineered barrier system (EBS). Considered host rocks are e.g. crystalline rocks, claystone, or rock salt. In all cases disposal containers are a crucial technical barrier to safely enclose the HLW, either spent nuclear fuel (SNF) or vitrified high-level waste (VHLW) from reprocessing. Depending on the repository concept and the respective safety case disposal containers guarantee the safe confinement of their radioactive inventory not just during handling, emplacement, and potential retrieval but also during the post-closure phase of the repository for a certain period. Required container lifetimes usually vary between 1,000 and 100,000 years depending on the selected host rock and repository concept. During container operation and their long-term disposal, they are subject to various mechanical, thermal, radiological, and geo-chemical/biological loads. Thus, mechanical stability and corrosion resistance in the long-term are among the most crucial challenges. Disposal container components lifetimes are typically calculated based on their time-dependent corrosion behaviour, with the implicit assumption that the design remains structurally stable for the required period. Even though, the durability of several component materials subjected to corrosion processes have been previously studied in detail, the interaction of mechanical processes and corrosion calls for further study, and assessment of the impact of joint degradation modes on component lifetimes will result in a more robust and defensible safety case. Besides, as corrosion occurs in a thin interfacial surface layer between the component outermost surface and the environment, specific R&D work is required to understand the long-term performance controlled by the entire engineered barrier system (EBS) and to feed simulation and extrapolations tools by representative experimental data for validation. Another approach to tackle the corrosion issue is to prevent and/or minimize it, thereby ensuring an even safer disposal. In this approach, materials much less prone to corrosion (e.g., copper, ceramic materials) can be used to fabricate the containers. Alternatively, protective coatings (e.g. copper coating) can be applied to current selected reference materials like steels. Both ways require validation of the materials durability under realistic, accelerated field conditions. The InCoManD work package 9 (Innovative and new Container/canister materials under disposal field conditions), part of the EURAD-2 European Partnership on Radioactive Waste Management (2024 – 2029), will address these issues through a collaborative project involving many countries across Europe (and beyond) with a shared goal. Building on the results of the ConCorD work package 15 (Container Corrosion under Disposal Conditions), part of the EURAD-1 programme (2019 - 2024), the InCoManD work package specifically aims to: (i) provide a better understanding of material degradation mechanisms, (ii) define optimised and innovative material solutions, (iii) develop comprehensive predictive models and common methodologies to enhance confidence in the results produced by each partner, and (iv) train new scientists in this field. T2 - safeND 2025 CY - Berlin, Germany DA - 17.09.2025 KW - Radioactive Waste Disposal KW - Disposal Container KW - Deep Geological Repository KW - Engineered Barrier System PY - 2025 DO - https://doi.org/10.5194/safend2025-40 AN - OPUS4-64254 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja T1 - Experiences and perspectives for the design evaluation of Konrad containers N2 - The former iron ore mine Konrad near Salzgitter is the approved final repository for radioactive waste with negligible heat production in Germany and should go into operation in the 2030s. The waste comes from operation and decommissioning of nuclear power plants, as well as from medicine, research and industry using radiation sources or radioactive materials. These types of waste are comparable to international low- and certain types of intermediate-level waste. The waste includes a large variety of products, materials and properties. The containers for such waste have the primary purpose of enabling handling and storing of the waste by safely enclosing the radioactive inventory and shielding of radiation. Due to the large variety of waste forms to be disposed of in the Konrad repository, different container types are specified to account for the different requirements related to each waste type. Each container design for waste disposal in Konrad has to be approved by BGE on the basis of the “final disposal conditions” (Endlagerungsbedingungen) and the respective “product control” (Produktkontrolle). For demonstrating the container’s compliance with the regulatory framework, the waste producers or container manufacturers have to apply for design approval on the basis of a comprehensive safety assessment including all relevant reports about analytical, numerical and experimental safety demonstrations and quality assurance measures for container manufacturing and operation. Usually, BGE commissions independent experts like BAM to evaluate these documents and the design testing (e.g. drop or fire tests). While the basic assessment principle is to verify the container design and quality to be in line with all regulatory requirements, there are often challenges associated with the container’s safety evaluation. As containers of different types have already been produced in large numbers and partially loaded with waste before the regulatory framework became effective (so-called “old” containers), they are considered in the regulations as well and safety assessments have to be provided in an equivalent way. As the requirements for the documentation of manufacturing quality were not yet known at the time these containers were manufactured, this is often challenging in practice. On the other hand, containers requiring the highest safety level (ABK II, sf) due to their nuclear content sometimes cause significant challenges and very long approval processes concerning safety demonstrations for severe accidental conditions like a 5 m drop without impact limiter onto a nearly unyielding target or a one hour 800 °C fire scenario. Furthermore, as the regulatory framework has not been updated for several decades, some requirements and the respective safety assessment methods have to be interpreted under consideration of the current state of knowledge in science and technology. T2 - safeND conference 2025 CY - Berlin, Germany DA - 17.09.2025 KW - Radioactive waste KW - Final disposal KW - Waste container KW - Design evaluation PY - 2025 AN - OPUS4-64989 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Banerjee, Ayantika T1 - Enhancing Requirements for HLW Disposal Containers and Developing Transparent Safety Evaluation Concepts in Collaboration between BAM and BASE (Research Project KAnnE) N2 - The research project KAnnE aims to identify, concretize, and quantify requirements for high-level radioactive waste (HLW) disposal containers in Germany, considering potential types of host rock and repository concepts. The primary goal is to establish a transparent and comprehensible regulatory framework that accounts for different host rocks and operational phases, ensuring the safe long-term containment of radioactive waste. Given the current general legal formulation of these requirements, this study provides a systematic approach to defining them more precisely by integrating scientific and regulatory perspectives. An extensive review is conducted to gather relevant information about safety and design requirements for disposal containers in the respective types of host rock. The analysis considers host rock properties and conditions, operational repository conditions, and their impact on the container design, including key factors such as structural integrity, corrosion resistance, and shielding. Additionally, design specifications, boundary conditions, and expected loads (thermal, mechanical, radiological, chemical, and biological) are systematically reviewed, with quantified values provided where available. The findings support a comprehensive evaluation of both quantitative and qualitative container requirements concerning potential German host rock types, waste forms, and repository concepts. By establishing a clearer basis for defining these requirements, this project serves as a foundation for further refinement, with a more detailed structuring of requirements currently in progress. Such regulatory basis allows a more targeted approach to container development and ensures a transparent evaluation within the repository licensing procedure. Additionally, it supports decision making on the most favorable container design by considering repository conditions that provide the highest level of safety over one million years. This contribution explains the goals and concept of the research project KAnnE, presents its preliminary findings and conclusions, and provides an outlook on the final project phase. T2 - safeND conference 2025 CY - Berlin, Germany DA - 17.09.2025 KW - Radioactive waste KW - Final disposal KW - Waste container KW - Requirements KW - Regulation PY - 2025 AN - OPUS4-64990 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zaghdoudi, Maha T1 - How to test the Arrhenius validity of elastomers during ageing N2 - The main task of the division "Safety of Storage Containers" at BAM is the safety assessment of storage containers for radioactive waste. A sufficient sealing of bolted lid systems for the safe containment of the waste for transport, storage and disposal is very important. Extensive knowledge of the change of the elastomer’s properties during ageing and the availability of reliable end-of-lifetime criteria is mandatory to guarantee long term safe enclosure. In a long-term test programme over 5 years we have studied the degradation and the change of sealing properties of several elastomers, including EPDM, at four different ageing temperatures (75 °C, 100 °C, 125 °C and 150 °C). Compression stress relaxation (CSR) and compression set (CS) experiments were carried out. It has been found that when