TY - CONF A1 - Wolff, Dietmar T1 - Long-term behavior of metal and elastomer seals as well as polyethylene as safety relevant components of transport and storage casks for radioactive materials (LaMEP) N2 - In Germany, the concept of dry interim storage in dual purpose metal casks before disposal is being pursued for spent nuclear fuel (SNF) and high level waste (HLW) management. The main safety relevant components are the thick-walled dual purpose metal casks. These casks consist e.g. of a monolithic cask body with integrated neutron shielding components (polymers, e.g. polyethylene) and a monitored double lid barrier system equipped with metal and elastomer seals. The metal seals of this bolted closure system guarantee the required leak-tightness whereas the elastomer seals allow for leakage rate measurement of the metal seals. This presentation provides an overview of BAM proactive R&D projects related to the long-term behavior and degradation effects of metal seals, elastomer seals and polyethylene used as neutron shielding material. Particular attention is paid to the approach and first results of the third-party-founded research project LaMEP with the aim of further closure of existing knowledge gaps of safety relevant aging effects of such cask components. T2 - Symposium Verlängerte Zwischenlagerung CY - Garching (Munich), Germany DA - 22.06.2017 KW - Metal seals KW - Elastomer seals KW - Neutron shielding material KW - Aging PY - 2017 AN - OPUS4-41312 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - von der Ehe, Kerstin A1 - Jaunich, Matthias A1 - Wolff, Dietmar A1 - Böhning, Martin A1 - Goering, Harald T1 - Radiation induced structural changes of (U)HMW polyethylene with regard to its application for radiation shielding N2 - The special properties of high molecular weight polyethylene (HMW-PE) and ultra high molecular weight polyethylene (UHMW-PE) result basically from their extreme chain lengths and their high degree of crystallinity. As high-performance polymers, they are used for a variety of applications. UHMW-PE in particular is often utilized for endoprothesis (due to its excellent slip and wear properties) and due to its high hydrogen content as a neutron moderator in casks for storage and transport of radioactive materials. To prepare the material for instance for its use as a total joint replacement, it is exposed to radiation for several reasons, such as sterilization and crosslinking, leading to partial improvement of the mechanical properties (e.g. fracture toughness, crack propagation resistance, wear resistance) and better chemical stability. To be applicable for long term radiation shielding purposes for instance over a period of 40 years, PE has to withstand any type of degradation affecting safety relevant aspects. The scope of our investigation comprises an estimation of the radiation impact on the molecular and supra molecular structure of two types of PE and to what extent these changes are detectable by thermo-analytical (TA) methods, such as Differential Scanning Calorimetry (DSC), Thermo Mechanical Analysis (TMA), Dynamic Mechanical Analysis (DMA) and Thermo Gravimetric Analysis (TGA). Additionally FT-IR spectroscopy as well as density and gas sorption measurements were carried out. Due to the poor solubility of HMW-PE and UHMW-PE, some classical analytical techniques are not applicable. But TA-methods represent a feasible approach to detect structural and morphological features of these materials as well as changes caused by external influences, such as thermal treatment and/or irradiation. With the combination of the applied TA-techniques it is possible to distinguish between crosslinking and degradation. T2 - PATRAM 2010 - 16th International symposium on the packaging and transport of radioactive materials CY - London, UK DA - 2010-10-03 PY - 2010 SP - 1 EP - 8 (T25/Paper 173) AN - OPUS4-24621 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias A1 - Wolff, Dietmar ED - Van Breugel, K. ED - Koenders, E.A.B. T1 - Approach for the investigation of long-term behaviour of elastomeric seals for transport and storage packages N2 - Elastomers are widely used as main sealing materials for Containers for low and intermediate Ievel radioactive waste and as additional component to metal seals in spent fuel and high active waste Containers. According to appropriate guidelines and regulations safe enclosure of the radioactive Container contents has to be guaranteed for long storage periods as well as down to temperatures of -40 °C for transportation. Therefore the understanding of seal behaviour in general is of high importance and ageing of elastomeric seals has to be considered with regard to possible dynamic events taking possibly place during transport after storage. T2 - 1st Ageing of materials & structures 2014 conference CY - Delft, The Netherlands DA - 26.05.2014 KW - O-Ring KW - Seal KW - Ageing KW - Elastomer KW - Compression set PY - 2014 SN - 978-94-6186-313-3 SP - 87 EP - 93 AN - OPUS4-30820 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias A1 - Wolff, Dietmar A1 - Stark, Wolfgang A1 - Völzke, Holger T1 - Investigation of elastomer seal behavior for transport and storage packages N2 - Rubbers are widely used as main sealing materials for containers for low and intermediate level radioactive waste and as additional component to metal seals in spent fuel and high active waste containers. According to appropriate guidelines and regulations safe enclosure of the radioactive container contents has to be guaranteed for long storage periods as well as down to temperatures of -40 °C for transportation. Therefore the understanding of seal behavior is of high importance. In this paper we focus on the behavior of elastomer seals at low temperatures with regard to poten-tial decrease of leak-tightness. In addition, changes in material properties due to aging effects over long periods of time and their influence on the seal performance is investigated. It is known that material properties of rubbers are strongly temperature dependent. At low tempera-tures this is caused by the rubber-glass transition (abbr. glass transition). During continuous cool-ing, the material changes from rubber-like entropy-elastic to stiff energy-elastic behavior, that al-lows nearly no strain or retraction due to the glass transition. Hence rubbers are normally used above their glass transition but the minimum working temperature limit is not defined precisely. Aging of elastomer seals is important, as possible dynamic loads may have to be considered during the whole interim storage period (so far approved in Germany for up to 40 years) and for transporta-tion after storage. For the investigations, fluorocarbon (FKM) and ethylene-propylene-diene (EPDM) rubbers were selected as they are often used in radioactive waste containers. Some materials were purchased from a commercial seal producer and some materials were compounded and cured at BAM. The elastom-ers where studied by several thermo-analytical methods and compression set to characterize the material behavior at low temperatures. Additionally component tests were performed to determine the breakdown temperature of the sealing function of complete elastomer O-rings. T2 - PATRAM 2013 - 17th International symposium on the packaging and transportation of radioactive materials CY - San Francisco, CA, USA DA - 18.08.2013 PY - 2013 SP - Paper 227, 1 EP - 8 PB - Omnipress AN - OPUS4-30377 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias A1 - Wolff, Dietmar A1 - Stark, Wolfgang T1 - Investigating low temperature properties of rubber seals N2 - To achieve the required tightness levels of Containers for low and intermediate level radioactive wastes rubbers are widely applied as main sealing materials. The save encapsulation of the radioactive Container contents has to be guaranteed according to legislation and appropriate guidelines for long storage periods as well as down to temperatures of-40 °C during transportation. Therefore the understanding of failure mechanisms that lead to leakage at low temperatures is of high importance. It is known that the material properties of rubbers are strongly influenced by temperature. At low temperatures this is caused by the rubber-glass transition (abbr. glass transition). During continuous cooling the material changes from rubber-like entropy-elastic to stiff energy-elastic behaviour, that allows nearly no strain or retraction. Therefore, rubbers are normally used above their glass transition but the minimum working temperature limit is not defrned precisely, what can cause problems during application. The temperature ränge where full functionality is possible is strongly dependent on the application conditions and the material. For this investigation mainly ethylene propylene diene (EPDM) and fluorocarbon rubbers (FKM) were selected as they are often used for radioactive waste Containers. Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) are typically used for the determination of the temperature ränge of the glass transition process. The standardized compression set measurement according to ISO 815 is common for investigation of rubber sealing materials as the test simulates the seal behaviour after release. To reduce the test time of the Standard tests a faster technique giving the same information was developed. Additionally, the breakdown temperature of the sealing function of complete O-ring seals is measured in a component test Setup to compare it with the results of the other tests. The experimental Setup is capable of measuring the leakage rate at low temperatures by the pressure rise method. A model was developed