The Power Burst Facility (PBF) is designed to operate under steady-state conditions to 20 MW (this value may be upgraded to 30 to 40 MW in the near future), with self-limiting power bursts having initial asymptotic periods as short as 1.3 msec, and with shaped power bursts. The core and thus the fuel rods to accomplish these design requirements involved a significant development program to determine the performance capability. The limiting performance capability was determined to be the axial and diametral growth of the fuel rods. The growth behavior of the fuel rods resulted from burst tests conducted in the Transient Reactor Test Facility and Capsule Driver Core reactors. In these tests, the fuel rods were subjected to repeated bursts (10 to 200 bursts/rod) in which fuel temperatures ranged from 1600 to ∼2600°C. The minimum reactor period was 3.0 msec. The PBF fuel rods, which are 47.5 in. long and 0.75 in. in diameter, experienced maximum axial growth on the order of 0.75 in. and maximum diametral growth of ∼ 0.040 in. in these tests.