the data does not cover a sufficient time frame necessary for the evolution of the degradation of a chosen property, a curvature in the Arrhenius relationship is observed. For CSR, the curvature was observed for samples aged up to 186 days. As for CS experiments, the curvature was detected for sample aged up to 2 years. To cover the possible lack of experimental long-term data at low temperatures, a numerical model for CSR was developed and longer ageing times for the simulation were adopted. A degradation-rate based model for the evolution of degradative processes is proposed. The main advantage of the model is the possibility to quickly validate the interpolation at lower temperatures within the range of slower chemical processes without forcing an Arrhenius straight-line extrapolation. The model was also applied to CS experiments and validated by the 5 years experimental results where the curvature was gone, and the degradation property has followed an Arrhenius relationship. In the figure the contribution of the two degradative processes are shown over CS and CSR respectively. T2 - 2nd advanced material science world congress CY - Online meeting DA - 14.06.2021 KW - Arrhenius KW - Processes KW - Compression set KW - Compression stress relaxation KW - Modelling PY - 2021 AN - OPUS4-52825 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja T1 - Analysis of O-ring seal failure in the context of radioactive waste containers N2 - At BAM, which is a federal institute for materials research and testing in Germany, it is one of our tasks to evaluate the safety of casks designed for transport and/or storage of radioactive material. This includes assessment of elastomeric seals applied in the casks. Besides examining the low-temperature behaviour and irradiation effects of elastomeric seals, it is our goal to estimate the service lifetime of the seals with regard to the requirements for long-term safety (40 years and more) of the containers. Therefore, we started an accelerated ageing programme with selected rubbers often used for seals (HNBR, EPDM and FKM) which are aged at four different temperatures (75 °C, 100 °C, 125 °C and 150 °C) up to five years. In order to assess sealability, O-rings were aged in compression by 25 % (corresponding to the compression during service) between plates as well as in flanges that allow leakage rate measurements. For comparison, uncompressed O-rings were aged as well. Further methods characterising seal performance are compression stress relaxation (CSR) reflecting the loss of sealing force of a compressed seal over time, and compression set (CS) which represents the recovery behaviour of a seal after release from compression. Additionally, material properties such as hardness, elastic modulus, glass transition temperature and viscoelastic loss factor as well as relaxation and recovery behaviour are examined in order to understand the underlying ageing mechanisms in each material. For obtaining results closely related to practical conditions, O-rings with a full-scale cord diameter of 10 mm were aged. However, this set-up can lead to heterogeneous aging caused by diffusion-limited oxidation (DLO) effects, resulting in distorted bulk properties such as compression stress relaxation and compression set. However, if DLO-affected data is excluded, extrapolations of CS data are possible using time-temperature shifts and Arrhenius graphs. For selecting an appropriate end-of-lifetime criterion, leakage rate measurements were performed, since leakage rate is the only characteristic directly correlated to the performance of the sealing system. A significant increase in leakage rate was considered as the end of the lifetime. However, the O-rings remained leak tight under static conditions and even exhibited an improved, i.e. decreased leakage rate while other properties already indicated strong deterioration. These tests were extended by seal tests with fast partial decompression. Overall an update will be given on the current investigations and results and the planned activities. T2 - Kautschuk Herbst Kolloquium 2022 CY - Online meeting DA - 08.11.2022 KW - Seal KW - Ageing KW - Compression set PY - 2022 AN - OPUS4-56397 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weber, Mike T1 - Coefficients of Friction in Dependence on Aging State of Elastomers – Experimental Identification and Numerical Simulation of the Experiment N2 - Elastomer seals are mounted as barrier seals in lid systems of containers designed for transport and disposal of negligible heat generating radioactive waste and as auxiliary seals in spent fuel storage and transportation casks (dual purpose casks (DPC)). When the behavior of mounted seals under normal and hypothetical accident conditions of disposal and transport is to be simulated, a comprehensive knowledge of their complex mechanical properties at every state of aging is necessary. In previous works, BAM’s efforts in experimental investigations on specimen artificially aged at different temperatures and times and the implementation of the found results in finite element material models were presented. Additionally, our approaches to reproduce the aging process itself and to extrapolate the results of artificially accelerated aging to longer times were presented. Numerical simulations have shown that the behavior of the seal during mounting and one-sided pressurizing and the resulting performance values such as leakage rate strongly depend on the coefficient of friction (COF) between flange and seal. The friction coefficient, in turn, depends on the aging state of the elastomer material as several publications suggest (see below). Dynamic COF between an exemplary ethylene propylene diene rubber (EPDM) material and a stainless steel ball were determined by using a self-designed linear oscillation tribometer. Unaged and artificially aged EPDM specimen stored for 30 days and 100 days at a temperature of 150 °C were tested. A stainless steel ball (d=10 mm) is brought in contact with the specimen’s surface und loaded by normal forces of 2.5 N, 5 N, 10 N and 20 N. During a reciprocating movement of the EPDM sheet, the horizontal force/friction force is continuously measured, and the COF can be derived. It is well known that friction is a complex phenomenon especially in soft materials. It cannot be excluded that the measured friction force is influenced by additional force components, resulting from the ball’s grooving through the elastomer’s surface. This force depends on the penetration depth of the ball and on the resistance of the elastomer in its different states of aging. The latter results from microstructural changes i.e., chain scission and additional crosslinking that occur during aging which in turn influence the softening or hardening of the material. A finite element (FE) ABAQUS® model was developed to reproduce the measurement process. It should help to better understand the physical mechanisms and to quantify the percentage of measured forces resulting from real friction on the one hand and forces resulting from unintended side effects that could falsify the result on the other hand. The behavior of the elastomer in its different states of aging is reproduced by a FE material model already presented in previous works of BAM. T2 - ASME 2022 Pressure Vessels & Piping Conference (PVP2022) CY - Las Vegas, NV, USA DA - 17.07.2022 KW - Radioactive Waste KW - Elastomers KW - Aging KW - Experiment KW - Seal Behavior KW - Numerical Simulation KW - Leakage Rate KW - Coefficient of Friction PY - 2022 AN - OPUS4-57095 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Völzke, Holger T1 - Research at BAM on Metal Seal Performance and Fuel Rod Integrity N2 - The presentation provides an update on preliminary results from research projects in the area of long term performance of metal seals and fuel rod integrity as safety relevant components of spent fuel transport and storage casks for spent nuclear fuel. T2 - Extended Storage Collaboration Program (ESCP) Winter Meeting 2020 CY - Online meeting DA - 09.11.2020 KW - Metal seal KW - Safety KW - Interim storage KW - Spent nuclear fuel KW - Fuel rod PY - 2020 AN - OPUS4-51615 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weber, Mike A1 - Zaghdoudi, Maha A1 - Brandt, Guido A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Coefficients of Friction in Dependence on Aging State of Elastomers – Experimental Identification and Numerical Simulation of the Experiment N2 - Elastomer seals are mounted as barrier seals in lid systems of containers designed for transport and disposal of negligible heat generating radioactive waste and as auxiliary seals in spent fuel storage and transportation casks (dual purpose casks (DPC)). When the behavior of mounted seals under normal and hypothetical accident conditions of disposal and transport is to be simulated, a comprehensive knowledge of their complex mechanical properties at every state of aging is necessary. In previous works, BAM’s efforts in experimental investigations on specimen artificially aged at different temperatures and times and the implementation of the found results in finite element material models were presented. Additionally, our approaches to reproduce the aging process itself and to extrapolate the results of artificially accelerated aging to longer times were presented. Numerical simulations have shown that the behavior of the seal during mounting and one-sided pressurizing and the resulting performance values such as leakage rate strongly depend on the coefficient of friction (COF) between flange and seal. The friction coefficient, in turn, depends on the aging state of the elastomer material as several publications suggest (see below). Dynamic COF between an exemplary ethylene propylene diene rubber (EPDM) material and a stainless steel ball were determined by using a self-designed linear oscillation tribometer. Unaged and artificially aged EPDM specimen stored for 30 days and 100 days at a temperature of 150 °C were tested. A stainless steel ball (d=10 mm) is brought in contact with the specimen’s surface und loaded by normal forces of 2.5 N, 5 N, 10 N