Design of an experiment that simulates spent nuclear fuel within transport casks

Spent nuclear fuel assemblies are placed within the basket structure of a thick walled cask for transport. The fuel rods generate heat from radioactive decay and the cask must dissipate this heat to the surroundings through the package walls. A goal of a transport package designer is to make sure that fuel rod cladding temperatures do not exceed the containment integrity limit. Therefore cask design is focused on maximizing the number of assemblies contained without surpassing the allowed temperature limit. Conservatism and uncertainty in the thermal analysis therefore leads to under-loading casks, increasing the number of shipments needed and increased public safety hazards. This work details the use of computational fluid dynamics (CFD) simulation software to help design an experiment that will be used to develop better thermal characterization models of spent nuclear fuel. The CFD code is benchmarked with previous experimental data, and is later used to establish key characteristics in the design of an experimental test rig. Simulations results show that geometric simplifications to the test rig can be made and also point to key characteristics that need to be addressed. The experiment design is then presented and will be used for future thermal measurements. The experimental data will be used in the future to develop thermal models of spent nuclear fuel assemblies under normal transport conditions.