that allows calculating the minimum working temperature limit of a seal by combining the results of the applied methods. T2 - WM2013 Conference CY - Phoenix, Arizona, USA DA - 24.02.2013 PY - 2013 SN - 978-0-9836186-2-1 SP - 1 EP - 12 CY - Phoenix, Arizona, USA AN - OPUS4-28853 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Grelle, Tobias A1 - Wolff, Dietmar A1 - Probst, Ulrich A1 - Jaunich, Matthias A1 - Völzke, Holger T1 - Component and material investigations on metal seals for high level radioactive waste containers N2 - In Germany casks for interim storage of spent nuclear fuel and high level radioactive waste are equipped with Helicoflex® metal seals as main sealing barrier of the double lid system. The long-term behaviour of those seals is investigated at Bundesanstalt für Materialforschung und –prüfung (BAM) in order to evaluate the safety function of the containment at different temperatures over storage periods of 40 years or more in case extended interim storage becomes necessary. Long-term investigations have been done for ageing times of up to 8.5 years at temperatures ranging from room temperature to 150 °C. It was found that the seal force and useable resilience decrease over time, which is mainly caused by creep deformation of the aluminium (or silver) outer jacket of the seals. This effect becomes stronger with increasing temperature. The ageing processes of the seal material and the overall seal behaviour is under investigation in order to derive analytical descriptions for the long-term seal performance. Thus, standardized tests on the basic seal materials, with focus on aluminium, and additional investigations on the seals as a component are conducted. The current investigations include compression and tension creep measurements as well as tensile testing. Furthermore, ageing of seal segments provides information on the development of the contact area width, jacket thickness and microstructural changes in dependence of time and temperature. The obtained data are used for the development of material models and an analytical approach to describe and predict the time and temperature dependent sealing behaviour in the long-term. T2 - 11th International Conference on the Transport, Storage and Disposal of Radioactive Materials CY - London, UK DA - 15.05.2018 KW - Metal seal KW - Creep KW - Long-term behavior PY - 2018 SP - 18535, 1 EP - 6 AN - OPUS4-45452 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Effects of heterogeneous aging in compressed HNBR and EPDM O-ring seals N2 - Seals used in containers for dangerous goods need to maintain leak tightness for several decades. For investigating the change in seal material properties during aging, a comprehensive aging program on both uncompressed and compressed EPDM and HNBR seals was started. In order to obtain 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. These effects depend on material, dimensions, time and temperature. Heterogeneous aging results in distorted bulk properties such as compression stress relaxation and compression set (CS) suggesting that HNBR has better performance than EPDM at 150 °C but which is not the case at 100 °C. The presence of heterogeneous material properties was shown by hardness measurements across the seal cross-section. If DLO-affected data is excluded, extrapolations of CS data are possible using time-temperature shifts and Arrhenius graphs. Exemplary CS values of 50 % and 80 % would be reached after approx. 10 years and 29 years, respectively for HNBR and after approx. 400 years and 1100 years, respectively for EPDM. KW - Ageing KW - Rubber KW - Compression KW - DLO KW - Extrapolation KW - Lifetime prediction PY - 2016 DO - https://doi.org/10.1016/j.polymdegradstab.2016.01.012 VL - 126 SP - 39 EP - 46 PB - Elsevier Science CY - Oxford AN - OPUS4-35775 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wolff, Dietmar A1 - von der Ehe, Kerstin A1 - Jaunich, Matthias A1 - Böhning, Martin T1 - Performance of neutron radiation shielding material (U)HMW-PE influenced by gamma radiation N2 - Due to their extreme high hydrogen contents high molecular weight (HMW-) and ultra-high molecular weight (UHMW-) polyethylene (PE) are a comprehensible choice as neutron radiation shielding material in thick walled metallic casks for storage and transport of radioactive materials. For this application it has to be taken into consideration that gamma radiation – that is a direct consequence of inserting radioactive material in such casks – has a high influence on the molecular structure of polyethylene. In order to be applicable for long-term neutron radiation shielding purposes during the whole storage period (in Germany for instance up to 40 years) PE has to withstand any type of degradation affecting safety relevant aspects. The scope of our work comprises an estimation of the influence of gamma radiation and temperature on the molecular and supra molecular structure of (U)HMW-PE used as cask components for neutron radiation shielding. Therefore it was investigated to what extent these changes are detectable by a combination of conventional polymer characterization techniques such as Differential Scanning Calorimetry (DSC), Thermo Mechanical Analysis (TMA), Dynamic Mechanical Analysis (DMA), and Thermo Gravimetric Analysis (TGA). Additionally optical (FTIR) and weighing methods were applied. For UHMWPE the results are compared with those published for similar UHMW-PE material that is used in medical technology. For this application, gamma irradiation is applied deliberately for purposes such as sterilization and crosslinking, the latter leading to partial improvement of mechanical properties and better chemical stability. As a result the so far observed structural changes of the irradiated material are not safety relevant for the application of polyethylene as neutron shielding material; moreover, some properties actually improve via irradiation. T2 - PSAM 11 ESREL 2012 - 11th International probabilistic safety assessment and management conference & The annual european safety and reliability conference CY - Helsinki, Finland DA - 25.06.2012 KW - (U)HMW-PE KW - Gamma irradiation KW - Shielding material KW - Cask for storage and transport of radioactive materials PY - 2012 SP - 1 EP - 8 AN - OPUS4-26176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Shirai, K. A1 - Namba, K. A1 - Wataru, M. A1 - Völzke, Holger A1 - Wolff, Dietmar A1 - Probst, Ulrich A1 - Jaunich, Matthias A1 - Schulz, Sebastian T1 - Numerical evaluation of the long-term sealing performance of the silver gasket for dual purpose metal cask under high temperature N2 - It is important to evaluate the effect of thermal ageing on the sealing performance of metal gaskets under high temperature for long-term usage. Therefore, in order to gain representative data for this kind of metal-sealed lid System, BAM is currently performing laboratory tests of different gasket types with aluminum and silver jackets at three different temperatures under static conditions up to four years so far, using test flanges for gaskets with full scale cross section diameter but much smaller outer diameter. On the other hand, in order to investigate the applicability of the numerical methodology to evaluate the long-term behavior of the metal gaskets, such as a correlation between seal pressure force and holding time, CRIEPI is developing a modeling method including material tests (tensile and creep tests) at high temperature. In this paper, the applicability of the finite element method (ABAQUS) to predict the recovery displacement and residual seal pressure force of the gasket complex was verified by comparing the calculated values with BAM’s laboratory test results under the joint research agreement between BAM and CRIEPI. T2 - PATRAM 2013 - 17th International symposium on the packaging and transportation of radioactive materials CY - San Francisco, CA, USA DA - 18.08.2013 KW - Metal seals KW - Extended storage KW - Long-term storage KW - Dual purpose cask PY - 2013 SP - 1 EP - 8 PB - Omnipress AN - OPUS4-31947 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jaunich, Matthias A1 - Grelle, Tobias A1 - Wolff, Dietmar T1 - Influence of partial release on sealing performance of elastomer O-rings at low temperatures N2 - For many sealing applications rubbers are applied due to their special material properties and easy use. In many applications as e.g. in aviation, traffic or process technology the material can be exposed to low temperatures during operation. Therefore it is important to know the material behaviour at those low temperatures to determine the temperature range that allows a safe operation of the seal. As rubbers are used as main sealing materials for containers for low and intermediate level radioactive waste and as additional component to metal seals in spent fuel and high acitve waste containers, a comprehensive elastomer investigation program is run at BAM. This program comprises investigations of elastomer overall performance, durability, influence of gamma irradiation and low temperature behaviour. In this paper we focus on the behaviour of elastomer seals below ambient temperatures after a fast partial release. Despite the primarily static application conditions of many seals their behaviour after partial compression release is of interest with regard to potential decrease of leak-tightness. For this investigation a special setup was designed which allows the partial release of compressed seal systems at different temperatures accompanied by leakage rate measurements. The results for FKM seals are presented and discussed. T2 - Technomer 2015 - 24. Fachtagung über