and 20 N. During a reciprocating movement of the EPDM sheet, the horizontal force/friction force is continuously measured, and the COF can be derived. It is well known that friction is a complex phenomenon especially in soft materials. It cannot be excluded that the measured friction force is influenced by additional force components, resulting from the ball’s grooving through the elastomer’s surface. This force depends on the penetration depth of the ball and on the resistance of the elastomer in its different states of aging. The latter results from microstructural changes i.e., chain scission and additional crosslinking that occur during aging which in turn influence the softening or hardening of the material. A finite element (FE) ABAQUS® model was developed to reproduce the measurement process. It should help to better understand the physical mechanisms and to quantify the percentage of measured forces resulting from real friction on the one hand and forces resulting from unintended side effects that could falsify the result on the other hand. The behavior of the elastomer in its different states of aging is reproduced by a FE material model already presented in previous works of BAM. T2 - ASME 2022 Pressure Vessels & Piping Conference (PVP2022) CY - Las Vegas, NV, USA DA - 17.02.2022 KW - Numerical Simulation KW - Radioactive Waste KW - Elastomers KW - Aging KW - Seal Behavior KW - Leakage Rate KW - Coefficient of Friction KW - Experiment PY - 2022 SP - 1 EP - 8 PB - American Society of Mechanical Engineers (ASME) CY - New York, NY, USA AN - OPUS4-57093 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Silbernagl, Dorothee A1 - Kömmling, Anja A1 - Zaghdoudi, Maha A1 - Ghasem Zadeh Khorasani, Media A1 - Jaunich, Matthias T1 - Data-driven nanomechanical study of filled fluoroelastomer aged in air and hydrogen atmosphere N2 - Fluoroelastomer (FKM) composites are typically used as sealing materials in challenging non-ambient environments. Depending on the environment, two main aging mechanisms, chemical aging, and physical aging, can be identified. Chemical aging, the degradation of the elastomer, is present for example in thermal-oxidative conditions and can be directly observed as it affects the bulk. Physical aging, relaxation and rearrangement of the elastomers segmental conformation is commonly observed at elevated temperatures and effects predominantly the elastomer interphase. As a highly localized nanoscopic effect it is usually observed indirectly by phenomological approaches and not systematically understood. In this study, as a typical example for chemical aging, filled FKM was aged in air (150°C, 100 days). Physical aging of FKM was realized by exposure to chemically inert H2 (150°C, 50 bar, 100 days), since temperature and gas-induced swelling is known to promote physical aging. The effects of both conditions are directly compared with the initial unaged material. We use atomic force microscopy (AFM) force spectroscopy as a method to resolve nanoscopic heterogeneous FKM. With this method the effect of aging on the spatially distinguishable material phases was directly observed. In thermal oxidative aged FKM the matrix shows a decrease in van der Waals interactions and stiffness, indicating dehydrofluorination and chain scission. In H2 aged FKM, the development of an immobilized amorphous interphase (IAP) was observed, indicating physical aging. By additionally evaluating a larger data set with supervised machine learning, these observations were validated for a larger, statistically representative sample area, allowing conclusions to be drawn about the macroscopic behaviour of the material. KW - Fluoroelastomer KW - Atomic force microscopy KW - Data-driven KW - Hydrogen KW - Ageing mechanism KW - Physical aging KW - Polymer interphase PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-648154 DO - https://doi.org/10.1016/j.polymdegradstab.2025.111715 SN - 0141-3910 VL - 242 SP - 1 EP - 10 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-64815 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zaghdoudi, Maha T1 - Oxidative ageing of elastomers: experiment and modelling N2 - During an extensive test programme at the Bundesanstalt für Materialforschung und prüfung, material property changes of EPDM O-rings were investigated at different ageing times and an ageing temperature of 125 °C. To exclude possible diffusion limited oxidation (DLO) effects that can distort the data, IRHD micro hardness measurements were performed over the cross-section of compressed O-rings. Continuous stress relaxation measurements were conducted on samples free of DLO effects. The additional effect of physical processes to irreversible chemical ones during a long-term thermal exposure is quantified by the analysis of compression set measurements under various test conditions. By combining the different experimental methods, characteristic times relative to the degradation processes were determined. On the basis of experimental data, a microphysically motivated model that takes into account reversible and irreversible processes was developed. The parameter identification strategy of the material model is based on our experimental investigations on homogeneously aged elastomer O-rings. The simulated results are in good agreement with the experiments. T2 - ACEX-14th International Conference on Advanced Computational Engineering and Experimenting CY - Malta DA - 04.07.2021 KW - Compression stress relaxation KW - Compression set KW - IRHD micro hardness KW - Modelling PY - 2021 AN - OPUS4-52968 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias T1 - An update on metal seal tests performed at BAM and implications for interim storage N2 - The investigation of the long-term performance of sealing systems employed in containers for radioactive waste and spent nuclear fuel is one research focus area for division 3.4 “Safety of Storage Containers” at the Bundesanstalt für Materialforschung und -prüfung. Metallic seals are in use in interim storage casks for used fuel and high active waste. Their change in performance over time is of high importance for maintaining safe enclosure. Therefore, investigations on these systems were started at BAM to get a general understanding of the relevant processes. Our investigations comprise investigations on different parameters which influence the seal performance and the main part is focussed on the time and temperature dependent behaviour. In this contribution an update on the performed tests and their respective results will be given in respect to the overview presented in 2020. The understanding of the long-term behaviour of the sealing systems and the performance evaluation during interim storage and subsequent transportation are our goals. T2 - SEDS-Workshop: Sicherheit der längerfristigen trockenen Zwischenlagerung CY - Garching, Germany DA - 15.05.2024 KW - Metal seals KW - Ageing KW - Leakage rate KW - Creep PY - 2024 AN - OPUS4-60640 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Übersicht über laufende Untersuchungen zur Langzeitalterung von Elastomerdichtungen N2 - Eine Aufgabe des Fachbereichs 3.4 Sicherheit von Lagerbehältern der Bundesanstalt für Materialforschung und -prüfung (BAM) ist es, die Sicherheit von Behältern zur Lagerung von radioaktivem Abfall mit vernachlässigbarer Wärmeentwicklung zu bewerten. Da solche Behälter vor der Entsorgung transportiert und gelagert werden, ist während dieser Zeit ein sicherer Einschluss des radioaktiven Inhalts von größter Bedeutung. Zur Abdichtung dieser Behälter sind Elastomer-O-Ringe weit verbreitet. Um für solche, wie auch für viele andere Anwendungen, eine Voraussage über die Lebensdauer dieser Komponenten treffen zu können, ist es unerlässlich zu verstehen, welchen Einfluss der durch Alterung hervorgerufene Abbau auf Dauer auf die Elastomerdichtungen hat. In einem Langzeittest wurden drei Kautschukarten (EPDM und FKM, die für die Anwendung relevant sind, und HNBR als Vergleich) über mehrere Jahre untersucht. Dabei wurden die Veränderungen der mechanischen Eigenschaften (z. B. Härte und Bruchdehnung) bei vier verschiedenen Alterungstemperaturen (75 °C, 100 °C, 125 °C und 150 °C) sowie das Dichtungsverhalten betrachtet. Um den Einfluss von Vernetzung und Kettenspaltung auf die beobachteten Alterungseffekte zu bestimmen, wurden Messungen zur kontinuierlichen und intermittierenden Druckspannungsrelaxation durchgeführt. Dadurch konnten Erkenntnisse über Kinetik und Mechanismus der Abbaureaktionen gewonnen werden. Zur Einschätzung des Dichtungsverhaltens wurden Durckverformungsrest und Leckagerate gemessen. Die Ergebnisse zeigen, dass die O-Ringe unter statischen Bedingungen auch dann dicht halten, wenn die Werte für Druckverformungsrest, Druckspannungsrelaxation und mechanische Eigenschaften schon auf einen fortgeschrittenen Alterungsabbau hindeuten. Aus diesem Grund wurde ein modifizierter Dichtigkeitsversuch mit einer geringen und schnellen teilweisen Entlastung der Dichtung entwickelt, mit dessen Hilfe sich ein Lebensdauerkriterium bestimmen lässt, das eine Sicherheitsspanne für thermische Schrumpfung und Vibrationen beinhaltet. KW - Alterung KW - O-ring KW - Elastomer Dichtung PY - 2020 SN - 0176-1625 VL - 73 IS - 07-08 SP - 326 EP - 332 PB - Gupta CY - Ratingen AN - OPUS4-51207 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar A1 - Albouy, P.