TRANSPORT AND STORAGE OF MOX FUELS METHODOLOGY FOR CRITICALITY ASSESSMENT METHODS

For spent fuel reprocessing i!l La Hague Plant, the authorization to unload these fuels into a pool is obtained further to analysis relative to their transport in cask and their storage in specific baskets. One of the major risks arising during these operations is the criticality risk, present at each of the following steps : • transport cask immersion • fuel assembly handling • loading, transfer and storage of fuel assembly baskets. For UOX type assemblies, the criticality-safety of the foregoing operations is chiefly based on the fissile material limitation, characterized by the mu initial enrichment, which depends on geometric parameters such as its cross-section and characteristics of fuel rods and their number per assembly. On the other hand, the criticality-safety analysis ofMOX type assemblies, which can be made from mixtures of batches of plutonium from various sources, leads to a larger number of variables: