The sodium-bonded uranium-metal fuel elements used as driver fuel in EBR-II exhibit a characteristic fission-product release when a leak occurs in the lower part of the element. Shutting off the primary pumps at reactor shutdown reduces the effective ambient pressure, and bond sodium bearing fission-product iodine is extruded into the primary coolant by the gas in the fuel element plenum. The decay of the extruded iodine produces a surge in the xenon activity which reaches a maximum 11 or more hours after the reactor is shut down. An experimental fuel element with an intentional leak was irradiated in the reactor during several different runs so that this effect could be observed under reasonably controlled conditions. A simple model fairly well relates the size of surge to reactor power, location of the leaking element in the core, and timing of pump operation.