-A. A1 - Häcker, Ralf A1 - Stock, Daniel T1 - Overview of ongoing research and future prospects on polyethylene neutron shielding materials at bam N2 - The extension of the interim storage period of radioactive waste before disposal will cause additional challenges for the nuclear waste management in Germany, so that an extensive knowledge of the long-term performance of casks, including their components and inventories, will be required for future extended storage licenses. Ultra-high and high molecular weight polyethylenes ((U)HMW-PE) are used for neutron shielding purposes in casks for storage and transport of spent fuel and high-level waste due to their extremely high hydrogen content. During their service life of several decades as cask components, the PE materials are exposed to neutron and gamma radiation from the radioactive inventory of the casks, mechanical assembling stresses and temperature. All these combined effects affect the material properties of such components which in turn may be crucial for some possible accident scenarios. At the Bundesanstalt für Materialforschung und -prüfung (BAM), the effects of high temperature exposure in combination with subsequent or previous irradiation were investigated with a comprehensive aging program including thermal aging at 125 °C for different aging periods up to 5 years and irradiation with doses ranging from 50 to 600 kGy. This contribution provides an overview of the ongoing research related to the structural changes of (U)HMW-PE induced by gamma irradiation and high temperature exposure and focuses on current research perspectives at BAM with regard to the prediction of the dynamic behavior of the material during extended interim storage in case of an accident scenario. First results of the coupled effect of temperature, radiation and mechanical loading will be presented. The effect of microstructural changes induced by gamma irradiation and high temperature on the mechanical behavior of (U)HMW-PE will be assessed. T2 - PATRAM22 CY - Juan-Les-Pins, Antibes, France DA - 11.06.2023 KW - (U)HMWPE KW - Ageing KW - Irradiation KW - WAXD KW - SHPB PY - 2023 SP - 1 EP - 10 AN - OPUS4-57707 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zaghdoudi, Maha T1 - Overview of ongoing research and future prospects on polyethylene neutron shielding materials at BAM N2 - The extension of the interim storage period of radioactive waste before disposal will cause additional challenges for the nuclear waste management in Germany, so that an extensive knowledge of the long-term performance of casks, including their components and inventories, will be required for future extended storage licenses. Ultra-high and high molecular weight polyethylenes ((U)HMW-PE) are used for neutron shielding purposes in casks for storage and transport of spent fuel and high-level waste due to their extremely high hydrogen content. During their service life of several decades as cask components, the PE materials are exposed to neutron and gamma radiation from the radioactive inventory of the casks, mechanical assembling stresses and temperature. All these combined effects affect the material properties of such components which in turn may be crucial for some possible accident scenarios. At the Bundesanstalt für Materialforschung und -prüfung (BAM), the effects of high temperature exposure in combination with subsequent or previous irradiation were investigated with a comprehensive aging program including thermal aging at 125 °C for different aging periods up to 5 years and irradiation with doses ranging from 50 to 600 kGy. This contribution provides an overview of the ongoing research related to the structural changes of (U)HMW-PE induced by gamma irradiation and high temperature exposure and focuses on current research perspectives at BAM with regard to the prediction of the dynamic behavior of the material during extended interim storage in case of an accident scenario. First results of the coupled effect of temperature, radiation and mechanical loading will be presented. The effect of microstructural changes induced by gamma irradiation and high temperature on the mechanical behavior of (U)HMW-PE will be assessed. T2 - PATRAM22 CY - Juan-les-Pins, France DA - 11.06.2023 KW - (U)HMWPE KW - Ageing KW - Irradiation KW - WAXD KW - SHPB PY - 2023 AN - OPUS4-57708 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja T1 - Aging of elastomer O-rings and PE neutron shielding materials for radioactive waste containers N2 - Our institution BAM in Berlin, Germany is concerned with research and testing of materials in the context of safety in chemistry and technology. Our working group is involved in the licensing procedures of casks for radioactive waste. Besides, we’re doing research on aging and lifetime prediction of elastomer O-rings and investigate degradation and thermal expansion of PE neutron shielding materials. T2 - Polymers in nuclear applications CY - Online meeting DA - 01.12.2021 KW - Rubber KW - Polyethylene KW - Thermal expansion KW - Lifetime KW - Degradation PY - 2021 UR - https://energiforsk.se/media/30631/bam_material_aging_analysis.pdf AN - OPUS4-54191 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Liu, Y. T1 - Cooperation in Advanced Technologies Associated with the Back End of Nuclear Fuel Cycle N2 - A Memorandum of Understanding (MOU) between Argonne National Laboratory (Argonne) and the German Bundesanstalt für Materialforschung und -prüfung (BAM) was signed in October 2014. Its objectives are to promote cooperation among scientists and specialists at Argonne and BAM and establish a framework for collaboration in advanced technologies associated with the back end of the nuclear fuel cycle. Collaborative activities involving Argonne and BAM may be implemented through the promotion of joint research activities and scientific workshops and conferences; exchange of technical information; and visits by scientists, specialists, and graduate, postgraduate, and Ph.D. students. The MOU was renewed in January 2020 for another five years. Highlights of the progress and achievements are provided in identified topical areas for collaboration on ageing management guidance, storage, transportation and disposal R&D, joint conference activities, and conclude with the benefits of the MOU in fostering Argonne and BAM collaboration. T2 - 26th International Conference on Structural Mechanics in Reactor Technology - SMiRT 26 CY - Potsdam, Germany DA - 10.07.2022 KW - Nuclear fuel cycle KW - Back end KW - Spent fuel performance KW - Storage KW - Transportation PY - 2022 AN - OPUS4-55862 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias A1 - Goral, Milan A1 - Sagradov, Ilja A1 - Wolff, Dietmar A1 - Völzke, Holger T1 - Aging investigations of metal seals used in containers for interim storage of spent fuel N2 - For bolted casks for used fuel and high level waste the sealing system has an important impact of ensuring safe enclosure of the inventory The used metal seals show some changes over time which have been addressed for nearly 15 years in running experiments at BAM The observed changes are temperature de pendent and therefore it is expected that test s at higher temperature allow for an acceleration of the effects and ideally the proposal of an ageing model covering the expected time of use . Nevertheless, questions concerning the influence of the experimental approach on the results and effects taking place at the initial days of ageing remain. To address these a new project was launched to give a better understanding of the seal behavior. T2 - PVP2024, Pressure Vessels & Piping Conference CY - Bellevue, WA, USA DA - 29.07.2024 KW - Metal seal KW - Aging KW - Interim storage PY - 2024 SN - 978-0-7918-8851-3 SP - 1 EP - 4 PB - ASME AN - OPUS4-61357 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias T1 - Tests of metallic seals at Bam 3.4 performed over more than 15 years N2 - The investigation of the long-term performance of sealing systems employed in containers for radioactive waste and spent nuclear fuel is one research focus area for division 3.4 “Safety of Storage Containers” at the Bundesanstalt für Materialforschung und -prüfung (BAM) in Germany. The time dependant behaviour of metallic seals, which are employed in interim storage casks for used fuel and high active waste, is of high importance for ensuring safe enclosure. Therefore, investigations on these systems were started at BAM to get a general understanding of the relevant processes. Our investigations comprise investigations on different parameters which influence the seal performance and the main part is focussed on the time and temperature dependent behaviour. In this contribution an overview of the performed tests and their respective results will be given. T2 - 5th sealing workshop by Maestral CY - Avignon, France DA - 05.11.2024 KW - Metal seal KW - Aging KW - Interim storage PY - 2024 AN - OPUS4-62048 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weber, Mike T1 - Reproducing and discussion of mechanisms in the contact area between metallic seals and flange during aging by finite element analysis (FEA) N2 - When the first site-specific interim storage licenses for DPCs (dual purpose casks), loaded with spent nuclear fuel or vitrified high-level waste from reprocessing were issued, a duration of 40 years was considered for interim storage license application and the long-term safety assessment of casks. In the meantime, the availability of a final repository is further delayed by several decades and thus interim storage for more than a century becomes a necessity. To assess the long-term performance of the typically used metal seals (e.g. Helicoflex), consisting of a helical spring (Nimonic), an inner stainless steel liner and an outer liner made from silver or aluminum, several experimental programs were conducted and are still ongoing. The investigated metal seals are typically mounted in mock-up flange systems and stored at increased temperatures to accelerate the aging process. In certain intervals the remaining seal force, the useable resilience and the corresponding leakage rate are determined. BAM has accompanied such programs for many years and started independent investigations in 2009. Although the remaining seal force is often used as “…one of the key parameters regarding sealing performances over time…” the presented results so far have shown that the courses of the leakage rate and the remaining seal force do not always correlate as expected. In 2016 BAM firstly published results of seals with aluminum liners where the measured leakage rate started to rise after a quite short time period (< 1 year) at 150 °C, although the seal force decreased only slightly compared to the previous measurement. After exceeding the required leakage rate of 10-8 Pa*m3/s it decreased again to acceptable values in the further course of aging. With reference to already published works, BAM