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Eingeladener Vortrag
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In accident scenarios of transport packages or hypothetical crashes of containers in a storage facility or repository, the materials resistance against dynamic failure of the involved components is a deciding factor for package and container integrity during the handling, transport and storage for each type of radioactive material. For example, different dynamic impact tests on containers and components like lid sealing systems and specimens made of ductile cast iron and shock-absorbing materials are carried out by BAM. In order to perform dynamic impact tests with packages and its parts BAM operates two free-fall drop test facilities with maximum capacities of 200 t and 55 t, and a test bench for guided drop tests. This latter drop test machine enables a clearly specified component loading by a precisely positioned test object or drop weight and has been used recently for numerous investigations. The paper gives an overview of the wide range of experimental testing methods carried out within guided Impact and bending tests. Examples of methodological challenges are presented, especially such experimental analysis of dynamic impact conditions. In addition to known applied methods of dynamic, non-contact displacement measurements like high-speed 3-D surface deformation a recently patented 2-D tracking method is presented. By means of in-situ determination of fracture parameters with relevance to the materials stress intensity factor, the method has been successfully applied for a typical specimen geometry. Also shown are the possibility of detecting in-situ He-leakage rates on laterally impact loaded lid sealing systems as well as a method of acceleration sensor-temperature control under test conditions in the low temperature range.
In accident scenarios of transport packages or hypothetical crashes of containers in a storage facility or repository, the materials resistance against dynamic failure of the involved components is a deciding factor for package and container integrity during the handling, transport and storage for each type of radioactive material. For example, different dynamic impact tests on containers and components like lid sealing systems and specimens made of ductile cast iron and shock-absorbing materials are carried out by BAM. In order to perform dynamic impact tests with packages and its parts BAM operates two free-fall drop test facilities with maximum capacities of 200 t and 55 t, and a test bench for guided drop tests. This latter drop test machine enables a clearly specified component loading by a precisely positioned test object or drop weight and has been used recently for numerous investigations. The paper gives an overview of the wide range of experimental testing methods carried out within guided Impact and bending tests. Examples of methodological challenges are presented, especially such experimental analysis of dynamic impact conditions. In addition to known applied methods of dynamic, non-contact displacement measurements like high-speed 3-D surface deformation a recently patented 2-D tracking method is presented. By means of in-situ determination of fracture parameters with relevance to the materials stress intensity factor, the method has been successfully applied for a typical specimen geometry. Also shown are the possibility of detecting in-situ He-leakage rates on laterally impact loaded lid sealing systems as well as a method of acceleration sensor-temperature control under test conditions in the low temperature range.
Täglich werden mehrere tausend Tonnen in Säcken verpackter Gefahrgüter über die Straßen transportiert. Laut den internationalen Gefahrgutvorschriften für den innerstaatlichen und grenzüberschreitenden Verkehr ADR müssen Gefahrgutsäcke aus Papier „staubdicht“ sein. Die Autobahnpolizei Münster wies bei einem Vortrag in der BAM darauf hin, dass im Rahmen polizeilicher LKW-Kontrollen Ladeflächen voller Staub vorgefunden wurden, ohne dass ein Defekt an einem Gefahrgutsack festgestellt werden konnte.
Ziel der Arbeit war es, eine Prüfkammer zu entwickeln, welche in der Lage ist, nach Fallversuchen mit Gefahrgutsäcken aus Papier den freigesetzten luftgetragenen Staub zu bestimmen. Eine anschließende Bewertung soll die gesundheitlichen Gefahren des entstandenen Aerosols aufzeigen. Durch die Auswertung erster Fallversuche wurde exemplarisch die „Dichtheit“ vorhandener Gefahrgutsäcke bestimmt und die Fraktionen der entstandenen Aerosole wurden mit den Arbeitsplatzgrenzwerten verglichen.
Kurzfassung. Die meisten Faserverbundbehälter, die in Europa für den Transport gefährlicher Stoffe oder als Speicherbehälter für Wasserstoff oder Erdgas in Fahrzeugen Verwendung finden, werden für eine nicht begrenzte Lebensdauer ausgelegt. In regelmäßigen Abständen sind für diese Druckbehälter wiederkehrende Prüfungen vorgeschrieben, die in der Regel aus visuellen Inspektionen und hydraulischen Innendruckprüfungen bestehen [1]. Die wiederkehrenden Prüfungen sind jedoch weder geeignet, die sichere Betriebsdauer festzulegen noch den Alterungszustand der Druckbehälter zu beurteilen. Aufgrund des weiter steigenden Drucks zur Kosten- und Gewichtsreduktion von Faserverbundbehältern und der damit einhergehenden Ausnutzung der existierenden Sicherheitsmargen gewinnen Methoden zur Beurteilung des Alterungsverhaltens dieser Druckbehälter immer mehr an Bedeutung.
Vor diesem Hintergrund wurde in der BAM das orhaben „Alterungsverhalten von Composite-Druckgefäßen mit Carbonfaser-Compositen unter gekoppelten Beanspruchungen (COD-AGE)“ gestartet, um die Alterung von Faserverbundbehältern mittels verschiedener zerstörungsfreier Prüfverfahren zu untersuchen. Die hier vorgestellten Ergebnisse wurden an einem Typ 4 Hybridbehälter mit Kunststoffliner gewonnen, in den im Rahmen des Herstellungsprozesses optische Glasfasern in verschiedenen Schichten integriert wurden. Der Behälter wurde mittels hydraulischem Innendruck und erhöhter Umgebungstemperatur zyklisch bis zum Lebensende belastet. Zwischen den einzelnen Lastsequenzen erfolgte eine an die wiederkehrende Prüfung im Betrieb angelehnte hydraulische Druckbelastung.
