For dual purpose “transport/storage” casks (like the TN24 casks family or casks for vitrified wastes), the confinement by way of metallic gaskets has long been the chosen solution. Their metallic nature leading to a good behaviour in long-term and high temperature conditions, they still have to satisfy the transport regulations requirements, which are not a given. In order to secure the supplying of such strategic parts of a cask and, above all, to keep developing efficient sealing solutions, TN International has found and qualified new metallic gaskets. For this qualification, a series of tests complying with the accident and normal conditions of transport/storage have been designed and performed on these new metallic gaskets. Indeed, the gaskets have to withstand three major types of “accidental” conditions: 1/ parallel sliding of the lid and the body, resulting in a lateral displacement of the contact surfaces, 2/ separation of the lid and the body, resulting in a decompression of the gasket, 3/ 30 minutes-800°C fire on the cask, resulting in a peak temperature of the gasket. They also have to withstand normal transport/storage conditions, that is to say thermal ageing for long period. Finally we wanted to know how these seals resisted to small particles present during the compression. Tests assemblies and procedures have been developed, in accordance with TN International cask design. Then lateral quasi-static displacement tests up to 3-mm, lateral dynamic displacement tests up to 3-mm, multiple decompression and recompression tests, over-400°C peak temperature tests, long term ageing tests and particle-resistance tests were carried out. The dimensional, visual and leaktightness results of these conservative and highly severe tests were fully satisfactory and allow to establish the safety and efficiency of these new metallic gaskets.

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