For the first time, Oak Ridge National Laboratory has completed testing of nuclear fuels using MiniFuel, an irradiation vehicle that allows for rapid experimentation. The compact experiment, which was irradiated at ORNL’s High Flux Isotope Reactor and then examined to see how the fuel responded, comprises a miniature target that holds pinhead-size fuel kernels. Conventional fuel tests use pellets with volumes more than 1,000 times that size. MiniFuel’s small size helps researchers better control variables and accelerate burnup conditions during irradiation. “Fuel performance testing is extremely complex, and it is difficult to interpret the data because so much is happening across the fuel pellet,” said ORNL’s Chris Petrie, who developed the concept. “With MiniFuel, we can isolate conditions, test specific fuel phenomena and acquire performance data much faster.” The first tests are focused on uranium nitride fuel for light water reactors—a fuel type lacking performance data.