Verarbeitung und Anwendung von Polymeren CY - Chemnitz, Germany DA - 12.11.2015 KW - O-ring KW - Glass-rubber transition KW - Compression set KW - Partial release PY - 2015 SN - 978-3-939382-12-6 SP - P 3.7, 1 EP - 6 CY - Chemnitz AN - OPUS4-35130 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Influence of gamma irradiation on low temperature properties of rubber seal materials N2 - In many fields the function of seal materials is required at low temperatures. Therefore the understanding of failure mechanisms at low temperatures is of high importance. In some applications elastomeric seals are used in environments with increased irradiation backgrounds, as e.g. in containers for radioactive waste. This paper reports on the influence of gamma irradiation on the low temperature properties of different fluorocarbon rubber (FKM) materials. The samples were irradiated with gamma doses of up to 600 kGy and the induced changes of material properties were tested by methods sensitive to the rubber-glass transition, like DSC and DMA. Additionally, compression set measurements were performed to give information about recovery behaviour at low temperatures. KW - Seal KW - O-ring KW - Low temperature KW - Gamma irradiation KW - Compression set KW - Dichtungen KW - O-Ringe KW - Tiefe Temperatur KW - Gamma-Bestrahlung KW - Druckverformungsrest PY - 2015 SN - 0948-3276 SN - 0022-9520 VL - 68 IS - 6 SP - 85 EP - 89 PB - Hüthig CY - Heidelberg AN - OPUS4-33552 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 - GEN A1 - Jaunich, Matthias A1 - Probst, Ulrich A1 - Schulz, Sebastian A1 - Wolff, Dietmar A1 - Stark, Wolfgang ED - Berger, K.-F. ED - Kiefer, S. T1 - Elastomere - Untersuchung des Tieftemperaturverhaltens im Dichtungseinsatz N2 - Aufgrund ihrer einfachen und zuverlässigen Anwendung werden Elastomere für viele Dichtungsaufgaben eingesetzt. In vielen Anwendungsbereichen, wie z.B. Verkehr, Luftfahrt und Verfahrenstechnik, können während des Einsatzes tiefe Temperaturen auftreten, bei denen die Funktionsfähigkeit der Dichtung erhalten bleiben muss. Daher ist die Untersuchung des Verhaltens von Elastomerdichtungen bei tiefen Temperaturen wichtig, um ihren Temperatureinsatzbereich nach unten abzugrenzen und dadurch einen verlässlichen Betrieb zu sichern. Ziel dieser Arbeit ist es, den sicheren Einschluss von gefährlichen Gütern unter verschiedenen Umgebungsbedingungen und über lange Zeiten zu ermöglichen bzw. die Materialauswahl entsprechend zu steuern. KW - Dichtung KW - Druckverformungsrest KW - Elastomer KW - Glasübergang PY - 2013 SN - 978-3-9811509-7-1 SP - 82 EP - 91 CY - Mannheim AN - OPUS4-29661 LA - deu 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 A1 - Hagenow, Peter A1 - Kasparek, Eva Maria A1 - Kömmling, Anja A1 - Noack, Volker A1 - Völzke, Holger A1 - Wolff, Dietmar T1 - Requirements for the use of elastomer seals in casks for final disposal of low and intermediate level waste N2 - Elastomer seals are widely used as barrier seals in containers for low and intermediate level radioactive waste and in some countries for spent fuel transportation casks. Depending on the area of use, the rubber materials have to demonstrate proper sealing performance with regard to mechanical, thermal and environmental conditions as well as irradiation during the entire operation period. In Germany the low and intermediate level radioactive waste is planned to be disposed in the Konrad repository in standardized containers. Many of these containers use an elastomer seal between lid and container body. Depending on the radiactive inventory and a possible containment of the waste in inner barrels and/or concrete structures, such containers may require a specific leak tightness. In such cases, specified leakage rates are shall not be exceeded by the the seals to keep potential activity releases from the inventories well below defined limits. Generally, all waste containers have to fulfill the waste acceptance criteria for the Konrad repository as defined by the reports BfS SE-IB-29/08 and SE-IB-30/08. From these criteria several requirements for seal performance are derived. The seals have to: - ensure full functionality until final container disposal, - maintain its function in case of a thermal or mechanical accident, - ensure encapsulation also at -20 °C. This combination of requirements is challenging especially as a seal exchange, which is typical for many other applications, is hardly possible and thus a sound understanding of how to perform safety evaluation of containers is required. Therefore BAM has initiated investigations on elastomer seal behaviour. This work focuses on low temperature behaviour and sealing performance concerning static conditions as well as partial loss of compression and ageing of elastomer seals. Concerning ageing, property changes caused by