Sowohl die hydraulische Alterung als auch die Druckrampen wurden mittels Schallemissionsprüfung (SEP) und verteilter faseroptischer Sensorik mit dem Ziel einer frühzeitigen Versagensvorhersage überwacht. Durch die Schallemissionsanalyse sollte untersucht werden, ob zum Lebensende hin ein signifikanter Anstieg der Schallemissionsaktivität und -intensität, unterteilt in verschiedene Lastbereiche, beobachtet werden kann. Zusätzlich zum kontinuierlichen Monitoring der Zyklierung sollten die Druckrampen separat untersucht werden, um hier Potenziale für die wiederkehrende Prüfung zu erkennen.
Kurzfassung. Die meisten Faserverbundbehälter, die in Europa für den Transport gefährlicher Stoffe oder als Speicherbehälter für Wasserstoff oder Erdgas in Fahrzeugen Verwendung finden, werden für eine nicht begrenzte Lebensdauer ausgelegt. In regelmäßigen Abständen sind für diese Druckbehälter wiederkehrende Prüfungen vorgeschrieben, die in der Regel aus visuellen Inspektionen und hydraulischen Innendruckprüfungen bestehen. Die wiederkehrenden Prüfungen sind jedoch weder geeignet, die sichere Betriebsdauer festzulegen noch den Alterungszustand der Druckbehälter zu beurteilen. Aufgrund des weiter steigenden Drucks zur Kosten- und Gewichtsreduktion von Faserverbundbehältern und der damit einhergehenden Ausnutzung der existierenden Sicherheitsmargen gewinnen Methoden zur Beurteilung des Alterungsverhaltens dieser Druckbehälter immer mehr an Bedeutung.
Vor diesem Hintergrund wurde in der BAM das Vorhaben „Alterungsverhalten von Composite-Druckgefäßen mit Carbonfaser-Compositen unter gekoppelten Beanspruchungen (COD-AGE)“ gestartet, um die Alterung von Faserverbundbehältern mittels verschiedener zerstörungsfreier Prüfverfahren zu untersuchen. Die hier vorgestellten Ergebnisse wurden an einem Typ 4 Hybridbehälter mit Kunststoffliner gewonnen, in den im Rahmen des Herstellungsprozesses optische Glasfasern in verschiedenen Schichten integriert wurden. Der Behälter wurde mittels hydraulischem Innendruck und erhöhter Umgebungstemperatur zyklisch bis zum Lebensende belastet. Zwischen den einzelnen Lastsequenzen erfolgte eine an die wiederkehrende Prüfung im Betrieb angelehnte hydraulische Druckbelastung.
Sowohl die hydraulische Alterung als auch die Druckrampen wurden mittels Schallemissionsprüfung (SEP) und verteilter faseroptischer Sensorik mit dem Ziel einer frühzeitigen Versagensvorhersage überwacht. Durch die Schallemissionsanalyse sollte untersucht werden, ob zum Lebensende hin ein signifikanter Anstieg der Schallemissionsaktivität und -intensität, unterteilt in verschiedene Lastbereiche, beobachtet werden kann. Zusätzlich zum kontinuierlichen Monitoring der Zyklierung sollten die Druckrampen separat untersucht werden, um hier Potenziale für die wiederkehrende Prüfung zu erkennen.
Accident safe packages for the transport of spent nuclear fuel and high-level waste shall fulfil international IAEA safety requirements. Compliance is shown by consecutive mechanical and thermal testing. Additional numerical analysis are usually part of the safety evaluation. For damage protection some package designs are equipped with wood filled impact limiters encapsulated by steel sheets.
The safety of these packages is established in compliance with IAEA regulations. Cumulative mechanical and fire tests are conducted to achieve safety standards and to prevent loss of containment. Mechanical reliability is proven by drop tests. Drop testing might cause significant damage of the impact limiter steel sheets and might enable sufficient oxygen supply to the impact limiter during the fire test to ignite the wood filling. The boundary conditions of the fire test are precisely described in the IAEA regulatory. During the test the impact limiter will be subjected to a 30 minutes enduring fire phase. Subsequent to the fire phase any burning of the specimen has to extinguish naturally and no artificial cooling is allowed.
At BAM a large-scale fire test with a real size impact limiter and a wood volume of about 3m³ was conducted to investigate the burning behaviour of wood filled impact limiters in steel sheet encapsulation. Until today burning of such impact limiters is not sufficiently considered in transport package design and more investigation is necessary to explore the consequences of the impacting fire. The objective of the large scale test was to find out whether a self-sustaining smouldering or even a flaming fire inside the impact limiter was initiated and what impact on the cask is resulting.
The amount of energy transferred from the impact limiter into the cask is of particular importance for the safety of heavy weight packages. With the intention of heat flux quantification, a new approach was made and a test bench was designed.
Packages for the transport of radioactive material shall withstand severe accidents. Therefore, the IAEA Regulations define different test scenarios to cover severe hypothetical accident conditions. One of these tests defined in detail is the thermal test, mainly consisting of a 30 minute fully engulfing 800 °C pool fire or an equally severe fire test. The heat fluxes into the package are of significant importance and depend substantially on the fire characteristics and the surface temperature of the package.
