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Integrity of the "POLLUX" cask for final disposal: Experimental results of the mechanical tests
(1995)
This paper describes the analytical, numerical and experimental investigations on the phenomenon of
interactions between cask components and content of packages for the transport of radioactive material during drop
tests required according to the IAEA Regulations for the Safe Transport of Radioactive Material.
Radial and axial gaps between cask components and content are usually necessary for thermal reasons but larger
gaps can exist because of the geometrical dimensions of the specified content. Consequently interactions between
content and cask components (lid system, cask body, etc.) are possible and can not be excluded during drop tests.
Interactions in this context are relative movements between cask and content which are mainly due to elastic spring
effects after releasing the cask for the free drop. These relative movements can cause interior collisions between
content and cask during the main impact of the package onto the unyielding target.
Drop tests with various types of Type A and Type B packages fully instrumented with strain gauges and
accelerometers showed that these interactions respectively interior collisions can be considerable relating to high forces
acting on cask lids, lid bolts and the content. Of course the real quantitative consequences of the interactions depend
upon different conditions, among others the drop orientation, the design characteristics of the impact limiters, the
dimensions of the gaps, the material characteristics of the contents, etc. .
In order to investigate more precisely the phenomenon of interactions BAM carried out finite element
calculations for the named casks using the ABAQUS/ Standard and ABAQUS/ Explicit computer code comparing them
with results obtained from experiments. Additionally, tests with a simplified model instrumented with accelerometers
were carried out accompanied by finite element calculations and analytical calculations using MATHEMATICA.
The investigations on the mentioned phenomena of interaction show that they should be considered in approval design
tests and/ or calculations.
Tests with different Type B casks confirm the existence of effects with stress peaks in cask components due to
interactions between the cask and its contents. These effects can be caused by a delayed strike of the content onto surrounding cask components which cannot be excluded if the content is movable. Some results of the drop tests with two different Type B casks and with a model designed for the study of this problem are presented in the paper. Results of calculations performed with the ABAQUS computer code and by use of analytical methods to simulate the measured effects are discussed.
ANF-18 - A new transport container for fresh PWR fuel assemblies according to IAEA requirements
(2001)
Internal Cask-Content-Collisions During Drop Test of Transport Casks for Radioactive Materials
(2012)
Federal Institute for Materials Research and Testing (BAM) is the competent authority for mechanical and thermal safety assessment of transport packages for spent fuel and high level waste in Germany. In context with package design approval of the new German high level waste cask CASTOR® HAW28M, BAM performed several drop tests with a half scale model of the CASTOR® HAW/TB2. The cask is manufactured by Gesellschaft für Nuklear Service mbH and was tested under accident transport conditions on the 200 tons BAM drop test facility at the BAM Test Site Technical Safety. For this comprehensive test program, the test specimen CASTOR® HAW/TB2 was instrumented at 21 measurement planes with altogether 23 piezo resistive accelerometers, five temperature sensors and 131 triaxial strain gauges in the container interior and exterior respectively. The strains of four representative lid bolts were recorded by four uniaxial strain gauges per each bolt. Helium leakage rate measurements were performed before and after each test in the above noted testing sequence. The paper presents some experimental results of the half scale CASTOR® HAW/TB2 prototype (14 500 kg) and measurement data logging. It illustrates the extensive instrumentation and analyses that are used by BAM for evaluating the cask performance to the mechanical tests required by regulations. Although some of the quantitative deceleration, velocity and strain values cannot be shown because of confidentially issues, they are provided qualitatively to illustrate the types of measurements and methodologies used at BAM.
BAM (Federal Institute for Material Research and Testing) is the competent authority for mechanical and thermal safety assessment of transport packages for spent fuel and high level waste (HLW) in Germany. In context with package design approval of the new German HLW cask CASTOR HAW28M, BAM performed several drop tests with a half-scale model of the CASTOR HAW/TB2. The test model was manufactured by GNS (Gesellschaft fur Nuklear Service mbH) and tested under accident transport conditions on the 200 tons BAM drop test facility at the BAM Test Site Technical Safety. For this comprehensive test program the test specimen CASTOR HAW/TB2 was instrumented at 21 measurement planes with altogether 23 piezo-resistive accelerometers, five temperature sensors and 131 tri-axial strain gauges in the container interior and exterior, respectively. The strains of four representative lid bolts were recorded by four uniaxial strain gauges per each bolt. Helium leakage rate measurements were performed before and after each test in the above noted testing sequence. The paper presents some experimental results of the half-scale CASTOR HAW/TB2 prototype (14,500 kg) and measurement data logging.