has developed a new detailed ABAQUS finite-element (FE) model to represent the behavior of the seal mounted in the mock-up flange during aging, mainly characterized by the creeping of the outer liner. The main goal of the numerical simulation is to reproduce and understand the changing distribution of contact stresses (outer liner/flange) during aging and to discuss if and how it could be causative for the observed early breach of the leak tightness criteria and its later recovery. T2 - PATRAM 2025, 21st International Symposium on the Packaging and Transportation of Radioactive Materials CY - San Antonio, Texas, USA DA - 27.07.2025 KW - Finite element analysis KW - Metallic seals KW - Aging KW - Contact area PY - 2025 AN - OPUS4-63883 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sagradov, Ilja T1 - Long-term tests on metal seals using continuous force measurement in compressed state N2 - In Germany, spent fuel and heat generating radioactive waste is stored in casks for transport and storage (DPCs). The storage licenses were granted for up to 40 years. Due to the delay in identifying a final repository site for such radioactive waste, the storage periods are to be extended significantly. The objective of our research work is to collect additional material data for metal seals in order to be able to better assess the long-term safety of the sealing system of the casks for a period of up to 100 years. A principal safety consideration for the DPCs is the long-term performance of bolted lid sealing systems utilizing metal seals to ensure the safe enclosure of the radioactive inventory during interim storage. To assess the sealing behavior, it is necessary to examine the aging-dependent residual restoring force for the metal seals and the usable resilience. By investigating the change in these values as a function of time and temperature, further insight can be gained into the assessment of long-term safety for extended interim storage. In the present study, the restoring force of metal seals with an outer aluminum jacket and a torus diameter of 9.9 mm was measured continuously. For this purpose, a specially designed device equipped with a load cell was used under isothermal conditions. As part of the investigation, the level and rate of decrease of the restoring seal force were recorded over test periods of one and two months. The seal temperature was set to 35 °C, 75 °C, 100 °C, 125 °C, and 150 °C, respectively. A direct correlation was observed between the temperature of the seal, the level of the restoring force after compressing and heating the seal, and the drop-off characteristics of the restoring force. It was found that in our test device the force level immediately after reaching the respective temperature is lower for higher seal temperatures, while the drop rate of the restoring force is higher. This paper describes the experimental setting and discusses first results in comparison with our long-term discontinuous measurements. T2 - 21st International Symposium on the Packaging and Transportation of Radioactive Materials - PATRAM 2025 CY - San Antonio, TX, USA DA - 27.07.2025 KW - Long-Term Safety Assessment KW - Extended Interim Storage KW - Metal Seal Aging KW - Restoring Force Degradation KW - Temperature-Dependent Performance PY - 2025 AN - OPUS4-63880 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Goral, Milan A1 - Wolff, Dietmar T1 - Insights for lifetime predictions of O-ring seals from five-year long-term aging tests N2 - O-rings made of HNBR, EPDM and FKM were aged in the compressed and uncompressed state at 150 °C, 125 °C, 100 °C, 75 °C, 60 °C and 23 °C for aging times of up to five years. Hardness was measured and increased with aging time and temperature for HNBR and EPDM, but it remained practically constant for FKM. Indenter modulus measurements were performed on the lateral O-ring surface (that was free of DLO effects) to assess an influence of the compression during aging, but none was detected. The equilibrium compression set (CS) exhibited faster and stronger degradation than hardness and was used for lifetime predictions using the time-temperature superposition (TTS) principle. With an end-of-lifetime criterion of 70 % CS, lifetimes of 4.5 years, 50 years and 526 years at 75 °C were estimated for HNBR, EPDM and FKM, respectively. The activation energies derived from an Arrhenius plot of the shift factors from the TTS were 85 kJ/mol, 99 kJ/mol and 78 kJ/mol for HNBR, EPDM and FKM, respectively, revealing that a higher activation energy does not necessarily mean that the material has a higher lifetime at lower temperatures. Furthermore, the measured lifetime of EPDM O-rings at 100 °C (5 years) was compared to that predicted on the basis of the lifetime at 150 °C as well as 125 °C using the corresponding shift factors. The error of the prediction was only ± 4 %. However, this precise prediction could only be achieved using the five-year long-term aging data. When using only data from aging times up to 0.5 years and 2 years, the lifetime of EPDM O-rings at 100 °C was underestimated by 31 % and 22 %, respectively. KW - HNBR KW - EPDM KW - FKM KW - DLO KW - Hardness KW - Compression set KW - Rubber KW - Elastomer KW - Degradation PY - 2020 DO - https://doi.org/10.1016/j.polymdegradstab.2020.109278 VL - 179 SP - 109278 PB - Elsevier Ltd. AN - OPUS4-51060 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Erroneous or Arrhenius: A Degradation Rate-Based Model for EPDM during Homogeneous Ageing N2 - To improve the predictive capability of long-term stress relaxation of elastomers during thermo-oxidative ageing, a method to separate reversible and irreversible processes was adopted. The separation is performed through the analysis of compression set after tempering. On the Basis of this separation, a numerical model for long-term stress relaxation during homogeneous ageing is proposed. The model consists of an additive contribution of physical and chemical relaxation. Computer simulations of compression stress relaxation were performed for long ageing times and the results were validated with the Arrhenius treatment, the kinetic study and the time-temperature superposition technique based on experimental data. For chemical relaxation, two decay functions are introduced each with an activation energy and a degradative process. The first process with the lower activation energy dominates at lower ageing times, while the second one with the higher activation energy at longer ageing times. A degradation-rate based model for the evolution of each process and ist contribution to the total system during homogeneous ageing is proposed. The main advantage of the model is the possibility to quickly validate the interpolation at lower temperatures within the range of slower chemical processes without forcing a straight-line extrapolation. KW - Kinetic study KW - Arrhenius KW - TTS KW - Modeling KW - Chemical processes KW - Stress relaxation PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-512931 DO - https://doi.org/10.3390/polym12092152 SN - 2073-4360 VL - 12 IS - 9 SP - 1 EP - 21 AN - OPUS4-51293 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Goral, Milan A1 - Kömmling, Anja A1 - Probst, Ulrich A1 - Wossidlo, Peter A1 - Jaunich, Matthias A1 - Wolff, Dietmar A1 - Völzke, Holger T1 - Langzeitversuche über 10 Jahre an Federkern-Metalldichtungen mit Aluminium- bzw. Silberummantelungen N2 - Federunterstützte Metalldichtungen mit Aluminium(Al)- oder Silber(Ag)-Ummantelung werden u.a. in Behältern für Wärme entwickelnde radioaktive Abfälle eingesetzt, da diese Dichtungen eine sehr gute Dichtheit gewährleisten sowie Langlebigkeit und Beständigkeit gegenüber erhöhten Temperaturen und radioaktiver Strahlung aufweisen. Auch wenn die Sicherheit solcher Behälter und der verwendeten Dichtungen vielfach belegt wurde, sind sie Gegenstand andauernder Forschung, etwa im Hinblick auf eine absehbar benötigte verlängerte Zwischenlagerdauer. Aus diesem Grund werden an der Bundesanstalt für Materialforschung und -prüfung (BAM) im Fachbereich 3.4 „Sicherheit von Lagerbehältern“ seit über 20 Jahren Versuche an solchen Metalldichtungen durchgeführt. Dabei sollen zusätzliche Erkenntnisse hinsichtlich der Sicherheitsreserven der Dichtungen in unterstellten Störfallszenarien (axiale Bewegung des Deckelsystems bzw. Aufweitung der Nutgeometrie) und insbesondere detailliertere Erkenntnisse zum Langzeitverhalten gewonnen werden. KW - Federunterstützte Metalldichtungen KW - Transport- und Lagerbehälter für radioaktive Stoffe KW - Langzeitversuche KW - Alterung KW - Dichtheit KW - Leckagerate KW - Helium-Dichtheitsprüfung PY - 2023 VL - 2023 SP - 43 EP - 63 PB - ISGATEC GmbH CY - Mannheim AN - OPUS4-56399 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weber, Mike A1 - Jaunich, Matthias A1 - Goral, Milan A1 - Völzke, Holger T1 - Reproducing and discussion of mechanisms in the contact area between metallic seals and flange during aging by finite element analysis (FEA) N2 - When the first site-specific interim storage licenses for DPCs (dual purpose casks), loaded with spent nuclear fuel or vitrified high-level waste from reprocessing were issued, a duration of 40 years was considered for interim storage license application and the long-term safety assessment of casks. In the meantime, the availability of a final repository is further delayed by several decades and thus interim storage for more than a century becomes a necessity. To assess the long-term performance of the typically used metal seals (e.g. Helicoflex), consisting of a helical spring (Nimonic), an inner stainless steel liner and an outer liner made from silver or aluminum, several experimental programs were conducted and are still ongoing. The investigated metal seals are typically mounted in mock-up flange systems and stored at increased temperatures to accelerate the aging process. In certain intervals the remaining seal force, the useable resilience and the corresponding leakage rate are determined. BAM has accompanied such programs for many years and started independent investigations in 2009. Although the remaining seal force is often used as “…one