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Keywords: impact, simulation, cask, safety, drop, foundation, unyielding, target.

Summary

The safety of a transport and storage cask for radioactive materials in an accident scenario inside a storage facility is investigated. A half-scale model of the cask was dropped without impact limiters from a height of 0.3m vertically onto the BAM test site foundation representing conservatively the hard ground inside the German Gorleben interim storage facility. The cask was equipped with a large number of strain gauges and accelerometers. High speed video recordings helped to understand important effects of the impact sequence.

After the drop test, a dynamic three-dimensional finite element (FE) calculation was carried out with a detailed numerical model of the cask and foundation. The calculation results were carefully compared with the measurements to find out all relevant parameters for a realistic simulation of the impact scenario and to verify the FE model for further investigations. The modeling and the calculations were performed with the ABAQUS/Explicit finite element code. The main criterion for a sufficiently accurate simulation of the drop test scenario is a good correlation between experimental data and calculation results at representative measuring points spatially distributed over the cask structure during the whole significant impact history. Representative strain histories are given in the paper. The very small impact angle of 0.05° came out of the evaluation of the video recordings and a variation analysis with different angles of 0.0°, 0.05° and 0.1° showing a significant influence on the results. Another verification performed is the consideration of the canisters inside the cask. A good correlation of test and calculation data is found. Therefore, the numerical model can be considered as a sufficient description of the physical reality. However, a post-analysis of the drop test is necessary to find the stresses and strains for the worst case accident scenario, i.e. an exactly flat impact.

Hereafter a full-scale cask model was built by enlarging the verified half-scale model without any other changes. It is postulated, that the full-scale model derived in this way is a suitable representation of the original cask design. Using this model a handling accident in the worst case scenario was analyzed. The simulation results for a drop test of the original cask from a height of 0.3m onto the BAM test site foundation do not show any critical strains in the cask structure.

Additionally the load-reducing effects of a more yielding real storage site foundation are investigated. For that purpose the foundation of the developed FE model was changed with the concrete foundation of the German Gorleben storage facility. It must be emphasized that only simplified material models were used because of the lack of verified constitutive laws describing the mechanical behaviour of the given storage site foundation including dynamic effects. Cask stresses are significantly smaller when the real and less stiff foundation of a storage facility is included in the FE calculations.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 88 PROCEEDINGS OF THE NINTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping and M. Papadrakakis Paper 21 Numerical Safety Assessment of a Transport and Storage Cask for Radioactive Materials without Impact Limiters by the 0.3m Drop Test onto an Unyielding Target L. Qiao, U. Zencker, G. Wieser and H. Völzke BAM Federal Institute for Materials Research and Testing, Berlin, Germany doi:10.4203/ccp.88.21 purchase the full-text of this paper Full Bibliographic Reference for this paper , "Numerical Safety Assessment of a Transport and Storage Cask for Radioactive Materials without Impact Limiters by the 0.3m Drop Test onto an Unyielding Target", in B.H.V. Topping, M. Papadrakakis, (Editors), "Proceedings of the Ninth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 21, 2008. doi:10.4203/ccp.88.21 Keywords: impact, simulation, cask, safety, drop, foundation, unyielding, target. Summary The safety of a transport and storage cask for radioactive materials in an accident scenario inside a storage facility is investigated. A half-scale model of the cask was dropped without impact limiters from a height of 0.3m vertically onto the BAM test site foundation representing conservatively the hard ground inside the German Gorleben interim storage facility. The cask was equipped with a large number of strain gauges and accelerometers. High speed video recordings helped to understand important effects of the impact sequence. After the drop test, a dynamic three-dimensional finite element (FE) calculation was carried out with a detailed numerical model of the cask and foundation. The calculation results were carefully compared with the measurements to find out all relevant parameters for a realistic simulation of the impact scenario and to verify the FE model for further investigations. The modeling and the calculations were performed with the ABAQUS/Explicit finite element code. The main criterion for a sufficiently accurate simulation of the drop test scenario is a good correlation between experimental data and calculation results at representative measuring points spatially distributed over the cask structure during the whole significant impact history. Representative strain histories are given in the paper. The very small impact angle of 0.05° came out of the evaluation of the video recordings and a variation analysis with different angles of 0.0°, 0.05° and 0.1° showing a significant influence on the results. Another verification performed is the consideration of the canisters inside the cask. A good correlation of test and calculation data is found. Therefore, the numerical model can be considered as a sufficient description of the physical reality. However, a post-analysis of the drop test is necessary to find the stresses and strains for the worst case accident scenario, i.e. an exactly flat impact. Hereafter a full-scale cask model was built by enlarging the verified half-scale model without any other changes. It is postulated, that the full-scale model derived in this way is a suitable representation of the original cask design. Using this model a handling accident in the worst case scenario was analyzed. The simulation results for a drop test of the original cask from a height of 0.3m onto the BAM test site foundation do not show any critical strains in the cask structure. Additionally the load-reducing effects of a more yielding real storage site foundation are investigated. For that purpose the foundation of the developed FE model was changed with the concrete foundation of the German Gorleben storage facility. It must be emphasized that only simplified material models were used because of the lack of verified constitutive laws describing the mechanical behaviour of the given storage site foundation including dynamic effects. Cask stresses are significantly smaller when the real and less stiff foundation of a storage facility is included in the FE calculations. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £145 +P&P)
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