This paper describes the transient behavior of TRIGA, a light-water-cooled reactor using fuel-moderator elements composed of uranium and zirconium hydride. The large, prompt negative temperature coefficient—an inherent characteristic of these fuel-moderator elements—limits reactor power transients primarily by means of fuel-element temperature rise rather than by void formation in the core. Step reactivity insertions of up to 1.6% resulted in peak powers of 250 Mw with no detectable boiling of the core water or expulsion of water from the core.