of the key parameters regarding sealing performances over time…” the presented results so far have shown that the courses of the leakage rate and the remaining seal force do not always correlate as expected. In 2016 BAM firstly published results of seals with aluminum liners where the measured leakage rate started to rise after a quite short time period (< 1 year) at 150 °C, although the seal force decreased only slightly compared to the previous measurement. After exceeding the required leakage rate of 10-8 Pa*m3/s it decreased again to acceptable values in the further course of aging. With reference to already published works, BAM has developed a new detailed ABAQUS finite-element (FE) model to represent the behavior of the seal mounted in the mock-up flange during aging, mainly characterized by the creeping of the outer liner. The main goal of the numerical simulation is to reproduce and understand the changing distribution of contact stresses (outer liner/flange) during aging and to discuss if and how it could be causative for the observed early breach of the leak tightness criteria and its later recovery. T2 - PATRAM 2025, 21st International Symposium on the Packaging and Transportation of Radioactive Materials CY - San Antonio, Texas, USA DA - 27.07.2025 KW - Finite element analysis KW - Metallic seals KW - Aging KW - Contact area PY - 2025 SP - 1 EP - 10 PB - INMM CY - Indianopolis, Indiana, USA AN - OPUS4-63882 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias A1 - Kömmling, Anja A1 - Böhning, Martin A1 - Silbernagl, Dorothee T1 - Comparison of ageing behavior of O-ring seals under hydrogen and air N2 - Elastomeric seals are essential components in the infrastructure which prevent leakage of gas and ensure proper function of technical devices and are therefore highly safety relevant. For proper function a remaining resilience and tolerance to pressure changes is required. The ageing of elastomers is an undesirable but inevitable process leading to a limited lifetime of rubber products such as seals. Independent of the application, as e.g. automotive, piping or container applications, a long lifetime or at least a timely exchange of a seal before occurrence of critical failure is desired. Hydrogen is a key element for the energy turnaround and therefore the compatibility of seals with hydrogen is essential. In addition to the effect of hydrogen uptake and release, which might also cause destructive effects such as rapid gas decompression, ageing at high temperature under hydrogen atmosphere is of interest too. Most of the existing work is addressing the performance of new materials and comprises only very limited investigations concerning long-term use and the behaviour of aged materials in contact with hydrogen. As ageing can lead to substantial changes of material properties, it must be evaluated whether these changes are beneficial or deteriorating for the component function. In this work we present and compare results of the characterization of three sealing materials (EPDM, HNBR, FKM) after ageing at high temperature under hydrogen and air. Despite the common assumption that ageing under hydrogen atmosphere should be less severe for the material in comparison to air ageing, this is not the case for every material. T2 - ASME PVP2025, Pressure Vessels & Piping Conference CY - Montreal, Quebec, Canada DA - 20.07.2025 KW - Aging KW - Seal KW - Compression set KW - Atomic force microscopy PY - 2025 SP - 1 EP - 7 AN - OPUS4-63889 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias T1 - Comparison of ageing behaviour of O-ring seals under hydrogen and air N2 - Elastomeric seals are essential components in the infrastructure which prevent leakage of gas and proper function of technical devices and are therefore highly safety relevant. For proper function a remaining resilience and tolerance to pressure changes is required. The ageing of elastomers is an undesirable but inevitable process leading to a limited lifetime of rubber products such as seals. Independent of the application, as e.g. automotive, piping or container applications, a long lifetime or at least a timely exchange of a seal before occurrence of critical failure is desired. Hydrogen is a key element for the energy turnaround and therefore the compatibility of seals with hydrogen is essential. In addition to the effect of hydrogen uptake and release, which might also cause destructive effects such as rapid gas decompression, ageing at high temperature under hydrogen atmosphere is of interest too. Most of the existing work is addressing the performance of new materials and comprises only very limited investigations concerning long-term use and the behaviour of aged materials in contact with hydrogen. As ageing can lead to substantial changes of material properties, it must be evaluated whether these changes are beneficial or deteriorating for the component function. In this work we present and compare results of the characterisation of three sealing materials (EPDM, HNBR, FKM) after ageing at high temperature under hydrogen and air. Despite the common assumption that ageing under hydrogen atmosphere should be less severe for the material in comparison to air ageing, this is not the case for every material. T2 - RubberCon 2023 CY - Edinburgh, Scotland DA - 09.05.2023 KW - Hydrogen KW - Ageing KW - Seal PY - 2023 AN - OPUS4-58178 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias T1 - Investigations at BAM on Fuel Cladding Integrity and DPC Seal Performance N2 - The presentation provides an update on preliminary results from research projects in the area of long term performance of metal seals and fuel rod integrity as safety relevant components of spent fuel transport and storage casks for spent nuclear fuel. T2 - Extended Storage Collaboration Program (ESCP) winter meeting 2022 CY - Charlotte, NC, USA DA - 07.11.2022 KW - Metal seal KW - Fuel cladding KW - Ring compression test KW - Brittle failure PY - 2022 AN - OPUS4-56400 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, M. A1 - Kömmling, Anja A1 - Böhning, Martin A1 - Jaunich, Matthias T1 - Ageing of elastomers in air and in hydrogen environment - A comparative study N2 - EPDM, HNBR and FKM materials were exposed at 150 ◦C to air under atmospheric pressure and to hydrogen at 50 bar for different ageing times. All measurements after hydrogen exposure were conducted on samples in degassed condition to assess irreversible effects resulting from that exposure and to compare them to those after ageing in air. Density, hardness, tensile properties, compression set, and hydrogen permeability of all samples were analysed. In both ageing environments, HNBR exhibited the most significant changes of material properties. However, for both EPDM and HNBR, considerably less severe ageing effects were observed under hydrogen in comparison to ageing in air. On the other hand, FKM showed about the same low level of deterioration in both ageing environments but exhibited poor resistance against damage due to rapid gas decompression in hydrogen environment that can lead to seal failure. The obtained results may serve as a guidance toward a better understanding for design and utilisation of elastomeric materials in future hydrogen infrastructure components. KW - Rapid gas decompression KW - Condensed matter physics KW - Hydrogen KW - Sustainability and the environment KW - Rubber sealing KW - Renewable energy PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597417 DO - https://doi.org/10.1016/j.ijhydene.2024.03.053 SN - 0360-3199 SN - 1879-3487 VL - 63 SP - 207 EP - 216 PB - Elsevier CY - Oxford AN - OPUS4-59741 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zaghdoudi, Maha A1 - Weber, Mike A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Numerical Modelling of Compression Stress Relaxation and Compression Set of Elastomer O-Ring During Aging N2 - Elastomer seals are used in many industrial applications due to their excellent mechanical properties at a wide range of temperatures. Their high versatility and recovery potential under several load conditions make them well suitable for the application in containers designed for transport, storage and/or disposal of radioactive materials. In containers for low and intermediate level radioactive waste, elastomer seals are used as barrier seals, and as auxiliary seals in storage and transportation casks (dual purpose casks) for heat generating radioactive waste, such as spent fuel and high-level waste. While a seal exchange at defined intervals is typical in many conventional applications, it is impossible or at least hard to perform when principles of minimization of radiation exposure have to be considered and prohibit an unnecessary cask handling. An extensive knowledge of the change of the elastomer’s properties during aging and the availability of reliable end-of-lifetime criteria to guarantee the permanent safe enclosure of the radioactive material is mandatory. As BAM is involved in most of the national cask licensing procedures and in the evaluation of cask-related long-term safety issues, great efforts have been already made and are still planned to scientifically support this task. Compression stress relaxation and compression set were identified as key indicators of elastomer long-term performance and quantitatively investigated in comprehensive test programs. Among other representative types of elastomers, specimens made from ethylene propylene diene rubber (EPDM) were tested before, during and after aging to capture the most important of their complex mechanical properties. In the presented study, exemplary results were used to simulate the compression stress relaxation and the compression set of elastomer O-rings during aging. Regarding the influence of temperature, the time-temperature superposition principle is applied in the relaxation analysis of elastomer O-rings. The proposed model is implemented in the commercial finite element software ABAQUS/Standard® [1] with a sequential temperature displacement coupling. Numerical results match the experimental compression stress relaxation measurements well. The prediction of