IMPACT ON THE TRANSPORTATION PACKAGE DESIGN FOR TRANSPORT FIRST & THEN INTERIM STORAGE VERSUS INTERIM STORAGE FIRST AND TRANSPORT - Presentation

In the United States of America (USA) currently because of the unavailability of the repository, all the fuel assemblies from the commercial nuclear power plants are stored on sites using dry storage systems which will be transported offsite in the future. The majority of these systems are dual purpose systems (storage and transport). However, in some countries, the fuel assemblies are stored in the interim storage facilities. In this case, the fuel assemblies needed to be transported from the nuclear power plants to the interim storage sites first and then put into storages. The impact on the storage system design is significantly dependent on the options selected. This paper examines the important aspects of the package design affected by the options. Some of the considerations are the heat rejection capability and the radiation shielding capability of the package. In the “Storage First” option, the system is designed for the maximum possible heat load, therefore the system design is normally dominated by the heat rejection capability (limited by the maximum fuel cladding temperature). However, for the “Transport First” option, the system design is limited due to shielding considerations and thermal design is usually controlled by the maximum seal temperatures. In addition, the crane capacities of the power plants also have a major effect on the system design. For the “Storage First” system (on-site storage), the canister can be transferred by the use of a transfer overpack (overpack to transfer the canister to the storage site) and put into storage at the Independent Spent Fuel Storage Installation (ISFSI). At the time of off-site transport, the canister can be transferred from the storage overpack to the transport overpack. In this scenario, the loaded transport overpack is not handled inside the fuel building. The fuel building crane will only need to lift the weight of the transfer overpack and canister. For the “Transport First” system, the fuel building crane needs to lift the weight of the transport overpack and canister. Normally, the onsite transfer overpack is lighter than the transport overpack, therefore for the same crane capacity; the “Storage First” system can accommodate higher capacities than the “Transport First” system. This paper examines the important design aspects of the two systems which include thermal and shielding; in addition, design interface requirements are also addressed.