New metallic gaskets qualification: resistance to accident conditions of transport in TN international casks

Abstract

For dual purpose 'transport/storage' casks (like the TN24 cask family or casks for vitrified wastes), the confinement by way of metallic gaskets has long been the chosen solution. Their metallic nature leads to a good behaviour in the long term and high temperature conditions but they still have to satisfy the requirements of transport regulations, which are extremely demanding. In order to secure the supply 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 conditions of transport have been designed and performed on these new metallic gaskets. Indeed, the gaskets have to withstand three major types of 'accident' conditions:

(i) parallel sliding of the lid and the body, resulting in a lateral displacement of the contact surfaces

(ii) separation of the lid and the body, resulting in a decompression of the gasket

(iii) 30 min exposure to an 800°C fire on the cask, resulting in a peak temperature of the gasket.

Test assemblies and procedures have been developed, in accordance with TN International cask design and, after that, lateral quasi-static displacement tests up to 3 mm, lateral dynamic displacement tests up to 3 mm, multiple decompression and recompression tests, and over 400°C peak temperature tests were carried out.

The dimensional, visual and leaktightness results of these conservative and highly severe tests were fully satisfactory and were used to establish the safety and efficiency of these new metallic gaskets.

Keywords:

• METALLIC GASKETS
• RESISTANCE TO ACCIDENTAL CONDITIONS
• TRANSPORT