Kerntechnische Entsorgung
Filtern
Dokumenttyp
- Vortrag (117)
- Beitrag zu einem Tagungsband (71)
- Posterpräsentation (28)
- Zeitschriftenartikel (21)
- Buchkapitel (7)
- Monografie (1)
- Beitrag zu einem Sammelband (1)
- Amtliche Bekanntmachung (1)
- Forschungsbericht (1)
Sprache
- Englisch (248) (entfernen)
Schlagworte
- Ageing (27)
- Drop test (17)
- Metal seal (17)
- Transport (17)
- Ring Compression Test (16)
- Spent Nuclear Fuel (16)
- Ageing Management (15)
- IAEA (15)
- Cladding Embrittlement (14)
- Compression set (13)
Organisationseinheit der BAM
- 3 Gefahrgutumschließungen; Energiespeicher (248) (entfernen)
Paper des Monats
- ja (2)
Eingeladener Vortrag
- nein (117)
Component and material investigations on metal seals for high level radioactive waste containers
(2018)
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.
Assessment of Quality Management for Transport Packages not requiring Authority Design Approval
(2018)
The poster presents the german approach for the assessment of quality management systems for transport packages for radioactive material not requiring authority design approval. As legal basis the IAEA regulations, the ADR as well as the GGVSEB are highlighted and examples for these transport packages are given. The GGR 016 is mentioned, main duties and responsibilities as well as the manufacturing and quality surveillance system are described.
Typical transport packages used in Germany are equipped with encapsulated wooden impact limiting devices. We would like to present the current status regarding the development of a Finite Element (FE) material model for the crush of wood for the FE-code LS-DYNA. The crush of is a phenomenon governed by macroscopic fracture. Here, we would like to reproduce fracture and failure mechanisms over the continuous volume. In a first step we altered an existing LS-DYNA material model for foams, which considers an ellipse shaped yield surface. For the use for longitudinal compression of wood, we modified the existing material model to consider the deviatoric strain for the evolution of the yield surface as well. This is in accordance with the results of crush tests with spruce wood specimens, where the crushing deformation was rather deviatoric for uniaxial stress states and rather volumetric for multiaxial stress states We rate the basic idea of this approach to be reasonable, though other problems exist regarding the shape of the yield surface and the assumption of isotropic material properties. Therefore we developed a new transversal isotropic material model with two main directions, which considers different yield curves according to the multiaxiality of the stress state via a multi-surface yield criterion and a non-associated flow rule. The results show the ability to reproduce the basic strength characteristics of spruce wood. Nevertheless, problems with regularization etc. show that additional investigations are necessary.
Typical transport packages used in Germany are equipped with encapsulated wooden impact limiting devices. We would like to present the current status regarding the development of a Finite Element (FE) material model for the crush of wood for the FE-code LS-DYNA. The crush of is a phenomenon governed by macroscopic fracture. Here, we would like to reproduce fracture and failure mechanisms over the continuous volume. In a first step we altered an existing LS-DYNA material model for foams, which considers an ellipse shaped yield surface. For the use for longitudinal compression of wood, we modified the existing material model to consider the deviatoric strain for the evolution of the yield surface as well. This is in accordance with the results of crush tests with spruce wood specimens, where the crushing deformation was rather deviatoric for uniaxial stress states and rather volumetric for multiaxial stress states We rate the basic idea of this approach to be reasonable, though other problems exist regarding the shape of the yield surface and the assumption of isotropic material properties. Therefore we developed a new transversal isotropic material model with two main directions, which considers different yield curves according to the multiaxiality of the stress state via a multi-surface yield criterion and a non-associated flow rule. The results show the ability to reproduce the basic strength characteristics of spruce wood. Nevertheless, problems with regularization etc. show that additional investigations are necessary.
The paper focuses on the preliminary determination of the bar length and the experimental performance of the 1m-puncture test in compliance with the guidelines of the IAEA under the given boundary conditions. Following aspects have to be considered concerning the determination of an appropriate length of the bar to obtain maximum damage to the specimen: the design of the package, its drop orientation and the impact point as well as a pre-damage of the package resulting from a previous 9m drop test. According to the Regulations the minimum length of the bar is defined as 20 cm, which has to be adapted to the outer surface of the package, especially to packages with large impact limiters.
In this context, two main aspects are important: First, the realisation of a maximum puncture load applied to the package while no other component of the package has contact with the impact target. Second, the reduction of the risk of buckling and maximising the stiffness of the bar by a length which is as short as possible. In order to optimize the bar length, finite element calculations are often done by simulating the global behaviour of the package during the puncture test. The evaluation of the conducted puncture test regarding IAEA compliance is done by analysing deceleration measurements. The paper presents a possible approach to determine the length of the bar and the construction of a form-fitted connection to the target showing various examples of puncture tests.