The crush test for light weight and low density type B packages was introduced for the first time into the 1985 edition of the International Atomic Energy Agency (IAEA) transport safety regulations. In the early 1970s, the need for an additional mechanical test besides or instead of the well known 9 m drop test was deliberated. Various authors and test facilities, including BAM and Sandia National Laboratories (SNL), were able to prove that the level of safety provided by IAEA drop and puncture tests in the regulations did not protect against dynamic crush forces to smaller packages. As early as the third PATRAM symposium held in 1971 (Richland, WA, USA), Robert F. Barker asked for '... a more strenuous crushing test for protecting small, light weight packages ...' BAM developed from research activities a proposal as to which types of packages should be subject to crush tests and how the crush tests should be performed, which was presented at the 5th PATRAM symposium held in 1978 (Las Vegas, NV, USA). At the IAEA, the possible need for a crush test was first mentioned in 1977. The subject for a discussion, besides the principal need for this test, was also the development of suitable set of crush test boundary conditions. It took more than four years of discussion until a dynamic crush test similar to today's test was recommended by experts to the IAEA regulatory revision panel. Finally, after a rigorous evaluation process in which also the boundary conditions were determined, the crush test was proposed to be incorporated into the IAEA regulations. BAM and SNL participated in the crush test development and implementation process right from the beginning in the early 1970s until its implementation in the IAEA regulations in 1985. Today, BAM performs crush test procedures according to para. 727(c) of TS-R-1, which have not been changed since their first implementation. Crush tests performed in 2002 at BAM will be discussed. These approval design tests were performed on birdcage pellet transport containers under normal and accident conditions according to the IAEA regulations.
For validation of structural integrity under normal and hypothetical accident conditions during transport and storage of dangerous goods the Federal Institute for Materials Research and Testing (BAM) focuses its safety related scientific research on advanced mechanical safety assessment methods including simulation of high rate impact of model components and structures.
An impact and crash test facility was recently developed for performing dynamic impact tests with component size specimen, or to crash specimens of impact limiter materials and structural components.
The paper presents experimental techniques of BAM drop test machine and options of several measurement methods and advancements in order to characterize typical shock-absorbing materials under impact loading conditions. Instrumented drop weight tests are performed to complete materials data base and energy absorption of shock-absorbing materials as well as to implement materials and structural parameters into FEA of reference structures.
Drop and fire testing of spent fuel and HLW transport casks at 'BAM test site technical safety'
(2011)
BAM, as a competent German government institute for the mechanical and thermal testing of radioactive material transport and storage containers, operates unique drop and fire test facilities for experimental investigations on the open air BAM Test Site Technical Safety. To be able to perform even drop tests with full scale spent fuel or HAW casks (i.e. the German CASTOR cask designs), BAM constructed in 2004 a large drop test facility capable to handle 200 ton test objects, and to drop them onto a steel plate covered unyielding target with a mass of nearly 2600 ton. Drop test campaigns of the 181 ton GNS CONSTOR V/TC, the 129 ton MHI MSF-69BG and a 1:2 scale model of the GNS CASTOR HAW28M (CASTOR HAW/TB2) have been performed since then. The experimental BAM drop testing activities can be supported also by drop testing of smaller packages (up to 2 ton) in an in-house test facility and by dynamic, guided impact testing of package components and material specimen inside a new drop test machine. In May 2008, a new modern fire test facility was put into operation. The facility provides two test stands fired with liquid propane. Testing in every case has to be completed by computational investigations, where BAM operates appropriate finite element modelling on appropriate computer codes, e.g. ABAQUS, LS-DYNA, ANSYS and other analytical tools.
Instrumented Measurements on Radioactive Waste Disposal Containers During Experimental Drop Testing
(2011)
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
The paper presents technical details of the drop test performance as well as some experimental results of tests carried out with the Japanese 'Yoyushindo-disposal' waste container for intermediate depth disposal. The tests were accompanied by various metrology to collect data as basis for safety assessment.
Packages for the transport of Spent Nuclear Fuel and high active radioactive waste are designed to withstand severe accidents. Specific mechanical and thermal tests are defined in the IAEA Regulations for the Safe Transport of Radioactive Materials in order to cover these hypothetical severe accidents. The thermal test mainly consists of a 30 minute fully engulfing fire. Components such as the package impact limiters can lead to supplementary energy release during the thermal test as they might continue burning after the fire phase. Local heat flux into the package can occur. Measurement of heat flux into the package is of importance to evaluate component temperatures and review their acceptance. The usability of heat flux sensors and temperature measurement equipment has to be tested to apply them in impact limiter fire testing. Further questions arise such as :“Is the infrared camera a useful tool to determine heat flux at the boundary surface?”