long-term thermooxidative conditions as well as gamma irradiation are investigated. This contribution presents an overview and explanation of the aims of the ongoing research and gives an update of the most relevant results. T2 - 13th Internationales Symposium "Konditionierung radioaktiver Betriebs- und Stillegungsabfälle CY - Dresden, Germany DA - 22.03.2017 KW - Disposal KW - Konrad repository KW - Seal PY - 2017 SP - 595 EP - 601 AN - OPUS4-39870 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Pourmand, P. A1 - Wolff, Dietmar A1 - Gedde, U.W. T1 - Influence of ageing on sealability of elastomeric O-rings N2 - At BAM, which is the 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 the assessment of the service lifetime of elastomeric seals that are part of the container lid system 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 1.5 years. In order to assess sealability, O-rings are 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 are 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, hardness is measured for information about the change of mechanical properties. The experimental results indicate that while hardness, CSR and CS show considerable degradation effects, the leakage rate stays relatively constant or even decreases until shrinkage combined with the loss of resilience of the aged seal leads to leakage. This demonstrates that static leakage rate, which is the only available direct seal performance criterion, has only limited sensitivity towards the degradation of the seal material. CS data is extrapolated using time-temperature shifts and Arrhenius graphs. An exemplary CS of 50 % would be reached after approx. 1.2, 17 and 29 years at 60 °C for HNBR, EPDM and FKM respectively. T2 - PolymerTec 2016 CY - Merseburg, Germany DA - 15.06.2016 KW - Compression KW - Leakage KW - Degradation KW - Rubber KW - Lifetime PY - 2017 DO - https://doi.org/10.1002/masy.201600157 SN - 1022-1360 SN - 1521-3900 VL - 373 IS - 1 SP - UNSP 1600157, 1 EP - 10 PB - WILEY-V C H VERLAG GMBH CY - Weinheim AN - OPUS4-40958 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Ageing of elastomeric seals for storage containers N2 - At BAM Federal Institute for Materials Research and Testing in Germany, it is our responsibility to evaluate the safety of casks designed for transport and/or storage of radioactive material. This includes the investigation of elastomeric seals applied in the containers. Besides examining the low-temperature behavior of elastomeric seals, it is our goal to evaluate the service lifetime of the seals with regard to the requirements for long-term safety (40 years and more) of the containers. Furthermore, we deem it necessary to exceed the requirements given in the ageing standard DIN 53508 and take into account diffusion-limited oxidation (DLO) effects and non-Arrhenius behavior when making lifetime predictions. Therefore, we started an ageing programme with selected rubbers (HNBR, FKM and EPDM) which are oven-aged at four different temperatures (75 °C, 100 °C, 125 °C and 150 °C) in order to extrapolate the data to service temperature using different models and check which one is appropriate. Samples are examined at different times up to 5 years. In order to be able to compare between compressed and relaxed rubber, they are aged in two conditions: the undeformed O-ring state as well as compressed between plates with a compression of 25 % corresponding to the actual compression during service. Additionally, we are ageing samples in flanges that allow leakage rate measurements which is the central performance criterion. Analysis methods include hardness as a quick indicator, compression set and compression stress relaxation as measures reflecting the actual properties of a compressed seal. Additionally, we are applying classical polymer analysis methods like dynamic mechanic analysis and thermogravimetric analysis which show changes in the polymeric structure due to chain scission and crosslinking. Furthermore, we are testing the leakage rate of the O-rings in order to correlate the changes in physical properties to the actual performance of the seal. First results of samples aged up to 100 days show a strong increase in hardness for HNBR, a moderate increase for EPDM and hardly a change for FKM. A similar result is seen in the compression set of samples aged 100 d at 100 °C in compression as HNBR has reached 60 %, EPDM 25 % and FKM 15 % compression set. However, after ageing at 150 °C, EPDM shows a worse performance with 95 % compression set compared to HNBR with only 80 %. This is probably due to DLO effects in HNBR that appear because of the fast ageing and low oxygen permeability in HNBR. This leads to a deficit of oxygen in the center of the sample which is thus protected from ageing and can retain elastic properties. The full paper shall discuss