In order to investigate the heat fluxes over a wide range of surface temperatures during a propane gas fire test and to get information about local fire impact a fire reference package, representing the outer geometry of a specific type of transport cask for radioactive waste, was designed. A closed steel sheet cylinder with a wall thickness of 10 mm was chosen as fire reference package. The cylinder was filled with refractory insulation material and instrumented with thermocouples distributed all over the cylinder. The local steel sheet temperatures measured allow the determination of local as well as global heat fluxes as a function of time and surface temperature.
With this fire reference package three open-air propane gas fire tests were performed at BAM’s open air fire test stand. The flame exposure time period was changed for the different fire tests. Furthermore, the wind conditions changed between and during the tests. Test stand parameters like wind shield location and propane gas volume flow were chosen constant for the three tests. The test results were used to determine the changes of heat flux into the fire reference package in relation to the package surface temperature. This data also allows the calculation of local characteristics of the propane gas fire as there are the flame temperature, the fire convection coefficient and the radiation exchange coefficient in a first approach. The recently conducted tests provide an initial picture of local fire characteristics of the propane gas fire test facility. The test shows that the propane gas fire covers the IAEA-fire over a wide range of surface temperatures with the chosen test stand parameters.
In order to investigate the heat fluxes over a wide range of surface temperatures during a propane gas fire test and to get information about local fire impact a fire reference package, representing the outer geometry of a specific type of transport cask for radioactive waste, was designed. A closed steel sheet cylinder with a wall thickness of 10 mm was chosen as fire reference package. The cylinder was filled with refractory insulation material and instrumented with thermocouples distributed all over the cylinder. The local steel sheet temperatures measured allow the determination of local as well as global heat fluxes as a function of time and surface temperature.
With this fire reference package three open-air propane gas fire tests were performed at BAM’s open air fire test stand. The flame exposure time period was changed for the different fire tests. Furthermore, the wind conditions changed between and during the tests. Test stand parameters like wind shield location and propane gas volume flow were chosen constant for the three tests. The test results were used to determine the changes of heat flux into the fire reference package in relation to the package surface temperature. This data also allows the calculation of local characteristics of the propane gas fire as there are the flame temperature, the fire convection coefficient and the radiation exchange coefficient in a first approach. The recently conducted tests provide an initial picture of local fire characteristics of the propane gas fire test facility. The test shows that the propane gas fire covers the IAEA-fire over a wide range of surface temperatures with the chosen test stand parameters.
Packages for the transport of radioactive material shall withstand severe accidents. Therefore, the IAEA Regulations define different test scenarios to cover severe hypothetical accident conditions. One of these tests defined in detail is the thermal test, mainly consisting of a 30 minute fully engulfing 800 °C pool fire or an equally severe fire test. The heat fluxes into the package are of significant importance and depend substantially on the fire characteristics and the surface temperature of the package.
In order to investigate the heat fluxes over a wide range of surface temperatures during a propane gas fire test and to get information about local fire impact a fire reference package, representing the outer geometry of a specific type of transport cask for radioactive waste, was designed. A closed steel sheet cylinder with a wall thickness of 10 mm was chosen as fire reference package. The cylinder was filled with refractory insulation material and instrumented with thermocouples distributed all over the cylinder. The local steel sheet temperatures measured allow the determination of local as well as global heat fluxes as a function of time and surface temperature.
With this fire reference package three open-air propane gas fire tests were performed at BAM’s open air fire test stand. The flame exposure time period was changed for the different fire tests. Furthermore, the wind conditions changed between and during the tests. Test stand parameters like wind shield location and propane gas volume flow were chosen constant for the three tests. The test results were used to determine the changes of heat flux into the fire reference package in relation to the package surface temperature. This data also allows the calculation of local characteristics of the propane gas fire as there are the flame temperature, the fire convection coefficient and the radiation exchange coefficient in a first approach. The recently conducted tests provide an initial picture of local fire characteristics of the propane gas fire test facility. The test shows that the propane gas fire covers the IAEA-fire over a wide range of surface temperatures with the chosen test stand parameters.
Depending on the specific plastic’s ageing sensitivities, the durations which plastic components remain in the environment can be very long. As, in the past, the advantages in ageing resistance and durability were highly evaluated, we now face the problem of quite stable plastic waste within the environment.
However, there is only little knowledge on the real timescales until macroscopic fragmentation for the different kinds of plastic under various environmental conditions.
Here, weathering methods are presented, which have been used for the failure prediction in specific outdoor conditions. Issues of uncertainty, reproducibility, or validation are discussed.
For the prediction of the plastic’s fragmentation, much longer time scales have to be considered. To do this within a limited project life span, various processes as well as their acceleration potential have to be evaluated separately, such as temperature increase or spectral shift.
The possibilities and limitations of such controlled acceleration will be discussed.
Bei der Bestrahlung und Bewitterung von polymeren Werkstoffen wird die Degradation durch eine Absorption von Strahlung initiiert und meistens durch weitere Klimagrößen, wie z.B. Wärme, Feuchte und atmosphärische Gase beeinflusst. Die Messung einer effektiven Bestrahlungsstärke und ihre zeitliche Integration sind deshalb von großer Bedeutung.
Photochemische Prozesse werden beim Sehen oder allgemeiner bei Farbstoffen schon durch sichtbare (VIS) Strahlung, dagegen bei der Erythembildung der Haut und der Photodegradation von Polymeren erst durch die energiereicheren Photonen der ultravioletten (UV) Strahlung initiiert. Die spektrale Empfindlichkeit des Auges und die Erythembildung sind im VIS- bzw. UV-Bereich sehr stark wellenlängenabhängig, was durch die Angabe der mit der spektralen Hellempfindlichkeit V() des Auges bewerteten VIS-Strahlung in Lux (lx) bzw. die mit der Erythem-Wirkfunktion bewertete UV Strahlung als dimensionsloser UV-Index berücksichtigt wird. Spektrale Empfindlichkeiten.
Die Photodegradation von Polymeren ist im UV-Bereich ebenfalls stark wellenlängenab-hängig, was bisher nicht berücksichtigt wurde. Seit Mitte der 70er Jahre, als die lx- bzw lxh- Messung bei der Strahlungsbeanspruchung langsam durch die Ermittlung der radiometrischen UV-Bestrahlungsstärke bzw. der UV-Bestrahlung im gesamten UV-Bereich abgelöst wurde, gab es hier bei der Bewitterungsprüfung keine weiteren Fortschritte auf dem Gebiet der Charakterisierung der Strahlungsbeanspruchung im UV-Bereich.
Seit Jahren liegen zahlreiche Ergebnisse über die spektrale Empfindlichkeit von Photo-degradationsprozessen vor, die zeigen, dass die spektrale Empfindlichkeit im Bereich der Globalstrahlung bei ca. 300 nm, am größten ist und im langwelligen UV-Bereich bei ca. 400 nm gegen Null geht. Die Messungen der radiometrischen Größen UV-Gesamt-bestrahlungsstärke und UV-Gesamtbestrahlung erfasst deshalb über weite Wellen-längenbereiche Strahlungsanteile, die für die Photodegradation bedeutungslos sind und mittelt über potenziell bedeutsame Änderungen im kurzwelligen UV-Bereich hinweg.
Es wird das Konzept eines neuen UV-Radiometers vorgestellt, dessen spektrale Empfindlichkeit einer mittleren spektralen Empfindlichkeit der Photodegradation von Polymeren entspricht. Die effektive UV-Bestrahlungsstärke und UV-Bestrahlung kann dadurch wesentlich genauer erfasst werden.
Weathering reference materials are used to characterize the harshness of an exposure, aiming on either reproducibility of a specific exposure or on the comparability between various kinds of weathering exposure.
The materials that are used as weathering reference materials differ in their sensitivities (as well as in interactions and interferences of the latter), conditioned by the different processes which lead to the respective property change. It is also essential to take into account the necessary measurement equipment for the respective property change, in order to allow timely intervention.
What are the key issues on choosing a weathering reference material?
What can be learned from the weathering reference materials, investigated so far?
Possibilities and limitations are discussed on the basis of existing weathering reference materials. Conclusions are drawn, for establishing new weathering reference materials.
Depending on the specific plastic’s ageing sensitivities, the durations which plastic components remain in the environment can be very long. As, in the past, the advantages in ageing resistance and durability were highly evaluated, we now face the problem of quite stable plastic waste within the environment.
However, there is only little knowledge on the real timescales until macroscopic fragmentation for the different kinds of plastic under various environmental conditions.
Here, weathering methods are presented, which have been used for the failure prediction in specific outdoor conditions. Issues of uncertainty, reproducibility, or validation are discussed.
For the prediction of the plastic’s fragmentation, much longer time scales have to be considered. To do this within a limited project life span, various processes as well as their acceleration potential have to be evaluated separately, such as temperature increase or spectral shift.
The possibilities and limitations of such controlled acceleration will be discussed.
In der Gesellschaft für Umweltsimulation GUS e.V. erarbeiten Fachleute aus Wissenschaft und Industrie in freiwilliger Selbstverantwortung Leitfäden und Bücher zur, Umweltsimulation und zur Wirkungssimulation von Umwelteinflüssen.
Diese beschreiben den Stand der Technik bzw. Stand der Wissenschaft und dienen als Anleitung für Umweltingenieure und Personen, die sich in die Arbeitsgebiete Produktqualifikation und Umweltsimulation einarbeiten und einiesen wollen.
Folgende Themenschwerpunkte werden in diesem Leitfaden behandelt: Wasser und seine Eigenschaften, Phasenübergänge, Transportvorgänge, Änderung von Materialeigenschaften durch Wasser, Messmethoden.
Exposure response function for a quantitative prediction of weathering caused aging of polyethylene
(2019)
The exposure response function of the carbonyl formation over the bulk has been determined for a high-density polyethylene of a thickness of 200 μm, which was used as a weathering reference material according to ISO TR 19032. To this end, spectral sensitivity was studied by local measurement of the effect of spectrally dispersed irradiation. Both the exposure device and the methodology of determination are described.
The temperature dependency of photooxidation was determined by UV exposure at various temperatures between 23 and 80 °C. Deviations from linearity and thus reciprocity below 40 °C are discussed and assumed to be related to diffusion limitations. An Arrhenius approach –based on data of linear carbonyl formation – has been incorporated into the exposure response function. Using this exposure response function, aging in terms of the distribution of a quantitative property change over a plastic component can be predicted for a specific outdoor location with real chronologic weather data as input for the exposure. Thus, artificial and natural weathering can be linked and compared. The established exposure response function has been validated by outdoor exposure results from the literature. If an estimated diffusion limitation is taken into consideration, calculations and published data are in good agreement.
Weathering reference materials (WRMs) are used to characterize the harshness of an exposure, aiming on either reproducibility of a specific exposure or on the comparability between various kinds of natural or artificial weathering exposure.
The materials that are used as weathering reference materials differ in their sensitivities (as well as in interactions and interferences of the latter), conditioned by the different processes which lead to the respective property change. It is also essential to take into account the necessary measurement equipment for the respective property change, in order to allow timely intervention.
What are the key issues on choosing a weathering reference material?
What can be learned from the weathering reference materials, investigated so far?
Possibilities and limitations are discussed on the basis of existing weathering reference materials. Conclusions are drawn, for establishing new weathering reference materials.
In Germany, spent nuclear fuel and high active waste from reprocessing is stored in transport and storage containers with double lid systems that are equipped with metal seals completing the primary sealing barrier. The tasks of the Bundesanstalt für Materialforschung und -prüfung (BAM) within the interim storage licensing procedures ruled by the German Atomic Energy Act include the long-term safety evaluation of the container design regarding the permanently safe enclosure of the inventory. In order to generate a knowledge base for the safety evaluation, research regarding the long-term behavior of the critical components is performed. So far, the containers are licensed for an interim storage period of 40 years. However, due to significant delays in establishing a final repository, the required time span for interim storage is expected to increase significantly. Thus, a widespread investigation program is run to gain systematic data on the long-term behavior of the seals and to develop prediction models.
Long-term seal investigations consider the development of their restoring seal force, their useable resilience and their achievable leakage rate caused by aging at temperatures ranging from room temperature up to 150 °C. This year, the total time span of the tests reaches 10 years. Furthermore, seal segments are aged at the selected temperatures for up to 300 days. From these segments additional information on the sealing behavior, changes of the seal contact and the material behavior is gained.
This contribution deals with the current results of the long-term seal investigations at BAM. Furthermore, insights of the more in-depth component and material investigations of the metal seals with focus on the seal contact development are discussed and the ongoing work aiming for an analytical description of the thermo-mechanical aging effects on metal seals are presented.
In Germany, spent nuclear fuel and high active waste from reprocessing is stored in transport and storage containers with double lid systems that are equipped with metal seals completing the primary sealing barrier. The tasks of the Bundesanstalt für Materialforschung und -prüfung (BAM) within the interim storage licensing procedures ruled by the German Atomic Energy Act include the long-term safety evaluation of the container design regarding the permanently safe enclosure of the inventory. In order to generate a knowledge base for the safety evaluation, research regarding the long-term behavior of the critical components is performed. So far, the containers are licensed for an interim storage period of 40 years. However, due to significant delays in establishing a final repository, the required time span for interim storage is expected to increase significantly. Thus, a widespread investigation program is run to gain systematic data on the long-term behavior of the seals and to develop prediction models.
Long-term seal investigations consider the development of their restoring seal force, their useable resilience and their achievable leakage rate caused by aging at temperatures ranging from room temperature up to 150 °C. This year, the total time span of the tests reaches 10 years. Furthermore, seal segments are aged at the selected temperatures for up to 300 days. From these segments additional information on the sealing behavior, changes of the seal contact and the material behavior is gained.
This contribution deals with the current results of the long-term seal investigations at BAM. Furthermore, insights of the more in-depth component and material investigations of the metal seals with focus on the seal contact development are discussed and the ongoing work aiming for an analytical description of the thermo-mechanical aging effects on metal seals are presented.
Übersicht über die gefahrgutrechtlichen Anforderungen zur Bauartprüfung und dem Qualitätsmanagement für Verpackungen für nicht zulassungspflichtige Versandstücke.
Heating oil storage tanks made of polyethylene grades have been on the market in Germany since the early 1970s. To ensure safety, their replacement is recommended by tank manufacturers after a period of 30 years. Polyethylene is subject to ageing by alteration of the properties during its life cycle. The degree of degradation and the nature of the process mainly depend on the chemical alteration of the polyethylene, the wall thickness of the tank and the environmental conditions. There are no data available on the long-term behaviour of the polyethylene grades, especially after a service life of more than 30 years.
The aim of this investigation was to find a suitable test method to determine the factual degree of damage in comparison to the uncontaminated polyethylene grades. Material data of the used polyethylene grades are available because the BAM was the competent authority for the tests and expert reports for the approval of these tanks until the middle of the 1990s. Therefore, tank sections from the bottom, the shell and the roof of 22 individual storage tanks produced of polyethylene grades A and B have been examined by Melt Flow Rate (MFR) and Attenuated Total Reflectance (ATR). Their service life was in the range between 20 and 41 years.
The MFR measurements of the tank sections showed differences in the values depending on the weight which was used (5 kg or 21.6 kg). An increase of the MFR was determined for the samples of polyethylene grade A, whereas a reduction of the MFR values was measured for most samples of polyethylene grade B. This grade is mainly subject to the internal ageing by cross-linkages, increased degree of branched molecules and loss of the plasticizer.
ATR analysis exhibits an absorption band at 909 cm‒1 predominantly in samples of polyethylene grade A indicating chain scission and concomitantly formed terminal vinyl groups. This absorption band can be used for the characterization of the ageing of the polyethylene grades.
Die BAM ist nahezu über die gesamte Wertschöpfungskette hinweg wissenschaftlich tätig. Von der sicheren und effizienten Wasserstofferzeugung (POWER-to-GAS), über die (Zwischen-)Speicherung von Wasserstoff in Druckgasspeichern bis hin zum Transport bspw. mittels Trailerfahrzeug zum Endverbraucher.
Komplettiert werden die Aktivitäten der BAM durch die sicherheitstechnische Beurteilung von wasserstoffhaltigen Gasgemischen, die Verträglichkeitsbewertung von Werkstoffen bis hin zur Detektion von Wasserstoffkonzentrationen über geeignete Sensorik, auch mittels ferngesteuerter Messdrohnen (sog. UAV-Drohnen).
Zudem untersucht die BAM proaktiv Schadensrisiken und Unfallszenarien für die Sicherheitsbetrachtung, um mögliche Schwachstellen aufzeigen und potenzielle Gefährdungen erkennen zu können.
The European Joint Programme on Radioactive Waste Management (EURAD) has been launched to coordinate activities on agreed priorities of common interest between European partners. The main actions include scientific and technical activities on radioactive waste characterization and processing, interim storage of radioactive waste as well as predisposal and disposal solutions. As part of the programme, the work package on Spent Fuel Characterization and Evolution until Disposal (SFC) was proposed and accepted by the European Commission. The objectives of this work package include the development of beyond-state-of-the-art characterization techniques for spent nuclear fuel during its evolution from reactor unloading until disposal, the understanding of the spent fuel performance during prolonged storage, transport and emplacement in a deep geological repository, the understanding of the behaviour of fuel, cladding, pellet-cladding interaction and ageing effect under normal and postulated accident scenarios until disposal, and contributions to operational safety concepts for fuel handling at spent nuclear fuel packaging facilities.
For many sealing applications rubber O-rings are applied due to their special properties and easy use. In many applications as e.g. in aviation, traffic or process technology the material can be exposed to a variety of conditions during operation as e.g. low temperatures, elevated temperatures and different media. Therefore, it is important to know the material behaviour and the seal performance under those conditions. Additionally ageing of seals is an important factor which has an influence on the long term reliability.
In this contribution we would like to discuss different aspects affecting the seal performance, lifetime estimation and address open questions which should be addressed to come to a deeper understanding of these seals commonly understood as typical machine elements.
Results of running investigations at the Bundesanstalt für Materialforschung und -prüfung (BAM), Division 3.4 “Safety of Storage Containers” are presented and discussed.
Elastomere werden vielfach in Produkten eingesetzt, die bei verschiedenen Temperaturen verwendet werden. O-Ringe sind kostengünstige Dichtelemente, die allerdings für die Funktionsfähigkeit und Sicherheit eines Produkts entscheidend sein können. Die untere Temperatur-einsatzgrenze ist dabei relevant und aus wissenschaftlicher Sicht nicht allgemein gültig zu definieren, da diese einerseits durch die Änderungen der Materialeigenschaften im Zuge des Gummi-Glas-Übergangs definiert werden, die Temperaturlage dieses Übergangs jedoch sehr stark von den jeweiligen Einsatzbedingungen (z.B. Frequenz) abhängt. Dadurch ergeben sich große Unterschiede zwischen statischen und dynamischen Anwendungen.
Verschieden Untersuchungen sollen vorgestellt und interpretiert werden, um das Auditorium auf verschiedene Herausforderungen aufmerksam zu machen und Lösungsansätze vorzustellen.
Editorial
(2019)
Dear Readers, a new year started for all of us (as I write these lines, possibly it was already some time ago when these lines are finally available) and this is the time for the so-called New Year’s resolutions. Setting goals and changing our behavior as well in a private as in a professional context.
For Scientists the resolutions may comprise tasks like finalizing a longago started publication, picking up the loose ends of an application for funding or just bringing the running projects in a greater structure.
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). Our investigations comprise investigations on metallic and elastomeric seals and covers experimental investigations to get a database on the component/material behaviour, work on analytical descriptions and numerical analysis. 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.
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). Our investigations comprise investigations on metallic and elastomeric seals and covers experimental investigations to get a database on the component/material behaviour, work on analytical descriptions and numerical analysis. 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.
For disposal of the German research reactor of the Technical University Munich FRM II a new transport and storage cask design was under approval assessment by the German authorities. The Bundesanstalt für Materialforschung und -prüfung (BAM) assessed the mechanical and thermal package safety and performed drop tests. The activity release approaches and subjects of quality assurance and surveillance for manufacturing and operation of the package were assessed by BAM as well.
The cask body is made of ductile cast iron and closed by two bolted lid systems with metal seals. The material of the lids is stainless steel. On each end of the cask a wood-filled impact limiter is installed to reduce impact loads to the cask under drop test conditions. In the cavity of the cask a basket for five spent fuel assemblies is arranged.
For the safety case a combination of experimental testing and analytical/numerical calculations were applied. In total, four drop tests were carried out at the BAM large drop test facility. Two tests were carried out as a full IAEA drop test sequence consisting of a 9m drop test onto an unyielding target and a 1m puncture bar drop test. The other two drop test were performed as single 9m drop tests and completed by additional analyses for considering the effects of an IAEA drop test sequence.
The main objectives of the drop tests were the investigation of the integrity of the package and its safety against release of radioactive material as well as the test of the fastening system of the impact limiters. Furthermore, the acceleration and strain signals measured during the tests were used for the verification of Finite-Element-Analysis (FEA) used for the safety analysis of the package design.
The finite-element models incorporated in the package design safety report include the cask body, the lid system, the inventory and the impact limiters with the fastening system. In this context special attention was paid to the modeling of the encapsulated wood-filled impact limiters.
Additional calculations using the verified numerical models were done by the applicant and assessed by BAM to investigate e.g. the brittle fracture of the cask body made of ductile cask iron within the package design approval procedure.
This paper describes the package design assessment from the view of the competent authority BAM including the applied assessment strategy, the conducted drop tests and the additional calculations by using numerical and analytical methods.
For disposal of the German research reactor of the Technical University Munich FRM II a new transport and storage cask design was under approval assessment by the German authorities. The Bundesanstalt für Materialforschung und -prüfung (BAM) assessed the mechanical and thermal package safety and performed drop tests. The activity release approaches and subjects of quality assurance and surveillance for manufacturing and operation of the package were assessed by BAM as well.
The cask body is made of ductile cast iron and closed by two bolted lid systems with metal seals. The material of the lids is stainless steel. On each end of the cask a wood-filled impact limiter is installed to reduce impact loads to the cask under drop test conditions. In the cavity of the cask a basket for five spent fuel assemblies is arranged.
For the safety case a combination of experimental testing and analytical/numerical calculations were applied. In total, four drop tests were carried out at the BAM large drop test facility. Two tests were carried out as a full IAEA drop test sequence consisting of a 9m drop test onto an unyielding target and a 1m puncture bar drop test. The other two drop test were performed as single 9m drop tests and completed by additional analyses for considering the effects of an IAEA drop test sequence.
The main objectives of the drop tests were the investigation of the integrity of the package and its safety against release of radioactive material as well as the test of the fastening system of the impact limiters. Furthermore, the acceleration and strain signals measured during the tests were used for the verification of Finite-Element-Analysis (FEA) used for the safety analysis of the package design.
The finite-element models incorporated in the package design safety report include the cask body, the lid system, the inventory and the impact limiters with the fastening system. In this context special attention was paid to the modeling of the encapsulated wood-filled impact limiters.
Additional calculations using the verified numerical models were done by the applicant and assessed by BAM to investigate e.g. the brittle fracture of the cask body made of ductile cask iron within the package design approval procedure.
This paper describes the package design assessment from the view of the competent authority BAM including the applied assessment strategy, the conducted drop tests and the additional calculations by using numerical and analytical methods.
Since 2005, several European countries, coordinated by the European Association of Competent Authorities (EACA), have been developing a guide on contents and structure of the documentation demonstrating the compliance with the regulations for packages for the transport of radioactive material (package design safety report, PDSR). This guide has been periodically improved, considering feedback from Designers and authorities.
Taking into account the successful application of this guide in Europe, in 2013 the International Atomic Energy Agency (IAEA) decided to establish a similar guide as an IAEA document for promotion of worldwide use. The development of this IAEA guide started from the latest version of the European PDSR guide. In 2016/2017, during a 120-day review period, comments on the draft were received from member states and international organizations. These were incorporated into the draft in a series of meetings in 2017.
In another meeting in December 2018 the draft was updated to be in line with the latest revision of the IAEA Regulations for the Safe Transport of Radioactive Material (SSR-6).
In this process the draft has been improved significantly, regarding structure as well as implementation of a graded approach depending on the package type, and clarified.
This paper points to the major considerations in developing the guide and important improvements over the last version of the European PDSR guide.
Motivation:
- Reduktion der CO 2 Emissionen von Verbrennungsmotoren durch den Einsatz von LNG als alternativer Kraftstoff
- Aktuell werden doppelwandige Edelstahltanks mit Vakuumisolation für den Transport eingesetzt
- Reduktion des Tankgewichts und Vereinfachung der Konstruktion soll durch die Substitution mit GFK inklusive einer Isolationsschicht erreicht werden
- Leichtere Überprüfung von einwandigen Tankkonstruktionen
- Günstiges Versagensverhalten von GFK im Brandfall
Zusammenfassung:
- Thermische Performance kann mit Isolation aus PU Schaum erreicht werden
- Messung der Abdampfrate bildet einfache Möglichkeit zur Bestimmung der thermischen Performance
- Mikrorisse in der Matrix führen zur Leckage -> Liner notwendig
- Biegemodul bis 30 MPa vergleichbar, danach Abfall um ca. 50 % bei tiefen Temperaturen
Ausblick:
- Prüfung von GFK Proben mit Fasern in 0°-Orientierung
- Prüfung der thermischen Performance mit Demonstratoreinheiten verschiedene Größen
- Entwicklung einer Skalierungsfunktion, um Ergebnisse von druckloser Prüfung auf Druckanstieg zu übertragen
This presentation describes the testing methods used to determine the thermal properties of insulation materials and mechanical properties of materials used for the load-bearing structure for pressure tanks (up to 4 bar) and cryogenic liquids (LNG, -162 °C at atmospheric pressure). Goal is to design a transportation tank that does not exceed 4 bars (relative) within 10 h, starting at atmospheric pressure. PUR-foam is a suitable material for the insulation. A 12,5 l small scale tank prototype reached 4 bar (relative) within 87 minutes, which is, regarding the influence of the size, a satisfying result. The mechanical properties change significantly at cryogenic temperatures. The bending modulus is similar at first, but decreases at a certain point by 2/3. However, the maximum stress is much higher and could not be reached within this testing setup.
Präsentation im Rahmen eines BAM-internen Kolloquiums über den aktuellen Stand der Forschung im ZIM-Vorhaben "Tieftemperatzr-Transporteinheit aus Faserverbundkunststoffen"
To reduce the emission of carbondyoxide (CO2) of combustion engines, liquefied natural gas (LNG) is used as an alternative fuel. LNG is transported via truck, ship or railway for long distances. Double walled stainless steel tanks are used for transportation, which are heavy and expensive. The vacuum insulation between the two walled structure ensures that the LNG stays liquid over the transportation time (boiling point of LNG: -162 ◦C). This causes a high temperature difference between the transported good and the ambient air.
A simplified tank construction is used to reduce the weight and price of the tank. Instead of stainless steel, glass fiber reinforced plastic (GFRP) is used. The design is changed to a single walled construction with a solid insulation material outside on the GFRP structure.
