Accident tolerant fuel cladding tube irradiations in the HFIR

The Advanced Fuels Campaign within the Fuel Cycle Research and Development program of the Department of Energy (DOE) Office of Nuclear Energy is currently investigating a number of advanced nuclear fuel cladding concepts to improve the accident tolerance of light water reactors (LWRs). Some of the leading candidates to replace traditional zirconium-based cladding are alumina- forming ferritic alloys (e.g., FeCrAl) and silicon carbide (SiC) composites. Oak Ridge National Laboratory has developed experimental designs to irradiate thin-walled cladding tubes with representative geometry in the High Flux Isotope Reactor (HFIR) under relevant LWR temperatures and in some cases under prototypic heat flux. These designs allow for post-irradiation examination (PIE) of cladding which closely resembles expected commercially viable geometries and microstructures. PIE will include studies of dimensional change, microstructure variation, mechanical performance, etc. The experiments were designed using relatively inexpensive rabbit capsules for the irradiation vehicle. The simplistic designs combined with the extremely high neutron flux in the HFIR allow for rapid testing of a large test matrix, thus reducing the time and cost for moving advanced cladding materials closer to commercialization. This work describes the capsule designs that have been developed at ORNL, some initial results, and plans for future irradiations.