Experience of Fabrication of Transport/Storage Packaging \"TN24\"

It is the basic plan of Japan that nuclear spent fuel would be reprocessed. More recently, however, recognition has gradually been taken of the necessity for an interim storage to support the reprocessing of the spent fuel. This trend of having an interim storage is common in many other countries, and various storage methods have been developed, using the package, pool, vault, silo, and others. Taking this experience into account, Kobe Steel Ltd. has been engaged since 1983 in a joint project with the French company, Transnucleaire, to develop ''TN24\", a dry-type storage packaging for nuclear spent fuel. The combination of Transnucleaire's design experience from developing the TN 12/TN 17 transport packaging, together with Kobe Steel's technologies and expertise in manufacturing and quality assurance, have made TN24 a high-efficiency storage package. In 1985, drop tests, using a 2/5-scale model of a TN24, demonstrated the soundness of the packaging under accident conditions. In 1986, a prototype model was manufactured and various cold tests were carried out in Japan. This prototype model was sent to the Idaho National Engineering Laboratory in the United States for storage tests using actual irradiated fuel assemblies. Recently Kobe Steel fabricated a Japanese version of the TN24 packaging, which has been adopted for actual use in the Tokyo Electric Power Company's Fukushima No. 1 site. This report describes the stages in the development of the TN24 packaging, from design to the present.