Goal of this work is the characterization of a suitable insulation material and configuration as well as the analysis of the mechanical properties of GFRP under cryogenic conditions. Several experiments are carried out. Numerical models of these experiments can then be used for parameter studies.
Elastomeric O-ring seals are used in a wide range of applications due to their excellent elasticity. However, like all polymers, elastomers degrade under the influence of e.g. time, temperature, oxygen, radiation and mechanical stress. Especially in applications where a replacement of seals after a certain time is hard or almost impossible, it is important to know the seal lifetime. Therefore, an extensive ageing programme with elastomers made of EPDM, HNBR and other materials was started with the aim of determining suitable methods for accelerated ageing and lifetime prediction.
In order to determine the lifetime of polymeric parts, the time-temperature superposition principle is commonly used to shift property changes obtained by accelerated ageing at higher temperatures to lower temperatures. If the shift factors yield a straight line in an Arrhenius diagram, a corresponding activation energy can be determined. However, we have found that the shift factors and thus the predicted lifetime depends on the test method that yielded the shifted data. For example, the shift factor between 125 °C and 150 °C ageing temperature was roughly the same (5/5/4.5 respectively) for hardness, density and maximum of loss factor tan measured on HNBR, but different for elongation at break (8) and compression set (2.2, excluding DLO-affected data). A possible explanation might be that while the different oxidation reactions proceed with a fixed activation energy, they have differing impact on the measured properties. For example, hardness is lowered by chain scission reactions, and increases by crosslinking reactions during ageing. As usually both chain scission and crosslinking reactions occur during ageing, the measured hardness increase reflects only the net effect of both reaction types. On the other hand, compression set is influenced additively by both reaction types: chain scission leads to an increase of the remaining deformation, as broken chains lose their recovery potential, and crosslinking reactions during ageing fix the compressed geometry, which also leads to less recovery. Thus, compression set reflects the total number of changes in the network and shows degradation effects much faster, which results in lower shift factors and lower activation energy. This phenomenon was observed for EPDM as well.
In order to verify our hypotheses and to gain further insights, temperature-dependent oxygen consumption measurements are currently being performed and results will be presented at the conference. The shift factors and activation energy determined by oxygen consumption measurements are expected to be close to the values for compression set.
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. One of the aims is to identify a suitable method for estimating 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) for 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. In order to understand the underlying ageing mechanisms in each material, material properties such as hardness, density and tensile properties were examined. Additionally, compression set (CS), which represents the recovery behaviour of a seal after release from compression, is measured. 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 ageing caused by diffusion-limited oxidation (DLO) effects especially for HNBR, resulting in distorted bulk properties such as compression set. However, if DLO-affected data is excluded, extrapolations of CS data are possible using time-temperature shifts.
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 even though material properties had already degraded strongly. For this reason, a modified, more demanding leakage test involving a fast small decompression of the seal was developed that allowed determining a more conservative end-of-lifetime criterion with a safety margin for EPDM seals. FKM, which is a very heat and oxidation resistant material, exhibited only little degradation, even though it had the smallest activation energy.
Safety of long term containment and storage of radioactive waste is an essential issue, which is increasingly gaining international attention. Extending interim storage beyond initial license periods is one of the major challenges worldwide.
BAM has been involved in all kinds of radioactive waste container safety evaluation for storage and transportation including their long term performance from the very beginning. Today, all work related to the safe management of radioactive waste is linked by the activity field “Nuclear Waste Management” within the Focus Area “Energy” at BAM and in conjunction with a research strategy and agenda. Most recently, the working group “Long Term Safety of Container Systems and Components” was established to launch and perform research projects related to safety issues concerning the extended interim storage of radioactive waste.
For example, within our project LaMEP, we investigate ageing effects of metal and elastomer seals as well as polymeric neutron shielding materials, which are container components that fulfil major safety functions. The results of the experiments help to understand the long term behaviour of these components. Likewise, our project BRUZL started at BAM in 2018 with the aim of developing a fracture mechanics approach to understand and describe a potential brittle failure mechanism of fuel cladding during long-term interim storage. BAM also contributes to the GRS project “Development of methods and models and international exchange for safety evaluation in the frame of interim storage of radioactive waste”. Additionally, BAM is involved in several international research programmes dealing with extended interim storage, such as the European Joint Programme on Radioactive Waste Management (EURAD), the Extended Storage Collaboration Program (ESCP) and IAEA Coordinated Research Projects.
The present contribution provides a comprehensive overview of BAM research activities contributing to national and international gap analyses and to filling knowledge gaps regarding the safe long term management of radioactive waste.
Determining a suitable and reliable end-of-lifetime criterion for O-ring seals is an important issue for long-term seal applications. Therefore, seal failure of ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) O-rings aged in the compressed state at 125 °C and at 150 °C for up to 1.5 years was analyzed and investigated under static conditions, using both non-lubricated and lubricated seals. Changes of the material properties were analyzed with dynamic-mechanical analysis and permeability experiments. Indenter modulus measurements were used to investigate DLO effects. It became clear that O-rings can remain leak-tight under static conditions even when material properties have already degraded considerably, especially when adhesion effects are encountered. As a feasible and reliable end-of-lifetime criterion for O-ring seals under static conditions should include a safety margin for slight dimensional changes, a modified leakage test involving a small and rapid partial decompression of the seal was introduced that enabled determining a more realistic but still conservative end-of-lifetime criterion for an EPDM seal.