Purpose and structure of the assembly SNEAK 12B

The core of assembly SNEAK 12B contains a central test zone with plutonium-uranium mixed-oxide fuel with 15 % enrichment, surrounded by a driver zone of enriched uranium. Its purpose is to check the validity of neutron physics calculational methods in the analysis of accidental situations of fast breeder reactors. The core with its assemblies and their contents are described, and the experimental program is outlined. It contains experiments in the unperturbed reference core, axial and radial fuel relocation configurations and steel blockages between fuel pins. Some safety relevant calculational results are presented