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Organisationseinheit der BAM
Drop testing of a container for the storage. transport and disposal of intermediate level waste
(2017)
Impact tests were performed, as part of a corresponding container’s substantiation, during design development of a shielded container. The container will be used for storage, transport, and disposal of intermediate level waste 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.
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.
Instrumented measurements on radioactive waste disposal containers during experimental drop testing
(2011)
In context with disposal container safety assessment of containers for radioactive waste the German Federal Institute for Materials Research and Testing (BAM) performed numerous drop tests in the last years. The tests were accompanied by extensive and various measurement techniques especially by instrumented measurements with strain gages and accelerometers. The instrumentation of a specimen is an important tool to evaluate its mechanical behavior during impact. Test results as deceleration-time and strain-time functions constitute a main basis for the validation of assumptions in the safety analysis and for the evaluation of calculations based on finite-element methods. Strain gauges are useful to determine the time dependent magnitude of any deformation and the associated stresses. Accelerometers are widely used for the measuring of motion i.e. speed or the displacement of the rigid cask body, vibration and shock events. In addition high-speed video technique can be used to visualize and analyze the kinematical impact scenario by motion analysis. The paper describes some selected aspects on instrumented measurements and motion analysis in context with low level radioactive waste (LLW) container drop testing
For disposal of the research reactor of the Technical University Munich FRM II a new transport and storage cask design was under approval assessment by the German authorities on the basis of International Atomic Energy Agency (IAEA) requirements. 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 the wood-filled impact limiters are installed to reduce impact loads to the cask under drop test conditions. In the cavity of the cask a basket for five spent fuel elements is arranged.
This design has been assessed by the Bundesanstalt für Materialforschung und -prüfung (BAM) in view to the mechanical and thermal safety analyses, the activity release approaches, and subjects of quality assurance and surveillance for manufacturing and operation of the package.
For the mechanical safety analyses of the package 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 tests 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 (FE) models applied in the safety analysis of the package design.
Packages for the transport of high-level radioactive material are designed to withstand severe accidents. Hypothetical severe accident conditions are defined in the IAEA Regulations for the Safe Transport of Radioactive Materials.
One of these accident conditions 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 depend substantially on the fire characteristics and the Surface temperature of the package.
Fire tests can be performed at BAM on a propane gas fire test facility. In order to investigate the heat fluxes over a wide range of surface temperatures in this test facility a fire reference package was designed for multiple use. The package represented the outer geometry of a specific transport cask for radioactive waste. The fire reference package is a closed steel sheet cylinder with a wall thickness of 10 mm, a length of 1500 mm and a diameter of 1050 mm. The package was instrumented with thermocouples and filled with heat resistant insulation material.
Three open-air fire tests were performed in the BAM propane gas fire test facility. The flames exposure time period varied slightly for the fire tests. The wind direction as well as the wind Speed were measured and changed between and during the tests. Test stand parameters such as wind shield location and propane gas volume flow were chosen constant for the three tests. The locally measured fire reference package steel sheet temperatures were used for the calculation of heat fluxes as function of time and surface temperature. The measured temperatures allowed further calculations. In a first approach effective fire characteristics of the propane gas fire, including the flame temperature, the fire convection coefficient and a Radiation exchange coefficient mathematically describing the determined average heat flux over the surface temperature were calculated.
Heavy-weight packages for the safe transport of radioactive material are equippedwith impact limiters often built ofwood-filled steel sheet structures to fulfil the requirements of the International Atomic Energy Agency (IAEA) regulations. The requirements definemechanical tests followed by a thermal test, including criteria ensuring the package design’s ability to withstand severe accidents and provide a high level of technical safety.
Impact limiters are a package component mainly designed for the packages to withstand severe mechanical accident scenarios. In drop tests the impact limiters absorb the kinetic energy during impact of the package. The package must then - with its pre-damaged impact limiters - endure a thermal test defined precisely in the IAEA regulations as a 30-min fully engulfing 800 °C-fire. After the fire, a wood-filled impact limiter may continue to release thermal energy from an ongoing combustion process, defining relevant package temperatures. The energy flow from a possible burning impact limiter to the package is important for the safety evaluation of transport packages. To investigate the combustion behaviour of densely packed layers of spruce wood, encapsulated in pre-damaged cylindrical metal enclosures, a test set-up has been realised. The set-up consists of a combustion chamber to perform these tests under defined boundary conditions. The temperature development of the test specimens will be observed fromoutside with a thermographic imager, with HD-Cameras, and the mass loss will be measured during the entire test. Airflow conditions in the combustion chamber are analysed using Computational Fluid Dynamics (CFD) calculations in OpenFOAM. The planned combustion test setup is described.
Packages for the transport of radioactive material are designed to en-dure severe accidents. Packages for the transportation of radioactive material must demonstrate that the package can withstand certain prescribed tests from the IAEA Regulations [1]. In addition to mechanical tests, a thermal test in form of a fire test must be carried out. As packages to be tested at BAM are signifi-cantly larger than previous package designs, BAM has expanded an existing fire test stand. A modular concept is chosen, which means that the arrangement of the burner nozzles can be adapted to the test specimen. The dimensions of the burner rings, the type, the orientation and the number of burner nozzles can be varied depending on the test specimen. In addition, various pumps can be used to set the corresponding mass flow. With the help of a calorimeter test, the fire test stand can be qualified for a specific size of packages regarding the boundary conditions of the IAEA Regulations [1]. Due to the typically wood filled impact limiters in German package designs, a fire test is necessary, as experiments have shown that possible openings that occurred during a mechanical test contributed to the igni-tion of the wood filled impact limiters within the prescribed 30 minutes of the IAEA Regulations [1]. From a series of experiments, two experiments are pre-sented to show the possibilities to obtain different temperatures and temperature rates in the test specimen. In addition to sensor data, the heat flux into the package is calculated to verify that the IAEA boundary conditions are satisfied. In addition to the temperature data, other data such as wind speed and wind direction are also recorded to explain subsequent effects in the measurement data in a comprehen-sible manner.