Criticality calculations for canned fast reactor fuel rods

The criticality analysis for an inventory of highly enriched MOX fuel rods, placed loosely within steel cans, has been conducted with Monte Carlo simulation calculations. Special emphasis was placed on investigating the aspects of this system that differentiate it from more commonplace LWR fuel assemblies, namely the high enrichment and the lack of a fixed fuel rod arrangement. The combination of optimal moderation and the most reactive arrangement of fuel rods within a can leads to a final result of keff + uncertainties + biases < 0.939 for a cask loaded with nine cans. Thus, criticality safety can be proven in spite of the unique challenges posed by this unusual inventory. (authors)