|"How SAFE are radioactive material transportation packages?"|
Demonstrating Target Hardness between an Unyielding Target vs. Concrete Target During 30-foot Drop Tests.
Purpose [ Back to top of page ]
The purpose of this series of tests is to visually demonstrate the severity of the Type B Hypothetical Accident Condition impact test (10 CFR Part 71.73 [NRC, 1998]). While the test is not intended to encompass all "real" accidents, it is intended to provide confidence in a package's ability to survive most accidents without a significant release of radioactive material. The relatively low speed of the impact test is often questioned. The rigor of the hypothetical accident condition test comes from the other conditions that are specified along with the speed. For the impact test, the requirement that all of the impact energy be absorbed by the package and none by the target provides added rigor.
Background [ Back to top of page ]
There have been other attempts to correlate the severity of the 9-meter (30 feet) drop onto an unyielding target with higher velocity impacts onto yielding targets. In 1975 Sandia National Laboratories conducted two 2,000-foot drop tests of shielded packages onto native desert soil and compared the package deformations to those that resulted from the regulatory impact test [Waddoups, 1975]. At about the same time Sandia tested several plutonium shipping containers for high-speed impacts onto soil, concrete, and the unyielding target [Schamaun, 1976]. In the mid 1980s, additional tests with a cask-like test unit were performed for impacts onto soil, two thicknesses of concrete, and the unyielding target with impact speeds from 30 to 60 MPH [Gonzales, 1986]. Since that time, Ammerman has published several papers on theoretical relationships between impact velocities on yielding targets to impact velocities on an unyielding target [Ammerman, 1992a, 1992b, 1998].
Results [ Back to top of page ]
It is expected that the van impact onto the concrete target will result in similar damage to the van as the drop onto the unyielding target. This is because, for a van, a concrete roadbed is nearly an unyielding target. This result will reinforce what people already believe. It is highly probable that the amount of damage to the van will be similar to the amount seen in very severe highway collisions, but not greater than the amount seen in "worst-case" accidents. The result that will provide the demonstration on the severity of the regulatory test will be the comparison between the regulatory impact of the DHLW 1/2-scale model and the impact of this cask onto the concrete target. For this cask, the results of the two tests will not be the same. There will be significant damage to the concrete target. This will communicate the point that what constitutes a rigid target depends on the stiffness of the object impacting it. For things that people are used to dealing with, such as vans and bodies, the concrete target is essentially rigid. For RAM casks it takes a much more substantial target to be essentially rigid. Targets of this type are rarely found in the "real world".
Actual results were nearly indistinguishable damage in the two van drop tests and no damage to the DHLW cask from impact onto the concrete target [the cask punched a hole through the concrete].
References [ Back to top of page ]
Ammerman, D. J., A Method for Relating Impacts with Yielding and Unyielding Targets, Proceedings of International High Level Radioactive Waste Management Conference, Las Vegas, Nevada, USA (April 1992a).
Ammerman, D. J., A Method for Comparing Impacts with Real Targets to Impacts onto the IAEA Unyielding Target, Proceedings of the 10th International Symposium on the Packaging and Transportation of Radioactive Materials, Yokohama, Japan (Sept. 1992b).
Ammerman, D. J., A Comparison of Regulatory Impacts to Real Target Impacts, Proceedings of the 12th International Symposium on the Packaging and Transportation of Radioactive Materials, Paris, France (May 1995).
Bonzon, L. L. and Schamaun, J. T., Container Damage Correlation with Impact Velocity and Target Hardness, IAEA-SR-10/21, Transport Packaging for Radioactive Materials, IAEA, Vienna, Austria (1976).
Gonzales, A., Target Effects on Package Response: An Experimental and Analytical Evaluation, SAND86-2275, Sandia National Laboratories, Albuquerque, NM, USA (May 1987).
Nuclear Regulatory Commission, 10 CFR Part 71.73 (1998) Waddoups, I. G., Air Drop Test of Shielded Radioactive Material Containers, SAND75-0276, Sandia National Laboratories, Albuquerque, NM, USA (Sept. 1975).