compression set values after long-term aging shows a relatively good agreement with the experimental results. Nevertheless, all input parameters derived from the specimen tests, additional assumptions concerning boundary conditions and modeling strategy are discussed with regard to the identified slight discrepancies. The possibility to extend the finite element model to represent the O-ring seal’s ability to recover after a (fast) partial release is taken into account. T2 - ASME 2020 Pressure Vessels & Piping Conference (PVP2020) CY - Online meeting DA - 03.08.2020 KW - Compression Set KW - O-ring KW - Simulation KW - Sequential analysis KW - Ageing KW - stress relaxation PY - 2020 SN - 978-0-7918-8388-4 DO - https://doi.org/10.1115/PVP2020-21270 SP - PVP2020-21270 PB - ASME AN - OPUS4-51490 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Zaghdoudi, M. A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar ED - Altenbach, H. ED - Hitzler, L. ED - Johlitz, M. ED - Merkel, M. ED - Öchsner, A. T1 - Analysis of Heterogeneous Ageing of HNBR O-Rings N2 - Abstract Hydrogenated nitrile butadiene rubber (HNBR) elastomer was thermo-oxidatively aged at different temperatures up to 150 °C. Fourier transform infrared spectroscopy (FTIR), compression stress relaxation (CSR) and international rubber hardness degree (IRHD) microhardness were used to characterise the chemo-mechanical changes of HNBR O-rings during thermo-oxidative ageing. FTIR shows the development of carbonyl, methyl and ester groups but the nitrile content was not affected by ageing. The effect of sample geometry during CSR was investigated. CSR data were converted through integrated kinetic laws. The conversion has proven its sensibility to detect heterogeneous ageing. This was confirmed by the IRHD measure-ments across the section of O-rings. The influence of compression during ageing was assessed through IRHD measurements across the section of compressed and uncom-pressed aged O-rings. The DLO effect was more pronounced in compressed O-rings. By applying the model of Wise et al., theoretical IRHD and oxidation profiles were determined on the basis of IRHD experimental data of compressed O-rings. Good agreements between the experimental and the theoretical IRHD profiles in the core region were obtained. However, near the edge, the theoretical IRHD values were overestimated. KW - Ageing KW - Rubber seals KW - Stress relaxation KW - Modelling PY - 2024 SN - 978-3-031-49042-2 DO - https://doi.org/10.1007/978-3-031-49043-9 SN - 1869-8433 SP - 331 EP - 348 PB - Springer Nature CY - Cham, Switzerland AN - OPUS4-59769 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Beckmann, Jörg T1 - Photolytically and Thermally Initiated Destruction on the Stability of (Ultra)High Molecular Polyethylene N2 - THz and mid IR spectroscopy of high-molecular PE (HMW) and ultra high-molecular PE (UHMW) reveals modifications of the molecular structure. Characteristic absorption bands are changed if the two materials are exposed by γ-Co60 radiation up to 600 kGy and subsequently stored at an annealing temperature of 398 K until for 729 days. UHMW-PE and HMW-PE behave differently during the ageing process because of their molecular weight and inherent structure distinctions. The spectroscopic data offer characteristic absorption bands, which have been used to describe the complete ageing process in more detail. For instance, the integral absorption in the B1u THz-region can be used to describe quantitatively the reduction of crystallinity. The formation of trans vinylene unsaturation and the decay of vinyl during ageing can be observed in detail in the mid IR range. T2 - 9th International Workshop on Terahertz Technology and Applications CY - Kaiserslautern, Germany DA - 03.03.2020 KW - Degradation KW - MID IR Spectroscopy PY - 2020 AN - OPUS4-50555 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Understanding the recovery behaviour and the degradative processes of EPDM during ageing N2 - Recovery is an important measure for seal applications representing to which extent the elastomer regains its initial shape after deformation and release of an applied force. Compression set (CS) indicates the degree of recovery. Ethylene propylene diene rubber (EPDM) was aged at 75 ◦C, 100 ◦C, 125 ◦C and 150 ◦C for different ageing times up to five years and compression set measurements were performed at different times after disassembly and after additional tempering. Short- and long-term recovery up to one year after release for samples aged at 125 ◦C and 150 ◦C was also studied. To assess the curvature in the Arrhenius diagram that may occur due to non-sufficiently aged specimens, a degradation-rate based model was fitted to the CS data after tempering. For each ageing temperature, two decay fit functions were proposed, each with an activation energy and a corresponding degradative process. The influence of ageing on the leak-tightness after fast small partial release is investigated and estimated through the analysis of the shift factors from time temperature superposition (TTS) of CS measurements at different times after disassembly. Shift factors of CS measurement after 1 s and after additional tempering are in good agreement. KW - Compression set KW - Ageing KW - Recovery KW - Degradative processes KW - Leakage rate PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-573699 DO - https://doi.org/10.1016/j.polymertesting.2023.107987 SN - 0142-9418 VL - 121 SP - 107987 PB - Elsevier Ltd. AN - OPUS4-57369 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Oxidative ageing of elastomers: Experiment and modelling N2 - During an extensive test programme at the Bundesanstalt für Materialforschung und prüfung, material property changes of EPDM O-rings were investigated at different ageing times and two ageing temperatures of 125∘C and 150∘C. To exclude possible diffusion-limited oxidation (DLO) effects that can distort the data, IRHD microhardness measurements were taken over the cross section of compressed O-rings. Continuous stress relaxation measurements were taken on samples free of DLO effects. The additional effect of physical processes to irreversible chemical ones during a long-term thermal exposure is quantified by the analysis of compression set measurements under various test conditions. By combining the different experimental methods, characteristic times relative to the degradation processes were determined. On the basis of experimental data, a microphysically motivated model that takes into account reversible and irreversible processes was developed. The parameter identification strategy of the material model is based on our experimental investigations on homogeneously aged elastomer O-rings. The simulated results are in good agreement with the experiments. KW - Compression stress relaxation KW - Compression set KW - IRHD microhardness KW - Modelling PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-545910 DO - https://doi.org/10.1007/s00161-022-01093-9 SN - 1432-0959 SP - 1 EP - 9 PB - Springer CY - Berlin AN - OPUS4-54591 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Goral, Milan A1 - Wolff, Dietmar A1 - Völzke, Holger ED - Krüssenberg, A. T1 - Overview of metal seal tests performed at BAM and implications for extended interim storage N2 - The investigation of the long-term performance of sealing systems employed in containers of radioactive waste and spent nuclear fuel is one research focus area for division 3.4 \Safety of Storage Containers" at the Bundesanstalt für Materialforschung und -prüfung. The behaviour of metallic seals, which are employed in interim storage casks for spent nuclear fuel and high active waste, over time is of high importance for ensuring safe enclosure. Therefore, investigations on these systems were started at BAM to get a general understanding of the relevant processes. Our investigations comprise investigations on different parameters which influence the seal Performance and the main part is focussed on the time and temperature dependent behaviour. Our aim is to understand the longterm behaviour of the sealing systems for evaluation of their performance during possible extended interim storage and subsequent transportation. In this contribution an overview of the performed tests and their respective results is given. A focus lies on a comparison between seals with large torus diameter in comparison to small diameters. T2 - Safety of Extended Dry Storage of Spent Nuclear Fuel SEDS2020: International online-workshop CY - Online meeting DA - 03.06.2020 KW - Metal seal KW - Seal performance KW - Long-term investigation KW - Ageing PY - 2020 DO - https://doi.org/10.3139/124.200071 SN - 0932-3902 VL - 85 IS - 6 SP - 440 EP - 443 PB - Carl Hanser Verlag CY - München AN - OPUS4-51833 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, M. A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Oxidative ageing of elastomers: experiment and modelling N2 - During an extensive test programme at the Bundesanstalt für Materialforschung und prüfung, material property changes of EPDM O-rings were investigated at different ageing times and two ageing temperatures of 125 ◦ C and 150 ◦ C. To exclude possible diffusion-limited oxidation (DLO) effects that can distort the data, IRHD microhardness measurements were taken over the cross section of compressed O-rings. Continuous stress relaxation measurements were taken on samples free of DLO effects. The additional effect of physical processes to irreversible chemical ones during a long-term thermal exposure is quantified by the analysis of compression set measurements under various test conditions. By combining the different experimental methods, characteristic times relative to the degradation processes were determined. On the basis of experimental data, a microphysically motivated model that takes into account reversible and irreversible processes was developed. The parameter identification strategy of the material model is based on our experimental investigations on homogeneously aged elastomer O-rings. The simulated results are in good agreement with the experiments. KW - Compression Set KW - Compression stress relaxation KW - Modelling KW - Ageing KW - Microhardness PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-609332 DO - https://doi.org/10.1007/s00161-022-01093-9 VL - 36 SP - 289 EP - 297 PB - Springer Nature AN - OPUS4-60933 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias T1 - Overview of metal seal tests performed at BAM and implications for extended interim storage N2 - The investigation of the long-term performance of sealing systems employed in containers for radioactive waste and spent nuclear fuel is one research focus area for division 3.4 “Safety of Storage Containers” at the Bundesanstalt für Materialforschung und -prüfung. The behaviour of metallic seals, which are employed in interim storage casks for used fuel and high active waste, over time is of high importance for ensuring safe enclosure. Therefore, investigations on these systems were started at BAM to get a general understanding of the relevant processes. Our investigations comprise investigations on different parameters which influence the seal performance and the main part is focussed on the time and temperature dependent behaviour. In this contribution an overview of the performed tests and their respective results will be given. A focus will lie on a comparison between seals with large torus diameter in comparison to small diameters. Our aim is to understand the long-term behaviour of the sealing systems for evaluation of their performance during possible extended interim storage and subsequent transportation. T2 - 4th Workshop on Safety of Extended Dry Storage of Spent Nuclear Fuel CY - Online meeting DA - 03.06.2020 KW - Seal performance KW - Metal seal KW - Leakage rate PY - 2020 AN - OPUS4-50843 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Overview of ongoing long-term ageing investigations on elastomer seals N2 - At the Bundesanstalt für Materialforschung und -prüfung (BAM) in Division 3.4 Safety of Storage Containers, one of our tasks is to evaluate the safety of containers designed for disposal of low and intermediate radioactive waste. As such containers might be transported before and stored until disposal, safe enclosure of the radioactive inventory is important for this time span. Elastomer O-rings are widely used as barrier seals in these containers. Thus, as for many other applications, an understanding of the practical effects of ageing degradation on elastomer seals during long-term exposure is mandatory for predicting the lifetime of such components. According to a long-term test programme on three kinds of rubbers (EPDM and FKM (relevant for application), HNBR (for comparison)), over several years we have studied the degradation and the change of mechanical properties (e.g. hardness, strain at break) at four different ageing temperatures (75 °C, 100 °C, 125 °C and 150 °C) as well as the change of sealing properties. Continuous and intermittent compression stress relaxation (CSR) measurements were performed in order to investigate the respective contribution of crosslinking and chain scission to the observed degradation effects. Thus, the degradation kinetics and mechanisms could be resolved more clearly. For assessing the seal performance, compression set (CS) and leakage rate measurements were conducted. The experimental results showed that the O-rings remained leak-tight under purely static conditions even when CSR, CS and mechanical properties already indicated far advanced degradation. For this reason, a modified leakage test involving a small and rapid partial decompression of the seal was developed that enabled determining an end-of-lifetime criterion for O-rings with a safety margin for thermal shrinkage and vibrations. KW - Seal KW - O-Ring KW - Ageing KW - Component tests PY - 2020 SN - 1863-7116 VL - 15 IS - 3 SP - 146 EP - 151 PB - Gupta CY - Ratingen AN - OPUS4-51161 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weber, Mike A1 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - A numerical approach to correlate compression stress relaxation and compression set of elastomer O-rings with tightness N2 - The excellent mechanical properties of elastomer seals at a wide range of temperatures as well as their high versatility and recovery potential under several load conditions make these materials well suitable for the application in containers designed for transport and disposal of negligible heat generating radioactive waste. While a seal exchange at defined intervals is typical in many conventional applications, it is impossible or at least hard to perform when principles of minimization of radiation exposure have to be considered which prohibit an avoidable cask handling. An extensive knowledge of the change of the elastomer properties during aging and the availability of reliable end-of-lifetime criteria to guarantee the safe enclosure of the radioactive material for the required time are mandatory. As BAM is involved in most of the national cask licensing procedures and in the evaluation of cask-related long-term safety issues, great efforts have already been made and are still ongoing to scientifically support this task. Among other representative types of elastomers, specimen made from ethylene propylene diene rubber (EPDM) were tested before, during and after aging to capture the with respect to application most important of their complex mechanical properties. Exemplary results of these investigations were used to calibrate material models implemented in the commercial finite element software ABAQUS/Standard®. The finite element model already presented in previous works uses a sequential temperature displacement coupling. The calculated compression stress relaxation (CSR) and compression set (CS) values do satisfactorily match the experimental results. In many investigations performed at BAM both values (CSR and CS) were identified as key indicators of elastomer’s long-term performance. However, the possibility to correlate these equivalent indicators with performance values such as tightness and leakage rate, measurable in the mounted state, is an important goal of our future work. In the presented study the ABAQUS® feature of “pressure penetration” is introduced in the suggested finite element model for this purpose. It provides the possibility to simulate the penetration of a gas into a possible gap between flange and O-ring causing an opening of a leakage path. Three dimensional and axis-symmetric finite element models were generated to represent flat and grooved flanges of different dimensions. The sensitivity of the feature to several input parameters is investigated and the observed behavior of the O-ring is correlated with the results of performed leakage tests. T2 - ASME 2021 Pressure Vessels & Piping Conference (PVP2021) CY - Online meeting DA - 13.07.2021 KW - Elastomer KW - Tightness KW - Leakage KW - Compression set KW - Compression stress relaxation PY - 2021 SN - 978-0-7918-8535-2 DO - https://doi.org/10.1115/PVP2021-61976 SP - 1 EP - 8 PB - American Society of Mechanical Engineers (ASME) CY - New York, NY, USA AN - OPUS4-54422 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weber, Mike T1 - A numerical approach to correlate compression stress relaxation and compression set of elastomer O-rings with tightness N2 - The excellent mechanical properties of elastomer seals at a wide range of temperatures as well as their high versatility and recovery potential under several load conditions make these materials well suitable for the application in containers designed for transport and disposal of negligible heat generating radioactive waste. While a seal exchange at defined intervals is typical in many conventional applications, it is impossible or at least hard to perform when principles of minimization of radiation exposure have to be considered which prohibit an avoidable cask handling. An extensive knowledge of the change of the elastomer properties during aging and the availability of reliable end-of-lifetime criteria to guarantee the safe enclosure of the radioactive material for the required time are mandatory. As BAM is involved in most of the national cask licensing procedures and in the evaluation of cask-related long-term safety issues, great efforts have already been made and are still ongoing to scientifically support this task. Among other representative types of elastomers, specimen made from ethylene propylene diene rubber (EPDM) were tested before, during and after aging to capture the with respect to application most important of their complex mechanical properties. Exemplary results of these investigations were used to calibrate material models implemented in the commercial finite element software ABAQUS/Standard®. The finite element model already presented in previous works uses a sequential temperature displacement coupling. The calculated compression stress relaxation (CSR) and compression set (CS) values do satisfactorily match the experimental results. In many investigations performed at BAM both values (CSR and CS) were identified as key indicators of elastomer’s long-term performance. However, the possibility to correlate these equivalent indicators with performance values such as tightness and leakage rate, measurable in the mounted state, is an important goal of our future work. In the presented study the ABAQUS® feature of “pressure penetration” is introduced in the suggested finite element model for this purpose. It provides the possibility to simulate the penetration of a gas into a possible gap between flange and O-ring causing an opening of a leakage path. Three dimensional and axis-symmetric finite element models were generated to represent flat and grooved flanges of different dimensions. The sensitivity of the feature to several input parameters is investigated and the observed behavior of the O-ring is correlated with the results of performed leakage tests. T2 - ASME 2021 Pressure Vessels & Piping Conference (PVP2021) CY - Online meeting DA - 13.07.2021 KW - Elastomer KW - Tightness KW - Leakage KW - Compression set KW - Compression stress relaxation PY - 2021 AN - OPUS4-54423 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -