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[en] In the process of testing spent fuel casks, BAM is gaining a lot of relevant data regarding the quality level of Ductile Cast Iron (DCI). This paper discusses the basic parameters governing the material behavior of ferritic and ferritic-pearlitic DCI and reviews the development of cask quality over the last years. The effect of microstructure and sample size on the fracture toughness of DCI is discussed. The results of a test program show the prominent effect of pearlite content and graphite nodule structure in the mechanical and fracture toughness characteristics of DCI. This observation is important for quality assurance programs for shipping and storage casks of radioactive materials
[en] The project was intended to further enlarge the pool of safe data giving proof of the suitability and qualification of the GGG-40 nodular cast iron to serve as a material for transport and storage casks for radioactive materials, and to present these data ready for acceptance by international standards. Preparatory work achieved a harmonization of methods and criteria applied for testing that have been adopted by the IAEA. The fracture safe design of the CASTOR VHLW prototype cask made of nodular cast iron has been proven for extreme load conditions. Tests for brittle fracture sensitivity of the material revealed good resistance of the material even in the area of the yield strength point and with artificial crack-type flaws at this spot. The cask stood the 14 m-drop test onto two hard objects and the resulting, extraordinary bending strain. Accompanying materials tests enhanced the information on the connection between chemical composition of the microstructure and the mechanical strength of the nodular cast iron. The tests included various casting methods (sand casting, die casting) in the manufacturing process, and the effects of transformation processes in the microstructure as a result of thermal treatment. The statistical evaluation of single test results within the framework of quality assurance tests for the qualification of transport and storage casks for radioactive materials has been supported by mechanical and fracture-mechanical analyses in 24 samples of nodular cast iron. (orig./HP)
[de]Entsprechend der Zielsetzung des Vorhabens stand die weitere Etablierung des Werkstoffes Sphaeroguss (GGG-40) im Bereich der Transport- und Lagerbehaelter fuer radioaktive Stoffe im internationelen Rahmen im Vordergrund. Es gelang eine weitgehende fachliche Uebereinstimmung hinsichtlich der Bewertungsmethoden und -kriterien zu erzielen und auf IAEA-Ebene zu etablieren. Die ausserordentliche Belastbarkeit eines Prototypbehaelters aus Sphaeroguss (CASTOR VHLW) konnte unter extremen Beanspruchungssituationen nachgewiesen werden. So war selbst bei Spannungen im Bereich der Material-Streckgrenze und vorhandenem rissartigen Fehler an dieser Stelle keine Sproedbruchneigung des Werkstoffes erkennbar. Den entsprechenden 14 m-Fall auf zwei harte Widerlager mit daraus folgender hoher Biegebeanspruchung ueberstand der Behaelter unbeschadet. Mittels begleitender Werkstoffuntersuchungen wurde die Kenntnisse ueber die Zusammenhaenge zwischen der chemischen Zusammensetzung der Gefuegeausbildung und den mechanischen Eigenschaften von Sphaeroguss erweitert. Dabei wurden unterschiedliche Giessverfahren (Sand- und Kokillenguss) in der Herstellung und die Auswirkungen von Umwandlungsprozessen im Gefuege infolge von Waermebehandlungen diskutiert. Die statistische Auswertung von Einzelergebnissen im Rahmen der Qualitaetssicherung bei der Begutachtung von Transport- und Lagerbehaeltern fuer radioaktive Stoffe wurden durch mechanische und bruchmechanische Untersuchungen an 24 Werkstoffen aus Gusseisen mit Kugelgraphit ergaenzt. (orig./HP)
[en] The IAEA Regulations for the Safe Transport of Radioactive Materials require the consideration of temperatures of -40 deg. C for Type B package designs. According to the German approval practice, this temperature shall be also taken into account during mechanical tests simulating accident situations with these packages. Therefore, the necessary safety analysis includes fracture mechanics assessments for all safety related components of the packages. In the past, these evaluations have been performed for components manufactured from ferritic steels by methods usually used for pressure vessels. Because of the restrictions of these methods if applied to thick-walled casks and the low-temperature embrittlement of ferritic steels which is additionally increased by high impact rates during accidents, BAM as the responsible German testing authority for Type B packages required the establishment of fracture mechanics analysis method that considers especially the test conditions for this package type. A proposal of the German cask designer Gesellschaft fuer Nuklear-Behaelter (GNB) provides the use of a method for these analyses which has been developed during the recent years in the European Communities for steel constructions (especially bridges) with the objective to establish an appropriate European standard. The paper discusses problems and necessary adaptions of the method if applied to Type B packages from the point of view of the testing authority. (authors)
[en] Beside the presentation of interesting parts of the experimental equipment the thermal shock behaviour of two ceramics will be discussed. Specimens of silicon carbide and zirconia were investigated in air and vacuum. The influence of the testing conditions on the strength will be addressed.
[en] In the process of testing spent fuel casks, BAM is gaining a lot of relevant data regarding the quality level of ductile cast iron (DCI). The basic parameters governing the material behaviour of ferritic and ferritic pearlitic DCI are discussed and the development of container quality over recent years is summarised. The high quality level of German DCI containers is outlined. The effect of microstructure, sample size and loading rate on the fracture toughness of DCI is discussed in the second part of the paper. (author)
[en] The degradation mechanisms of state-of-the-art Nb-Ti/Cu superconductors are described, based on in-situ synchrotron X-ray diffraction measurements during heat treatment. A quantitative description of the Nb-Ti/Cu degradation in terms of critical current density, Cu stabiliser resistivity and mechanical composite strength is presented. In an applied magnetic field a significant critical current degradation is already observed after a 5-minute 400 0C heat treatment, due to variations of -Ti precipitate size and distribution within the Nb-Ti alloy filaments. A strong degradation of the strand mechanical properties is observed after several minutes heating above 550 0C, which is also the temperature at which the formation of Cu-Ti intermetallic phases is detected. Several minutes heating at 250 0C are sufficient to increase the RRR of the strongly cold work strands inside a Rutherford type cable from about 80 to about 240. Heating for several minutes at 400 0C does not cause a significant conductor degradation in self-field and, thus, leaves enough temperature margin for the electrical interconnection of Nb-Ti/Cu conductors with common low temperature solders.