the changes in material properties observed to date and the impact on the performance of elastomeric seals. T2 - IRC 2015 - International rubber conference CY - Nürnberg, Germany DA - 29.06.2015 KW - Elastomer KW - Rubber KW - Aging KW - Lifetime KW - Seal KW - Cask KW - Compression PY - 2015 SP - 1 EP - 10 AN - OPUS4-34939 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wolff, Dietmar A1 - Jaunich, Matthias A1 - Stark, Wolfgang T1 - Investigating the performance of rubber seals at low temperatures N2 - Rubbers are widely used as main sealing materials for Containers for low and intermediate level radioactive waste and as additional component to metal seals in spent fuel and high active waste containers. The save enclosure of the radioactive container inventory has to be guaranteed according to legislation and appropriate guidelines for long term storage periods as well as down to temperatures of -40 °C for transportation. Therefore the understanding of failure mechanisms that lead to leakage at low temperatures is necessary to ensure a proper material choice which is certainly also influenced by additional factors as e.g. the aging behavior. T2 - 14th International high-level radioactive waste management conference CY - Albuquerque, New Mexico, USA DA - 28.04.2013 KW - Rubber seals KW - Elastomers KW - Compression set KW - Low temperature KW - Leakage rate PY - 2013 SN - 978-1-62748-644-6 SP - 1 EP - 7(Paper # 6888) PB - Omnipress AN - OPUS4-28530 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 - CONF A1 - Jaunich, Matthias A1 - Kömmling, Anja A1 - Horn, Jutta A1 - Völzke, Holger A1 - Wolff, Dietmar T1 - Long-Term Performance of Elastomer seals - From Aging Tests to Lifetime Estimations N2 - Elastomers show a high versatility which makes them ideal materials for sealing applications in various fields. Especially under changing application conditions the high recovery potential of this class of material is beneficial to compensate temperature or pressure fluctuation, and geometrical changes resulting from mechanical loads in e.g. accident conditions. Out of these reasons elastomers are also used in containers for low and intermediate level radioactive waste and for spent fuel transportation casks. In casks designed for low and intermediate level waste elastomer seals can act as primary seal responsible for the containment function whereas in spent fuel storage and transportation casks (dual purpose casks (DPC)) elastomer seals are used as auxiliary seals to allow leakage rate measurements of metal barrier seals. An inherent prerequisite for this kind of application is the Long time-scale of operation without or with limited possibility of seal replacement. In Germany an interim storage license for DPC`s is typically issued for 40 years, a timeframe which might increase in the future due to challenges of the final repository siting procedure. For low and intermediate level waste, also long time periods are required before final disposal can be achieved. Therefore, the performance of elastomer seals over extended time periods is, as for other applications, of high importance. A typical approach to ensure long-term functionality is to perform accelerated aging tests to calculate an estimated lifetime by assuming e.g. Arrhenius like equations for the timetemperature relationship. This approach requires a suitable end of life criterion considering the application of interest. This often can represent a challenge on its own. As BAM is involved in most of the cask licensing procedures and especially responsible for the evaluation of cask-related long-term safety issues we initiated several test programs for investigating the behavior of elastomer seals. Experiments concerning the low temperature performance down to -40 °C and the influence of gamma irradiation have been started first. Currently the thermal aging behavior of elastomer seals, which is the topic of this contribution, is examined. For our aging investigations we use a broad approach to first determine the property changes in different elastomer materials due to thermo-oxidative aging at elevated temperatures and secondly, we test how the typical methods of lifetime extrapolation can be applied to these results. This Approach enables us to detect and exclude undesired side effects which very often influence lifetime estimations. In this contribution, our recent results are extended. The results show that lifetime estimation based on single material properties can be misleading and therefore a combination of several methods is recommended. T2 - ASME 2018 Pressure Vessels and Piping Conference CY - Prague, Czech Republic DA - 15.07.2018 KW - Seal performance KW - Rubber KW - Ageing PY - 2018 VL - PVP2018 SP - 84631-1 EP - 84631-8 AN - OPUS4-46346 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 -