Type B(U) packages for the transport of radioactive material have to withstand accident conditions of transport defined in the regulations of the IAEA International Atomic Energy Agency in form of different mechanical (drop) tests with a subsequent thermal test. According to the regulatory requirements the orientation of the package in drop tests shall be such to cause the most damaged state in the components performing the safety functions.
For the package lid system a 9-m drop onto the unyielding target with lid side downwards is often the most damaging orientation. The impact loads acting on the lid in this orientation result mainly from interaction between lid and internal content. In case of a movable content its impact onto the inner side of the lid can cause additional load peaks on the lid and the lid bolts. The intensity of the internal collision depends on the position of content relating to lid at the time of package first contact with target. Due to physical limitations an axial gap, which could be set in “pre-drop” configuration of package or which could spontaneously appear during the drop test, usually does not cover the maximum size possible in specific package design. In this context, the combination of drop tests with post-test analysis can be helpful to better estimate the effect of internal impact.
The paper summarized some aspects of this issue based on the BAM experience in the design assessment of Type B(U) transport packages. Additionally the paper shall support applicants in German approval procedures to reduce rounds of questions and ensure delivery of reliable safety case documents to the authorities. International discussions of this issue at the IAEA and a joint proposal by France and Germany to improve Advisory Material text will be introduced.
Internal cask content collisions during drop test of transport casks for radioactive materials
(2013)
In transport casks for radioactive materials, significantly large axial and radial gaps between cask and internal content are often present because of certain specific geometrical dimensions of the content (e.g. spent fuel elements) or thermal reasons. The possibility of inner relative movement between content and cask will increase if the content is not fixed. During drop testing, these movements can lead to internal cask content collisions, causing significantly high loads on the cask components and the content itself. Especially in vertical drop test orientations onto a lid side of the cask, an internal collision induced by a delayed impact of the content onto the inner side of the lid can cause high stress peaks in the lid and the lid bolts with the risk of component failure as well as impairment of the leak tightness of the closure system. This paper reflects causes and effects of the phenomenon of internal impact on the basis of experimental results obtained from instrumented drop tests with transport casks and on the basis of analytical approaches. Furthermore, the paper concludes the importance of consideration of possible cask content collisions in the safety analysis of transport casks for radioactive materials under accident conditions of transport.
A management system based on international, national or other standards acceptable to the competent authority shall be established and implemented for all activities including design, manufacture, testing, documentation, use, maintenance, inspection in accordance with IAEA SSR-6. Hereby, quality assured testing and documentation can substantially contribute to the demonstration of package design compliance with the regulations. Nowadays, a drop test campaign within the approval process of packages for radioactive materials can be a very complex and extensive project including various test and measurement techniques. On this basis of procedures and documents the experimental tests of packages and containers are performed with quality proofed results and a high reliability. A complete traceability and direct transferability of package design test results can give particular importance to the type approval procedure.
Internal cask content collisions during drop test of transport casks for radioactive materials
(2013)
In context with new cask designs and their approval procedure, the experimental testing of impact limiters under drop test conditions becomes more and more important in order to assess the damage mechanics behaviour and safety margins for validation reasons. In recent years, various designs of impact limiters have been tested by the Federal Institute for Materials Research and Testing within specific component testing and particularly with regard to type B package design approval procedures. The paper focuses on the experimental realisation of impact limiter tests and presents implemented measurement techniques to determine the amount of deformation and to explain the impact behaviour by means of photogrammetric metrology and three-dimensional fringe projection method, high speed motion analysis and adjusted deceleration measurements.
In context with new cask designs and their approval procedure the experimental testing of impact limiters under drop test conditions becomes more and more important in order to assess the damage mechanics behavior and safety margins for validation reasons.
In recent years various designs of impact limiters have been tested by the Federal Institute for Materials Research and Testing (BAM) within specific component testing and particularly with regard to type B package design approval procedures.
The paper focuses on the experimental realization of impact limiter tests and presents implemented measurement techniques to determine the amount of deformation and to explain the impact behavior by means of photogrammetric metrology and 3-d fringe projection method, high-speed motion analysis and adjusted deceleration measurements.
