LEAKAGE TESTING DURING LATERAL DISPLACEMENT OF METALLIC SEALS UNDER MECHANICAL ACCIDENT IMPACT

In context with approval design tests, the IAEA regulations for the safe transport of radioactive material specify tests for demonstrating ability to withstand normal and accident conditions of transport. For 9-m drop test onto an unyielding target the drop orientation of the package must be chosen in a manner so that maximum damage occurs with regard to the safety criteria. With respect to leak tightness after drop test impacts a horizontal or slap-down orientated test model can cause a lateral displacement of the packaging’s lids, affecting the leakage rate of the closure lid system strongly. In Germany dual purpose casks with double lid sealing system composed of primary and secondary lid with bolts, metallic seals as well as cask body sealing surfaces are mainly used. Besides free drop tests with full-scale and half-scale models within licensing approval procedure BAM develops experimental testing methods to simulate defined stresses and deformations by means of components testing. In order to investigate the relation between lateral lid displacement and leakage rate, BAM performs impact tests with small scaled flange-lid systems of transport packages in a drop test machine for guided drop tests. The test setup is realized in a way that the flange part is fixed while a drop weight is impacting onto the lid’s edge. The dynamic displacement of the lid is measured simultaneously. Because of capturing the drop weight after first impact during a short rebound phase by pneumatic arrest mechanism a secondary impact on lid’s edge is excluded. The guided drop tests were accompanied by various measurements such as leakage rate recording during and after impact, identification of lateral shifting by electro-optical displacement transducer as well as decelerations of the lid and the impacting weight. This paper describes the test setup, the test and measurement techniques as well as first results concerning the relation between lateral lid displacement and leaktightness.