BAM is the German Federal Institute for Materials Research and Testing and the competent authority for mechanical and thermal safety assessment of transport packages for spent fuel and high level waste. In context with safety assessment of RAM packages BAM performed numerous drop tests in the last decades. The tests were mostly accompanied by extensive and various measurement techniques especially by instrumented measurements with strain gages and accelerometers.
The procedure of drop testing and the resulting measurement analysis are the main methods to evaluate the safety against mechanical test conditions. Measurement techniques are dedicated to answer questions in regard to the structural integrity of a RAM package, the mechanical behavior of the prototype as well as of its content under impact conditions.
Test results like deceleration-time functions constitute a main basis for the validation of assumptions in the safety analysis and for the evaluation of numerical calculations. In this context the adequate selection of accelerometers and measurement systems for the performance of drop tests is important. Therefore it is not only necessary to find suitable positions for the accelerometers at the test specimens, but also to consider technical boundary conditions as e.g. temperature.
BAM is the German Federal Institute for Materials Research and Testing and the competent authority for mechanical and thermal safety assessment of transport packages for spent fuel and high level waste. In context with safety assessment of RAM packages BAM performed numerous drop tests in the last decades. The tests were mostly accompanied by extensive and various measurement techniques especially by instrumented measurements with strain gages and accelerometers.
The procedure of drop testing and the resulting measurement analysis are the main methods to evaluate the safety against mechanical test conditions. Measurement techniques are dedicated to answer questions in regard to the structural integrity of a RAM package, the mechanical behavior of the prototype as well as of its content under impact conditions.
Test results like deceleration-time functions constitute a main basis for the validation of assumptions in the safety analysis and for the evaluation of numerical calculations. In this context the adequate selection of accelerometers and measurement systems for the performance of drop tests is important. Therefore it is not only necessary to find suitable positions for the accelerometers at the test specimens, but also to consider technical boundary conditions as e.g. temperature.
Transport and storage of radioactive materials are performed in countries with policy of either closed or open nuclear fuel cycle. The related technologies have been established by accumulation of experiences and researches including demonstrative tests using full scale or scale models and analyses. Those are essential before commercialization, but are often costly and time consuming. Such demonstrative works should not be repeated meaninglessly, but can be shared through this kind of book and used by readers and the future generations to advance the technology effectively. This book systematically provides findings from lots of valuable researches on safety of transport and storage of radioactive materials under normal and accident conditions that have an impact on basis of safe regulations, designs, and operations.
Drop testing of a container for the storage, transport and disposal of intermediate level waste
(2018)
Impact tests were performed, as part of a corresponding container’s substantiation, during design development of a shielded container proposed for use at Sellafield for waste retrieval from the First Generation Magnox Storage Pond (FGMSP) in the UK.
The mechanical test program comprised a 9m free drop test onto an unyielding target in a container long lid edge down orientation at ambient conditions. Further, a 0,5m free drop test onto a punch target was performed. Here, the container was orientated with the lid downwards in a way that the punch, a mild steel bar, impacts a filter lid.
The test specimen was instrumented with strain gauges and accelerometers for the drop tests. Transient strains at selected points of the inner and outer container walls, at the shielding lid, as well as at the lid bolts were measured during the container’s impact. Furthermore, decelerations of the container body, container lid, and the skip were measured. The complex geometrical changes of the container due to impact were determined by optical 3d- deformation measures using the projected fringes method in combination with multi-image photogrammetry.
This paper summarizes the performance of the drop tests and various drop test results in context with the design development as well as aspects regarding the associated Finite Element (FE) analyses and post-test evaluation.
For transport operations according IAEA regulations SSR-6, the package shall be securely stowed and the package shall be capable to withstand specific effects, e.g. accelerations, during routine transport conditions. The supporting IAEA Advisory Material SSG-26 provides information how to do that. General information and detailed load factors for use in safety demonstrations are provided.
Up to now package designers in different countries use other load factors for the design of attachment points than those specified in the IAEA guidance material. In particular the acceleration factors vary between different countries and lead to difficulties during the validation of foreign approval certificates. The background of the existing guidance including specified load values was not clear enough. The application of specified values and the boundary conditions, i.e. transport conditions, seemed to be improvable.
The IAEA started a discussion process to review the existing guidance text. An international working group was constituted in 2013. Representatives came from different stakeholders, e.g. transport operators, competent authorities and modal organizations. The discussions concluded especially on the transport conditions which has to be considered for stowage design, including on the one hand the relevance of the load factors used for strength and fatigue analysis and, on the other hand the criteria which have to be considered for the attachment points. In addition, complementary questions relative to the operational aspects were discussed. Revised load values for different transport modes were proposed. The values are derived from standards and include safety factors now.
As a result of those discussions, the international working group wrote new guidance material for stowage in transport, addressing all the previously quoted topics.