BAM safety related research of containers for radioactive material focuses on advanced mechanical safety assessment methods for verification of the structural integrity and leak tightness under normal conditions of transport and hypothetical accident conditions during transport and storage. An essentially unyielding target with a rigid surface is required for impact tests performed for package approval according to IAEA regulations. In addition to specification of a target, e.g. with a combined mass more than 10 times that of the specimen for drop tests, unyielding target characteristics have been investigated with various package designs and different impact tests. The unyielding target of the BAM drop test facility, a reinforced concrete block together with an embedded and anchored mild steel plate, provides relatively large mass and stiffness with respect to the packages being tested. For monitoring reasons accelerometers and strain gauges are embedded in the concrete block of the foundation at several positions. Additionally, dynamic impact responses like vibrations and rigid body motion can be measured by seismic accelerometers. The mechanical characterisation of the target's rigidity is based on experimental results from various drop tests. Test containers with weights of 181 000 kg, 127 000 kg and 8010 kg hit the target with velocities up to 13·5 m s-1 in the horizontal and vertical drop positions. The rigidity of the impact target can be demonstrated with experimental results confirmed by analytical approaches. Some conclusions can be drawn about experimental testing as well as analytical calculations in order to compare impact effects.
This paper presents a comparison between full scale prototype and reduced scale model drop test data in regard to similarity mechanics. Together with a current BAM research project, the paper contributes to the further development of mechanical evaluation methods for safety assessment of RAM transport and storage packages including the transferability of package impact response from reduced scale models to full scale packages.
This paper presents technical details of the drop test performance as well as some experimental results of tests carried out with the Japanese 'Yoyushindo-Disposal' waste container for intermediate depth disposal. The drop test program comprised three single 8 m drop tests at the specimen's corner edge orientation onto a concrete slab. The slab was connected to the unyielding IAEA target of the BAM's 200 t drop test facility. The three tested specimens had masses between 20 000 and 28 000 kg depending on their content mass. The tests were accompanied by various metrology, such as strain and deceleration measurements, optical three-dimensional deformation methods, leak tightness testing and test installation for potential particle release measurements to collect a set of data for establishing a basis for safety assessment.
Extended drop tests of DCI casks with artificial flaws demonstrating the existing safety margins
(1995)
Three drop test campaigns have been performed with DN 30 Protective Structural Packaging (PSP) developed by DAHER NUCLEAR TECHNOLOGIES GmbH for the transport of natural, enriched and reprocessed uranium hexafluoride (up to 5 wt%) in 30B cylinders.
The mechanical prototype testing is intended to demonstrate that the package DN30 complies with regulatory requirements under normal and hypothetical accident conditions of transport (NCT, ACT) relevant to IF, AF and B(U)F packages, respectively.
The paper includes the results of the latest test campaign carried out in 2015-2016 at the drop test facility of BAM, Germany with new full scale prototypes of the DN30 PSP and 30B cylinders. Repetition of drop test sequences became necessary after changing to Polyisocyanurate foam as shock absorbing material with variable foam densities. Furthermore, the mechanical behavior of the UF6 content of the 30B cylinder is now simulated by a mixture of cement and steel grid as modified surrogate material; instead of small steel balls. The behavior of this new content simulation is assumed to be more realistic with respect to the properties of real UF6.
In context with Japanese disposal and transport container safety assessment the German Federal Institute for Materials Research and Testing (Bundesanstalt für Materialforschung und -prüfung) per-formed extensive drop test series with prototypes of RAM packages in recent years.
The paper presents two cooperative projects focused on project management, testing performance and experimental results.
In the first project, a full-scale prototype of a package for transport and storage of spent fuel elements with a total mass of 127,000 kg and its reduced-scale model which was similar to the prototype in both geometry and design were drop tested in 9 m and 1 m puncture tests at various drop orientations under regulatory conditions. In context with a corresponding research project the test data was used in combination with numerical methods to investigate the phenomenon of internal cask- content collisions during drop tests. Here, technological gaps between basket or radioactive content and cask body or primary lid can be a reason for significant high dynamic loadings of cask components and its internals due to additional impact interactions in the cask cavity caused by inner relative movement between content and cask. Further investigations were carried out in the field of similarity mechanics comparing experimental drop test data of the full-scale prototype and reduced-scale model in regard to the transferability of package impact response from reduced-scale models to full-scale packages.
In the second project, drop tests with a waste container for intermediate depth disposal were per-formed being contracted by Kobe Steel, Ltd. and a consortium of Japanese electric power plant com-panies. The drop test program comprised three single 8-m drop tests in a specimen’s corner edge orientation. For drop tests according to legal regulations for interim storage or final disposal it is often necessary to use a target which represents the real ground of the storage facility. In such cases the container hits directly onto a well-defined concrete slab on top of the IAEA target. Here, the directly impact target for the drop tests were concrete slabs manufactured in Japan and connected by mortar to the impact pad of the unyielding IAEA target.